Experimental Study on Physical and Mechanical Characteristics of Silty Clay for High-Speed Railway Subgrade Filler
|School||Southwest Jiaotong University|
|Course||Road and Railway Engineering|
|Keywords||Roadbed filler Silty clay Physical and mechanical properties Conventional soil test Dynamic triaxial test|
Railway embankment as an important part of the track structure based mainly constituted by the loose earth and rock material. Have sufficient strength to achieve the roadbed subgrade strength and stability of the structure by natural conditions, the upper load the roadbed fill a variety of factors such as the impact, stiffness, uniformity and long-term stability requirements, strict control on the roadbed filler very necessary. Fine particles of soil is widely distributed in China, railway construction is often due to the lack of quality packing and extensive use of fine-grained soil as subgrade fill. Therefore, significant experimental study of the physical and mechanical properties the roadbed fine particles of soil filler. Sand silty clay taken from the test section of the Wuhan-Guangzhou high-speed railway Wuhan containing comprehensive indoor soil test, research work and conclusions are as follows: (1) the test soil samples particle density, particle analysis, limit water rate, compaction, infiltration, consolidation routine soil test. Determined according to the classification criteria of the soil sample silty clay containing sand (CLS); For the the unit volume compactive same railway geotechnical test standards Z1, Z2, Z3, compaction cylinder size and compaction layered the specimen compaction test results are less affected negligible; stable soil consolidation faster, saturated soil compression than the optimum moisture content 95% degree of compaction of the sample belongs to moderate compression large; 92% and 95 % degree of compaction sample permeability coefficient of approximately i × 10-7cm / s (i = 1 ~ 10), the smaller the higher the permeability of the degree of compaction. (2) by direct shear test, triaxial CU test, CD trials, the average primary stress setting consolidated drained shear (p) test measures the different test conditions of soil shear strength. P test as triaxial CU test CD test the resulting effective stress shear strength index decreases in turn; the saturated specimens consolidation of 95% degree of compaction slow direct shear test shear strength parameters obtained with triaxial CD test is basically the same larger, the difference does not exceed 3%; triaxial CU test, with the degree of compaction to improve the stress-strain curve of the soil by strain hardening to strain softening transformation sample shear strength index is influenced by the degree of compaction; different undermine the standard values ??of soil internal friction angle greater impact, less impact on cohesion; static triaxial test specimen with increasing shear loads in the elastic state first produce axial plastic deformation, when the axial strain up to a certain extent, the sample began to appear lateral plastic deformation and subsequent presentation to volumetric expansion, until the pore pressure drop shear failure. The specimen lateral deformation volume expansion state has tightly appeared static deviator stress corresponding to approximately 60.5% of the ultimate static strength. (3) the static triaxial trial process, coordinate axis and random error correction method to test with axial strain curve correction and partial differential transformer (LVDT) displacement sensor axial strain tests, can effectively Elimination of the specimen contacts the end portion to bring the test error; LVDT local displacement sensor sample is installed by the role of the ferrule, the intensity increased by about 5% to 10%. (4) by unidirectional compression vibration, one-way pull pressure vibration and bi-directional vibration load triaxial test comparing the the of different vibration load the sample dynamic nature. Saturated sample of 95% degree of compaction in unidirectional compression vibration triaxial tests, mainly for vibration compaction and dilatancy damage, increase in the amplitude of the dynamic stress at different stages of the samples showed the start of lateral deformation, start volume expansion the start hole pressure decreasing in the different state. Dynamic triaxial test and two-way dynamic triaxial test unidirectional tension and compression, the plastic deformation of the specimen to the main compression zone, gradually vibration density, pore pressure gradually increases, causing the soil to soften, destruction phase exhibit pore pressure fluctuations Obviously, increasing axial deformation and dynamic stress attenuation significantly. 95% degree of compaction of saturated specimen dynamic strength test confining pressure is substantially linear growth law; one-way the compressed dynamic triaxial test and one-way tension and compression dynamic triaxial test impact strength of the vibration frequency of the sample move small.