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<front>
<journal-meta>
<journal-id journal-id-type="publisher-id">Front. Ecol. Evol.</journal-id>
<journal-title>Frontiers in Ecology and Evolution</journal-title>
<abbrev-journal-title abbrev-type="pubmed">Front. Ecol. Evol.</abbrev-journal-title>
<issn pub-type="epub">2296-701X</issn>
<publisher>
<publisher-name>Frontiers Media S.A.</publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.3389/fevo.2023.1212654</article-id>
<article-categories>
<subj-group subj-group-type="heading">
<subject>Ecology and Evolution</subject>
<subj-group>
<subject>Original Research</subject>
</subj-group>
</subj-group>
</article-categories>
<title-group>
<article-title>Empirical prediction of blast-induced vibration on adjacent tunnels</article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author" corresp="yes">
<name>
<surname>Li</surname><given-names>Wenxin</given-names>
</name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<xref ref-type="aff" rid="aff2"><sup>2</sup></xref>
<xref ref-type="author-notes" rid="fn001"><sup>*</sup></xref>
<uri xlink:href="https://loop.frontiersin.org/people/2294640"/>
</contrib>
<contrib contrib-type="author" corresp="yes">
<name>
<surname>Wang</surname><given-names>Xiao</given-names>
</name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<xref ref-type="author-notes" rid="fn001"><sup>*</sup></xref>
<uri xlink:href="https://loop.frontiersin.org/people/2295035"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname>Chen</surname><given-names>Lianjun</given-names>
</name>
<xref ref-type="aff" rid="aff3"><sup>3</sup></xref>
</contrib>
<contrib contrib-type="author">
<name>
<surname>Wang</surname><given-names>Chunguang</given-names>
</name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
</contrib>
<contrib contrib-type="author">
<name>
<surname>Liu</surname><given-names>Jinxiao</given-names>
</name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
</contrib>
</contrib-group>
<aff id="aff1"><sup>1</sup><institution>College of Energy and Mining Engineering, Shandong University of Science and Technology</institution>, <addr-line>Qingdao</addr-line>, <country>China</country></aff>
<aff id="aff2"><sup>2</sup><institution>Mine Disaster Prevention and Control-Ministry of State Key Laboratory Breeding Base, Shandong University of Science and Technology</institution>, <addr-line>Qingdao</addr-line>, <country>China</country></aff>
<aff id="aff3"><sup>3</sup><institution>College of Safety and Environment Engineering, Shandong University of Science and Technology</institution>, <addr-line>Qingdao</addr-line>, <country>China</country></aff>
<author-notes>
<fn fn-type="edited-by">
<p>Edited by: Shaobo Chai, Chang&#x2019;an University, China</p>
</fn>
<fn fn-type="edited-by">
<p>Reviewed by: Yonggang Gou, Hohai University, China; Longgang Tian, Southeast University, China; Jiacheng Song, The University of Tokyo, Japan, in collaboration with reviewer LT</p>
</fn>
<fn fn-type="corresp" id="fn001">
<p>*Correspondence: Wenxin Li, <email xlink:href="mailto:li17753299337@163.com">li17753299337@163.com</email>; Xiao Wang, <email xlink:href="mailto:x.wang@sdust.edu.cn">x.wang@sdust.edu.cn</email>
</p>
</fn>
</author-notes>
<pub-date pub-type="epub">
<day>19</day>
<month>06</month>
<year>2023</year>
</pub-date>
<pub-date pub-type="collection">
<year>2023</year>
</pub-date>
<volume>11</volume>
<elocation-id>1212654</elocation-id>
<history>
<date date-type="received">
<day>26</day>
<month>04</month>
<year>2023</year>
</date>
<date date-type="accepted">
<day>01</day>
<month>06</month>
<year>2023</year>
</date>
</history>
<permissions>
<copyright-statement>Copyright &#xa9; 2023 Li, Wang, Chen, Wang and Liu</copyright-statement>
<copyright-year>2023</copyright-year>
<copyright-holder>Li, Wang, Chen, Wang and Liu</copyright-holder>
<license xlink:href="http://creativecommons.org/licenses/by/4.0/">
<p>This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.</p>
</license>
</permissions>
<abstract>
<p>The blast-induced vibration during excavation by the drilling and blasting method has an important impact on the surrounding buildings/structures and auxiliary equipment. In particular, with the development of tunnel engineering, the impact of blasting vibration on tunnel construction has attracted extensive attention. Based on literature data statistics, this paper first explored the performance of several commonly used empirical equations in predicting the propagation and attenuation characteristics of blasting vibration on adjacent tunnels. Secondly, the relationships between the empirical parameters of the blasting vibration prediction equation and the geological strength index (GSI) of tunnel surrounding rock were discussed, and two new blasting vibration prediction equations based on site rock GSI were established to approximately predict blast-induced vibration on adjacent tunnels. Finally, the application feasibility of the established prediction equation in practical engineering was discussed based on field test data. The research results show that under the condition of multiple groups of data, the prediction performance of various prediction models does not differ significantly. With the increase of the GSI of the surrounding rock mass of the adjacent tunnel, the site coefficients <italic>&#x3b2;</italic> and <italic>k</italic> of the blasting vibration prediction equation in predicting PPV (peak particle velocity, resultant velocity) both show a decreasing trend as a whole. The site coefficient <italic>k</italic> is generally within 3,000. Two new empirical prediction equations of blasting vibration propagation and attenuation on adjacent tunnels under different site conditions were established: Eq. (14) for <italic>PPV</italic> and Eq. (15) for <italic>PPV</italic><sub>i</sub> (max) (maximum value of the three component velocities; i = x, y, z represent peak component particle velocity). The verification analysis of five sites shows that these two equations have a certain practical application value. Compared with other empirical equations, these two equations do not need regression fitting blasting vibration data, they only used the GSI of the site rock mass, and they are more easy to use in the field when there is a lack of monitoring data.</p>
</abstract>
<kwd-group>
<kwd>blast-induced vibration</kwd>
<kwd>tunnel</kwd>
<kwd>PPV/PPVi (max)</kwd>
<kwd>empirical equations</kwd>
<kwd>prediction performance</kwd>
<kwd>geological strength index</kwd>
</kwd-group>
<counts>
<fig-count count="10"/>
<table-count count="3"/>
<equation-count count="15"/>
<ref-count count="46"/>
<page-count count="14"/>
<word-count count="6636"/>
</counts>
<custom-meta-wrap>
<custom-meta>
<meta-name>section-in-acceptance</meta-name>
<meta-value>Environmental Informatics and Remote Sensing</meta-value>
</custom-meta>
</custom-meta-wrap>
</article-meta>
</front>
<body>
<sec id="s1" sec-type="intro">
<label>1</label>
<title>Introduction</title>
<p>The drilling and blasting method is a widely used method for tunnel construction, resource mining, and other rock engineering aspects since it has the advantages of simple construction, strong adaptability to geological conditions, and low cost (<xref ref-type="bibr" rid="B24">Ocak and Bilgin, 2010</xref>; <xref ref-type="bibr" rid="B30">Wang et&#xa0;al., 2022</xref>). However, it also brings many negative effects such as blasting vibration, air shock wave, flying rock, noise, and toxic gas and dust (<xref ref-type="bibr" rid="B22">Murmu et&#xa0;al., 2018</xref>). Among these negative effects, blasting vibration can very easily cause damage to nearby buildings/structures or related facilities (<xref ref-type="bibr" rid="B44">Zhou and Jenssen, 2009</xref>; <xref ref-type="bibr" rid="B16">Li et&#xa0;al., 2013</xref>).</p>
<p><italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> and frequency are common parameters for evaluating blasting vibration hazards (<xref ref-type="bibr" rid="B20">Lu, 2005</xref>; <xref ref-type="bibr" rid="B35">Wu and Hao, 2005</xref>). Both of them are necessary to determine the response of neighboring buildings/structures in different geological formations. In particular, when the frequency of blasting vibration is close to the natural vibration frequency of surrounding buildings/structures or related facilities, the blasting vibration may be amplified several times due to resonance, and the harm to surrounding buildings/structures or related facilities will also increase (<xref ref-type="bibr" rid="B29">Sisikind et&#xa0;al., 1980</xref>). For this reason, most blasting vibration safety standards take into account the frequency dependence of the vibration damage potential (<xref ref-type="bibr" rid="B3">BS3785-2, 1993</xref>; <xref ref-type="bibr" rid="B21">Lu et&#xa0;al., 2012</xref>; <xref ref-type="bibr" rid="B40">Yilmaz, 2016</xref>).</p>
<p>However, <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> is still the basis of many blasting vibration safety standards and is also considered to be the most important parameter for evaluating blasting vibration hazards (<xref ref-type="bibr" rid="B23">Nateghi et&#xa0;al., 2009</xref>; <xref ref-type="bibr" rid="B40">Yilmaz, 2016</xref>). A large number of monitoring, tests, and theoretical studies show that the PPV is mainly related to the explosive charge, distance between blasting source and monitoring points, and site conditions, and the widely used blasting vibration prediction equation was established (<xref ref-type="bibr" rid="B22">Murmu et&#xa0;al., 2018</xref>) as:</p>
<disp-formula>
<label>(1)</label>
<mml:math display="block" id="M1">
<mml:mrow>
<mml:mi>P</mml:mi>
<mml:mi>P</mml:mi>
<mml:mi>V</mml:mi>
<mml:mo stretchy="false">/</mml:mo>
<mml:mi>P</mml:mi>
<mml:mi>P</mml:mi>
<mml:msub>
<mml:mi>V</mml:mi>
<mml:mi>i</mml:mi>
</mml:msub>
<mml:mo>=</mml:mo>
<mml:mi>k</mml:mi>
<mml:mo>&#xb7;</mml:mo>
<mml:mi>S</mml:mi>
<mml:msup>
<mml:mi>D</mml:mi>
<mml:mrow>
<mml:mo>&#x2212;</mml:mo>
<mml:mi>&#x3b2;</mml:mi>
</mml:mrow>
</mml:msup>
</mml:mrow>
</mml:math>
</disp-formula>
