粉质黏土深基坑土钉墙支护作用机理模型试验研究

以相似理论为基础,确定模型试验的相似比,然后按照相似比的要求选定相似材料,建立试验所需的土钉墙物理模型。设计合理的测试系统、加载系统模拟基坑开挖、土钉墙支护及降雨过程。测试整个试验过程中的土钉墙的墙顶水平位移、土钉内力、土压力等。试验结果表明,基坑开挖引起土体应力重新分布是影响土钉墙墙顶水平位移变化的主要因素,且每步开挖均都会引起墙顶水平位移呈台阶式增大,在土钉墙的施工阶段墙顶最终水平位移达基坑开挖深度的2.3‰;在墙顶的均布荷载不是很大的情况下,墙顶水平位移会随荷载的增大近似呈线性增大,且降雨是引起粉质黏土基坑位移的重要因素;基坑开挖过程中,墙侧土压力呈现先增大后减小再逐渐增加的变化规律;随基坑开挖深度增加,土钉受力逐渐由尾部向内部发展。

Model tests on supporting mechanism of soil nailing wall in silty clay deep foundation

Based on the similarity theory, the similitude ratio of model tests is confirmed, the similar materials are selected according to the similitude ratio, and the physical model for soil nailing wall is established. The reasonable test system, loading system and precipitation testing procedure are designed. The horizontal displacement of soil nailing wall top, axial force of soil nails and earth pressure are tested and analyzed. The results show that the primary factor that affects the displacement of soil nailing wall is the soil stress redistribution caused by pit excavation, and every excavation makes the horizontal displacement of the wall top present stepped increases. The horizontal displacement reaches 2.3‰ of excavation depth at the excavation and supporting stage. The rainfall is an important factor of the horizontal displacement. If the loading on the top of the wall is not very large, the horizontal displacement of the wall top increases with the growth of excavation depth. With the pit excavation the lateral earth pressure of soil nailing wall first increases and then decreases but its overall trend is to increase. During the pit excavation, the forces on soil nails develop from the end to the inside.