Study On Soil Pressure Of Abutment Founded On Piles And Its Influence Factors Under Earthquake Action

Studies on Wenchuan Earthquake show that,the collapse of abutments are mainly due to overloads of seismic soil pressure.Hence,the key problem in a seismic design of abutments is to determine the seismic soil pressure on the backwall properly.Abutment founded on piles,a kind of widely used abutment,is seldom studied about its seismic soil pressure.At present,in china,the calculation of seismic soil pressure on abutments in design code is based on Mononobe-Okabe method.In the assumption of this method,the displacement of abutments is enough to cause fracture and glide plane in the earth filling behind abutments.In this case,the soil pressure is called active earth pressure.When determining the seismic soil pressure on the backwall,it is appropriate for gravity abutments.However,for the abutments founded on piles,due to limitation of its displacement,there may not be any fracture plane in the soil behind the abutment.In that case,when the earthquake occurs,the seismic soil pressure on the abutment cannot be reasonably predicted any more using Mononobe-Okabe method,so it is imperative to conduct research on the seismic response of abutment founded on piles.Seismic response of abutments founded on piles under earthquake are analyzed by using ABAQUS finite element software in this thesis.Main works are as follows:(1)Calculation methods of seismic soil pressure in Chinese,Europe,Japanese and New Zealand codes are introduced and the differences are compared by using some calculation examples.Similarities and differences in the design codes between other countries and us are summarized.(2)Abutments founded on piles model is set up by finite element method.The characteristics of seismic response of abutments founded on piles under horizontal seismic wave are studied,including the size and action point of resultant force of soil pressure on the backwall and distribution characteristics of soil pressure on the abutment and its internal force.The seismic response of abutments founded on piles at different peak accelerations and seismic wave time are also studied and modification suggestions for Chinese design code are proposed.After that,the impact of parameters of site condition on seismic soil pressure on the abutments founded on pile are analyzed.(3)The characteristics of seismic response of abutments founded on piles under combined action of horizontal.and vertical Kobe seismic wave are studied.The result of seismic soil pressure and internal force of abutments founded on piles are compared with that only under horizontal seismic wave,so that the impact of vertical seismic wave on the seismic soil pressure on abutments founded on piles can be obtained.