<p>where <italic>k</italic> and <italic>&#x3b2;</italic> are site-specific constants that describe the characteristic of propagating media, blasting design, and geology; scaled distance, <italic>SD</italic> = <italic>R</italic>/<italic>Q<sup>a</sup>
</italic>, is the ratio of distance of monitoring point from the geometric center of the blasting area, <italic>R</italic> (m), to the maximum charge per delay, <italic>Q<sup>a</sup>
</italic> (kg); <italic>a</italic> is the scaled distance relationship constant. <xref ref-type="table" rid="T1"><bold>Table&#xa0;1</bold></xref> summarizes the common forms and extended forms of Eq. (1).</p>
<table-wrap id="T1" position="float">
<label>Table&#xa0;1</label>
<caption>
<p>Summary of commonly used PPV prediction equations.</p>
</caption>
<table frame="hsides">
<thead>
<tr>
<th valign="top" align="left">Equation ID</th>
<th valign="top" align="left">References</th>
<th valign="top" align="left">Empirical equations</th>
</tr>
</thead>
<tbody>
<tr>
<td valign="top" align="left">#1</td>
<td valign="top" align="left">USBM (<xref ref-type="bibr" rid="B4">Devine, 1962</xref>)</td>
<td valign="top" align="left"><italic>PPV</italic>/<italic>PPV<sub>i</sub>
</italic> = <italic>k</italic> (<italic>R</italic>/<italic>Q</italic><sup>1/2</sup>)<sup>-</sup><italic><sup>&#x3b2;</sup>
</italic>
</td>
</tr>
<tr>
<td valign="top" align="left">#2</td>
<td valign="top" align="left">
<xref ref-type="bibr" rid="B2">Ambraseys and Hendron (1968)</xref>
</td>
<td valign="top" align="left"><italic>PPV</italic>/<italic>PPV<sub>i</sub>
</italic> = <italic>k</italic> (<italic>R</italic>/<italic>Q</italic><sup>1/3</sup>)<sup>-</sup><italic><sup>&#x3b2;</sup>
</italic>
</td>
</tr>
<tr>
<td valign="top" align="left">#3</td>
<td valign="top" align="left">
<xref ref-type="bibr" rid="B10">IS: 6922-1973 (1973)</xref>
</td>
<td valign="top" align="left"><italic>PPV</italic>/<italic>PPV<sub>i</sub>
</italic> = <italic>k</italic> (<italic>R</italic>/<italic>Q</italic><sup>2/3</sup>)<sup>-</sup><italic><sup>&#x3b2;</sup>
</italic>
</td>
</tr>
<tr>
<td valign="top" align="left">#4</td>
<td valign="top" align="left">
<xref ref-type="bibr" rid="B5">Ghosh and Daemen (1983)</xref>
</td>
<td valign="top" align="left"><italic>PPV</italic>/<italic>PPV<sub>i</sub>
</italic> = <italic>k</italic> (<italic>R</italic>/<italic>Q</italic><sup>1/2</sup>)<sup>-</sup><italic><sup>&#x3b2;</sup>e</italic><sup>-</sup><italic><sup>&#x3bb;R</sup>
</italic>
</td>
</tr>
<tr>
<td valign="top" align="left">#5</td>
<td valign="top" align="left">
<xref ref-type="bibr" rid="B5">Ghosh and Daemen (1983)</xref>
</td>
<td valign="top" align="left"><italic>PPV</italic>/<italic>PPV<sub>i</sub>
</italic> = <italic>k</italic> (<italic>R</italic>/<italic>Q</italic><sup>1/3</sup>)<sup>-</sup><italic><sup>&#x3b2;</sup>e</italic><sup>-</sup><italic><sup>&#x3bb;R</sup>
</italic>
</td>
</tr>
<tr>
<td valign="top" align="left">#6</td>
<td valign="top" align="left">
<xref ref-type="bibr" rid="B6">Gupta et&#xa0;al. (1987)</xref>
</td>
<td valign="top" align="left"><italic>PPV</italic>/<italic>PPV<sub>i</sub>
</italic> = <italic>k</italic> (<italic>R</italic>/<italic>Q</italic><sup>1/2</sup>)<sup>-</sup><italic><sup>&#x3b2;</sup>e</italic><sup>-&#x3bb;(</sup><italic><sup>R</sup>
</italic><sup>/</sup><italic><sup>Q</sup>
</italic><sup>)</sup>
</td>
</tr>
<tr>
<td valign="top" align="left">#7</td>
<td valign="top" align="left">
<xref ref-type="bibr" rid="B26">Roy (1991)</xref>
</td>
<td valign="top" align="left"><italic>PPV</italic>/<italic>PPV<sub>i</sub>
</italic> = <italic>n</italic> + <italic>k</italic> (<italic>R</italic>/<italic>Q</italic><sup>1/2</sup>)<sup>-1</sup>
</td>
</tr>
<tr>
<td valign="top" align="left">#8</td>
<td valign="top" align="left">
<xref ref-type="bibr" rid="B40">Yilmaz (2016)</xref>
</td>
<td valign="top" align="left">
<inline-formula>
<mml:math display="inline" id="im1">
<mml:mrow>
<mml:mi>P</mml:mi>
<mml:mi>P</mml:mi>
<mml:mi>V</mml:mi>
<mml:mo stretchy="false">/</mml:mo>
<mml:mi>P</mml:mi>
<mml:mi>P</mml:mi>
<mml:msub>
<mml:mi>V</mml:mi>
<mml:mi>i</mml:mi>
</mml:msub>
<mml:mo>=</mml:mo>
<mml:mi>k</mml:mi>
<mml:msup>
<mml:mrow>
<mml:mrow>
<mml:mo stretchy="false">(</mml:mo>
<mml:mrow>
<mml:mi>R</mml:mi>
<mml:mo stretchy="false">/</mml:mo>
<mml:msup>
<mml:mi>Q</mml:mi>
<mml:mrow>
<mml:mn>2</mml:mn>
<mml:mo stretchy="false">/</mml:mo>
<mml:mn>3</mml:mn>
</mml:mrow>
</mml:msup>
</mml:mrow>
<mml:mo stretchy="false">)</mml:mo>
</mml:mrow>
</mml:mrow>
<mml:mrow>
<mml:mo>&#x2212;</mml:mo>
<mml:mi>&#x3b2;</mml:mi>
</mml:mrow>
</mml:msup>
<mml:msup>
<mml:mi>e</mml:mi>
<mml:mrow>
<mml:mo>&#x2212;</mml:mo>
<mml:mi>&#x3bb;</mml:mi>
<mml:mo stretchy="false">(</mml:mo>
<mml:mi>R</mml:mi>
<mml:mo stretchy="false">/</mml:mo>
<mml:msup>
<mml:mi>Q</mml:mi>
<mml:mrow>
<mml:mn>1</mml:mn>
<mml:mo stretchy="false">/</mml:mo>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:msup>
<mml:mo stretchy="false">)</mml:mo>
</mml:mrow>
</mml:msup>
</mml:mrow>
</mml:math>
</inline-formula>
</td>
</tr>
</tbody>
</table>
</table-wrap>
<p>Note: <italic>R</italic> is the distance of monitoring point from the geometric center of the blasting area; <italic>Q</italic> is the maximum charge per delay; <italic>k</italic> and <italic>&#x3b2;</italic> are site-specific constants that describe the characteristic of propagating media, &gt;0; <italic>&#x3bb;</italic> represents the inelastic attenuation factor of site, &gt;0; <italic>n</italic> represents the energy diminishing influenced by rock properties and geological discontinuities (e.g., faults, fractures, joints, fissures, and bedding planes), and is a decay constant,&lt;0.</p>
<p>Generally, the prediction equations shown in <xref ref-type="table" rid="T1"><bold>Table&#xa0;1</bold></xref> are often used to predict <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> on the ground surface and strata (<xref ref-type="bibr" rid="B44">Zhou and Jenssen, 2009</xref>; <xref ref-type="bibr" rid="B11">Jayasinghe et&#xa0;al., 2019</xref>; <xref ref-type="bibr" rid="B15">Li et&#xa0;al., 2021</xref>). In recent years, with the continuous development of underground tunnel engineering, some equations in <xref ref-type="table" rid="T1"><bold>Table&#xa0;1</bold></xref> are also used to predict <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> on tunnel structures. For example, based on empirical equations provided by USBM (<xref ref-type="bibr" rid="B4">Devine, 1962</xref>) or <xref ref-type="bibr" rid="B2">Ambraseys and Hendron (1968)</xref>; <xref ref-type="bibr" rid="B28">Singh (2002)</xref> and <xref ref-type="bibr" rid="B1">Abolghasemifar et&#xa0;al. (2018)</xref> investigated the response and attention characteristics of blasting vibration on the roof, pillar/sidewall, and/or floor of underground coal mines from adjacent open-pit blasting/underground tunneling; <xref ref-type="bibr" rid="B43">Zhao et&#xa0;al. (2016)</xref>; <xref ref-type="bibr" rid="B27">Sharafat et&#xa0;al. (2019)</xref>, and <xref ref-type="bibr" rid="B42">Zhang et&#xa0;al. (2021)</xref> analyzed the attention characteristics on underground rock tunnel floor from adjacent tunnel blasting; and <xref ref-type="bibr" rid="B45">Zhou et&#xa0;al. (2018)</xref>; <xref ref-type="bibr" rid="B33">Wang et&#xa0;al. (2019)</xref>, and <xref ref-type="bibr" rid="B46">Zhu et&#xa0;al. (2021)</xref> discussed the attention characteristics on underground rock tunnel sidewall from adjacent tunnel blasting. These studies show that it is feasible to use empirical equation to predict blasting vibration on adjacent tunnel structures. However, there are few literature that explored and compared the prediction performance of different empirical equations shown in <xref ref-type="table" rid="T1"><bold>Table&#xa0;1</bold></xref> for predicting PPV/PPV<sub>i</sub> on adjacent tunnels. In addition, there are few studies on the relationship between the parameters of prediction equations and the geological parameters of tunnel surrounding rock. When there are no blasting vibration data, the application of blasting vibration prediction equation is usually limited.</p>
<p>In this paper, first, based on the collected data of blasting vibration response on the adjacent tunnel structures, the prediction performance of various empirical equations shown in <xref ref-type="table" rid="T1"><bold>Table&#xa0;1</bold></xref> in predicting <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> was investigated, and some of the empirical equations were recommended to predict <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> on the adjacent tunnels. Secondly, the relationships between the empirical parameters of blasting vibration prediction equation and the mechanical properties of tunnel surrounding rock were analyzed. Finally, the application feasibility of the established prediction equation in practical engineering was discussed based on field data. This study has some practical value for the safety control of blast-induced tunnel disasters, especially in the case of lack of on-site blasting vibration data.</p>
</sec>
<sec id="s2">
<label>2</label>
<title>Performance of different empirical equations in predicting <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> on adjacent tunnels</title>
<sec id="s2_1">
<label>2.1</label>
<title>Data collection</title>
<p>Within the scope of this study, to compare the prediction performance of different empirical equations in predicting <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> on adjacent tunnels, the results of the vibration measurements on adjacent tunnels from previous studies were analyzed carefully. A total of 21 sets of data were collected from eight references, as shown in <xref ref-type="table" rid="T2"><bold>Table&#xa0;2</bold></xref>. Among these data, three sets of data are about <italic>PPV</italic>, four sets of data are about <italic>PPV</italic>x, six sets of data are about <italic>PPV</italic>y, and eight sets of data are about <italic>PPV</italic>z.</p>
<table-wrap id="T2" position="float">
<label>Table&#xa0;2</label>
<caption>
