浅层岩溶瞬变电磁响应规律试验研究
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摘要
针对浅层岩溶塌陷产生的工程与环境问题,研究瞬变电磁对浅层岩溶的响应规律。通过分析将浅层岩溶概化为充填与半充填两类地电模型,采用时域有限差分法进行三维正演计算,对比分析电性差异、规模差异以及埋深差异情况下的瞬变电磁衰减曲线特征和视电阻率曲线变化规律。通过数值试验发现:浅层岩溶充填物的电阻率越低、规模越大,瞬变电磁衰减曲线中的异常响应幅值越大;浅层岩溶的瞬变电磁异常响应主要集中在早期;瞬变电磁对具有一定规模的充填模型与半充填模型均有较好的识别能力。选择某已知区域进行现场试验,瞬变电磁能够圈定岩溶异常,并发现未揭露的潜在岩溶发育区。数值试验和现场试验表明,瞬变电磁探测浅层岩溶需要更早的观测时间和更小的关段时间。
The characteristics of transient electromagnetic field in detecting shallow karst was studied focusing on the engineering and environmental problems caused by karst collapse. The shallow karst was generalized to be two types of geophysical models. The method of three dimensional finite difference in the time domain was used to simulate the transient electromagnetic responses. The resistivity,the karst size and the buried depth were selected as the comparison parameters. The numerically calculated differences of responses are bigger when the filled karst has the low resistivity and large size. The responses from the karst are mainly in the early stage. The transient electromagnetic field can identify nicely both the filled and half-filled shallow karsts. A field experiment was used to verify the numerical results in Guangxi. The transient electromagnetic profile revealed the known karst and found the unknown karst. The numerical and field experiments indicated that early observation and short time for turn off were better for small loop transient electromagnetic survey for shallow karst.
The characteristics of transient electromagnetic field in detecting shallow karst was studied focusing on the engineering and environmental problems caused by karst collapse. The shallow karst was generalized to be two types of geophysical models. The method of three dimensional finite difference in the time domain was used to simulate the transient electromagnetic responses. The resistivity,the karst size and the buried depth were selected as the comparison parameters. The numerically calculated differences of responses are bigger when the filled karst has the low resistivity and large size. The responses from the karst are mainly in the early stage. The transient electromagnetic field can identify nicely both the filled and half-filled shallow karsts. A field experiment was used to verify the numerical results in Guangxi. The transient electromagnetic profile revealed the known karst and found the unknown karst. The numerical and field experiments indicated that early observation and short time for turn off were better for small loop transient electromagnetic survey for shallow karst.
引文
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[12]席振珠,刘剑,龙霞,等.瞬变电磁法三分量测量方法研究[J].中南大学学报:自然科学版,2010,41(1):272–276.(XI Zhenzhu,LIU Jian,LONG Xia,et al.Three-component measurement in transient electromagnetic method[J].Journal of Central South University:Science and Technology,2010,41(1):272–276.(in Chinese))
[13]XUE G Q,CHENG J L,ZHOU N N,et al.Detection and monitoring of water-filled voids using transient electromagnetic method:a case study in Shanxi,China[J].Environmental Earth Sciences,2013,70(5):1–8.
[14]EZERSKY M,LEGCHENKO A,AL-ZOUBI A,et al.TEM study of the geoelectrical structure and groundwater salinity of the Nahal Hever sinkhole site,Dead Sea shore,Israel[J].Journal of Applied Geophysics,2011,75(1):99–112.
[15]VRBANCICH J.An investigation of seawater and sediment depth using a prototype airborne electromagnetic instrumentation system-a case study in Broken Bay,Australia[J].Geophysical Prospecting,2009,57:633–651.
[16]YANG DIKUN,OLDENBURG DOUGLAS W.Three-dimensional inversion of airborne time-domain electromagnetic data with applications to a porphyry deposit[J].Geophysics,2012,77(2):B23–B34.
