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.