Abstract:

The detection of water-bearing structures and karst-fractured groundwater is the key problem needed to be resolved. Due to its high resolution and sensitivity to the low resistivity body, the DC resistivity method is introduced to predict the water-bearing structures in the front of tunnel face. First, the analytical formula of the spheriform water-bearing structures advanced detection in the whole space is deduced. Based on the analysis of large forward modeling results with finite element numerical simulation method, the apparent resistivity data in 3-D space with tunnel is translated into the data of advanced detection in the whole space with comparison method. The disturbance induced from inhomogeneous resistivity around the MN pole is discussed; and the method to identify and eliminate this disturbance is studied. Then the damped least squares inversion method is designed on the base of the analytical formula of the spheriform structures detection in the whole space. With this method, the inversion for multi-group spheriform water-bearing structures models is done. In addition, the anomaly law of the advanced detection of water-bearing structures with other shape is studied; and concept of equivalent sphere is raised. A fast inversion method is designed on the base of the analytical formula of the spheriform structures detection in the whole space. At last, the result of physical model test verifies the feasibility and effectiveness of finite element numerical method and damping least squares inversion method, which lay a foundation for the advanced detection of water-bearing structures with DC resistivity method in practical engineering.

Key words: advanced geological prediction, water-bearing structures, DC resistivity method, forward modelling, inversion, damping least squares inversion method, physical model test