<p>Collected data about blast-induced vibration propagation and attention on adjacent tunnels.</p>
</caption>
<table frame="hsides">
<thead>
<tr>
<th valign="top" align="left">No.</th>
<th valign="top" align="left">References</th>
<th valign="top" align="left">Blasting information</th>
<th valign="top" align="left">Monitoring tunnel types, shapes, sizes, and locations</th>
<th valign="top" align="left">Geological conditions and characteristics</th>
<th valign="top" align="left">Positions of measuring points</th>
<th valign="top" align="left">Selected no. of data</th>
<th valign="top" align="left">Range of recorded <italic>Q</italic> (kg)</th>
<th valign="top" align="left">Range of recorded <italic>R</italic> (m)</th>
<th valign="top" align="left">Range of recorded <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> (mm/s)</th>
</tr>
</thead>
<tbody>
<tr>
<td valign="top" align="left">1</td>
<td valign="top" rowspan="2" align="left">
<xref ref-type="bibr" rid="B18">Liu and Chen, 2008</xref>
</td>
<td valign="top" rowspan="2" align="left">Blasts in development tunnel; horizontal between blasting tunnel and monitoring tunnel is 11&#xa0;m.</td>
<td valign="top" rowspan="2" align="left">Highway tunnel; Horseshoe; Span of the tunnel is about 10&#xa0;m; Hubei, China</td>
<td valign="top" rowspan="2" align="left">Sericite sodium feldspar quartz schist; the shallow rock mass is seriously weathered and joint and fissures are developed.</td>
<td valign="top" rowspan="2" align="left">Sidewall</td>
<td valign="top" rowspan="2" align="left">4</td>
<td valign="top" rowspan="2" align="left">15</td>
<td valign="top" rowspan="2" align="left">16.3&#x2013;22.2</td>
<td valign="top" align="left">30.3&#x2013;53.2 (<italic>PPV</italic>y)</td>
</tr>
<tr>
<td valign="top" align="left">2</td>
<td valign="top" align="left">32.5&#x2013;55.9 (<italic>PPV</italic>z)</td>
</tr>
<tr>
<td valign="top" align="left">3</td>
<td valign="top" rowspan="2" align="left">
<xref ref-type="bibr" rid="B14">Li et&#xa0;al., 2010</xref>
</td>
<td valign="top" rowspan="2" align="left">Blasts in development tunnel; the blasting tunnel is 30&#x2013;40 m along the monitoring tunnel</td>
<td valign="top" rowspan="2" align="left">Hydropower tunnel; Semicircular straight wall; Span and height of the tunnel are 22&#x2013;24 m and 19&#x2013;20 m, respectively; Jinsha River, China</td>
<td valign="top" rowspan="2" align="left">Dense basalt, porphyritic basalt and breccia (aggregate) lava, with hard lithology and <italic>UCS</italic> &gt; 100 MPa; rock mass is complete&#x2013;relatively complete</td>
<td valign="top" rowspan="2" align="left">Sidewall</td>
<td valign="top" rowspan="2" align="left">15</td>
<td valign="top" rowspan="2" align="left">70&#x2013;104</td>
<td valign="top" rowspan="2" align="left">40.5&#x2013;<break/>125.4</td>
<td valign="top" align="left">11.4&#x2013;72 (<italic>PPV</italic>y)</td>
</tr>
<tr>
<td valign="top" align="left">4</td>
<td valign="top" align="left">7.9&#x2013;44.7 (<italic>PPV</italic>z)</td>
</tr>
<tr>
<td valign="top" align="left">5</td>
<td valign="top" align="left">
<xref ref-type="bibr" rid="B43">Zhao et&#xa0;al., 2016</xref>
</td>
<td valign="top" align="left">Blasts in development tunnel; the blasting tunnel is 4&#xa0;m below the monitoring tunnel</td>
<td valign="top" align="left">Cargo line tunnel; Straight wall; Span and height of the tunnel are 11.6&#xa0;m and 7.918&#xa0;m, respectively; Nanjing in China</td>
<td valign="top" align="left">Weathered (strongly weathered&#x2013;slightly weathered) sandstone</td>
<td valign="top" align="left">Floor</td>
<td valign="top" align="left">35</td>
<td valign="top" align="left">2.4&#x2013;7.4</td>
<td valign="top" align="left">4&#x2013;8.94</td>
<td valign="top" align="left">56&#x2013;394(<italic>PPV</italic>z)</td>
</tr>
<tr>
<td valign="top" align="left">6</td>
<td valign="top" rowspan="3" align="left">
<xref ref-type="bibr" rid="B1">Abolghasemifar et&#xa0;al., 2018</xref>
</td>
<td valign="top" rowspan="3" align="left">Blasts in development tunnels</td>
<td valign="top" rowspan="3" align="left">Coal mine opening; Shahrood in Northern Iran.</td>
<td valign="top" rowspan="3" align="left">Sandstone; <italic>UCS</italic>: 48.8&#x2013;53.2 MPa</td>
<td valign="top" rowspan="3" align="left">Roof</td>
<td valign="top" rowspan="3" align="left">29</td>
<td valign="top" rowspan="3" align="left">1.8&#x2013;4.8</td>
<td valign="top" rowspan="3" align="left">20.5&#x2013;74.8</td>
<td valign="top" align="left">0.49&#x2013;9.65 (<italic>PPV</italic>x)</td>
</tr>
<tr>
<td valign="top" align="left">7</td>
<td valign="top" align="left">0.29&#x2013;15.61 (<italic>PPV</italic>y)</td>
</tr>
<tr>
<td valign="top" align="left">8</td>
<td valign="top" align="left">0.15&#x2013;5.84 (<italic>PPV</italic>z)</td>
</tr>
<tr>
<td valign="top" align="left">9</td>
<td valign="top" rowspan="4" align="left">
<xref ref-type="bibr" rid="B45">Zhou et&#xa0;al., 2018</xref>
</td>
<td valign="top" rowspan="4" align="left">Blasts in development tunnel; horizontal distance between blasting tunnel and monitoring tunnel is 36&#xa0;m.</td>
<td valign="top" rowspan="4" align="left">Water-sealed propane storage tunnel; Horseshoe; Span and height of the tunnel are 23&#xa0;m and 25&#xa0;m, respectively; Yantai, China</td>
<td valign="top" rowspan="4" align="left">Hard and mainly weakly weathering biotite monzonitic granite. It has high integrity and undeveloped joints.</td>
<td valign="top" rowspan="4" align="left">Sidewall</td>
<td valign="top" rowspan="4" align="left">15</td>
<td valign="top" rowspan="4" align="left">22&#x2013;69</td>
<td valign="top" rowspan="4" align="left">49.8&#x2013;131.4</td>
<td valign="top" align="left">4.84&#x2013;28.87 (<italic>PPV</italic>x)</td>
</tr>
<tr>
<td valign="top" align="left">10</td>
<td valign="top" align="left">2.33&#x2013;10.2 (<italic>PPV</italic>y)</td>
</tr>
<tr>
<td valign="top" align="left">11</td>
<td valign="top" align="left">3.81&#x2013;12.06 (<italic>PPV</italic>z)</td>
</tr>
<tr>
<td valign="top" align="left">12</td>
<td valign="top" align="left">5.54&#x2013;29.11 (<italic>PPV</italic>)</td>
</tr>
<tr>
<td valign="top" align="left">13</td>
<td valign="top" rowspan="3" align="left">
<xref ref-type="bibr" rid="B33">Wang et&#xa0;al., 2019</xref>
</td>
<td valign="top" rowspan="3" align="left">Blasts in development tunnel; horizontal distance between blasting tunnel and adjacent tunnel is 21&#x2013;38 m.</td>
<td valign="top" rowspan="3" align="left">Highway tunnel; Excavation area is more 130.4 m<sup>2</sup>, with a width of 16.34&#xa0;m and a height of 10.45&#xa0;m; Yan&#x2019;an City in China.</td>
<td valign="top" rowspan="3" align="left">Strong&#x2013;medium weathered sandstone</td>
<td valign="top" rowspan="3" align="left">Sidewall</td>
<td valign="top" rowspan="3" align="left">12</td>
<td valign="top" rowspan="3" align="left">15.2&#x2013;16.8</td>
<td valign="top" rowspan="3" align="left">32&#x2013;66.4</td>
<td valign="top" align="left">3.7&#x2013;23 (<italic>PPV</italic>x)</td>
</tr>
<tr>
<td valign="top" align="left">14</td>
<td valign="top" align="left">3&#x2013;16.1 (<italic>PPV</italic>y)</td>
</tr>
<tr>
<td valign="top" align="left">15</td>
<td valign="top" align="left">10.1&#x2013;42 (<italic>PPV</italic>z)</td>
</tr>
<tr>
<td valign="top" align="left">16</td>
<td valign="top" rowspan="2" align="left">
<xref ref-type="bibr" rid="B42">Zhang et&#xa0;al., 2021</xref>
</td>
<td valign="top" rowspan="2" align="left">Blasts in development tunnel; Vertical distance between the blasting tunnel and monitoring tunnel is 9.55 m</td>
<td valign="top" rowspan="2" align="left">Air defense tunnel; Horseshoe; Span and height of the tunnel are 2.3&#xa0;m and 3.05&#xa0;m; Wuhan in China</td>
<td valign="top" rowspan="2" align="left">Weak-weathered limestone, and clay layers (large proportion)</td>
<td valign="top" rowspan="2" align="left">Floor</td>
<td valign="top" rowspan="2" align="left">13</td>
<td valign="top" rowspan="2" align="left">14&#x2013;15</td>
<td valign="top" rowspan="2" align="left">13.71&#x2013;22.82</td>
<td valign="top" align="left">1.35&#x2013;6.5 (<italic>PPV</italic>z)</td>
</tr>
<tr>
<td valign="top" align="left">17</td>
<td valign="top" align="left">1.82&#x2013;6.55 (<italic>PPV</italic>)</td>
</tr>
<tr>
<td valign="top" align="left">18</td>
<td valign="top" rowspan="4" align="left">
<xref ref-type="bibr" rid="B46">Zhu et&#xa0;al., 2021</xref>
</td>
<td valign="top" rowspan="4" align="left">Blasts in development tunnel; horizontal and vertical distances between blasting tunnel and monitoring (below) tunnel are 91&#x2013;200 m and about 32&#xa0;m.</td>
<td valign="top" rowspan="4" align="left">Railway tunnel; Horseshoe; Span and height of the tunnel are 10&#x2013;15 m and 10&#x2013;15 m; Guangdong, China</td>
<td valign="top" rowspan="4" align="left">Weakly weathered granite, which is cyan gray or gray white color, massive structure, relatively complete rock mass, hard texture.</td>
<td valign="top" rowspan="4" align="left">Sidewall</td>
<td valign="top" rowspan="4" align="left">26</td>
<td valign="top" rowspan="4" align="left">33.6&#x2013;37.8</td>
<td valign="top" rowspan="4" align="left">163.34&#x2013;631.08</td>
<td valign="top" align="left">0.5&#x2013;8.9 (<italic>PPV</italic>x)</td>
</tr>
<tr>
<td valign="top" align="left">19</td>
<td valign="top" align="left">0.1&#x2013;9.1 (<italic>PPV</italic>y)</td>
</tr>
<tr>
<td valign="top" align="left">20</td>
<td valign="top" align="left">0.7&#x2013;16.2 (<italic>PPV</italic>z)</td>
</tr>
<tr>
<td valign="top" align="left">21</td>
<td valign="top" align="left">1.9&#x2013;20.6 (<italic>PPV</italic>)</td>
</tr>
</tbody>
</table>
<table-wrap-foot>
<fn>
<p>i = x (horizontal longitudinal direction), y (horizontal radial direction), z (vertical direction); UCS: uniaxial compressive strength.</p>
</fn>
</table-wrap-foot>
</table-wrap>
