复合地基沉降影响因素的半解析元分析

采用半解析有限元，将复合地基的位移水平两个方向上选取解析函数，竖向离散为多项式，并将复合地基视为横观各向同性材料，克服了有限元法中人为设定计算边界、计算量大的弊端，将三维沉降问题转化为一维问题计算，收敛速度很快，显著减少了计算工作量，提高了计算精度．通过改变复合地基置换率、加固深度，桩土模量比和水平加固范围，研究了复合地基的加固效果．计算结果表明，增大置换率，桩土模量比和水平加固范围，对减小沉降作用很小，而增加加固深度能明显的减小复合地基沉降．因此，在以控制沉降量为主要目的复合地基优化设计中，应首先考虑增加加固深度．

Study on the affecting factors of composite foundation settlement by semi-analytical element method

Based on the principle of semi-analytical method and the assumption of transversely isotropic material of composite foundation,a semi-analytical element method,which it used to calculate the settlement of composite foundation,has been presented in which the displacements are modeled by means of analytic functions in two horizontal directions and discretized as polynomial expressions.For one direction discrete and two directions analytical,this method can simplify the 3-dimensional computation of displacement to one dimension,which can save computation time dramatically for its quick convergence.Furthermore it can simulate infinite soil field,avoide introducing the redundant boundary condition compared with FEM,and can acquire precise results.An example has been calculated with semi-analytical element method by changing the substitution ratio,improving the depth and modulus ratio of pile to soil of composite foundation.The results indicate that increasing the substitution ratio and the modulus ratio of pile to soil has negligible effect to reduce displacement,while improving the depth can affect the settlement obviously.So it is reasonable to increase the improved depth to reduce composite foundation settlement where the optimum design is controlled by ground settlement.