The Effect Detection Of Grouting And Stability Analysis Of The Roadbed Of Covered Karst Of Hangzhou-Changsha Passenger Dedicated Railway

Hangzhou-Changsha passenger dedicated railway is an important part of Shanghai-Kunming passenger dedicated railway, which is one of the "four vertical and four horizontal" high-speed railway passenger transport network. The distance of the limestone section of the Hangzhou-Changsha railway is about200km, where the karst collapse, mostly covered karst, happens frequently. Because the railway cannot avoid going through those places, the reinforcement methods need to be taken.On the basis of survey summary of geological environment, this paper does research in the effect detection of grouting and stability analysis of the roadbed of covered karst of Hangzhou-Changsha railway. Comprehensive geophysical prospecting method composed by high frequency electromagnetic method and the transient Rayleigh wave method, water pressure test method, core-drilling method are applied to testing and estimating the effect of grouting in the study area. According to the result of testing, some related technical requirements and suggestions are proposed. The numerical simulation is also used to analyze and evaluate the stability of the study area in three different condition, including the natural conditions, the train-loading conditions before reinforcement, and the train-loading condition after reinforcement. The mainly research results are as follows:(1) Karst caves in the study area are mainly and strongly developed in bedrock, controlled by the stratum lithology. The cave height has no significant correlation with the thickness of Karst roof and the thickness of covering layer. Due to the effect of erosion and corrosion of the groundwater, the development of the karst cave is mainly vertical.(2) Comprehensive geophysical prospecting method composed by high frequency electromagnetic method and the transient Rayleigh wave method, water pressure test method, core-drilling method are applied to testing the pilot hole in the study area. Results show that this area needs subsequent grouting treatment.(3) The numerical simulation is used to analyze the stability of the roadbed of covered karst in the study area before and after the reinforcement, and evaluate the effect of reinforcement. In this paper, the finite element software ANSYS is applied to the numerical analysis on the area of DK696+275～400、DK697+400～600. Based on the engineering geological conditions, geological model is set up, the stability of which is discussed in the state of the natural conditions, the train-loading conditions before reinforcement, and the train-loading condition after reinforcement. According to the result of analyzing the stress, strain and strength of model under various conditions, the roadbed of covered karst after the grouting reinforcement satisfies the requirement of the bearing capacity of foundation soil.