Performance of Cement-Fly Ash-Gravel Pile-Supported High-Speed Railway Embankments over Soft Marine Clay

The Beijing-Tainjin high-speed railway were constructed between two major cities in China. Since part of the railway is over soft marine clay, appropriate ground improvement, cement-fly ash-gravel piles, was selected to improve the soft marine clay to meet technical requirements for the high-speed railway. This article presents the field measurements in the railway embankment project including the load distribution between soils and piles, excess pore pressure, and settlement and lateral displacement. The test results show that the stress concentration to the piles reduced the excess pore pressure effectively. The proportion of the load carried by soils was small, and thus the settlement was significantly reduced. The compression of the rigid piles contributed to less than 21% of the total settlement. The majority of the settlement was contributed by the penetration of the piles and the compression of the soft soil below the pile tips. The average compression thickness below the pile tips was 22 m, which is equivalent to one times the width of the treated area. The measured differential settlement of the embankment was approximately 3 mm.