基于激发极化法的隧道含水地质构造超前探测研究

STUDY OF ADVANCED DETECTION FOR TUNNEL WATER-BEARING GEOLOGICAL STRUCTURES WITH INDUCED POLARIZATION METHOD

突(涌)水地质灾害是制约隧道等地下工程建设的瓶颈问题之一,隧道施工期含水地质构造的超前探测尤其是水量预测已经成为亟待研究和解决的重要工程科技难题。针对上述难题,提出以激发极化法等地球物理方法为先导的解决思路,研发隧道含水构造超前探测专用激发极化仪器。提出从视电阻率数据着手解决含水构造定位难题的思路和基于三维电阻率反演方法的隧道含水构造超前探测三维成像方法及其计算效率优化方案。解答隧道超前探测的基本问题(如三维全空间点源电场求解、三维测量观测方式、干扰识别与去除方法、反演目标区域等),利用反演算例验证断层、溶洞等含导水地质构造三维成像的有效性。针对含水体的水量预测难题,提出基于二电流激发极化半衰时之差法的隧道含水构造水量预测方法,通过物理模型试验发现半衰时之差与水量之间存在线性正相关关系,二者之间的这种单调线性正相关关系为解决实际工程中含水构造的水量预测难题奠定了基础。最终形成激发极化法隧道含水地质构造超前探测技术体系,并将该技术用于隧道地质预报实践中,预报结果与实际开挖情况基本一致。实际应用效果表明,激发极化超前预报技术可有效解决隧道施工期含水构造超前探测的定位难题,尤其可实现含水体水量的估算,拓展了超前地质预报工作的功能,具有良好的应用前景和推广价值。

The water inrush hazards have become one of the bottleneck problems that constrain the construction of underground engineering such as tunnels.The advanced detection of the water-bearing geological structures especially estimation of the water volume in tunnel construction period has become an important scientific and engineering problem to be studied and solved urgently.For the above problems,the solving method with the induced polarization（IP） method as the guide is proposed.The advanced geological prediction with IP method in tunnel faces with a lot of new problems to be studied and solved urgently in contrast with shallow exploration.The special IP instrument for tunnel advanced detection is developed.The thought for solving the problem of water-body location with apparent resistivity is presented;and the three-dimensional（3D） tomography method of water-bearing structures advanced detection based on 3D resistivity inversion method and its computation scheme is proposed.The basic problems of tunnel advanced detection are solved（e.g.solution of point source field in 3D whole space,3D measurement mode,recognition and removal of the measurement disturbance,inversion target region）.The feasibility and effectiveness of 3D tomography for water-bearing structures has been proved by massive inversion examples.For the problem of water volume estimation,the method based on half-decay time difference of two-current induced polarization is put forward.It is found that the relation between difference of half-decay time and water volume is linear positive correlation by physical model test.And this linear positive correlation lays a solid foundation for water volume prediction of water-bearing structures in practical engineering.In the end,advanced detection technical system with IP method for tunnel water-bearing geological structures is formed.And this technical system is introduced into geological forecast work in tunnel engineering.The prediction results are basically identical with the practical excavation results.Practical application demonstrates that the problem of advanced detection for tunnel water-bearing structures especially the water volume estimation is solved effectively with prediction technique of IP method;and it has good application prospect and popularization value which extends the function of advanced geological prediction technique.