[17]CHRISTENSEN NIELS B.Difficulties in determining electrical anisotropy in subsurface investigations[J].Geophysical Prospecting,2000,48(1):1–19.
[18]PODGORSKI J E,AUKEN E,SCHAMPER C,et al.Processing and inversion of commercial helicopter time-domain electromagnetic data for environmental assessments and geologic and hydrologic mapping[J].Geophysics,2013,78(4):E149–E159.
[19]周胜,席振铢,宋刚,等.深海拖曳式瞬变电磁的响应规律[J].中南大学学报:自然科学版,2012,43(2):605–610.(ZHOU Sheng,XI Zhenzhu,SONG Gang,et al.Responses of the towed transient electromagnetic sounding on deep seafloor[J].Journal of Central South University,2012,43(2):605–610.(in Chinese))
[20]LI H,XUE G Q,ZHOU N N,et al.Appraisal of an array TEM method in detecting a mined-out area beneath a conductive layer[J].Pure and Applied Geophysics,2015,172(10):2 917–2 929.
[21]刘树才,刘志新,姜志海.瞬变电磁法在煤矿采区水文勘探中的应用[J].中国矿业大学学报,2005,36(4):414–417.(LIU Shucai,LIU Zhixin,JIANG Zhihai.Transient electromagnetic detecting technique for water hazard to the roof of fully mechanized sub-level caving face[J].Journal of China University of Mining and Technology,2005,36(4):414–417.(in Chinese))
[22]SUN H F,LI X,LI S C,et al.Multi-component and multi-array TEM detection in karst tunnels[J].Journal of Geophysics and Engineering,2012,9(4):359–373.
[23]RENINGER P A,MARTELET G,LASSEUR E,et al.Geological environment of karst within chalk using airborne time domain electromagnetic data cross-interpreted with boreholes[J].Journal of Applied Geophysics,2014,106:173–186.
[24]张志豪,李荣先,梁延广,等.地下溶洞调查物探技术探讨[J].工程地质学报,2012,20(5):877–887.(ZHANG Zhihao,LI Rongxian,LIANG Yanguang,et al.Discussions on geophysical prospecting technology of underground karst cave investigation[J].Journal of Engineering Geology,2012,20(5):877–887.(in Chinese))
[25]孟庆鑫,潘和平.地–井瞬变电磁响应特征数值模拟分析[J].地球物理学报,2012,55(3):1 046–1 053.(MENG Qingxin,PAN Heping.Numerical simulation analysis of surface-hole TEM responses[J].Chinese Journal of Geophysics,2012,55(3):1 046–1 053.(in Chinese))
[26]孟庆鑫,潘和平.井中磁源瞬变电磁三维时域有限差分数值模拟[J].中南大学学报:自然科学版,2013,44(2):649–655.(MENG Qingxin,PAN Heping.3D FDTD numerical simulation for transient electromagnetic of magnetic source in borehole[J].Journal of Central South University,2013,44(2):649–655.(in Chinese))
[27]赵博超,朱蓓,王弘元,等.浅谈岩溶塌陷的影响因素与模型研究[J].中国岩溶,2015,34(5):515–521.(ZHAO Bochao,ZHU Bei,WANG Hongyuan,et al.Influence factors and mathematical models of karst collapses[J].Carsologica Sinica,2015,34(5):515–521.(in Chinese))
[28]葛德彪,闫玉波.电磁波时域有限差分方法[M].西安:西安电子科技大学出版社,2005:12–13.(GE Debiao,YAN Yubo.Finite difference time domain method of electromagnetic wave[M].Xi?an:Xidian University Press,2005:12–13.(in Chinese))
[29]余文华,苏涛,MITTRA R,等.并行时域有限差分[M].北京:中国传媒大学出版社,2005:25–45.(YU Wenhua,SU Tao,MITTRA R,et al.Parallel finite difference time domain method[M].Beijing:Communication University of China Press,2005:25–45.(in Chinese))
[30]王长清.电磁场计算中的时域有限差分法[M].北京:北京大学出版社,1994:1–66.(WANG Changqing.Finite difference time domain method in computational electromagnetic[M].Beijing:Peking University Press,1994:1–66.(in Chinese))
[31]WANG T,HOHMANN W G.A finite-difference,time-domain solution for three-dimensional electromagnetic modeling[J].Geophysics,1993,58(6):797–809.