<p>The blasting conditions, geological conditions, and tunnel characteristics of the data acquisition site are different. As far as the sources of blasting vibration are concerned, most of them come from the blasting of adjacent excavated tunnels. The geological conditions of blasting vibration site vary widely, including not only slightly weathered rock mass with high compressive strength, but also strongly weathered, cataclastic rock mass with low compressive strength. The shape and scale of the monitoring tunnel are also different. Generally, the span of the monitoring tunnels are between 10 and 30&#xa0;m. The relationship between monitoring tunnel and adjacent blasting tunnel mainly includes horizontal parallel, vertical parallel, and intersection. The distance between monitoring tunnel and blasting tunnel is generally between 4 and 50&#xa0;m. The monitoring points are mainly on the side wall, floor, and roof the adjacent tunnels.</p>
<p>The details of the data sets used in this work including <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub>, maximum charge per delay, and distances are evaluated by using different empirical equations shown in <xref ref-type="table" rid="T1"><bold>Table&#xa0;1</bold></xref>. The performance assessment method will be explained in the following section.</p>
</sec>
<sec id="s2_2">
<label>2.2</label>
<title>Performance assessment method</title>
<p>Regression analysis technique was used to analyze the relationships between <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> and the maximum charge per delay, the distance between blasting source, and monitoring points. In order to establish a relationship among those parameters, simple and multiple linear regression analyses were performed using the data given in <xref ref-type="table" rid="T2"><bold>Table&#xa0;2</bold></xref>.</p>
<p>If the dependent variable is a linear combination of the one independent variable, it is called simple linear regression. Similarly, if the dependent variable is a linear combination of the several independent variables, it is called multiple linear regression. The basic simple and multiple linear regression models for one and two independent variables are given below:</p>
<disp-formula>
<label>(2)</label>
<mml:math display="block" id="M2">
<mml:mrow>
<mml:mi>Y</mml:mi>
<mml:mo>=</mml:mo>
<mml:mi>A</mml:mi>
<mml:mo>+</mml:mo>
<mml:mi>B</mml:mi>
<mml:msub>
<mml:mi>X</mml:mi>
<mml:mn>1</mml:mn>
</mml:msub>
</mml:mrow>
</mml:math>
</disp-formula>
<disp-formula>
<label>(3)</label>
<mml:math display="block" id="M3">
<mml:mrow>
<mml:mi>Y</mml:mi>
<mml:mo>=</mml:mo>
<mml:mi>A</mml:mi>
<mml:mo>+</mml:mo>
<mml:mi>B</mml:mi>
<mml:msub>
<mml:mi>X</mml:mi>
<mml:mn>1</mml:mn>
</mml:msub>
<mml:mo>+</mml:mo>
<mml:mi>C</mml:mi>
<mml:msub>
<mml:mi>X</mml:mi>
<mml:mn>2</mml:mn>
</mml:msub>
</mml:mrow>
</mml:math>
</disp-formula>
<p>where <italic>Y</italic> is the dependent variable, <italic>X</italic><sub>1</sub> and <italic>X</italic><sub>2</sub> are the independent variables, and <italic>A</italic>, <italic>B</italic>, and <italic>C</italic> are the constants.</p>
<p>As shown in <xref ref-type="table" rid="T1"><bold>Table&#xa0;1</bold></xref>, for equation ID = 1&#x2013;4, the <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> is the dependent variable, <italic>SD</italic> = <italic>R</italic>/<italic>Q<sup>a</sup>
</italic> is the independent variable, and <italic>k</italic> and <italic>&#x3b2;</italic> are the constants greater than 0. Therefore, these types of equations are suitable for simple regression analysis. Basic equations are linearized by taking the natural logarithm of both sides, and we get</p>
<disp-formula>
<label>(4)</label>
<mml:math display="block" id="M4">
<mml:mrow>
<mml:mi>P</mml:mi>
<mml:mi>P</mml:mi>
<mml:mi>V</mml:mi>
<mml:mo stretchy="false">/</mml:mo>
<mml:mi>P</mml:mi>
<mml:mi>P</mml:mi>
<mml:msub>
<mml:mi>V</mml:mi>
<mml:mi>i</mml:mi>
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<mml:mo>=</mml:mo>
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<mml:mi>S</mml:mi>
<mml:mi>D</mml:mi>
</mml:mrow>
</mml:math>
</disp-formula>
<p>Equation ID = 7 is also a simple regression analysis, as <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> is the dependent variable, <italic>SD</italic> = <italic>R</italic>/<italic>Q<sup>1/2</sup>
</italic> is the independent variable, and <italic>n</italic> is the constant less than 0. The basic equation for a simple regression analysis is:</p>
<disp-formula>
<label>(5)</label>
<mml:math display="block" id="M5">
<mml:mrow>
<mml:mi>P</mml:mi>
<mml:mi>P</mml:mi>
<mml:mi>V</mml:mi>
<mml:mo stretchy="false">/</mml:mo>
<mml:mi>P</mml:mi>
<mml:mi>P</mml:mi>
<mml:msub>
<mml:mi>V</mml:mi>
<mml:mi>i</mml:mi>
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<mml:mo>=</mml:mo>
<mml:mi>n</mml:mi>
<mml:mo>+</mml:mo>
<mml:mi>k</mml:mi>
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<mml:mrow>
<mml:mrow>
<mml:mo stretchy="false">(</mml:mo>
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</disp-formula>
<p>Equation ID = 5&#x2013;6 and 8 are suitable for multiple linear regression. In these types of equations, <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> is the dependent variable; <italic>SD</italic>, <italic>R</italic>, <italic>R</italic>/<italic>Q</italic>, and <italic>R</italic>/<italic>Q</italic><sup>0.5</sup> are the independent variables; and, <italic>k</italic>, <italic>&#x3b2;</italic>, and <italic>&#x3bb;</italic> are the constants greater than 0. Basic equations are linearized by taking the natural logarithm of both sides, and we get</p>
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<disp-formula>
<label>(7)</label>
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<mml:mo>=</mml:mo>
<mml:mn>6</mml:mn>
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</disp-formula>
<disp-formula>
<label>(8)</label>
<mml:math display="block" id="M8">
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<mml:mi>&#x3b2;</mml:mi>
<mml:mi>ln</mml:mi>
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<mml:mi>D</mml:mi>
<mml:mo>&#x2212;</mml:mo>
<mml:mi>&#x3bb;</mml:mi>
<mml:mo stretchy="false">(</mml:mo>
<mml:mi>R</mml:mi>
<mml:mo stretchy="false">/</mml:mo>
<mml:msup>
<mml:mi>Q</mml:mi>
<mml:mrow>
<mml:mn>1</mml:mn>
<mml:mo stretchy="false">/</mml:mo>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:msup>
<mml:mo stretchy="false">)</mml:mo>
<mml:mo>,</mml:mo>
<mml:mtext>for&#xa0;equation&#xa0;ID</mml:mtext>
<mml:mo>=</mml:mo>
<mml:mn>8</mml:mn>
</mml:mrow>
</mml:math>
</disp-formula>
<p>Two statistical criteria, namely, determination coefficient (<italic>R</italic><sup>2</sup>) and root-mean-square error (RMSE), were used to evaluate the performance of the empirical equations shown in <xref ref-type="table" rid="T1"><bold>Table&#xa0;1</bold></xref> in predicting <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> on adjacent tunnels. The expressions of the <italic>R</italic><sup>2</sup> and RMSE are as follows (<xref ref-type="bibr" rid="B37">Yan et&#xa0;al., 2020a</xref>):</p>
<disp-formula>
<label>(9)</label>
<mml:math display="block" id="M9">
<mml:mrow>
<mml:msup>
<mml:mtext>R</mml:mtext>
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<mml:mn>1</mml:mn>
</mml:mrow>
<mml:mi>n</mml:mi>
</mml:munderover>
</mml:mstyle>
<mml:mrow>
<mml:msup>
<mml:mrow>
<mml:mrow>
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<mml:mn>2</mml:mn>
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<disp-formula>
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<mml:mtext>RSME</mml:mtext>
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</disp-formula>
<p>where <italic>N</italic> is the number of data sets, and <italic>y<sub>i</sub>
</italic>, <italic>y<sub>p</sub>
</italic>, and <italic>y<sub>mean</sub>
</italic> are the measured, predicted, and mean of values, respectively. Theoretically, if <italic>R</italic><sup>2</sup> approaches 1, and RMSE approaches 0, the predicted equation is optimal.</p>
</sec>
<sec id="s2_3">
<label>2.3</label>
<title>Result analysis</title>
<p>
<xref ref-type="fig" rid="f1"><bold>Figure&#xa0;1</bold></xref> shows the performance of different empirical equations in predicting <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> on different adjacent tunnel structures (roof, sidewall, or floor). It can be seen from the figure that the prediction performance of various empirical equations in predicting <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> at different sites is different. Under different site conditions, various equations may become the best prediction equation; that is, under each site condition, the best prediction equation is uncertain.</p>
<fig id="f1" position="float">
<label>Figure&#xa0;1</label>
<caption>
<p>Performance of different empirical equations in predicting <bold>(A)</bold> <italic>PPV</italic>x, <bold>(B)</bold> <italic>PPV</italic>y, <bold>(C)</bold> <italic>PPV</italic>z, and <bold>(D)</bold> <italic>PPV</italic> on adjacent tunnels; MPs: measuring points; RSME&#xd7;10: the value of RSME in the figure should enlarge 10 times.</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fevo-11-1212654-g001.tif"/>
</fig>
<p>For some site data, the prediction accuracy of empirical equations is high, <italic>R</italic><sup>2</sup> can reach more than 0.9, and RMSE is small. However, the prediction accuracy of empirical equations is relatively low in predicting <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> in some site data, <italic>R</italic><sup>2</sup> is lower than 0.4, and the value of RSME is relatively large. This shows that it is feasible to use empirical equation to predict the propagation of blasting vibration in adjacent tunnels, but there is also the risk of insufficient prediction.</p>
<p>For the same set of data of most sites, whether the data are monitored on the tunnel roof, floor, or sidewall, the prediction accuracy of various prediction equations is not very different (the difference of <italic>R</italic><sup>2</sup> is less than 0.2). However, for the data from mining tunnels (<xref ref-type="bibr" rid="B1">Abolghasemifar et&#xa0;al., 2018</xref>), the prediction accuracy of each prediction model varies greatly, and the prediction accuracy is not particularly high. The main reasons may be the complexity of mining tunnel, the obvious effect of various roadway cavity effects (<xref ref-type="bibr" rid="B28">Singh, 2002</xref>), and the applicability of most prediction equations is not good.</p>
