上海浅层饱和粉细砂层中某基坑的围护及变形监测

SUPPORT AND DEFORMATION CONTROL OF A FOUNDATION EXCAVATION WITH COMPOSITE SOIL-NAILED WALL SUPPORT IN SHALLOW SATURATION FINE AND SILITY SAND LAYER IN SHANGHAI

在动水压力作用下，上海浅层饱和粉细砂层中的基坑容易产生流砂的现象。以上海某基坑围护设计施工方案为例，对一种较为经济的基坑围护方法给予介绍，该方法较好地解决了基坑坡脚土隆起和流砂等问题；同时指出实行信息化监测和动态设计是基坑围护安全的重要辅助手段。利用重力式挡土墙理论和极限平衡理论进行体外和体内破坏稳定性分析，得出符合要求的安全储备验算结果。实测结果表明，饱和粉细砂层基坑在一定深度范围内（≤6m）采用复合土钉墙挡土结构是安全可行的；对于5．7m深饱和粉细砂层中的基坑，地面沉降影响范围达9～10m，且沉降大小随距离增加而衰减；基坑最大位移发生在向内的凸角。

For the foundation excavation with shallow saturation-fine and sility sand layer which easily results drift sand under hydrodynamic pressure, an economical support system is adopted. Taking the design and construction plan of an apartment foundation excavation in Shanghai as the study object, the project increased the inserting depth of the water insulation curtain, raised the angle of the last rank of soil nailing, and took the wholly pressed grouting technology, which solved the bulge of the slope toe soil and drift sand effectively. To ensure safe construction, informational real-time testing system and dynamic design are important assisting means. The support parameters are analyzed by theory of gravity retaining wall and limit equilibrium. The testing results show that it＇s safe and practicable to adopt the composite soil-nailed wall support for the the foundation excavation saturation with shallow sand layer （less than 6 meters） ; for the 5.7m foundation excavation with shallow fine and sility sand layer, the subsidence coverage of the ground is 9 - 10m, and the subsidence decreases with the increase in distance ; the biggest displacement appears at the internal protrude angle.