地基固结和再固结过程中桩基础轴力与沉降计算方法

Method for calculating axial force and settlement of pile foundation in consolidating and reconsolidating ground

在地基固结和液化后再固结过程中,土体会对桩基础产生负摩阻力。负摩阻力作用下桩基础的轴力和沉降常采用中性面方法计算,但事实上中性面方法的几个基本假定可能导致计算结果相对实际产生显著偏差。针对地基固结和震后再固结过程中负摩阻力引起的桩基础的轴力和沉降进行研究,采用随固结过程更新桩土摩擦力峰值的非线性温克尔地基梁方法,建立相应计算方法。该方法能够充分考虑固结过程对桩基础轴力和最终沉降的影响,并给出轴力和沉降的变化过程。与离心模型试验对比的结果显示,在采用合理的固结计算方式的基础上,该方法能够有效地计算地基固结和震后再固结过程中桩基础的轴力与沉降,对沉降的计算精度高于传统中性面方法。

The neutral plane solution has been widely used to estimate downdrag settlements and drag loads mobilized in piles in consolidating soil profiles. However, some of the basic assumptions made by the neutral plane solution may cause the calculated results to significantly deviate from the actual values. A beam on nonlinear Winkler foundation(BNWF) solution, in which the shaft friction capacity is updated as consolidation progresses proportional to the effective stress, is proposed to analyze the axial force and settlement of piles during consolidation and post-earthquake reconsolidation. The proposed method fully considers the effect of consolidation process on the axial force and final settlement of piles. The axial force and downdrag settlement by the proposed BNWF solution is compared with the measured ones from centrifuge tests on piles in both consolidating and reconsolidating ground. The proposed method produces more accurate estimates of pile settlement than the traditional neutral plane solution.