<p>In order to comprehensively evaluate which empirical equations can be better applied to the prediction of blasting vibration propagation on adjacent tunnels, we analyze the average value of the prediction performance of empirical equations under various site conditions. The average values of <italic>R</italic><sup>2</sup> and RSME are calculated as follows:</p>
<disp-formula>
<label>(11)</label>
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</mml:msup>
<mml:mtext>&#xa0;or&#xa0;RSME</mml:mtext>
</mml:mrow>
</mml:math>
</disp-formula>
<p>where <inline-formula>
<mml:math display="inline" id="im2">
<mml:mover accent="true">
<mml:mi>&#x3be;</mml:mi>
<mml:mo>&#xaf;</mml:mo>
</mml:mover>
</mml:math>
</inline-formula> represents the average value of the <italic>R</italic><sup>2</sup> or RSME in all the data sets, <italic>n</italic> represents the number of data sets, and <inline-formula>
<mml:math display="inline" id="im3">
<mml:mrow>
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<mml:mi>&#x3be;</mml:mi>
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</mml:math>
</inline-formula> represents the value of the <italic>R</italic><sup>2</sup> or RSME in one data set.</p>
<p>
<xref ref-type="fig" rid="f2"><bold>Figure&#xa0;2</bold></xref> shows the comprehensive performance of different empirical equations in predicting PPV/PPV<sub>i</sub> on adjacent tunnels. It can be seen from the figure that under the condition of multiple groups of data, the prediction difference of various prediction models is not very large. In terms of the data collected in this paper, the maximum differences of <italic>R</italic><sup>2</sup> and RSME between various prediction equations are 0.071 and 0.091. Therefore, it can be concluded that any equation in <xref ref-type="table" rid="T1"><bold>Table&#xa0;1</bold></xref> can be used to predict the propagation and attenuation characteristics of blasting vibration on adjacent tunnels. However, considering the simplicity of application, that is, the fewer the parameters of the equation, the better, it is suggested that the first three equations are used [especially the equation provided by <xref ref-type="bibr" rid="B2">Ambraseys and Hendron (1968)</xref> since it has the best prediction performance among the three equations] to predict the propagation and attenuation characteristics of blasting vibration on adjacent tunnels.</p>
<fig id="f2" position="float">
<label>Figure&#xa0;2</label>
<caption>
<p>Comprehensive performance of different empirical equations in predicting <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> on adjacent tunnels.</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fevo-11-1212654-g002.tif"/>
</fig>
</sec>
</sec>
<sec id="s3">
<label>3</label>
<title>Relationships between <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> prediction equation coefficients and tunnel geology</title>
<p>It is very important to study the relationship between the relevant parameters of empirical equations and tunnel geological characteristics for the prediction of blasting vibration on adjacent tunnels, especially when there is no blasting vibration data. In this section, the relationships between them were studied.</p>
<p>According to <xref ref-type="fig" rid="f3"><bold>Figure&#xa0;3</bold></xref>, the site coefficients <italic>k</italic> and <italic>&#x3b2;</italic> (attenuation index, which can be used to represent the attenuation characteristics of blasting vibration on tunnels) are not consistent in different empirical equations for prediction <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> in the same site. In this study, the site coefficients <italic>k</italic> and <italic>&#x3b2;</italic> in the empirical equation provided by <xref ref-type="bibr" rid="B2">Ambraseys and Hendron (1968)</xref> were adopted to analyze the relationships with tunnel geological conditions since it has the best prediction performance of the first three equations.</p>
<fig id="f3" position="float">
<label>Figure&#xa0;3</label>
<caption>
<p>Prediction <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> using different empirical equations. <bold>(A)</bold> PPVx; <bold>(B)</bold> PPVy; <bold>(C)</bold> PPVz; <bold>(D)</bold> PPV. Data from <xref ref-type="bibr" rid="B46">Zhu et&#xa0;al. (2021)</xref>.</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fevo-11-1212654-g003.tif"/>
</fig>
<p>Here, the data for studying the relationship between the relevant parameters of empirical Eq. (2) in predicting <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> on adjacent tunnels and tunnel geological conditions were still from the literature review. Because the vibration response on adjacent tunnel structures near the blasting source is the largest and is also the vibration response area that is most concerning for engineers, we mainly consider the data of the blasting vibration on the adjacent tunnel structures near the blasting source in the process of literature collection. Moreover, since the analysis of this section is focused on the relationship between the relevant parameters of empirical Eq. (2) and tunnel geological conditions, the influence of tunnel shape and scale on the response of <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> was neglected during data summary.</p>
<p>There are many indicators to describe site characteristics, such as rock quality designation (RQD), rock mass rating (RMR), geological strength index (GSI), and Q-system (Q) (<xref ref-type="bibr" rid="B41">Zhang, 2016</xref>). Here, the GSI was adopted to describe the site geological information because it is easier to obtain according to the description of the site presented in the literature. GSI, which was introduced by <xref ref-type="bibr" rid="B7">Hoek (1994)</xref>, is a system of rock mass characterization used to estimate rock mass strength for different geological conditions as identified by field observations. The GSI classification was set up to address the two principal factors considered to have an important influence on the mechanical properties of a rock mass, i.e., the structure (or blockiness) and the condition of the joints. The basic version of the GSI chart, for use with jointed rocks, is reproduced in <xref ref-type="fig" rid="f4"><bold>Figure&#xa0;4</bold></xref>, from <xref ref-type="bibr" rid="B8">Hoek and Marinos (2000)</xref>.</p>
<fig id="f4" position="float">
<label>Figure&#xa0;4</label>
<caption>
<p>Basic GSI chart (<xref ref-type="bibr" rid="B8">Hoek and Marinos, 2000</xref>).</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fevo-11-1212654-g004.tif"/>
</fig>
<p>
<xref ref-type="table" rid="T3"><bold>Table&#xa0;3</bold></xref> shows the collected data about surrounding rock mass information of adjacent tunnels and the corresponding site coefficients obtained based on regression analysis using empirical Eq. (2). It can be seen from the table that the site coefficients <italic>k</italic> and <italic>&#x3b2;</italic> of empirical Eq. (2) in predicting <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> on the adjacent tunnels are different under different site conditions.</p>
<table-wrap id="T3" position="float">
<label>Table&#xa0;3</label>
<caption>
<p>Collected data about surrounding rock mass information of adjacent tunnels and the corresponding site coefficients.</p>
</caption>
<table frame="hsides">
<thead>
<tr>
<th valign="top" rowspan="2" align="left">References</th>
<th valign="top" rowspan="2" align="left">Blasting source and monitoring point locations</th>
<th valign="top" rowspan="2" align="left">Geological conditions and characteristics of surrounding rock</th>
<th valign="top" colspan="2" align="left">Site coefficients for <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> unit is mm/s</th>
</tr>
<tr>
<th valign="top" align="center"><italic>k</italic>
</th>
<th valign="top" align="center"><italic>&#x3b2;</italic>
</th>
</tr>
</thead>
<tbody>
<tr>
<td valign="top" align="left">
<xref ref-type="bibr" rid="B18">Liu and Chen, 2008</xref>
</td>
<td valign="top" align="left">Adjacent tunnel blasting; HPD: 11&#xa0;m; Sidewall</td>
<td valign="top" align="left">Sericite sodium feldspar quartz schist; the shallow rock mass is seriously weathered and joint and fissures are developed. GSI: 20&#x2013;30</td>
<td valign="top" align="left">1,715.8 for <italic>PPV</italic>y; 1,607 for <italic>PPV</italic>z</td>
<td valign="top" align="left">1.83 for <italic>PPV</italic>y; 1.77 for <italic>PPV</italic>z</td>
</tr>
<tr>
<td valign="top" align="left">
<xref ref-type="bibr" rid="B14">Li et&#xa0;al., 2010</xref>
</td>
<td valign="top" align="left">Adjacent tunnel blasting; HPD: 30&#x2013;40 m; Sidewall</td>
<td valign="top" align="left">Dense basalt, porphyritic basalt, and breccia (aggregate) lava, with hard lithology and UCS &gt; 100 MPa; rock mass is complete&#x2013;relatively complete; GSI: 70&#x2013;85.</td>
<td valign="top" align="left">1,574 for <italic>PPV</italic>y; 1,413 for <italic>PPV</italic>z</td>
<td valign="top" align="left">1.46 for <italic>PPV</italic>y; 1.5 for <italic>PPV</italic>z</td>
</tr>
<tr>
<td valign="top" rowspan="2" align="left">
<xref ref-type="bibr" rid="B39">Ye et&#xa0;al., 2011</xref>
</td>
<td valign="top" align="left">Adjacent tunnel blasting; HPD: 13&#xa0;m; tunnels</td>
<td valign="top" align="left">Completely weathered rock mass; GSI: 15&#x2013;25</td>
<td valign="top" align="left">2,800 for <italic>PPV</italic>
</td>
<td valign="top" align="left">2.08 for <italic>PPV</italic>
</td>
</tr>
<tr>
<td valign="top" align="left">Adjacent tunnel blasting; VD: 14.4&#xa0;m or above; Sidewall</td>
<td valign="top" align="left">Weakly weathered&#x2013;unweathered granite; relatively hard&#x2013;hard rock, and the rock mass is relatively complete; GSI: 80&#x2013;85</td>
<td valign="top" align="left">570 for <italic>PPV</italic>
</td>
