The Deformation Analysis Of Stone Columns Composite Foundation Subjected To Earthquake

Artificial reinforced foundation would be put into practice, when natural foundation can not satisfy aseismatic requirements under intense earthquake action. Stone column composite foundation is specifically effective in protecting saturated sands from liquefying, which makes it the first choice to treat liquifiable sand foundations. So far, the research concerning the anti-liquefaction effect of the stone column composite foundation mainly focuses on the strength. However, as far as the safety of anti-earthquake is concerned, the problem of transformation should also be taken into consideration. The present thesis mainly researches the liquefaction and transformation of the stone column composite foundation under the action of earthquake, which mainly consists of the following aspects:(1) Analyze and compare the responding influence of natural sand foundations under cyclic loading and E1 Centro earthquake wave.(2) While numerical simulating stone columns composite foundation is exposed to various amplitudes of earthquake-waves, change parameters of stone columns, including column distance, column diameter and permeation coefficient, and compare excess pore pressure variations of inter-column soil of various depth of stone column composite foundation, and the characteristics of vertical deformation.(3) Analyze the excess pore pressure ratio change and transformation of inter-pile soil of various depths during earthquake, when the stone column composite foundation is effected by El Centra earthquake wave and with different loading conditions.(4) Calculate the deformation of consolidation settlement after earthquake under various working conditions.After the systemical and theoretical study on the liquefaction and deformation of stone columns reinforced composite foundation, it is hoped to make the following important conclusions:(1) The stone column demonstrates remarkable effect in improving anti-liquefaction of the foundation; it can effectively reduce the ascending deformation of soil units generated by earthquake liquefaction undergrounds; the underlying reason of stone columns reducing the ascending deformation due to the earthquake liquefaction of inter-column soil of various depth lies in that stone columns reduce the shear stress and effective drainage effect on liquefiable soil, thereby effectively suppressing the deformation and mobility of foundation soil layer.(2) While the anti-liquefaction of stone columns increase with different engineering parameters, the increasing ratio of its excess pore pressure decreases, and the vertical deformation of inter-column soil units reduces, which can significantly inhibit deformation of the field.(3) Within the foundation bearing capacity, the increase of the load on the upper part of the composite foundation can effectively reduce the excess pore water pressure of the foundation generated by the effect of dynamic load during earthquake, which is of equal effect to the compaction of stone columns. However, with the increase of the load on the upper part, the foundation liquefies and its bearing capacity reduces, which results in bigger vertical settlement and lateral deformation during strong earthquake.(4) It is found through composite modulus method that the vertical settlement of the composite foundation is caused by dissipation of post-earthquake pore pressure. The earthquake amplitude has a significant influence on post-earthquake settlement, and the bigger the amplitude is, the greater the settlement will be. The settlement varies with the change of stone columns parameters, which demonstrates that stone columns should be distributed rationally and the influence on aseismatic performance of stone columns from soil impurities should be reduced to the greatest extent in course of construction.The larger the load on the upper part is, the smaller the excess pore pressure of composite foundation is, and the post-earthquake settlement will decrease consequently..