冻融循环对长春典型土层深基坑开挖变形及稳定性影响分析

Analysis of Effects of Freeze-thaw Cycles on Deformation and Stability of Deep Foundation Pit Excavation in Typical Soil Layers in Changchun

为了探究冻融循环作用对长春典型粉质黏土为主的土层下深基坑开挖的变形及稳定性影响,以吉林大学第一医院地下停车场工程为研究对象,通过有限元软件Plaxis2d进行数值模拟,对适用于长春典型土层受一次冻融循环影响下的土体工程相关参数折减系数进行甄选,确定对基坑变形影响最大的三个参数土体粘聚力c、内摩擦角φ和弹性模量E分别进行0.99、0.98和0.96的系数折减能有效地反映其受一次冻融循环下地变形特性,与实测值作比较误差较小。在此基础上分析三者对桩锚式基坑变形的影响程度,发现受冻融影响下的土体参数改变后对基坑支护变形影响最大的是内摩擦角φ,下降10%时基坑桩身水平位移增大27%;其次是弹性模量E下降10%时桩身水平位移增大21%;而粘聚力c对基坑变形影响较小。

In order to explore the influence of freeze-thaw cycle on the deformation and stability of deep foundation pit excavation under typical silty clay in Changchun,the underground parking lot project of the First Hospital of Jilin University was taken as the research object and numerical simulation was conducted by finite element software Plaxis2d.The reduction coefficients of soil engineering parameters applicable to typical soil layer in Changchun under the influence of a freeze-thaw cycle are selected.The reduction coefficients of 0.99,0.98 and 0.96 of soil cohesion c,internal friction angle φ and elastic modulus E,which have the greatest influence on foundation pit deformation,are determined to effectively reflect the soil deformation characteristics under a freeze-thaw cycle.Compared with the measured value,the error is small.On this basis,the influence degree of the three factors on the deformation of pile-anchor foundation pit is analyzed,and it is found that the internal friction angleφis the biggest influence on the deformation of foundation pit support after the soil parameter changes under the influence of freeze-thaw,and the horizontal displacement of foundation pit pile increases by 27% when only 10%is decreased,followed by the elastic modulus E value,which increases the horizontal displacement of pile body by 21% when 10% is decreased.The cohesive force c has little influence on the deformation of foundation pit.