<td valign="top" align="left">1.35 for <italic>PPV</italic>
</td>
</tr>
<tr>
<td valign="top" align="left">
<xref ref-type="bibr" rid="B13">Jiang and Zhou, 2012</xref>
</td>
<td valign="top" align="left">Surface blasting; HPD: 50&#xa0;m; VD: 14&#xa0;m; Sidewall corner</td>
<td valign="top" align="left">Medium-hard and mainly weakly weathering dolomitic limestone; rock mass above tunnel are strongly weathered; average GSI: 30&#x2013;0.</td>
<td valign="top" align="left">2,053.7 for <italic>PPV</italic>z</td>
<td valign="top" align="left">1.664 for <italic>PPV</italic>z</td>
</tr>
<tr>
<td valign="top" align="left">
<xref ref-type="bibr" rid="B43">Zhao et&#xa0;al., 2016</xref>
</td>
<td valign="top" align="left">Adjacent tunnel blasting; VD: 4&#xa0;m; floor</td>
<td valign="top" align="left">Weathered (strongly weathered&#x2013;slightly weathered) sandstone; GSI: 25&#x2013;50</td>
<td valign="top" align="left">726 for <italic>PPV</italic>z</td>
<td valign="top" align="left">1.1 for <italic>PPV</italic>z</td>
</tr>
<tr>
<td valign="top" align="left">
<xref ref-type="bibr" rid="B1">Abolghasemifar et&#xa0;al., 2018</xref>
</td>
<td valign="top" align="left">Adjacent tunnel blasting; Roof</td>
<td valign="top" align="left">Sandstone; UCS: 48.8&#x2013;53.2 MPa; RMR: 50&#x2013;54; GSI: 40&#x2013;50</td>
<td valign="top" align="left">481.2 for <italic>PPV</italic>x; 1,883.7 for <italic>PPV</italic>y; 210.6 for <italic>PPV</italic>z</td>
<td valign="top" align="left">1.72 for <italic>PPV</italic>x; 2.09 for <italic>PPV</italic>y; 1.51 for <italic>PPV</italic>z</td>
</tr>
<tr>
<td valign="top" align="left">
<xref ref-type="bibr" rid="B45">Zhou et&#xa0;al., 2018</xref>
</td>
<td valign="top" align="left">Adjacent tunnel blasting; HPD: 36&#xa0;m; Sidewall</td>
<td valign="top" align="left">Hard and mainly weakly weathering biotite monzonitic granite. It has high integrity and undeveloped joints. GSI: 75&#x2013;5</td>
<td valign="top" align="left">1,291.4 for <italic>PPV</italic>x; 53.8 for <italic>PPV</italic>y; 83.1 for <italic>PPV</italic>z; 1,152.7 for <italic>PPV</italic>
</td>
<td valign="top" align="left">1.48 for <italic>PPV</italic>x; 0.66 for <italic>PPV</italic>y; 0.76 for <italic>PPV</italic>z; 1.43 for <italic>PPV</italic>
</td>
</tr>
<tr>
<td valign="top" align="left">
<xref ref-type="bibr" rid="B33">Wang et&#xa0;al., 2019</xref>
</td>
<td valign="top" align="left">Adjacent tunnel blasting; HPD: 21&#x2013;38 m; Sidewall</td>
<td valign="top" align="left">Strong&#x2013;medium weathered sandstone; GSI: 25&#x2013;40</td>
<td valign="top" align="left">450.7 for <italic>PPV</italic>x; 2,060.2 for <italic>PPV</italic>y; 1,033.8 for <italic>PPV</italic>z</td>
<td valign="top" align="left">1.42 for <italic>PPV</italic>x; 1.64 for <italic>PPV</italic>y; 1.65 for <italic>PPV</italic>z</td>
</tr>
<tr>
<td valign="top" align="left">
<xref ref-type="bibr" rid="B36">Wu et&#xa0;al., 2019</xref>
</td>
<td valign="top" align="left">Adjacent tunnel blasting; HPD: 35&#x2013;300 m; Sidewall/corner</td>
<td valign="top" align="left">Surrounding rock is relatively broken; GSI: 15&#x2013;25</td>
<td valign="top" align="left">2,467.5&#x2013;1,586.7 for <italic>PPV</italic>y; 464.3&#x2013;871.6 for <italic>PPV</italic>z; 1,786&#x2013;1,833.4 for <italic>PPV</italic>
</td>
<td valign="top" align="left">2.54&#x2013;2.31 for <italic>PPV</italic>y; 1.32&#x2013;1.08 for <italic>PPV</italic>z; 1.83&#x2013;1.69 for <italic>PPV</italic>
</td>
</tr>
<tr>
<td valign="top" align="left">
<xref ref-type="bibr" rid="B9">Huang et&#xa0;al., 2022</xref>
</td>
<td valign="top" align="left">Adjacent tunnel blasting; HPD: 30&#xa0;m; Sidewall</td>
<td valign="top" align="left">Basalt and breccia-agglomerated lava in the upper part of each layer, and the rock is hard and complete. The attitude of stratum is gentle and has no fault distribution; GSI: 70&#x2013;85</td>
<td valign="top" align="left">1,230&#x2013;1,643 for <italic>PPV</italic>y; 1,175&#x2013;1,361 for <italic>PPV</italic>z</td>
<td valign="top" align="left">1.46&#x2013;1.67 for <italic>PPV</italic>y; 1.49&#x2013;1.62 for <italic>PPV</italic>z</td>
</tr>
<tr>
<td valign="top" align="left">
<xref ref-type="bibr" rid="B34">Wen, 2020</xref>
</td>
<td valign="top" align="left">Adjacent tunnel blasting; HPD: 6&#xa0;m; Sidewall</td>
<td valign="top" align="left">Stratum is weakly weathered granite and tuff lava; rock mass is relatively complete; block structure; GSI: 65&#x2013;80</td>
<td valign="top" align="left">489.1 for <italic>PPV</italic>x; 941.5 for <italic>PPV</italic>y; 315.8 for <italic>PPV</italic>z; 1,070 for <italic>PPV</italic>
</td>
<td valign="top" align="left">1.36 for <italic>PPV</italic>x; 1.45 for <italic>PPV</italic>y; 1.08 for <italic>PPV</italic>z; 1.36 for <italic>PPV</italic>
</td>
</tr>
<tr>
<td valign="top" align="left">
<xref ref-type="bibr" rid="B38">Yan et&#xa0;al., 2020b</xref>
</td>
<td valign="top" align="left">Adjacent tunnel blasting; VD: 22.4&#x2013;45.1 m; Sidewall</td>
<td valign="top" align="left">Weakly weathered granite, greenish gray, massive structure, joints and fissures are developed, and the rock mass is relatively broken; GSI: 65&#x2013;75</td>
<td valign="top" align="left">1,406 for <italic>PPV</italic>
</td>
<td valign="top" align="left">1.31 for <italic>PPV</italic>
</td>
</tr>
<tr>
<td valign="top" align="left">
<xref ref-type="bibr" rid="B12">Ji et&#xa0;al., 2021</xref>
</td>
<td valign="top" align="left">Adjacent tunnel blasting; HPD: 16&#x2013;18 m; Sidewall, inside rock mass</td>
<td valign="top" align="left">Strongly weathered rock mass and easier to lose stability than ordinary tunnel surrounding rock; GSI: 20&#x2013;30</td>
<td valign="top" align="left">110.9&#x2013;172.6 for <italic>PPV</italic>x; 151.2&#x2013;193.9 for <italic>PPV</italic>y; 104.7&#x2013;145.3 for <italic>PPV</italic>z</td>
<td valign="top" align="left">1.36&#x2013;1.44 for <italic>PPV</italic>x; 1.4&#x2013;1.42 for <italic>PPV</italic>y; 1.27&#x2013;1.29 for <italic>PPV</italic>z</td>
</tr>
<tr>
<td valign="top" align="left">
<xref ref-type="bibr" rid="B19">Liu et&#xa0;al., 2021</xref>
</td>
<td valign="top" align="left">Adjacent tunnel blasting; HPD: 2.3&#xa0;m or above; Sidewall</td>
<td valign="top" align="left">Moderately to weakly weathered tuff, joint fissures are relatively developed, and groundwater is not developed; GSI: 50&#x2013;70</td>
<td valign="top" align="left">819.51&#x2013;960.8 for <italic>PPV</italic>
</td>
<td valign="top" align="left">1.51&#x2013;1.52 for <italic>PPV</italic>
</td>
</tr>
<tr>
<td valign="top" align="left">
<xref ref-type="bibr" rid="B17">Ling et&#xa0;al., 2021</xref>
</td>
<td valign="top" align="left">Adjacent tunnel blasting; HPD: 91&#x2013;200 m; VD: 32&#xa0;m; tunnels</td>
<td valign="top" align="left">Moderately weathered and slightly weathered tuff, with hard rock core and fresh rock; GSI: 50&#x2013;60</td>
<td valign="top" align="left">145.7 for <italic>PPV</italic>x; 124.3 for <italic>PPV</italic>y; 152.4 for <italic>PPV</italic>z</td>
<td valign="top" align="left">1.52 for <italic>PPV</italic>x; 1.42 for <italic>PPV</italic>y; 1.58 for <italic>PPV</italic>z</td>
</tr>
<tr>
<td valign="top" align="left">
<xref ref-type="bibr" rid="B25">Peng et&#xa0;al., 2021</xref>
</td>
<td valign="top" align="left">Adjacent tunnel blasting; HPD: 22&#xa0;m; Sidewall</td>
<td valign="top" align="left">High-quality granite stratum; UCS: 55&#x2013;89 MPa, E: 28&#x2013;1 GPa; GSI: 60&#x2013;80</td>
<td valign="top" align="left">1,018.4 for <italic>PPV</italic>
</td>
<td valign="top" align="left">1.47 for <italic>PPV</italic>
</td>
</tr>
<tr>
<td valign="top" align="left">
<xref ref-type="bibr" rid="B32">Wang et&#xa0;al., 2021</xref>
</td>
<td valign="top" align="left">Foundation pit blasting; HPD: 10&#xa0;m; tunnels</td>
<td valign="top" align="left">Strong weathered rock mass, BM: 416.7 MPa, SM: 192.3 MPa; TS: 0.5 MPa; GSI: 15&#x2013;35</td>
<td valign="top" align="left">1,600 for <italic>PPV</italic>
</td>
<td valign="top" align="left">1.7 for <italic>PPV</italic>
</td>
</tr>
<tr>
<td valign="top" align="left">
<xref ref-type="bibr" rid="B42">Zhang et&#xa0;al., 2021</xref>
</td>
<td valign="top" align="left">Adjacent tunnel blasting; VD: 9.55&#xa0;m; Floor</td>
<td valign="top" align="left">Weak-weathered limestone, and clay layers (large proportion); predicted GSI: 5&#x2013;20</td>
<td valign="top" align="left">10,622.8 for <italic>PPV</italic>z; 5,983.3 for <italic>PPV</italic>
</td>
<td valign="top" align="left">2.95 for <italic>PPV</italic>z; 2.62 for <italic>PPV</italic>
</td>
</tr>
<tr>
<td valign="top" align="left">
<xref ref-type="bibr" rid="B46">Zhu et&#xa0;al., 2021</xref>
</td>
<td valign="top" align="left">Adjacent tunnel blasting; HPD: 91&#x2013;200 m; VD: 32&#xa0;m; Sidewall</td>
<td valign="top" align="left">Weakly weathered granite, which is cyan gray or gray white color, massive structure, relatively complete rock mass, hard texture; GSI: 65&#x2013;75</td>
<td valign="top" align="left">1,119 for <italic>PPV</italic>x; 115 for <italic>PPV</italic>y; 8,739.6 for <italic>PPV</italic>z; 3,984 for <italic>PPV</italic>
</td>
<td valign="top" align="left">1.32 for <italic>PPV</italic>x; 0.83 for <italic>PPV</italic>y; 1.73 for <italic>PPV</italic>z; 1.46 for <italic>PPV</italic>
</td>
</tr>
</tbody>
</table>
<table-wrap-foot>
<fn>
<p>BM, bulk modulus; SM, shear modulus; UCS, uniaxial compressive strength; E, elastic modulus; TS, tensile strength; HPD, horizontal parallel distance; VD, vertical distance.</p>
</fn>
</table-wrap-foot>
</table-wrap>
<p>
