Influence characteristics of isolation piles on deformation of existing shallow foundation buildings under deep excavation

Urban deep excavation will affect greatly on the deformation of adjacent existing buildings, especially those with shallow foundations. Isolation piles has been widely used in engineering to control the deformation of buildings adjacent to the excavation, but its applicability is still controversial. Based on a typical engineering, numerical calculation models were established and verified through monitoring data to study the influence characteristics of isolation piles on the deformation of existing shallow foundation buildings. Results reveal that adjacent buildings will increase building settlement delta v and the deformation of diaphragm walls delta h, while the isolation piles can effectively decrease these. The surface settlement curve is changed from "groove" type to "double groove" type. Sufficiently long isolation pile can effectively decrease delta v, while short isolation piles will lead to a negative effect. When the building is within the range of the maximum settlement location P, maximum building rotation theta m will increase with the pile length L and the relative position between isolation pile and building d/D increase (d is the distance between piles and diaphragm walls, D is the distance between buildings and diaphragm walls), instead, theta m will decrease for buildings outside the location P, and the optimum was obtained when d/D=0.7.