Conventional tunnel DC resistivity advanced detection method for survey behind the tunnel face is influenced by the tunnel body and working environment which greatly increase the difficulty of data interpretation. Using the principle of same current repelling each other, and with reference to the vertical ground resistivity sounding and DC laterlog technology the authors proposed a vertically focused advanced detection scheme on the tunnel face and the wall which is good for tunnel space. Finite element numerical simulation method (FEM) was used to simulate the effect of focused advanced detection method in three-dimensional tunnel space. Compressed storage technology and preconditioned iterative algorithm greatly improved the efficiency of forward modeling as well. Comparison between the FEM modeling results and analytical results of full space tunnel models and physical simulation results in soil bin showed that the accuracy of forward simulation meets the requirement and the designed focusing detection device of the vertical gradient and the potential can achieve the purpose of focused advanced detection. The results that simulated complex models in the conditions of vertical focused observation showed that the scheme can effectively detect the iii geologic bodies in front and side tunnel.%常规坑道直流电阻率超前探测方法在掌子面后方观测,受到坑道腔体和工作环境的影响较大,增加了资料解释的难度.利用同性电流相斥原理,并参考地面电阻率垂向测深和直流侧向测井技术设计出适合坑道空间掌子面和侧壁测量的垂直聚焦电位和梯度电位超前探测方案.应用有限元数值模拟技术,对三维坑道空间中掌子面和侧壁探测方案的聚焦超前探测效果进行模拟研究.采用压缩存储技术及预条件迭代算法大大提高正演模拟的效率.有限元数值计算结果与全空间坑道模型解析解和土槽物理模拟实验结果对比,说明正演模拟结果可靠,设计的梯度及电位垂直聚焦探测装置能够实现聚焦超前探测的目的.对坑道垂直聚焦观测条件下的掌子面和侧壁组合模型进行模拟计算,结果表明该方案能够有效探测前方和旁侧存在的不良地质体.
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