基于分离相似概念的地铁异形基坑三维开挖模型试验

THE MODEL TEST OF THE IRREGULAR FOUNDATION PIT OF THE SUBWAY BASED ON THE RESPECTIVE SIMULATION THEORY

以厦门吕厝站地铁基坑开挖工程为工程原型,采用分离相似设计方法确定了模型试验所需要关键参数的相似比,制作了异形基坑试验模型,并设计了合理的监测系统。通过模拟基坑实际的开挖过程,根据取得的监测数据,分析了地表沉降、地连墙变形和受力等变化规律。结果表明:与基坑边缘距离越大,地表沉降影响越小,且墙体边长及开挖深度越大沉降越显著;地表沉降曲线形式与沉降数值大小有关,基坑开挖表现出明显的空间效应和角隅效应,地表沉降主要发生在坑内土体开挖阶段;随开挖的进行,土层卸荷对地表沉降影响逐渐减小,地连墙弯矩大小与开挖深度呈正相关,最大弯矩值出现在基坑最深开挖面附近。

According to the foundation pit excavation of the Lücuo station in Xiamen Subway Line 1,the similar ratio of the key parameters of the model is obtained with the respective similitude theory.Besides,the whole model is made and the monitoring system is designed.By simulating the actual excavation process and analyzing the monitoring data,the ground settlement,the deformation and stress distribution of the diaphragm are given.The results show that,the ground settlement is negatively correlated with the distance away from the diaphragm and positively correlated with the length of the diaphragm and the depth of excavation.The shapes of the curve are related to the total settlement caused by the excavation unloading,and the spatial and corner effect are obvious.The ground settlement mainly occurs in the stage of excavation.The influence of excavation on the ground settlement is gradually reduced with the excavation progress developing.The bending moment of the diaphragm is positively correlated with depth of excavation.The maximum bending moment of the diaphragm is at the excavation face of the foundation pit.