[32]孙怀凤,李貅,李术才,等.考虑关断时间的回线源激发TEM三维时域有限差分正演[J].地球物理学报,2013,56(3):1 049–1 064.(SUN Huaifeng,LI Xiu,LI Shucai,et al.Three dimensional FDTD modeling of TEM excited by loop source considering ramp time[J].Chinese Journal of Geophysics,2013,56(3):1 049–1 064.(in Chines))
[33]孙怀凤.隧道含水构造三维瞬变电磁场响应特征及突水灾害源预报研究[博士学位论文][D].济南:山东大学,2013.(SUN Huaifeng,Three-dimensional transient electromagnetic responses of water bearing structures in tunnels and prediction of water inrush sources[Ph.D.Thesis][D].Jinan:Shandong University,2013.(in Chinese))
[34]王华军.时间域瞬变电磁法全区视电阻率的平移算法[J].地球物理学报,2008,51(6):1 936–1 942.(WANG Huajun.Time domain transient electromagnetism all time apparent resistivity translation algorithm[J].Chinese Journal of Geophysics,2008,51(6):1 936–1 942.(in Chinese))
[2]牛建军,杜立志,谷成.岩溶探测中的弹性波CT方法[J].吉林大学学报:地球科学版,2004,34(4):630–633.(NIU Jianjun,DU Lizhi,GU Cheng.The application of elastic CT method in karst prospecting[J].Journal of Jiling University:Earth Science,2004,34(4):630–633.(in Chinese))
[3]陈灿华,廖秀英,陈绍裘.高速公路不同地层路基中岩溶洞穴的探测[J].中南大学学报:自然科学版,2004,35(6):1 014–1 018.(CHEN Canhua,LIAO Xiuying,CHEN Shaoqiu.Explore karst in different strata of highway roadbed[J].Journal of Central South University of Technology:Natural Science,2004,35(6):1 014–1 018.(in Chinese))
[4]BELGACEM R,BATOBO O,HAKIM G,et al.Electrical resistivity tomography(ERT)applied to karst carbonate aquifers:case study from Amdoun,Northwestern Tunisia[J].Pure and Applied Geophysics,2016,173(4):1 289–1 303.
[5]葛双成,邵长云.岩溶勘察中的探地雷达技术及应用[J].地球物理学进展,2005,20(2):476–481.(GE Shuangcheng,SHAO Zhangyun.Technique and application of GPR in karst prospecting[J].Progress in Geophysics,2005,20(2):476–481.(in Chinese))
[6]苏茂鑫,钱七虎,李术才,等.一种岩溶地质条件下的城市地铁超前预报方法[J].岩石力学与工程学报,2011,30(7):1 428–1 434.(SU Maoxin,QIAN Qihu,LI Shucai,et al.A method of metro advanced geological prediction under karst geology condiction[J].Chinese Journal of Rock Mechanics and Engineering,2011,30(7):1 428–1 434.(in Chinese))
[7]陈灿华,陈绍求.电测深法在岩溶探测中的应用[J].中南工业大学学报:自然科学版,2000,31(1):9–12.(CHEN Canhua,CHEN Shaoqiu.Application of resistivity sounding method to exploring krast[J].Journal of Central South University of Technology:Natural Science,2000,31(1):9–12.(in Chinese))
[8]PARK M K,PARK S Y,YI M,et al.Application of electrical resistivity tomography(ERT)technique to detect underground cavities in a karst area of South Korea[J].Environmental Earth Sciences,2014,71:2 797–2 806.