<xref ref-type="fig" rid="f5"><bold>Figure&#xa0;5</bold></xref> shows the relationships between the site coefficient <italic>&#x3b2;</italic> and rock mass GSI. It can be seen from the figure that with the increase of the GSI of the surrounding rock mass, the site attenuation coefficient <italic>&#x3b2;</italic> of empirical Eq. (2) in predicting <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> on the adjacent tunnels shows a gradual decreasing trend as a whole; that is, the blasting vibration attenuation on adjacent tunnels will decrease as the GSI of the surrounding rock mass increases. By contrast, it was found that the fluctuation of <italic>&#x3b2;</italic> of empirical Eq. (2) in predicting <italic>PPV</italic><sub>i</sub> (<italic>&#x3b2;</italic>(<italic>PPV</italic><sub>i</sub>)) is much higher than in predicting <italic>PPV</italic> (<italic>&#x3b2;</italic>(<italic>PPV</italic>)), especially when the GSI of rock mass is lower than 30. In general, the fluctuation center of <italic>&#x3b2;</italic>(<italic>PPV</italic><sub>i</sub>) is located in the fluctuation center of <italic>&#x3b2;</italic>(<italic>PPV</italic>). Based on this law, if the relationship between the site attenuation coefficient <italic>&#x3b2;</italic>(<italic>PPV</italic>) and the GSI was obtained, the site attenuation coefficient <italic>&#x3b2;</italic> of empirical Eq. (2) in predicting <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> on the adjacent tunnels under different surrounding rock geological conditions can be evaluated approximately. Through fitting analysis, the following characteristic relationship between <italic>&#x3b2;</italic> (<italic>PPV</italic>) and GSI of surrounding rock mass was obtained as:</p>
<fig id="f5" position="float">
<label>Figure&#xa0;5</label>
<caption>
<p>Relationship between GSI and site coefficients <italic>&#x3b2;</italic>.</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fevo-11-1212654-g005.tif"/>
</fig>
<disp-formula>
<label>(12)</label>
<mml:math display="block" id="M12">
<mml:mrow>
<mml:mi>&#x3b2;</mml:mi>
<mml:mo stretchy="false">(</mml:mo>
<mml:mi>P</mml:mi>
<mml:mi>P</mml:mi>
<mml:mi>V</mml:mi>
<mml:mo stretchy="false">)</mml:mo>
<mml:mo>=</mml:mo>
<mml:mn>3.5965</mml:mn>
<mml:mo>&#xd7;</mml:mo>
<mml:mi>G</mml:mi>
<mml:mi>S</mml:mi>
<mml:msup>
<mml:mi>I</mml:mi>
<mml:mrow>
<mml:mo>-</mml:mo>
<mml:mn>0.3925</mml:mn>
</mml:mrow>
</mml:msup>
<mml:mo>+</mml:mo>
<mml:mn>0.7447</mml:mn>
<mml:mo>,</mml:mo>
<mml:msup>
<mml:mi>R</mml:mi>
<mml:mn>2</mml:mn>
</mml:msup>
<mml:mo>=</mml:mo>
<mml:mn>0.840</mml:mn>
</mml:mrow>
</mml:math>
</disp-formula>
<p>
<xref ref-type="fig" rid="f6"><bold>Figure&#xa0;6</bold></xref> shows the relationship between site coefficient <italic>k</italic> of empirical Eq. (2) in predicting <italic>PPV</italic>/<italic>PPV</italic>i and GSI of tunnel surrounding rock. With the increase in GSI of tunnel surrounding rock, the change law of site coefficient <italic>k</italic> of empirical Eq. (2) in predicting <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> also shows a decreasing trend as a whole. Except for some discrete points (data surrounded by circles), the value of <italic>k</italic> of most cases is generally within 3,000, whether in predicting <italic>PPV</italic> (<italic>k</italic>(<italic>PPV</italic>)) or <italic>PPV</italic><sub>i</sub> (<italic>k</italic>(PPV<sub>i</sub>)). Furthermore, the value of <italic>k</italic>(<italic>PPV</italic><sub>i</sub>) is generally less than <italic>k</italic>(<italic>PPV</italic>) at the same level of GSI.</p>
<fig id="f6" position="float">
<label>Figure&#xa0;6</label>
<caption>
<p>Relationship between GSI and site coefficient <italic>k</italic>.</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fevo-11-1212654-g006.tif"/>
</fig>
<p>Through fitting analysis, the following characteristic relationship between <italic>k</italic>(<italic>PPV</italic>) and GSI of surrounding rock mass was obtained as:</p>
<disp-formula>
<label>(13)</label>
<mml:math display="block" id="M13">
<mml:mrow>
<mml:mi>k</mml:mi>
<mml:mo stretchy="false">(</mml:mo>
<mml:mi>P</mml:mi>
<mml:mi>P</mml:mi>
<mml:mi>V</mml:mi>
<mml:mo stretchy="false">)</mml:mo>
<mml:mo>=</mml:mo>
<mml:mn>2500</mml:mn>
<mml:mo>&#x2212;</mml:mo>
<mml:mn>20</mml:mn>
<mml:mo>&#xd7;</mml:mo>
<mml:mi>G</mml:mi>
<mml:mi>S</mml:mi>
<mml:mi>I</mml:mi>
<mml:mo>,</mml:mo>
<mml:msup>
<mml:mi>R</mml:mi>
<mml:mn>2</mml:mn>
</mml:msup>
<mml:mo>=</mml:mo>
<mml:mn>0.654</mml:mn>
</mml:mrow>
</mml:math>
</disp-formula>
<p>Based on these relationships, the blasting vibration prediction equation on adjacent tunnels can be approximately rewritten as:</p>
<disp-formula>
<label>(14)</label>
<mml:math display="block" id="M14">
<mml:mrow>
<mml:mi>P</mml:mi>
<mml:mi>P</mml:mi>
<mml:mi>V</mml:mi>
<mml:mo>=</mml:mo>
<mml:mrow>
<mml:mo stretchy="false">(</mml:mo>
<mml:mrow>
<mml:mn>2500</mml:mn>
<mml:mo>&#x2212;</mml:mo>
<mml:mn>20</mml:mn>
<mml:mo>&#xd7;</mml:mo>
<mml:mi>G</mml:mi>
<mml:mi>S</mml:mi>
<mml:mi>I</mml:mi>
</mml:mrow>
<mml:mo stretchy="false">)</mml:mo>
</mml:mrow>
<mml:mo>&#xd7;</mml:mo>
<mml:mi>S</mml:mi>
<mml:msup>
<mml:mi>D</mml:mi>
<mml:mrow>
<mml:mo>&#x2212;</mml:mo>
<mml:mrow>
<mml:mo stretchy="false">(</mml:mo>
<mml:mrow>
<mml:mn>3.5965</mml:mn>
<mml:mo>&#xd7;</mml:mo>
<mml:mi>G</mml:mi>
<mml:mi>S</mml:mi>
<mml:msup>
<mml:mi>I</mml:mi>
<mml:mrow>
<mml:mo>&#x2212;</mml:mo>
<mml:mn>0.3925</mml:mn>
</mml:mrow>
</mml:msup>
<mml:mo>+</mml:mo>
<mml:mn>0.7447</mml:mn>
</mml:mrow>
<mml:mo stretchy="false">)</mml:mo>
</mml:mrow>
</mml:mrow>
</mml:msup>
</mml:mrow>
</mml:math>
</disp-formula>
<p>It is worth noting that the equation is an approximate prediction and is suitable for use without regression analysis of blasting vibration data. The unit of the <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> is mm/s. As for <italic>PPV</italic><sub>i</sub>, due to the direct relationship between site coefficient (<italic>k</italic> and <italic>&#x3b2;</italic>) and geological structure, it is not suitable to establish a relatively effective equation based on GSI. However, considering that the maximum value of the three component velocities (<italic>PPV</italic><sub>i</sub> (max)) is generally slightly or moderately less than the <italic>PPV</italic>, the <italic>PPV</italic><sub>i</sub> (max) can be calculated by multiplying a reduction coefficient <italic>&#x3b6;</italic> on the basis of Eq. (14), as:</p>
<disp-formula>
<label>(15)</label>
<mml:math display="block" id="M15">
<mml:mrow>
<mml:mi>P</mml:mi>
<mml:mi>P</mml:mi>
<mml:msub>
<mml:mi>V</mml:mi>
<mml:mi>i</mml:mi>
</mml:msub>
<mml:mo stretchy="false">(</mml:mo>
<mml:mi>max</mml:mi>
<mml:mo stretchy="false">)</mml:mo>
<mml:mo>=</mml:mo>
<mml:mi>&#x3b6;</mml:mi>
<mml:mo>&#xb7;</mml:mo>
<mml:mrow>
<mml:mo stretchy="false">(</mml:mo>
<mml:mrow>
<mml:mn>2500</mml:mn>
<mml:mo>&#x2212;</mml:mo>
<mml:mn>20</mml:mn>
<mml:mo>&#xd7;</mml:mo>
<mml:mi>G</mml:mi>
<mml:mi>S</mml:mi>
<mml:mi>I</mml:mi>
</mml:mrow>
<mml:mo stretchy="false">)</mml:mo>
</mml:mrow>
<mml:mo>&#xd7;</mml:mo>
<mml:mi>S</mml:mi>
<mml:msup>
<mml:mi>D</mml:mi>
<mml:mrow>
<mml:mo>&#x2212;</mml:mo>
<mml:mrow>
<mml:mo stretchy="false">(</mml:mo>
<mml:mrow>
<mml:mn>3.5965</mml:mn>
<mml:mo>&#xd7;</mml:mo>
<mml:mi>G</mml:mi>
<mml:mi>S</mml:mi>
<mml:msup>
<mml:mi>I</mml:mi>
<mml:mrow>
<mml:mo>&#x2212;</mml:mo>
<mml:mn>0.3925</mml:mn>
</mml:mrow>
</mml:msup>
<mml:mo>+</mml:mo>
<mml:mn>0.7447</mml:mn>
</mml:mrow>
<mml:mo stretchy="false">)</mml:mo>
</mml:mrow>
</mml:mrow>
</mml:msup>
</mml:mrow>
</mml:math>
</disp-formula>
<p>Usually, the range of <italic>&#x3b6;</italic> is 0.7&#x2013;1 according to the actual investigation and literature review.</p>
</sec>
<sec id="s4">
<label>4</label>
<title>Engineering applicability analysis</title>
<p>In Section 3, the relationships between parameters <italic>k</italic> and <italic>&#x3b2;</italic> of Eq. (2) in predicting the propagation of blasting vibration on the adjacent tunnel and tunnel geology were discussed, and a <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> prediction equation considering GSI information is preliminarily formed. In order to explore whether these parameters have engineering practicability, this section carried out checking calculation based on several site vibration data.</p>
<sec id="s4_1">
<label>4.1</label>
<title>Data from literature</title>
<p>In this section, the field test data from <xref ref-type="bibr" rid="B31">Wang and Liu (2009)</xref>; <xref ref-type="bibr" rid="B43">Zhao et&#xa0;al. (2016)</xref>; <xref ref-type="bibr" rid="B45">Zhou et&#xa0;al. (2018)</xref>, and <xref ref-type="bibr" rid="B25">Peng et&#xa0;al. (2021)</xref> were used to verify the validity of the equation. In the research of <xref ref-type="bibr" rid="B31">Wang and Liu (2009)</xref>, the blasting source is from tunnel excavation and the parallel distance between the excavated tunnel and the monitoring tunnel is 17.5&#x2013;23 m. The rock mass in the tunnel passing area is hard and the rock mass integrity is good. The surrounding rock mass of the tunnel is mainly slightly weathered, and the GSI of the rock mass is 70&#x2013;80. The monitoring points is on the floor (corner) of the adjacent tunnel near the blasting sources. The site characteristics of the studies by <xref ref-type="bibr" rid="B43">Zhao et&#xa0;al. (2016)</xref>; <xref ref-type="bibr" rid="B45">Zhou et&#xa0;al. (2018)</xref>, and <xref ref-type="bibr" rid="B25">Peng et&#xa0;al. (2021)</xref> are shown in <xref ref-type="table" rid="T2"><bold>Table&#xa0;2</bold></xref>.</p>
<p>
<xref ref-type="fig" rid="f7"><bold>Figure&#xa0;7</bold></xref> shows the comparison of the <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> between the field tests and the ones predicted by Eqs. (14) and (15) based on GSI. It can be seen from the figure that the statistical Eq. (14)/(15) can approximately predict the propagation and attenuation of blasting vibration on adjacent tunnels. Of course, the prediction accuracy here may not be the best. In particular, sometimes the prediction accuracy of <italic>PPV</italic><sub>i</sub> (max) is very low, as shown in panel (a) with <italic>&#x3b6;</italic> = 0.7 and panel (b) with <italic>&#x3b6;</italic> = 1. However, the range of <italic>PPV</italic><sub>i</sub> (max) estimated based on Eq. (15) is still acceptable, which is also very helpful for empirical estimation without blasting vibration data.</p>
<fig id="f7" position="float">
<label>Figure&#xa0;7</label>
<caption>
