Study on Composite Foundation with Variable Stiffness Combination Pile in Loess and Its Working Performance

Considering the special engineering geological conditions of terrace loess in Northwest China, in order to better fit the local conditions and meet the settlement control index of high-speed railway subgrade, a composite foundation with variable stiffness combination pile isproposed, and the field load tests are carried out, and bearing characteristics, pile-soil stress ratio and variation characteristics of soil compaction coefficient around pile are discussed. Through numerical simulation, the stress and deformation distribution characteristics of variable stiffness composite pile and soil around pile are deeply studied. The results show that, compared with the cement soil compaction pile, the composite foundation with variable stiffness composite pile can more effectively control the settlement, and the pile-soil stress ratio at the surface is closer to the flexible pile, which has the deformation coordination ability of the flexible pile composite foundation. The composite foundation with variable stiffness composite piles can produce soil arching effect, so as to give better play to the end bearing role of piles and reduce the load on the soil between piles in the lower layer of composite foundation, so as to meet the special engineering geological conditions of terrace loess area.