Application Research Of Cross Hole Direct Current Resistivity CT In Continuous Wall Leakage Detection

With the rapid development of the global economy and the acceleration of domestic urbanization,many cities are actively promoting the construction of water conservancy or high-rise buildings to meet the growing demand for a safe and comfortable living environment in today’s society.However,in these construction processes,the construction of some underground works involved must first carry out the construction of underground continuous walls.During the entire construction process,there may be leakage in different situations due to various reasons such as engineering construction or later groundwater erosion.Therefore,before subsequent construction,these leakage channels on the continuous wall need to be detected and remediation measures taken in time to reduce losses.Cross-hole direct current resistivity CT method,its principle is a geophysical method to achieve detection by using the resistivity difference between media.At present,in the field of urban underground continuous wall detection,the application of this method is relatively rare,in order to improve its application level,this paper will focus on the following points:(1)In-depth discussion of the relevant principles of cross-hole direct current resistivity CT method,including the relevant principles of two-pole,three-pole and four-pole devices and device coefficients.Through the study of the forward evolution principle,the finite difference method and the finite element method in forward simulation are listed.In addition,the inversion principle is analyzed in detail,including the derivation principle and inversion process of the damping least squares inversion method.(2)Through forward numerical simulation,the potential change characteristics of direct current resistivity detection combined underground-ground are studied,so as to achieve the goal of underground continuous wall census by using this undergroundground combination method.On the basis of the census,the characteristics of underground apparent resistivity detected by cross-hole direct current resistivity CT method are studied through forward evolution.Then,through inversion,the different resistivity response characteristics of the commonly used devices of the cross-hole direct current resistivity CT method are studied,and the response characteristics of the two different devices under different hole spacing and different continuous walls are studied separately by using the control variable method,and it is concluded that the bipole-bipole device is more suitable for continuous wall leakage detection with longer hole spacing and larger resistivity,and the dipole-dipole device is more suitable for continuous wall leakage detection with closer hole spacing and relatively small resistivity.(3)Through inversion imaging,taking specific engineering examples as the research object,and taking the above numerical simulation results as the basis for detection,a series of data processing was carried out on the research area to obtain inversion images for analysis,and the results were confirmed with the results obtained by drilling coring and rainfall tests,and it was successfully concluded that this method can effectively detect the possible leakage of continuous walls.After theoretical and practical results,it is shown that the cross-hole direct current resistivity CT detection system has excellent performance in the leakage detection of urban underground continuous wall,and has the advantages of high precision,flexibility and reliability,and can effectively detect leakage channels,which has broad application prospects.The research work in this paper provides a more comprehensive detection method for underground continuous wall,which not only has important guiding significance in theory,but also has very good engineering application value in practical application.