中低压缩性土地区桩承式加筋路堤现场试验研究

将桩承式加筋路堤技术应用于中低压缩性土地区高速铁路桥台和涵洞之间填方路基的处理,通过逐渐改变CFG桩桩长形成刚度均匀变化的地基加固区,严格控制线路纵向差异沉降。通过现场试验对桥台、涵顶和路基中心地基沉降进行了长期观测,同时对桩承式加筋路堤桩间土沉降、孔隙水压力、格栅上下表面土压力和格栅变形进行了长期监测分析。研究结果表明:桩承式加筋路堤可有效减小中低压缩性土地基沉降,总沉降小且很快趋于稳定;桩承式加筋路堤通过土拱效应和张拉膜效应将路堤荷载向桩帽传递,格栅下桩土应力比明显高于格栅上,张拉膜效应明显,格栅上桩土应力比接近1.0,土拱效应较弱;格栅在路肩处发挥的作用强于线路中心处。

Experimental investigation of geogrid-reinforced and pile-supported embankment on soils with medium-low compressibility

The geogrid-reinforced and pile-supported embankment is adopted to treat the subgrade of high-speed railways between the bridge abutment and culvert on the soils with medium-low compressibility. The subgrade with uniformly variable stiffness is formed by varying the lengths of CFG piles gradually aiming at controlling the longitudinal differential settlement strictly. The settlements of bridge abutment, culvert and subgrade center are monitored based on full scale field tests. Meanwhile, the settlement of the surrounding soils of pile, the pore water pressure, the earth pressure above/below the geogrid, and the geogrid deformation are measured. The experimental results demonstrate that the total and layered settlements of the subsoils with medium-low compressibility are reduced effectively, and the total settlements are very small and reach the stable value soon. The embankment load is transferred to pile caps by the combined action of soil arching effect and tensioned membrane effect. The pile-soil pressure ratio below the geogrid is significantly larger than that above the geogrid, which suggests that an obvious tensioned membrane effect exists. The pile-soil pressure ratio to 1.0 above the geogrid means that the soil arching effect is not obvious. Superior performance of the geogrid is observed at the road shoulders compared with that at the rails center.