基坑土体变形性状研究

Research on Deformation Character of Foundation Pit Soil

为提高用于基坑设计计算的土体参数的合理性、准确性 ,以准确预测基坑开挖中围护结构及周边土体位移 ,针对基坑开挖过程中基坑周边土体中可能出现的应力状态 ,用应力路径三轴试验进行模拟 ,进行一系列饱和原状土的三轴K0 固结不排水剪切试验。通过应力路径试验获知基坑开挖过程中土体的应力应变关系近似呈加工硬化双曲线型 ,推导了土体的弹性模量公式 ,并在试验数据的基础上拟合确定了该公式中初始弹性模量的取值方法。将应力路径研究结果和常规三轴压缩试验获得的参数分别应用于同一实际工程进行有限元计算。有限元计算结果与实测数据进行对比分析后认为 :应力路径试验方法较之常规三轴压缩试验方法获得的参数更理想 ,推导出的弹性模量计算式 ,可用于基坑工程变形计算 ,可供基坑工程设计参考。

In order to improve rationality and correctness of soil parameters (used for foundation pit design so as to predict correctly the displacement of soil and maintenance structure around the pit during the process of pit excavation),this paper uses stress path triaxial test to simulate the possible stress state of soil around the pit during the process of excavation. The test does a series of triaxial K_0 concretion non-drainage experimentations of saturated original state soils. According to stress path experimentations,the shape of stress-strain curve is near to machining rigidification hyperbola,the equation of elastic modulus is induced and the initial value of elastic modulus is given based on experimentation data fitting. This paper applies the results of stress path and parameters gained by routine triaxial compress test to the same practical engineering respectively and gives a calculation with FEM. Comparing the results of FEM calculation with data which are measured,parameters gained by the stress path test method are more ideal than parameters gained by routine triaxial compress test. The elastic modulus formula which is induced may be used to calculate foundation pit distortion and may be used as a reference for foundation pit design.