Theoretical Study On Earthquake-Induced Soil Pressures Of Light Weight Abutment Founded On Piles

The abutment founded on piles has become more and more widely used. It’s the key point to determine the seismic earth pressure reasonably in the process of designing an abutment. Mononobe-Okabe method is the way to determine seismic earth pressure of an abutment in different countries’current codes and scholar’s researches, which is based on the assumption that an abutment’s displacement will be enough so that the backfill generate a failure plane, and the corresponding earth pressure is called active earth pressure. For this reason, it’s appropriate for gravity abutment on non-rock foundation to determine the seismic earth pressure. As the displacement of gravity abutments on non-rock foundation and abutments founded on piles are restrained, the backfill may not rupture, and Mononobe-Okabe method cannot reasonably predict seismic earth pressure in actual earthquake anymore. In addition, with the increase of height of abutment, the flexibility of abutment gets smaller and the beam segment inertia force can cause deformation of abutment, which will cause the change of seismic soil pressure. It is necessary to study the earthquake response of the abutment. The main researches are as follows:(1)Present situation of study on anti-earthquake of abutment is summarized. Differences in codes of different countries and scholars’researches on the computational method of seismic soil pressure of abutment are revealed.(2)The key point of dynamic response analysis of abutment-soil system is to determine an appropriate dynamic artificial boundary. On the basis of viscous-spring artificial boundary, the corresponding boundary conditions are input by programming and the robustness of the boundary conditions is validated by an example. Meanwhile, the input mode of exogenous fluctuation is studied.(3) There are several different boundary conditions and the corresponding input method of an earthquake wave in the numerical simulation. By comparing their differences of the responses, a boundary condition and input method are determined.(4) A finite element model of abutment-soil system is established, and it’s characteristics of dynamic response are studied, which include earth pressure magnitude and distribution, distribution of internal force of pile and parapet. The influence of friction factor of abutment back and fill on dynamic response of the whole system is researched. The influence of Dynamic response of the system under different action of seismic waves is discussed. soil pressure distribution and action point under different peaks of the seismic wave are determined on the basis of the research, the computational method of design code has been revised. The influence of beam quality on seismic soil pressure of abutment is discussed and a revised method is put forth to calculate the pressure of soil due to earthquake on abutment founded with piles.