深基坑双排桩支护体系承载机理研究

目的研究分析不同开挖阶段双排桩支护体系位移、应力、应变变化规律，为基坑支护设计的优化、施工提供了有效的理论依据．方法通过MidasGTS有限元数值分析法，对不同开挖阶段，双排桩支护结构位移、受力情况进行分析，得到在不同的开挖阶段双排桩支护体系的位移、受力特征．结果基坑开挖后双排桩支护结构桩顶水平位移最大，随着双排桩支护结构深度的增加，位移逐渐减小，第一、二次开挖后前排桩最大位移值为1．058mm、42．5mm，第一、二次开挖后后排桩最大位移值1．062mm、42．5mm，前排桩比后排桩值偏大；基坑开挖后，基底处剪切应力最大，双排桩支护结构桩顶、基底处弯矩值较大．结论基坑开挖后，双排桩支护结构桩顶水平位移最大，随着双排桩支护结构的深度的增加，位移逐渐减小，且前排桩位移值比后排桩位移值偏大；随着基坑开挖深度的加深，桩底处弯矩逐渐减小，最大弯矩处逐渐上移，桩顶位置值显著增大，前后排桩弯矩值变化是一致．

Study on the Load Bearing Mechanism of Double-Row Piles Supporting System in Deep Foundation Pit

For the optimization of supporting structure, the displacement, stress and strain variation rules of the double-row piles supporting system in different excavation stages have been numerically investigated. The Midas GTS finite element analysis is applied to investigate the displacement, stress and bending moment distribution of double-row piles supporting structure in different excavation stages. The results of Midas GTS finite element analysis show that：after the excavation of foundation pit, the pile-top horizontal displacement is the maximum. The horizontal displacement reduces gradually with depth increasing. The displacements of front row pile after the first and second excavation are up to 1. 058 mm and 42.5 mm,respectively. The dis- placements of back row pile after the first and second excavation are up to 1. 062 mm and 42.5 ram, respec- tively. After the excavation of foundation pit, the highest shear stress appears at the bottom of the base. The bending moment of the top and bottom of double-row piles reaches higher values. After excavation of the foundation pit, the pile-top horizontal displacement is the maximum. With the increasing depth of excava- tion, the pile-top horizontal displacement and the pile-bottom bending moment generally decrease, and the displacement of front-row piles is larger than that of back-row piles. The position of the maximum bending moment moves upward and the pile-top bending moment significantly increases. The bending moment change of the front-row piles is consistent with the back-row piles.