水上基坑围护结构方案设计与分析

结合某紧邻高桩码头的大型水上客运综合体深基坑工程的方案设计，提出一种既满足围护结构水上施工作业条件，又能最大限度减少前方码头结构设计变更的复合钢板桩基坑围护方案。针对地下连续墙和复合钢板桩两种水上基坑围护方案，采用Plaxis软件分别建立平面应变有限元计算模型，分析了不同施工工况下两种方案围护结构的变形及受力特性。研究表明，复合钢板桩能与前方码头结构同步进行水上施工，该方案减小了码头后方接岸斜坡堤回填与基坑开挖工程量，基坑开挖阶段降低了作用于围护结构的土压力，对基坑变形控制及稳定均有利。基坑开挖至坑底时复合钢板桩最大侧向变形仅为地下连续墙的1/3，变形性态也明显优于地下连续墙。此复合钢板桩基坑围护方案可为类似基坑工程的设计和施工提供有益参考。

Schematic design and performance of retaining structure for waterfront excavation

In combination with the schematic design of a large-scale waterfront deep excavation for passenger station adjacent to the front wharf on piles,a kind of composite steel sheet pile retaining structure scheme for the foundation excavation is proposed to satisfy the waterfront construction condition of retaining structure and to minimize the design alteration of the front wharf on piles.The two-dimensional finite element numerical models are established with Plaxis to study the deformation and mechanical performance of the two feasible waterfront retaining structure schemes,including diaphragm walls and composite steel sheet piles.The calculated results show that the composite steel sheet piles can be constructed in parallel with the front wharf on piles in water so as to avoid massive backfill and subsequent excavation.This leads to the decrease of earth pressure loading on the retaining structure during inside excavating and strutting,which brings positive effects on deformation control and overall stability of the excavation.The maximum lateral deflection of the composite steel sheet piles is only one third of the diaphragm walls when the pit is excavated to the bottom,which means the steel sheet piles with two rows and the cast-in-place concrete can exert the stiffness of the composite load-carrying structure effectively.The proposed composite steel sheet pile retaining structure scheme can provide a useful reference for the design and construction of similar waterfront excavation projects.