Dynamic Triaxial Test Of Soils From Yigong Rock Avalanche

Around at8pm on April9th2000, a large rock avalanche (rock fall-debris flow) occurred in the Yigong village of Bomi county, southeastern Tibet, the resulted deposits of the landslide formed a dam that entirely blocked the Yigong River. The volume of the landslide deposits is more than3.0x108m3. The oversize rock collapse and huge debris of Yigong landslide ranks the largest non-earthquake event occurred in China over the past century, with total vertical drop of up to3km, the long run-out is8km, and the maximum speed of44m/s. There appear some phenomena extremely rare in other landslides, therein sandboils is the unique phenomena as a strong evidence for liquefaction of the Yigong landslide.In this thesis, by use of MTS dynamic triaxial testing system the test of liquefaction strength of soils, sampling from Yigong landslide deposition, is made to simulate the scene of saturated environment in the different confining pressure by the effect of impact load and vibration loads. The main contents including as follows:(1) Making the soil sample by the disturbed soil on the debris flow of Yigong landslide for the consolidated-undrained triaxial test by the random impact load and vibration loads.(2) Making the experiment with different confining pressure as a control condition, for simulating the liquefaction phenomena in deep soils of Yigong debris mass.(3) Analysis the time curves of liquefied soil in the different confining pressure by the effect of random impact load. The liquefaction process is divided by times according to the different behavior of hysteresis loop, during which the development characteristics of axial strain are analyzed. According to the developments of axial strain with the effective stress path and the pore pressure the deformation characteristics of liquefaction is analyzed.(4) The pore pressure-time curves of the liquefaction process for soil samples under random vibration loads and the pore pressure-time curves with different confining pressure are analyzed thoroughly. Considering the stress-strain curves, the relationship between stress and strain during the process of liquefaction is studied. In addition, the related liquefaction curves and the load-strain hysteresis loop under random as well as regular vibration are discussed comparatively.