应用切线模量法计算天然地基沉降的探讨

Discussion on the application of tangent modulus method in settlement calculation of natural foundation

依据地基土层的c、φ、E0三个参数模拟载荷试验时,变形计算深度取2倍的载荷板宽度或直径,初始切线模量按变形模量取值;模拟实际基础沉降时,变形计算深度按高层建筑勘察标准取值,初始切线模量按2倍的变形模量取值,当采用硬塑-坚硬的黏性土作天然地基筏板基础时,变形模量取4倍的压缩模量;当采用密实的砂层作天然地基筏板基础时,变形模量取3倍的压缩模量,运用切线模量法进行载荷试验的模拟和实际基础下的沉降计算,通过两个实例的分析,得到了不同基底压力下的安全系数和沉降值,满足了地基强度安全和变形控制的双控原则,可为地基基础的初步设计提供更好的参考。并指出后续应用时应考虑初始切线模量随基础尺寸、土层深度的变化规律,载荷试验数据的时间效应修正等问题。

When the three parameters of c、φ、E0 of the foundation soil layer are used to simulate the load test,the deformation calculation depth is taken as twice the width or diameter of the load plate,and the initial tangent modulus is taken as the deformation modulus.When simulating the actual foundation settlement,the deformation calculation depth is taken according to the survey standard for high-rise buildings,and the initial tangent modulus is taken as twice the deformation modulus.When the hard plastic clay soil is used as the raft foundation of natural foundation,the deformation modulus is taken as 4 times the compression modulus.When the dense sand layer is used as the raft foundation of natural foundation,the deformation modulus is taken as 3 times of the compression modulus.The tangent modulus method is used to simulate the load test and calculate the settlement under the actual foundation.Through the analysis of two examples,the safety factors and settlement values under different foundation pressure are obtained,which satisfies the double control principle of foundation strength safety and deformation control,and can provide a better reference for the preliminary design of foundation.The subsequent application should consider the change of the initial tangent modulus with the size of the foundation and the depth of the soil layer,and the correction of the time effect of the load test data.