负温对基坑悬臂桩水平冻胀力影响的模拟研究

Simulation studies of effect in foundation pit cantilever pile of horizontal frost heaving force under negative temperature

寒冷地区基坑悬臂桩支护工程,在桩后土体水平冻胀力作用下,易出现桩体倾斜、水平裂缝、剪断等问题.负温是水平冻胀力产生的关键因素,采用数值模拟方法,分别模拟粉质黏土、黏土在一定的负温变化下,桩体水平冻胀力的大小和分布模式,结果表明：负温越低,土体冻结速率越大,水平冻胀力越大;桩身范围内,水平冻胀力大致呈上下小、中间大的抛物线型分布,最大值出现在基坑的中下部,为开挖深度的0.5~0.8倍,力值约为冻胀前土压力的2~15倍,同时拟合出最大水平冻胀力与温度、桩顶位移之间的关系公式;此外,桩体水平位移随负温增加而增加,桩顶位置处,冻胀引起的水平位移为开挖引起位移量的0.88~11.38倍.

Supporting project of foundation pit cantilever pile in cold area,under the horizontal frost heaving force of soil,the pile may be appear these problems,such as tilt,horizontal crack or cut. Negative temperature is key factor of horizontal frost heaving force,with numerical simulation method,simulated silt clay,clay under certain negative temperature change,the size and distribution of pile horizontal frost heaving force,results showthat negative temperature is lower,the greater soil freezing rate,the larger horizontal frost heaving force; In the length of pile,horizontal frost heaving force is roughly fluctuation and large middle parabolic distribution,maximum value appeared in the foundation pit of the part,is 0. 5- 0. 8 times depth of excavation,frost heaving force value is 2- 15 times to the initial soil pressure. And fitting out formula of maximum horizontal frost heaving force with temperature or displacement of pile top in respectively. In addition,the horizontal displacements of pile increases with decrease of temperature,horizontal displacement caused by frost heave is 0. 88 to 11. 38 times of excavation displacement in pile top.