Static Triaxial Experimental Study Of Silty Clay For Passenger Dedicated Line Railway Subgrade

Subgrade is the basis of track,and also the key engineering of railway. Subgrade include five parts,are subgrade body, foundation bed, water supply and drainage facilities, foundation and ancillary buildings. The state of roadbed have a great impact of the transport efficiency and driving safety. Subgrade is constitute of the three-phase homogeneous material, possessing ela-stic, plastic and viscous.Its nature are complex, also the strength of the material and structural problems are difficult to master. In the natural environment, subgrade suffer a variety of adve-rse impacting of geological phenomena, rainstorm, temperature, earthquake and floods, which are caused by the complexity of the subgrade. For this reason, the subgrade engineering design must conform to the actual situation of the geological and geotechnical,in order to ensure the security and economy. In this thesis carrying out indoor triaxial tests using silty clay taken from Jilin to Hunchun railway passenger line and Wuhan to Guangzhou high speed railway passenger line. The main research work and conclusions are as follows:(1) Taking advantage of complex wall getting instrument to obtain undisturbed soil samples. As required, to every sample conduct editing number, packaging, transporting and storaging, storing in a cool and damp place to spare. On the basis of well-preserved, undis-turbed soil samples are cutted standard size samples getting help from cutting sample instrument and other assisting tools, then wrapped in plastic and stored in a moisturizing equipment. On the basis of air-dried, crushed powder and sifted, the soil samples reshaped were configurated corresponding to the target moisture content of soil samples according to the requirements of dry density and moisture content. To infiltration of day and night, the soil samples are divided into five parts with the sample, then strike dense stratified. Each contact surface planing hair, the same group sample density difference does not exceed0.02g/cm3.(2) In the triaxial consolidated undrained test, different damage criteria obtain different shear strength index and have greater impact on the cohesion values, lesser affect on internal friction angle; the standard base on peak deviatoric stress obtaining resist shear strength, using the effective stress method, the ultimate strain standard smaller1.7%to6.3%, pore water pressure standards smaller3.8%to21.2%, the peak effective principal stress than the standard deviation of0.3%to13.1%, effective stress path of the standard deviation of0.2%to4.8%; using total stress method, the ultimate strain standard smaller1.1%to4.7%, pore water pressure standards smaller21.5%to39.4%, the ratio of peak effective principal stress is smaller6.0%to20.0%. In the shearing process, the sample with the shear load increases gradually by an elastic state transition for the plastic deformation occurs in the axial direction, the sample lateral plastic deformation occurs slowly when the axial strain reaches a certain level, then the sample volume expansion until the hole pressure decreased sample was sheared breaking, the sample lateral deformation volume expansion state have appeared one after another.(3) In the process of static triaxial testing, the use of the coordinate axis and random error correction method with axial strain test curve correction and partial differential transformer (LVDT) displacement sensor for axial strain measurement, can effectively eliminate samplethe end portion caused by exposure to the test error; installed LVDT local displacement sensor sample by the ferrule role, strength of approximately5%to10%.(4) Taking advantage of three-way equal pressure consolidation test and consolidated drained shear test, calculated eight parameters of the Duncan-Chang model. On the basis of three-way equal pressure consolidation and equal P test, according to the Hydraulic Ministry of Electric Power (SDS01-79), to determine the K-G model parameters of the model. By three-way equal pressure consolidation, the consolidated drained shear test, consolidated undrained shear tests were calculated the two splicing Cambridge model. Three model parameters.are M,λ, κ.