Model Test On Grouting Quality Detection Of Karst Subgrade By High Density Resistivity Method

The grouting method is usually used to strengthen karst subgrade. However, due to the complexity and concealment of grouting, it appears important to detect the grouting reinforcement effect. High density resistivity method is a kind of methods widely used to detect the grouting. But because of the influence of various complex geological factors on the detecting result, especially the presence of groundwater and all kinds of geological structure, there is certain uncertainty in the interpretation of the measurement results. In order to detect the grouting quality more effectively by high density resistivity method, it is necessary to determine the influence of the groundwater and various geological structure on the measurement results.This thesis carried out the forward research by combining the model test and numerical simulation. In the model test, a solid model is set up which size is300cmx50cmx50cm. it is built by sandstone plate dislocatedly, which size is50cmx50cmx5cm, on the background of the detection of grouting to treat karst subgrade in Nanning-Guangzhou railway. Three kinds of geological structure are designed, that is cave, fracture zone and fractured rock mass. To establish a model of variable of the underground water level of karst subgrade, the model is located in the sink which size is500cmx100cmx70cm. After artificial grouting, the model is measured by the high density resistivity method and the micro electrode. So this model is used to study the forward analysis about the detection of grouting effect of different geological structure under different groundwater level. At the same time, choose one geological model, and use ANSYS finite element software to simulate the process of grouting and calculate the quality of grouting. And then compare and analysis the simulation results and test results to ensure the results accurate and reliable.Test results show that high density resistivity method is able to detect grouting quality under three kinds of groundwater environment, the condition that there is no groundwater before and after grouting, the condition that there is groundwater before and after grouting, and the condition that there is groundwater before grouting but no groundwater after. And high density resistivity method is not suitable for detecting grouting effect when there is groundwater after grouting but no groundwater before.