软土地区型钢水泥土搅拌墙墙土相互作用试验研究

软土地区采用型钢水泥土搅拌墙(SMW工法)支护形式优势非常明显,但目前对SMW工法墙-土相互作用机理的研究不够透彻,制约了其推广与应用。为深入探索墙-土相互作用机理,针对软土地区SMW工法建立了大比尺试验模型,对各工况墙顶位移、墙侧土压力以及型钢应变进行了测试。试验结果表明:SMW工法墙顶位移速率变化随基坑挖深增加呈U型趋势,而位移呈S型发展,位移时间效应显著,挡墙存在明显的最优嵌固比;实测墙背主动土压力呈抛物线型分布,基坑墙体位移值和位移速率均影响极限土压力发展,实测极限主动土压力大小间于Rankine主动土压力和静止土压力之间,而实测极限被动土压力远小于理论值;水泥土和型钢的组合挡墙承载能力和刚度明显优于型钢,且二者变形协同性较好,建议在SMW工法支护结构设计时考虑水泥土对组合挡墙的刚度贡献。

Experimental Study on the Wall-soil Interaction of Soil Mixing Wall in Soft Soil Area

The cement-soil wall (SMW construction method) as a retention technique enjoys many advantages in soft soil areas, but at present, the wall-soil interaction mechanism of SMW construction method is not well understood, which restricts its popularization and application. To further explore the wall-soil interaction mechanism, a large-scale test model was built according to the SMW construction method in soft soil areas, and various tests were conducted under different displacements of the top wall, lateral earth pressures of the side wall and section steel strains. The experimental results indicated that there was a U-shaped curve between the displacement rate and the foundation depth, while there was a S-shaped curve for the displacement; the displacement exhibited remarkable time effects and an optimal embedment ratio was obtained for the retaining wall. It was also observed that there was a parabolic distribution of the measured active earth pressure at the back of the wall; both the displacement and displacement rate of the foundation pit wall would affect the development of the ultimate earth pressure; the measured limit active earth pressure ranged between the Rankine active earth pressure and the earth pressure at rest, while the measured limit passive earth pressure was far smaller than the theoretical value. Compared with section steel retaining walls, the composite retaining walls of cement-soil and section steel had better bearing capacity, rigidity and deformation compatibility. It was therefore suggested that the contribution made by cement-soil to the rigidity of composite retaining wall shall deserve consideration when designing supporting structures using the SMW construction method.