<p>Comparison of the <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> between the field tests and the approximation predicted by Eqs. (14) and (15). <bold>(A)</bold> Data from <xref ref-type="bibr" rid="B31">Wang and Liu (2009)</xref>; <bold>(B)</bold> data from <xref ref-type="bibr" rid="B43">Zhao et&#xa0;al. (2016)</xref>; <bold>(C)</bold> data from <xref ref-type="bibr" rid="B45">Zhou et&#xa0;al. (2018)</xref>; <bold>(D)</bold> data from <xref ref-type="bibr" rid="B25">Peng et&#xa0;al. (2021)</xref>.</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fevo-11-1212654-g007.tif"/>
</fig>
</sec>
<sec id="s4_2">
<label>4.2</label>
<title>Data from project test</title>
<p>Since the analyzed data in <xref ref-type="fig" rid="f7"><bold>Figure&#xa0;7</bold></xref> is from literature, this may be the reason for obtaining favorable results. More field data from another site to analyze the feasibility of field use of Eqs. (14) and (15) are needed.</p>
<p>In this section, the analysis is carried out according to the monitoring data of the blasting excavation project of a double line subway tunnel in Guangzhou, China. The clear distance between the two excavated tunnels is 5.5&#xa0;m, which is a typical small spacing tunnel project. The radius of the tunnel is about 5&#xa0;m and the buried depth is about 45&#xa0;m. According to the geological report and field observation, the tunnels pass through the slightly weathered granite and the rock mass is relatively complete, with few fractures. The GSI range is 70&#x2013;85. Above the slightly weathered granite, there are mainly moderately weathered granite and soil layers. The tunnel section and geological information are summarized in <xref ref-type="fig" rid="f8"><bold>Figure&#xa0;8</bold></xref>.</p>
<fig id="f8" position="float">
<label>Figure&#xa0;8</label>
<caption>
<p>Site geological profile and blast-hole layout.</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fevo-11-1212654-g008.tif"/>
</fig>
<p>The bench blasting method was utilized during the process of tunnel excavation, and the area of the upper bench is approximately 70% of the tunnel section. Before the field tests, the upper bench of the tunnels has been excavated, and the initial lining support was achieved by a concrete structure (C25) with a thickness of 300&#xa0;mm. The purpose of our test is to analyze the attenuation characteristics of blasting vibration on the adjacent tunnel side wall (near the excavated tunnel) under the lower bench blasting of the excavated tunnel. The blast-hole layout of the lower bench blasting is shown in <xref ref-type="fig" rid="f8"><bold>Figure&#xa0;8</bold></xref>.&#xa0;A millisecond electric detonator was used for initiation, and the detonator section included one section (MS1), five sections (MS5), and nine sections (MS9). The corresponding delay times of MS1, MS5, and MS9 were 0 ms, 110 ms, and 310 ms, respectively (<xref ref-type="bibr" rid="B30">Wang et&#xa0;al., 2022</xref>).</p>
<p>The layout of on-site measuring points (on the adjacent tunnel sidewall) is shown in <xref ref-type="fig" rid="f9"><bold>Figure&#xa0;9</bold></xref>. L<sub>i</sub> is the horizontal distance between monitoring point M<sub>1</sub> and the blasting plane. Two monitoring times were carried out; L<sub>i</sub> for the first time and the second time tests are 0&#xa0;m and 5&#xa0;m. The TC-4850 vibrometer was employed in the monitoring of blasting vibration. The vibration sensor is a three-way vibration velocity sensor that can simultaneously monitor the vibration velocity in horizontal longitudinal (<italic>X</italic>), horizontal radial (<italic>Y</italic>), and vertical (<italic>Z</italic>) directions of the measurement points. The maximum charge per delay of the two tested blasting are 16.8&#xa0;kg and 21&#xa0;kg.</p>
<fig id="f9" position="float">
<label>Figure&#xa0;9</label>
<caption>
<p>Monitoring points layout.</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fevo-11-1212654-g009.tif"/>
</fig>
<p>
<xref ref-type="fig" rid="f10"><bold>Figure&#xa0;10</bold></xref> shows the <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> obtained from field tests and approximately predicted by Eqs. (14) and (15). The comparison results further show that Eqs. (14) and (15) can approximately predict the propagation and attenuation law of <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> on the adjacent tunnels. However, since Eqs. (14) and (15) cannot 100% accurately predict <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub>, it is still recommended to monitor blasting vibration anytime and anywhere in practical projects, especially important large-scale projects, so as to effectively control blasting vibration disasters. When there is a lack of effective field test data, Eqs. (14) and (15) are recommended to predict the blasting vibration on adjacent tunnels.</p>
<fig id="f10" position="float">
<label>Figure&#xa0;10</label>
<caption>
<p><italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> (max) obtained from field monitoring tests and the approximation predicted based on <bold>(A)</bold> Eq. (14), <bold>(B)</bold> Eq. (15).</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fevo-11-1212654-g010.tif"/>
</fig>
</sec>
</sec>
<sec id="s5" sec-type="conclusions">
<label>5</label>
<title>Conclusions</title>
<p>Based on literature data statistics, this paper first explored the performance of several commonly used empirical equations in predicting the propagation and attenuation characteristics of blasting vibration on adjacent tunnels. Secondly, the relationships between the empirical parameters of blasting vibration prediction equation provided by <xref ref-type="bibr" rid="B2">Ambraseys and Hendron (1968)</xref> and the geological strength index (GSI) of tunnel surrounding rock were discussed, and two new blasting vibration prediction equations based on site rock GSI were established to approximately predict <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> (max) on adjacent tunnels. Finally, the application feasibility of the two prediction equations in practical engineering was discussed based on field project tests. Some meaningful conclusions were obtained as follows.</p>
<p>It is feasible to use empirical equation to predict the propagation of blasting vibration on adjacent tunnels, but there is also the risk of insufficient prediction since the empirical equation does not have high prediction ability for all sites. The prediction performance of various empirical equations in predicting <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> at different sites is different. Under the condition of multiple groups of data, the prediction difference of various prediction models is not very large. Considering the simplicity of application, that is, the fewer the parameters of the equation, the better, it is suggested that the equations provided by USBM (<xref ref-type="bibr" rid="B4">Devine, 1962</xref>), <xref ref-type="bibr" rid="B2">Ambraseys and Hendron (1968)</xref>, and Bureau of Indian Standards (<xref ref-type="bibr" rid="B10">IS: 6922-1973, 1973</xref>) are used [especially the equation provided by <xref ref-type="bibr" rid="B2">Ambraseys and Hendron (1968)</xref> since it has the best prediction performance among the three equations] to predict the propagation and attenuation characteristics of blasting vibration on adjacent tunnels.</p>
<p>With the increase in GSI of the surrounding rock mass of the adjacent tunnel, the propagation attenuation rate (site attenuation coefficient <italic>&#x3b2;</italic>) of blasting vibration on the tunnel structure shows a decreasing trend as a whole. The following characteristic relationship between site attenuation coefficient <italic>&#x3b2;</italic> of the empirical equation provided by <xref ref-type="bibr" rid="B2">Ambraseys and Hendron (1968)</xref> in predicting <italic>PPV</italic> and GSI was obtained as Eq. (12). With the increase in GSI of tunnel surrounding rock, the site coefficient <italic>k</italic> of the empirical equation in predicting <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> also shows a decreasing trend as a whole and the <italic>k</italic> generally within 3,000. The relationship between site coefficient <italic>k</italic> of the empirical equation in predicting PPV and GSI was obtained as Eq. (13) according to statistical analysis.</p>
<p>Two new empirical prediction equations of blasting vibration propagation and attenuation on adjacent tunnels under different site conditions were established to approximately predict <italic>PPV</italic>/<italic>PPV</italic><sub>i</sub> (max) on adjacent tunnels, e.g., Eq. (14) for <italic>PPV</italic> and Eq. (15) for <italic>PPV</italic><sub>i</sub> (max). The verification analysis of five sites shows that these two equations have a certain practical application value. Compared with other empirical equations, these two equations do not need regression fitting blasting vibration data, they only used the GSI of the site rock mass, and they are more easy to use in the field when there is a lack of monitoring data.</p>
</sec>
<sec id="s6" sec-type="data-availability">
<title>Data availability statement</title>
<p>The original contributions presented in the study are included in the article/supplementary material. Further inquiries can be directed to the corresponding authors.</p>
</sec>
<sec id="s7" sec-type="author-contributions">
<title>Author contributions</title>
<p>All authors listed have made a substantial, direct, and intellectual contribution to the work and approved it for publication.</p>
</sec>
</body>
<back>
<sec id="s8" sec-type="funding-information">
<title>Funding</title>
<p>This work was supported by the Elite Program of Shandong University of Science and Technology (No.0104060540171).</p>
</sec>
<sec id="s9" sec-type="COI-statement">
<title>Conflict of interest</title>
<p>The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.</p>
</sec>
<sec id="s10" sec-type="disclaimer">
<title>Publisher&#x2019;s note</title>
<p>All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.</p>
</sec>
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