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

For the foundation ex cavation 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 rea-l 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 soi-l nailed wall support for the the foundation ex cavation saturation with shallow sand layer (less than 6 meters); for the 51 7m foundation ex cavation 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.