冻土直墙用于基坑支护的研究

APPLICATION OF LINEAR FROZEN SOIL WALL TO SUPPORT OF FOUNDATION PIT

根据相似理论并考虑工程因素,推导了直线形冻土墙用于基坑支护时其温度、变形的相似准则方程,进行了模化设计,对砂土冻土墙的温度分布和变形特征进行了模拟试验研究。研究表明:冻土墙的温度分布曲线近似为直线;用一定厚度的泡沫塑料板对冻土墙保温是可行的和方便的;冻土墙变形由转动变形、弹性变形及较大的蠕变变形组成;墙体变形随其厚度增大呈非线性减小,而随土压力增大呈非线性增大;墙体暴露时间与其变形之间呈幂函数关系。在此基础上对冻土墙的设计方法进行了探讨,提出了冻土墙厚度设计的变形约束条件和冻土墙有效厚度的概念。认为冻土墙有效厚度的确定必须综合考虑冻土墙的温度分布特性、墙体的抗倾覆稳定性、强度条件和变形约束条件等几个方面的因素。

Based on the similarity theory and the engineering factors,the equations of similarity rule are deduced on the temperature and deformation of a linear frozen soil wall for protecting deep foundation pit. The simulation design and model tests are made to study the temperature and deformation of frozen soil wall. The results indicate that the temperature distribution of frozen soil wall is approximately linear. It is feasible to use foam plates to keep the low temperature of frozen soil wall. The deformation of frozen wall is composed of rotational,elastic and bigger creep deformations,and it nonlinearly increases with the ground pressure and nonlinearly decreases with wall thickness. There is a power function relationship between wall抯 exposing time and the deformation. The design method for frozen soil wall is also discussed. The deformation constraint condition and the concept of effective thickness are put forward for frozen soil wall,and all the factors should be comprehensively considered for the determination of effective thickness of frozen soil wall,such as the temperature distribution,the stability against overturn,the deformation constraint condition and the strength condition of frozen wall for protecting deep foundation pit.