深基坑剪力键支护模型优化研究

为寻求深基坑剪力键支护模型的优化形式,在剪力键支护体系构想与模型试验的基础上,设计了3组剪力键与直立桩之间不同组合形式的试验方案,在模拟基坑开挖过程中,对各方案中支护模型的桩顶水平位移、桩身内力及基坑外侧填土表面的沉降进行监测,同时设计了4个系列12组剪力键模型方案进行有限元数值模拟。结果表明:斜向桩与腰梁连接的节点位于直立桩桩身处的剪力键组支护效果优于斜向桩与腰梁连接的节点位于相邻直立桩中间的剪力键组; 腰梁位于直立桩上部的剪力键组支护效果优于腰梁位于直立桩中部和下部的剪力键组; 腰梁高度对支护效果的影响大于斜向桩与直立桩连接节点位置的影响; 剪力键模型的支护效果与斜向桩和竖向的夹角非正相关,并且在实际工程中夹角越大所占用的地下空间越大,基于数值模拟可认为斜向桩与竖向的夹角30°为剪力键支护结构的适宜角度; 斜向桩与腰梁连接的节点位于直立桩桩身处、斜向桩与竖向夹角30°且腰梁位于直立桩上部的剪力键组是较优的支护形式,这些成果可为剪力键支护技术的开发与应用中提供借鉴。

Optimization Research on Deep Foundation Pit Shear Bond Supporting Model

In order to find the optimal form of deep foundation pit shear bond supporting model based on the conception and model test of the shear bond supporting system in the early stage, a scheme including 3 tests for various combinations of shear bonds and vertical piles was designed. In the process of simulating the foundation pit excavation, the horizontal displacement of the pile top, the internal force of the pile body and the settlement of the fill surface were monitored, and the finite element numerical simulations including 4 series and 12 sets of shear bond model plan were carried out. The results show that the shear bond supporting system which has the joint of the inclined pile and the waist beam close to upright pile is better than that with joint at the middle of the adjacent upright piles, the supporting system with the waist beam at the upper part of the upright piles is better than that at the middle or lower part of the upright piles, and the influence of the height of waist beam on supporting effect is greater than that of joint position between inclined pile and vertical pile. Supporting effect of the shear bond model is not positively correlated to the angle between inclined pile and vertical direction, and the larger the angle in practical engineering, the larger the underground space will be occupied, so it can be assumed that 30° will be an appropriate angle for the shear bond support system based on numerical simulations. Thus, the model group with joints connecting the oblique piles and the waist beam close to upright piles,the angle of 30° between inclined pile and vertical direction, and the waist beam at the upper part of the upright piles is considered to be a superior supporting system, which can be used for reference in the development and application of shear bond support technology.