深基坑双排桩支护结构在地震作用下的力学特性研究

Study on Mechanical Characteristics of Double Row Pile Supporting Structure in Deep Foundation Pit Under Earthquake

以武汉时代广场深基坑项目为背景,运用有限元数值软件建立三维数值模型,结合黏弹性人工边界并对所选地震波进行基线处理,并针对双排桩设计参数和场地土体参数进行地震作用下的敏感性分析.结果表明:①双排桩的桩排距在3~5倍桩直径时,可以提升结构的整体稳定性,但桩排距大于5倍桩直径时,排架结构对双排桩水平位移的限制作用将减弱;②通过减小双排桩的桩间距可以有效地减小桩身的最大水平位移值,从技术和经济的角度综合考虑,最佳桩间距为1.6~2倍桩直径;③桩弹性模量从25 GPa提高到40 GPa,桩土位移及桩身内力变化不太明显,因此当桩弹性模量达到一定值后,再提高其值对支护结构意义并不大;④不同的场地条件,土层物理参数相差很大,其地震动荷载的响应存在着较大的差别.

Taking the deep foundation pit project of Wuhan Times Square as the background,a three-dimensional numerical model was established by using finite element numerical software,and the selected seismic waves were baseline processed by combining with viscoelastic artificial boundary.The sensitivity analysis of double-row pile design parameters and site soil parameters under earthquake action was carried out.The results show that:①When the pile spacing of double-row piles is 3~5 times the pile diameter,the overall stability of the structure can be improved,but when the pile spacing is greater than 5 times the pile diameter,the limiting effect of bent structure on the horizontal displacement of double-row piles will be weakened.②The maximum horizontal displacement of pile body can be effectively reduced by reducing the pile spacing of double-row piles.Considering comprehensively from the technical and economic point of view,the optimal pile spacing is 1.6~2 times the pile diameter.③When the elastic modulus of pile is increased from 25 GPa to 40 GPa,the displacement of pile and soil and the internal force of pile body do not change obviously,so when the elastic modulus of pile reaches a certain value,it is of little significance for the supporting structure to increase its value.④Under different site conditions,the physical parameters of the soil layer are quite different,and the response of the ground motion load is quite different.