Field tests on plastic tube cast-in-place concrete piles for reinforcing soft ground of highways

Based on a case of plastic tube cast-in-place concrete piles for reinforcing soft ground of a highway, the characteristics of the plastic tube cast-in-place concrete pile supported embankment system are studied by measuring the pile-soil stress, surface settlement, horizontal displacement, and pore water pressure at different depths. The test results show that the critical height of the plastic tube cast-in-place pile-supported embankment is about 1.26 times the net pile space. The load-sharing ratio approaches 89% at the end of monitoring. The settlements of piles and soils and the differential settlements between piles and soils mainly occur during the period of embankment construction. The measured maximum differential settlement between piles and soils is about 30 mm; and the stress concentration ratio linearly increases with the differential settlement between piles and soil. The lateral displacements at different depths near the embankment toe increase with the increasing embankment height. The maximum lateral displacement is 12.86 mm and located 2.5 m in depth under the surface at the end of embankment construction. The lateral displacement-settlement ratio and the increment ratio of lateral displacement are reduced and stabilized with the increase of the embankment height, which indicates that the plastic tube cast-in-place concrete pile-supported embankment system can prevent the development of lateral displacement and improve the whole stability of embankment effectively.