软土地基基坑开挖对临近桩变形影响的时效分析

为解决软土地基基坑开挖条件下，邻近桩基水平位移随时间逐渐发展的问题，结合两阶段分析方法，第一阶段引入三维分数阶Merchant黏弹性模型来描述软土的蠕变特性，采用对应性原理和Laplace积分变换方法，求得附加应力的Mindlin时域解；第二阶段将桩基看作Pasternak地基上的Timoshenko梁，将所得附加应力加载在桩基上，建立桩基的变形微分方程，利用有限差分法对方程进行求解，得到考虑桩基剪切效应及桩土剪切层厚度的桩基水平位移时域解. 通过与已有文献中的算例进行对比，验证了该方法的正确性. 最后，对三维分数阶Merchant黏弹性模型参数（剪切模量、体积模量、黏滞系数、分数阶）进行了影响因素分析. 结果表明，所得方法能够较好地反映基坑开挖引起邻近桩基水平位移随时间的发展规律.

Time-Effect Analysis on Influence of Excavation on Adjacent Pile Deformation in Soft Soil

In order to solve the problem that the horizontal displacement of adjacent pile foundation gradually develops with time under the condition of foundation pit excavation in soft soil foundation, a two-stage method is used for analysis. In the first stage, a three-dimensional fractional Merchant viscoelastic model is introduced to describe the rheological properties of soft soil. Combining with the correspondence principle and the Laplace transformation method the Mindlin time-domain solution of the additional stress is obtained. In the second stage, regarding the pile foundation as Timoshenko beam on the Pasternak foundation, the additional stress is loaded on the pile foundation, and the differential equation of pile foundation deformation is established. On this basis, the time-domain solution of horizontal displacement of the pile foundation considering the shear effect of the pile foundation and the thickness of the pile-soil shear layer is obtained through the finite difference method. The correctness of the proposed method is verified by comparing it with the results of existing literature. Finally, the influencing factors of the three-dimensional fractional Merchant viscoelastic model parameters (shear modulus, volume modulus, viscosity coefficient, fractional order) are analyzed. The results show that the numerical solution can well reflect the development law of horizontal displacement of adjacent pile foundations caused by foundation pit excavation with time.