Settlement Calculation Research on Medium&Low Compressible Ground of High Speed Railway Subgrade
|School||Central South University|
|Course||Traffic and Transportation Engineering|
|Keywords||the medium&low compressible ground groundreinforcemen consolidation settlement back analysis|
Settlement characteristics of medium&low compressible ground is lack of research as a result of shallow ground treatment generally used in the ordinary highway engineering and multi-storey housing construction of the ground.With the extremely strict control standard of post-construction settlement in high-speed railway,especiallly ballastless track, how to choose the reasonable ground reinforcement measures and settlement calculation methods on the basis of medium&low compressible ground properties becomes an important aspect of the research on the High Speed Railway subgrade.This paper analyzed and studied the physical and mechanical properties, ground reinforcement effect and the composite ground final settlement and post-construction settlement calculation method of the medium&low compressible soil by the means of indoor soil test, on-site monitoring, theoretical derivation and back analysis,which wre based on the Capacity Expansion and Renovation Project of Ganzhou-Longyan Railway, Shanghai-Nanjing Intercity Railway Section III, and the Beijing-Shanghai high-speed railway Zhenjiang trail section, Kunshan trail section. The main work and conclusions are as follows:(1) The physical and mechanical properties of medium&low compressible soil can be summarized as low natural moisture content (20%-27%), small void ratio (0.6-0.8),moderate or even low compression (0.5-0.13), nearly saturation, high undrained strength (90-140kPa). The degree of saturation of medium&low compressible soil from this paper’s trail section is different from the drought area in northern,which is generally unsaturated.(2) On-site monitoring shows that CFG pile net composite ground,or even sand pile composite ground whose subgrade had consolidated for4a,can meet the subgrade post-settlement control standard of the medium&low compressible soil ballastless track. About6m-high filling subgrade can effectively speed up the percentage of settlement completion during subgrade filling, reducing the preloading time of medium&low compressible soil.(3) The relative error between the practical engineering method and the on-site monitoring data is about60%.Considering the high relative error,this paper derives the analytical solution on the basis of pile-soil interaction.The relative error between the analytical solution and the on-site monitoring data is about17%-26%,which is significantly lower than practical engineering method.(4)Based on the previous settlement observation data of medium&low compressible composite ground,this paper summarized exponential decay law between consolidation coefficient and time from saturated and unsaturated medium&low compressible soil. With the help of exponential decay law,the paper calculated the future consolidation degree,whose variation law was similar to the measured settlement consolidation degree. The estimated consolidation degree can be used to calculate post-construction settlement.