Study On The Influence Of Surrounding Rock Stability Effected By Karst Cave And Its Detecting Method

In the process of tunneling building, many problems about karst caves will happen. Exist of karst cave can be a great threat to the stability of surrounding rock. If a karst cave is rich in water, it can be a big problem in the process of tunnel building. It is known to all that many places in southwest of china is with karst landform. In the process of economy development, problems concerning karst landform are increasing. Therefore, it's important to study surrounding rock's stability influenced by karst cave.This thesis is based on high way tunnel, theory analysis, field monitoring, numerical simulation methods were used. Based analyzing factors influencing surrounding rock's stability, stress and displacement calculation method was built. According to geological forecasting method, TSP and GPR methods were compared about their advantages and disadvantages. Next, ANSYS was used to analyze the stability of surrounding rock concerning different place, size of karst cave. Based on excavation method of tunnel, numerical simulation method was applied to study the stability of surrounding rock, and the result was compared with results got from field monitoring. In these ways, the influence to surrounding rock's stability was studied. This thesis is of great importance in excavation method of surrounding rock. Main study results are as follows:(1) Different geological forecasting methods were analyzed. According to geological condition of real practice. TSP method was used in section DK14+845-965. GPR method was used to detect abnormal areas detected by TSP method. The results showed TSP can be a good detecting method for the whole tunnel. In complicated areas, GPR method can be a verification method for TSP method.(2) ANSYS was used to study the influence of karst cave under different place, size and length to surrounding rock stability. The results showed: the top and bottom karst cave can be a big influence to vertical displacement of vault and haunch, it has little influence to horizontal displacement; when the karst cave is located 45 degree side of tunnel, which can greatly influence horizontal displacement of tunnel.(3) According to numerical simulation method and real condition of tunnel engineering, right side of tunnel with a karst cave 45 degree of it was studied. Based on monitoring results of monitoring points and numerical simulation method, the results showed: the side with karst cave has a larger displacement than the side did not have karst cave; with the existence of karst cave, slope displacement is larger; results from field monitoring is almost the same with numerical simulation method. Therefore, numerical simulation and field monitoring methods can be together used in the monitoring for surrounding rock.