Settlement Control Of Soft Soil And Dynamic Analysis Of High-Speed

The most pivotal technical problem of building high-speed railway on soft soil is strictly controlling post-construction settlement of subgrade and its elastic deformation of top surface.According to test results of Kunshan experiments, the character and deformation rule of soft soil in this area have been analyzed. And the reinforcing effects on soft soil have been estimated in this paper, including vacuum-surcharge preloading, surcharge preloading, and preloading combined with sand piles. E-lgp method is proposed to calculating primary consolidate settlement of the ground, which is improved by three kinds of soft soil improvements mentioned above. But the actual settlement of foundation is different from the theoretic settlement which is used to give a reference design. When calculate the final settlement of foundation using kinds of methods, the results are different from each other, but it is proposed to using hyperbola method in east China. Under allowable time limit, the post-construction settlement of subgrade can be controlled within five centimeters, which is improved by mentioned improvements. If the project is very urgent, vacuum-surcharge preloading or preloading combined with sand piles is proposed to improve the soft soil.The current finite element software ANSYS has been used to doing dynamic analysis of soft soil and subgrade in this paper. As can be seen from the results, the stiffness of top and bottom layer of bedding have little effect on deformation of top subgrade, but the stiffness of soft soil has great effect on it. When the stiffness of surface layer of bedding, acceleration of the top surface of subgrade decline rapidly, but it is not evident when the stiffness of bottom bedding increase from 50MPa to 90MPa, while the increase of stiffness of soft soil has hardly any effect on it. For dynamic stress distributing on the surface of subgrade, the result from finite element analysis inosculate actual dynamic stress preferably. Aimming at soft soil, it is advised to adopt stiffness of the top layer of bedding vary from 160MPa to 180MPa, and the stiffness of the bottom layer of bedding vary from 160MPa to 180MPa.