Numerical Simulation Of Design Parameters Of Karst Foundation In Expressway

The problem refereed to stability of underground caverns, reasonable treating limits and grouting parameters in the Karst areas is universal existence, which impacts engineering seriously and is not completed resolved. The treatment problems in Karst areas are becoming more and more common, where more railways and other engineering are built. So the stability of underground caverns and grouting parameters in the Karst areas are gradually become one important factors of influence on construction and operation successfully.Based on the grouting treatment in the section of Shuangfeng to Pingtai in expressway, the model is built and calculated by Fast Lagrange method in this thesis. Through simulating stability of underground caverns and changing regularity of grouting diffusion radius in Karsts, it is obtained the variation of diffusion radius in the different condition. The main researching contents in this thesis include following aspects:Combined with the local actual working condition, appropriate geotechnical parameters and permeability parameters are selected.Through calculating the variation of stability of underground caverns along with their radius, offset distance and buried depth, their maximum safety roof thickness is got, further more the displacement of foundation settlement along with radius of caverns, offset distance and buried depth is obtained in such conditions.The variation curves of grouting diffusion radius with grouting pressure and slurry viscosity is obtained. The reasonable routing diffusion radius is put forward for treating the section of Karst in expressway, which are supplied guidance of drilling spacing for site construction combined with electrical sounding and borehole data.Numerical simulation shows that:safety roof thickness of underground caverns in soil is 22m in Karst foundation in expressway, and the corresponding thickness in rock is 5m. The treatment width of underground caverns in soil and in rock respectively is 7m and 6m outside of slope toe in Karst foundation in expressway. According to the actual grouting, diffusion radius of slurry is from 2.9m to 3.2m, and the variation curves is obtained which is about the diffusion radius changing with grouting pressure and slurry viscosity. On account of slurry diffusing in Karst foundation, the situation of grouting by breakthrough walls is denied through numerical simulation.