Experimental Study On Creep Characteristics Of Slip Soil And Its Influence On The Stability Of The Landslide

This paper is based on the field investigation and a large number of the sliding zone soil samples of Lama ancient landslide by the Meigu river. And the creep properties of the sliding zone soil are studied. On this basis, combined with the characteristics of the engineering geological condition of Lama ancient landslide, the dynamic stability of the slope is evaluated and the mechanism of partial revival of the ancient landslide is also analyzed and evaluated, using the changing strength parameter over time of the sliding soil obtained by creep tests. The main results obtained are as follows:(1) Using the direct shear creep test instrument own modified, the slip zone soil of Lama ancient landslide is carried out direct shear creep tests. The test results show that the creep characteristics of the slip zone soil of Lama ancient landslide subject to different vertical stress and the effects of different levels of shear stress is very significant. Under the same conditions of shear stress level, direct shear creep properties of sliding soil with increasing vertical stress decreases. While under the influence of the same vertical stress with increasing shear stress level, creep behavior is increasingly evident, creep curves showing overall attenuation constant, acceleration and other states.(2) In this paper, the empirical of power relationship and logarithmic relationship is established using the empirical model theory and based on the test results. By comparing the two empirical model found that the relationship of the power models are better able to react nonlinear creep characteristics of slip zone soil. And a power-law with less parameters, easy to use and other advantages, can provide a theoretical basis for the analysis of landslide deformation.(3) On the basis of the experimental results, the long-term strength theory of soil rock and soil and failure criterion under long-term load, this paper established a long-term strength equation which can well describe the power-law creep characteristics of the Lama ancient landslide. Compared the experimental values with the theoretical value obtained by the long-term strength of the equation, the calculated values can be seen a good agreement with the theoretical value in the case of the use of long-term equation. Which indicate that the theoretical calculation method is accurate and reliable. Therefore, the calculation of slope stability analysis has a reliable theoretical basis for the use of long-term strength of the theory in engineering practice.(4) According to the long-term strength parameters of different time condition obtained by long-term strength theory, the stability calculation of four different surfaces landslide are carried out. Compared those computational results with results by routine testing parameters, it shows: slope stability using rheological parameters calculated by the time of the impact is obvious. In the long-term load effect, the reducing of rock and soil strength parameters are controlling factors affecting slope stability.(5) In this paper, the revival mechanism of local ancient landslide is analyzed. In the long process of geological history, the ancient landslide was in stable state, the shear stress of slip zone soil is less than the long-term strength. At this time, slide zone soil is in the state of attenuation creep, creep rate tending to zero. There will not have a constant velocity or acceleration phenomenon. The amount of deformation is essentially the same. However, the human activity such as switching station building on the ancient landslide has destroyed the original equilibrium state of the ancient landslide. So, the shear stress levels is more than the value of long-term strength of sliding soil. In this case, creep rate increases. At this time, constant creep state began to appear. As time increases, the micro-cracks and other defects inside the soil develop further and the strength parameters reduce further. This time, the creep deformation began transformed into a stage from the constant to the acceleration, until the rapid destruction of the landslide. Therefore, the governance of the resurrection of the ancient landslide which is happening creep deformation, should try to choose the moments that creeping early stages, at which the strength of soil reduce smaller.