Water-bearing Structure Detection By Complex Conductivity Method Based On The Dynamic Stern Layer Model

The construction of urban rail transit plays an important supportive role in the development of urban clusters and metropolitan areas in China.With the development of cities,the scale of subway tunnel construction will continue to expand,playing a more powerful backbone role in public transportation.During the tunnel construction process,series of engineering accidents such as surface subsidence or settlement,water inflow,and mud inflow may occur due to the influence of water-bearing structures,causing losses in personnel and property.It is necessary to strengthen the prediction and early warning of water-bearing structures to avoid accidents.Compared with traditional polarization methods,the complex conductivity induced polarization method based on the Dynamic Stern Layer Model can establish a quantitative relationship between electrical parameters and other physical parameters,improve the identification ability of water-bearing structures,and is an effective method for detecting water-bearing structures.This study focuses on the research of low-frequency(<10kHz)complex conductivity induced polarization method based on the Dynamic Stern Layer Model for shallow subsoil and rock masses.The research was conducted through a combination of theoretical analysis,laboratory experiments,numerical simulations,field model tests,and field applications,and the following research achievements were obtained:(1)Improved the understanding of the micro-polarization principle in soil and rock masses,and clarified the theoretical relationship of induced polarization physical parameters.This study demonstrated the correlation between pore size distribution and relaxation time distribution through data fitting and obtained the range of correlation correction coefficients for volcanic rocks and carbonates.Based on the Dynamic Stern Layer Model,starting from the microelectrochemical theory,the induced polarization principle of low-frequency complex conductivity in soil and rock materials was explained,and the theoretical relationship of induced polarization physical parameters was revealed.The equivalent circuit model of complex conductivity induced polarization was established,and the charging and discharging curve equations in the time-domain and frequency-domain complex conductivity induced polarization were derived,intuitively demonstrating the micro-polarization mechanism of complex conductivity induced polarization in soil and rock materials.(2)Verified the universal applicability of the Dynamic Stern Layer Model theory in soil and rock masses.This study conducted complex conductivity spectrum tests on samples of bentonite,soil,volcanic rocks,limestone,and dolomite,expanding the spectrum database of complex conductivity in soil and rock masses.The effects of physical parameters such as pore water conductivity,cation exchange capacity,and formation factor on complex conductivity in soil and rock masses were explained,and the correlation relationships between normalized polarizability rate,normalized conductivity,and surface conductivity were verified.(3)Established a unified calculation method for physical parameters of soil and rock masses.This study conducted comparative studies on formation factors,surface conductivities,cation exchange capacities,particle densities,porosities,and other physical parameters of different soil and rock masses,and provided empirical reference values for some soil and rock mass parameters in the Dynamic Stern Layer Model through data fitting,establishing parameter calculation formulas from conductivity and polarization rate to normalized polarizability rate,volumetric water content,cation exchange capacity,and permeability.(4)Proposed a method for distinguishing the six parameters of geological bodies,and optimized the design of detection parameters.This study established a numerical simulation model for complex conductivity induced polarization,studied the influence of different formations,water-bearing structures,and detection parameter conditions of subway tunnels on the actual detection effect of complex conductivity induced polarization,proposed a method for distinguishing the six parameters of geological bodies based on conductivity,polarization rate,normalized polarizability rate,volumetric water content,cation exchange capacity,and permeability,and optimized the design of detection parameter schemes.(5)Proposed a data precise picking method for time-domain induced polarization detection.Based on the equation of time-domain charge-discharge curve,this study proposed a precise picking method for time-domain detection data for decay curve data.The theoretical analysis indicated the significant impact of precise data picking on the imaging of polarization rate.The imaging advantages of this precise picking method were tested through field model experiments.(6)Verified the effectiveness and advantages of the complex conductivity induced polarization method based on the Dynamic Stern Layer Model for detecting water-bearing structures.This study conducted field model tests on high-conductivity geological bodies and highly polarized geological bodies,and together with field engineering applications,verified the feasibility and advantages of the method in detecting water-bearing structures.