Test And Theory Analyses On Silty Soil Liquefaction

As a major cause of site damage during earthquakes, soil liquefaction is an important subject in earthquake engineering and geotechnical engineering. Since Casagrande's works, significant progress has occurred. But, most of these are applicable for sandy soils. Based on the foundation "Liquefaction Test Study On The Rapid Railroad Bed" supported by the Railway Department, some works on the liquefaction of silty soils have been carried out. In this dissertation, after making a short review of the works on seismically induced soil liquefaction, some research results are presented, which include the following contents.(1)Depending on the dynamic triaxial test, the liquefaction strength of the silty soils is studied and two new models are proposed to evaluate the pore water pressure and the strain of the saturated silty soils during earthquake. And then, the two models are applied into analyzing the earthquake response of soil systems and estimating seismic soil liquefaction hazard. It is testified that the relative density of the silty soil deposit is an important influential factor of the seismically induced soil liquefaction.(2)Using the small shaking table test, the liquefiability of the silty soils under K0-consolidation state is studied. It proves the model of calculating the pore water pressure is available. Considering the similitude law for shaking table test, we study the test results and obtain some conclusions which are a) generally, the silty soil in test box liquefies and the liquefied time has relation with the amplitude of acceleration, b) when the intensity is on and above eight degree, the silty soil deposit will be liquefied dramatically, c) the relationship of the pore water pressure is relevant to the cycle loading which represents when the cycle loading ranges from little to great, the relationship isrepresent as a concave curve, or else as a protruding curve and tends to stability.(3)Based on the triaxial compression test and the resonant column test, some studies are made such as a) the Duncan-Chang parameters of constitutive model, b) the dynamic shear modulus ratio and c) the damping ratio of the site soil deposits. In order to deal with the test data, a computer program is compiled.(4) To determine liquefaction potential in site, several viable approaches are used, and these are (1) the Standard Penetration Test (SPT), (2) measurement of in-situ shear wave velocity (Vs), and (3) use of test data and Seed & Idriss method. Considering the non-linear of the soil, we calculate the earthquake response of the soil with the Hardin-Drnevich model and the finite element method. Finally, we estimate the liquefaction capability of the site during earthquake in Xuzhou, Jiangsu Province.