粉质黏土深基坑土钉墙支护作用机理模型试验研究

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

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。

Based onthesimilaritytheory,the similitude ratio of model tests is confirmed, the similar materials areselected according to the similitude ratio,and thephysicalmodel for soil nailing wallis established. The reasonable test system,loading system andprecipitationtesting procedure aredesigned.Thehorizontaldisplacement of soil nailing walltop, axial force of soil nails and earth pressureare tested and analyzed. The results show thatthe primary factorthat affects the displacement of soil nailing wallis the soil stress redistribution caused by pit excavation, and everyexcavation makes the horizontal displacement of the wall top present stepped increases.Thehorizontal displacement reaches2.3‰of excavation depth at the excavation and supporting stage. The rainfall isan 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 topincreases with the growth of excavation depth. With the pit excavation the lateral earth pressure of soil nailing wall first increases and then decreases butits overall trendis toincrease.During the pit excavation, the forces onsoil nails develop fromthe end to the inside.