城市地铁岩溶隐患多孔电阻率联合成像技术研究*

为有效解决二维电法在探测异常体空间形态上的不足，基于有限差分算法，建立溶洞与跨孔电阻率组合模型，探讨溶洞剖面投影位置及偏移距与电阻率响应变化特征，将跨孔电阻率数据体进行跨孔三维联合反演成像。结果表明:溶洞模型距跨孔探测剖面较近时，实际投影至剖面上位置不同，导致探测效果差异较大；随溶洞模型偏移距增大，溶洞投影中心位置电阻率整体表现为前期缓慢、中期迅速、后期减缓并最终趋于稳定的非线性变化趋势，溶洞模型旁侧效应影响范围约8 m。三维联合反演结果能立体可视化展示溶洞空间发育形态，在城市地铁超前地质灾害精准探测方面具有一定应用价值。

Study on multi-hole resistivity combined imaging technology of karst hidden dangers in urban subway

In order to effectively solve the shortcomings of the two-dimensional electrical method in detecting the spatial morphology of anomalous bodies,based on the finite difference algorithm,a combined model of karst cave and cross-hole resistivity was established,and the response variation characteristics of resistivity section caused by the projection position and offset of the karst cave profile were discussed.The idea of conducting multi hole three-dimensional resistivity combined imaging on the inter hole profile resistivity data volume was proposed,and the verification was conducted combining with the advanced detection engineering case of karst cave in the urban subway.The results showed that when the karst cave model was closer to the cross hole detection profile,the position of actual projection to the profile was different,and the detection effect had greater difference.As the offset of karst cave model increased,the resistivity at the center of karst cave projection overall presented the non linear increase stage of slow in the early stage,rapid in the middle stage,slowing down in the later stage and eventually tending to be stable,and the side effect influence range of the cave model was about 8 m.Compared with the 2D cross-hole resistivity CT inversion,the 3D combined inversion could stereoscopically and visually display the spatial development morphology of karst caves in the survey area.The research results have certain application value in the advanced accurate detection of geological disasters in urban subway.