[9]牛之琏.时间域电磁法原理[M].长沙:中南大学出版社,2007:69–70.(NIU Zhilian.Theory of time domain electromagnetic[M].Changsha:Zhongnan University Press,2007:69–70.(in Chinese))
[10]李貅.瞬变电磁测深的理论与应用[M].西安:陕西科学技术出版社,2002:5–8.(LI Xiu.Theory and application of transient electromagnetic sounding[M].Xi?an:Shaanxi Science and Technology Press,2002:5–8.(in Chinese))
[11]焦险峰,刘志新.瞬变电磁法浅层分辨率物理模型实验研究[J].中国矿业大学学报,2014,43(4):738–741.(JIAO Xianfeng,LIU Zhixin.Physical model and experimental research on shallow resolution if transient electromagnetic method[J].Journal of China University of Mining and Technology,2014,43(4):738–741.(in Chinese))
[12]席振珠,刘剑,龙霞,等.瞬变电磁法三分量测量方法研究[J].中南大学学报:自然科学版,2010,41(1):272–276.(XI Zhenzhu,LIU Jian,LONG Xia,et al.Three-component measurement in transient electromagnetic method[J].Journal of Central South University:Science and Technology,2010,41(1):272–276.(in Chinese))
[13]XUE G Q,CHENG J L,ZHOU N N,et al.Detection and monitoring of water-filled voids using transient electromagnetic method:a case study in Shanxi,China[J].Environmental Earth Sciences,2013,70(5):1–8.
[14]EZERSKY M,LEGCHENKO A,AL-ZOUBI A,et al.TEM study of the geoelectrical structure and groundwater salinity of the Nahal Hever sinkhole site,Dead Sea shore,Israel[J].Journal of Applied Geophysics,2011,75(1):99–112.
[15]VRBANCICH J.An investigation of seawater and sediment depth using a prototype airborne electromagnetic instrumentation system-a case study in Broken Bay,Australia[J].Geophysical Prospecting,2009,57:633–651.
[16]YANG DIKUN,OLDENBURG DOUGLAS W.Three-dimensional inversion of airborne time-domain electromagnetic data with applications to a porphyry deposit[J].Geophysics,2012,77(2):B23–B34.
[17]CHRISTENSEN NIELS B.Difficulties in determining electrical anisotropy in subsurface investigations[J].Geophysical Prospecting,2000,48(1):1–19.
[18]PODGORSKI J E,AUKEN E,SCHAMPER C,et al.Processing and inversion of commercial helicopter time-domain electromagnetic data for environmental assessments and geologic and hydrologic mapping[J].Geophysics,2013,78(4):E149–E159.
[19]周胜,席振铢,宋刚,等.深海拖曳式瞬变电磁的响应规律[J].中南大学学报:自然科学版,2012,43(2):605–610.(ZHOU Sheng,XI Zhenzhu,SONG Gang,et al.Responses of the towed transient electromagnetic sounding on deep seafloor[J].Journal of Central South University,2012,43(2):605–610.(in Chinese))
[20]LI H,XUE G Q,ZHOU N N,et al.Appraisal of an array TEM method in detecting a mined-out area beneath a conductive layer[J].Pure and Applied Geophysics,2015,172(10):2 917–2 929.
[21]刘树才,刘志新,姜志海.瞬变电磁法在煤矿采区水文勘探中的应用[J].中国矿业大学学报,2005,36(4):414–417.(LIU Shucai,LIU Zhixin,JIANG Zhihai.Transient electromagnetic detecting technique for water hazard to the roof of fully mechanized sub-level caving face[J].Journal of China University of Mining and Technology,2005,36(4):414–417.(in Chinese))
[22]SUN H F,LI X,LI S C,et al.Multi-component and multi-array TEM detection in karst tunnels[J].Journal of Geophysics and Engineering,2012,9(4):359–373.
