Passenger Dedicated Line Weathered Granite Improved Soil Embankment Stability Study

The construction of the passenger rail line has entered a new period of rapid development in China, so it is the objective requirement of the new high-speed railway that major efforts should be devoted to develop ballastless track. In terms of ballastless track passenger dedicated line the controlling standard for deformation and stability of the subgrade is very strict. Some soil types that have been used in ordinary railway (highway) embankment filling may not be directly used for the construction of high-speed railway. In the wetter Southern areas, repeated erosion of the rain may lead to the stability problem of the roadbed, which has become one of the important issues that must be covered in high-speed railway construction.In accordance with the features of Wuhan-Guangzhou passenger rail line through a wide range of weathered granite completely, and lack of A,B group fillings and so on, combined with the Ministry of Railways scientific and technological projects, based on a comprehensive analysis of domestic and foreign granite roadbed research, through laboratory test of road performance of weathered granite completely and its improved soil,and through the combination of theoretical analysis and numerical analysis , the stability of the embankment was studied in this paper.The main research work and conclusions are as follows:Through a series of laboratory tests of the weathered granite soil and remodeling soil the paper drawns that water stability of weathered granite completely soil is so poor that can not satisfy the requirements of subgrade strength, stiffness and long-term water stability of ballast-less track passenger line, and makes clear that a similar kind of cutting soil should not be directly used for the filling embankment of the passenger rail line.Improved through the incorporation of different proportions of lime or cement to the weathered granite, its water stability will be improved. Through large-scale testing of different incorporation improved soils ,such as the particle size distribution, compression characteristics, compaction degree, permeability, wetlands, ability of anti-erosion and anti-collapse, etc, as well as statistical analysis of test data,the paper respectively, obtained the laws of the unconfined compressive strength and water stability coefficient changed with the relevant factors and their mathematical expression.Based on the difference on engineering properties of weathered granite completely along the passenger line, as well as the strength and water stability analysis of lime or cement improved soils, the suggestion is put forward on improved materials, mixture ratio, degree of compaction, etc of different sections of weathered granite completely in this paper. For example:Nearby DK2097 +560, mixing materials of improved soil that used for the bottom subgrade filling material should be selected with 5% to 6% of lime, and the compaction degree Kh can be controlled within 0.93 to 0.95;Nearby DK2116 +200, mixing materials of improved soil that used for the bottom subgrade filling material should be selected with 5% to 6% of cement, and the compaction degree Kh can be controlled over 0.93 .The Strength Reduction FEM is used to analyze the failure and deformation character of the embankment up the flat ground and sloping ground,and do multivariate sensitivity analysis of relevant factors using orthogonal analysis.And it clearly indicates that filling rate, groundwater as well as the slope ratio are the major impact factors of embankment failure pattern.Combined with practical engineering examples, this article taking into account the dissipation from seepage of soil and pore water pressure, carries out simulation calculation for a section of a typical embankment by FEM analysis software, and in-depth analysises the embankment stability under steady-state seepage.