Study On Model Experiment And Numerical Simulation Of Resistivity Sounding Measurement In Grouting Quality Detection Of Karst Subgrade

Engineering practice shows that the grouting method has become the main method of prevention and treatment of karst collapse. However, due to the complexity and concealment of grouting, it is appeared very important to detect grouting quality. At present, the method of resistivity sounding measurement is a kind of common geophysical techniques and it has been used to detect grouting quality in Karsts, but it is lack of system research and the theoretical guidance for electrical sounding measurement to detect the grouting quality of karst subgrade. This thesis is based on the grouting to treat karst subgrade in Nanning-Guangzhou railway, the method of resistivity sounding measurement to detect grouting quality of karst subgrade is studied by model experiment and numerical simulation, which will provide the theory basis for the engineering practice.Firstly, the method of resistivity sounding measurement to detect grouting quality of karst subgrade is studied in this thesis. The models of karsts caverns and fractures models are set in model test separately and apparent resistivity are measured before and after grouting to analyze the variation of apparent resistivity before and after grouting. The results showed that the apparent resistivity after grouting is significantly lower than that before grouting, and its changing rate is related to detection time. Detecting to grouting should be carried out between 7～15 days after grouting, and it is considered that the effect of grouting is good when the changing rate apparent resistivity is over 20%. Based on model experiments, combined with the results of numerical simulation the effect of detecting grouting quality by the method of resistivity sounding measurement can be studied better. Then, the layer models, grooves models, models of karsts caverns and fractures models are set in Numerical simulations separately, the variation of apparent resistivity before and after grouting are analyzed. The results showed that the apparent resistivity after grouting is significantly lower than that before grouting, which is in accordance with that of model test. Comprehensively analyzing the results of model test and numerical simulation, it is showed that the effect of grouting is preferred when the changing rate apparent resistivity is over 20%.