Forward modeling and application of ground penetrating radar in blind underground cavities of opencast mining
YANG Daoxue1，2，ZHAO Kui1，2，ZENG Peng1，2，LI Ruixue1，2，WANG Xiaojun1，2，ZHONG Wen1，2，GONG Cong1，2
(1. School of Resources and Environmental Engineering，Jiangxi University of Science and Technology，Ganzhou，Jiangxi 341000，China；2. Jiangxi Provincial Key Laboratory of Mining Engineering，Jiangxi University of Science and Technology，
Ganzhou，Jiangxi 341000，China)
摘要金属矿山露天开采过程中经常遇到地下不明空区导致的安全隐患，探地雷达(ground penetrating radar，GPR)是探测不明空区主要的手段之一。针对GPR探测空区类型解译过程中容易出现误判和漏判现象，首先推导基于卷积完全匹配层的交替方向隐式时域有限差分算法(convolutional perfect matching layer-alternating direction implicit finite difference time domain，CPML-ADI-FDTD)的探地雷达正演公式及编写相关程序，进行ADI-FDTD算法与时域有限差分(finite difference time domain，FDTD)算法数值稳定性模拟实验，结果表明：ADI-FDTD算法可以突破传统FDTD算法时间尺度限制，提高了探地雷达正演效率。由此，建立三心拱巷道及其交叉巷道的正演模拟，通过频谱、功率谱及其瞬时相位对巷道充水情况、巷道汇合情况进行分析并得到相关的解译准则，最终进行了工程实例的推断和解译，钻探结果表明探地雷达探测解译结果与实际状况基本完全相吻合。
Abstract：During opencast mining of metal mines，hidden safety hazards caused by unknown underground airspaces are often encountered，and ground penetrating radar(GPR) detection of goaf is one of the commonly used means. Aiming at the misjudgment and omission in the interpretation of GPR detection airspace types，the alternating-direction implicit finite-difference time domain(CPML-ADI-FDTD) based on convolutional perfect matching layer and the related program were deduced，and the numerical simulation experiments of ADI-FDTD algorithm and finite difference time domain(FDTD) algorithm were carried out. The results show that ADI-FDTD algorithm can use a larger time scale to improve the forward modeling efficiency of ground penetrating radar. The forward simulation of a three-core arch roadway and its crossing roadway was established. Through spectrum，power spectrum and its instantaneous phase，the water-filling situation and the convergence of roadways were analyzed and the relevant interpretation criteria were obtained. Finally，An engineering example was deduced and interpreted，which was verified by the drilling results.
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2019, Vol. 38 
