软土基坑中内插H型钢重力式挡土墙支护的变形及稳定性的有限元研究

基于硬化土模型（HS模型），利用PLAXIS有限元分析软件对上海地区某软土浅基坑中内插H型钢的重力式挡土墙支护开展有限元分析，根据数值试验结果和监测数据对基坑变形和稳定性进行研究。研究发现，（1）内插H型钢重力坝围护在浅基坑局部开挖7~8 m范围内有着较好的可行性和工程效果，在浅基坑支护中可作为重力式围护的补充手段；（2）使用PLAXIS的HS硬化土模型模拟基坑开挖具有较好的精度和与实际情况较接近的结果，HS模型的参数可以根据工程经验进行取值；（3）实际基坑监测结果表明浅基坑的局部深坑处的内插H型钢重力坝在两端重力坝的约束下其位移发展受到一定控制，可显著提高基坑的整体稳定性，且内插H型钢可以增加围护体本身的刚度，可抵抗部分土压力弯矩，一定程度上控制了围护体的位移；（4）实际工程中对内插H型钢重力坝的局部开挖深度要谨慎选择，首先在周边环境保护条件较为宽松的条件下采用，局部深坑深度建议在7~8 m之间，并且基坑整体开挖深度建议在5~6 m之间。通过对软土浅基坑中内插H型钢的重力式挡土墙支护的研究，能对相关基坑支护工程提供更可靠的技术支持。

Application of gravity retaining wall with H-shaped steel in soft soil foundation pit

Based on the hardening-soil model, finile element analyzing method was carried out on supporting system of gravity retaining wall with embedded H-shaped steel through PLAXIS FEM software; and researches was conducted on the deformation and stability of the support system with the simulation results and on-site monitoring data. Researches show that (1) Gravity retaining wall with H-shaped steel shows good feasibility and engineering functions in the range of 7-8 m of local excavation of shallow foundation pit, which can be the supplementary means of gravity-style enclosure. (2) Good precision and results close to actual situations can be obtained by hardening-soil model(HS model for short) embedded in PLAXIS FEM software to simulate the foundation pit, and parameters of HS model can be obtained according to engineering experience. (3) On-site monitoring data of foundation pit shows that the displacement development of gravity retaining wall with H-shaped steel was controlled under the restriction of retaining wall on both ends, which is good for global stability; and that H-shaped steel can well improve the stiffness of supporting system and resist some of bending moment produced by soil mechanics, which to some extent controlled the support system’s displacement. (4) In actual engineering local excavating depth of gravity retaining wall with H-shaped steel should be carefully chosen, which is advisably used under the condition of loose requirement for surroundings’ protection, with a advisable excavating depth of 7-8 m in local foundation excavation and the global excavating depth of 5-6 m. Through the research of gravity retaining wall support with H-shaped steel in shallow foundation pit in soft soil area, more reliable technique supports can be offered for relevant supporting engineering of foundations.