基于改进西原模型的厚冲积地层基坑结构回弹参数敏感性分析

通过在传统西原本构模型中串联Newton体,可准确追踪黄河厚冲积黏土地层中土体卸荷后的非稳定蠕变力学行为特征。以济南省文化艺术中心大厦深基坑为工程背景,采用现场监测数据分析、统计建模和FLAC^3D二次开发数值模拟相结合的方法进行模型优化和改进西原方程的参数辨识,分析了围护桩的不同插入比、桩边尺寸及桩间净距3种情况下基坑卸荷导致的底板上移规律,以及立柱桩入土深度、插桩位置及桩型对基坑开挖过程中立柱桩的回弹特性的影响。结果表明底板上移对参数的敏感程度大小为围护桩净距＞插入比＞桩边长;立柱桩回弹对参数的敏感程度大小为立柱桩入土深度＞插桩位置＞桩型。利用此规律可有效降低基坑开挖对工程桩及底板隆起的影响,确保了济南省文化艺术中心大厦深基坑的施工安全、优质,为同类地层深基坑控制立柱桩及底板隆起提供了设计经验和参考。

Sensitivity Analysis of Foundation Pit Rebound in Thick Alluvial Clay Based on Improved Nishihara Model

The upward displacement of pile and floor is a damage for the balance of support system during the excava -tion foundation of pit in thick alluvial clay Nishihara model improved with Newton fluid could well describe the behav -ior of creep deformation during pit excavation ,and also trace the behavior of interface between pile and soil .The regu-larities of upward displacement of floor in the presence of different ratios of inserted pile depth to excavation depth , side lengths and spacings of support pile ,as well as the rebound of column pile in the presence of different depths in soil,positions and types of column pile were analyzed via field data ,improved Nishihara model and secondary develop -ment of FLAC 3D .The deep foundation pit of Culture Center of Jinan Province was taken as an engineering background . Results revealed that the sensitivity of the upward displacement of pit floor to different factors follows the order of :dis-tance of adjacent support pile >ratio of inserted depth to excavation depth >length of support pile; and the sensitivity of the rebound of column pile follows the order of depth of column pile in soil >position of pile>shape of plie.The results could be a guidance for reducing the influence of excavation on the upward displacement of pile and floor .