[23]RENINGER P A,MARTELET G,LASSEUR E,et al.Geological environment of karst within chalk using airborne time domain electromagnetic data cross-interpreted with boreholes[J].Journal of Applied Geophysics,2014,106:173–186.
[24]张志豪,李荣先,梁延广,等.地下溶洞调查物探技术探讨[J].工程地质学报,2012,20(5):877–887.(ZHANG Zhihao,LI Rongxian,LIANG Yanguang,et al.Discussions on geophysical prospecting technology of underground karst cave investigation[J].Journal of Engineering Geology,2012,20(5):877–887.(in Chinese))
[25]孟庆鑫,潘和平.地–井瞬变电磁响应特征数值模拟分析[J].地球物理学报,2012,55(3):1 046–1 053.(MENG Qingxin,PAN Heping.Numerical simulation analysis of surface-hole TEM responses[J].Chinese Journal of Geophysics,2012,55(3):1 046–1 053.(in Chinese))
[26]孟庆鑫,潘和平.井中磁源瞬变电磁三维时域有限差分数值模拟[J].中南大学学报:自然科学版,2013,44(2):649–655.(MENG Qingxin,PAN Heping.3D FDTD numerical simulation for transient electromagnetic of magnetic source in borehole[J].Journal of Central South University,2013,44(2):649–655.(in Chinese))
[27]赵博超,朱蓓,王弘元,等.浅谈岩溶塌陷的影响因素与模型研究[J].中国岩溶,2015,34(5):515–521.(ZHAO Bochao,ZHU Bei,WANG Hongyuan,et al.Influence factors and mathematical models of karst collapses[J].Carsologica Sinica,2015,34(5):515–521.(in Chinese))
[28]葛德彪,闫玉波.电磁波时域有限差分方法[M].西安:西安电子科技大学出版社,2005:12–13.(GE Debiao,YAN Yubo.Finite difference time domain method of electromagnetic wave[M].Xi?an:Xidian University Press,2005:12–13.(in Chinese))
[29]余文华,苏涛,MITTRA R,等.并行时域有限差分[M].北京:中国传媒大学出版社,2005:25–45.(YU Wenhua,SU Tao,MITTRA R,et al.Parallel finite difference time domain method[M].Beijing:Communication University of China Press,2005:25–45.(in Chinese))
[30]王长清.电磁场计算中的时域有限差分法[M].北京:北京大学出版社,1994:1–66.(WANG Changqing.Finite difference time domain method in computational electromagnetic[M].Beijing:Peking University Press,1994:1–66.(in Chinese))
[31]WANG T,HOHMANN W G.A finite-difference,time-domain solution for three-dimensional electromagnetic modeling[J].Geophysics,1993,58(6):797–809.
[32]孙怀凤,李貅,李术才,等.考虑关断时间的回线源激发TEM三维时域有限差分正演[J].地球物理学报,2013,56(3):1 049–1 064.(SUN Huaifeng,LI Xiu,LI Shucai,et al.Three dimensional FDTD modeling of TEM excited by loop source considering ramp time[J].Chinese Journal of Geophysics,2013,56(3):1 049–1 064.(in Chines))
[33]孙怀凤.隧道含水构造三维瞬变电磁场响应特征及突水灾害源预报研究[博士学位论文][D].济南:山东大学,2013.(SUN Huaifeng,Three-dimensional transient electromagnetic responses of water bearing structures in tunnels and prediction of water inrush sources[Ph.D.Thesis][D].Jinan:Shandong University,2013.(in Chinese))
[34]王华军.时间域瞬变电磁法全区视电阻率的平移算法[J].地球物理学报,2008,51(6):1 936–1 942.(WANG Huajun.Time domain transient electromagnetism all time apparent resistivity translation algorithm[J].Chinese Journal of Geophysics,2008,51(6):1 936–1 942.(in Chinese))