基坑被动区加固的位移控制效果及参数分析

DISPLACEMENT CONTROL EFFECTS AND PARAMETER ANALYSIS OF PASSIVE ZONE IMPROVEMENT OF FOUNDATION PITS

以武汉地铁2号线积玉桥站为背景,采用三维弹塑性数值模拟的方法,考虑地下水渗流及土体的固结,研究被动区加固下地下连续墙的水平位移及坑外地表沉降的分布规律,并将计算值与现场实测结果进行对比,验证数值计算模型的合理性。以此模型为基础,对裙边加固和抽条加固的主要参数及布置形式进行深入的探讨。研究结果表明,被动区加固对变形的控制效果是非常显著的。裙边加固宽度和裙边加固深度都存在一个有效范围,当超出该有效范围后,加固效果的提高幅度不显著。当裙边加固宽度与加固深度相当时,加固效果最优。在裙边加固参数不变的情况下,被动区加固的作用效果主要与抽条加固的置换率有关,与其断面形状、布置形式等基本无关。

Based on the deep foundation pit of Jiyuqiao Station of Wuhan Metro Line 2,a three-dimensional elastoplastic numerical simulation model is established. In this model,the groundwater seepage and soil consolidation effect are both considered. The ground settlement and lateral displacement of diaphragm wall are calculated;and the basic deformation characteristics of the foundation pit are studied. Then,the calculated results are compared with field data to verify the rationality and accuracy of the numerical model. Finally,the main factors and arrangement pattern of passive zone improvement,which both have influences on the magnitude and distribution of the foundation pit deformation,are analyzed. The results show that the displacement control effects of passive zone improvement are significant. Preferably,the width and depth of skirt border improvement should not be too large. When the width（or depth） exceeds a certain value,the increasing rate of improving effect will be very little. The optimum improving effect can be obtained when the width and depth of skirt border improvement are approximately equal. On the assumption that the parameters of skirt border improvement are unchanged,the improving effect is mainly determined by the replacement ratio of the strip improvement;and it is basically irrelevant to the arrangement pattern of passive zone improvement.