The Influences Of Excavation On Adjacent Piles Considering Dewatering And Porosity-Depth Relationship

The excavation of foundation pit would give rise to a series of phenomena. Additional deformation and stress relaxation of soil adjacent to the pile would be induced, which could cause additional displacements and additional inner forces of piles of adjacent building, then the bearing capacity of piles would be reduced. As a result, the building would incline, subside additionally and even collapse. Therefore, it is meaningful both on theory and practice to study the effects of excavation on existing piles of adjacent building, as well as how to reduce these adverse effects effectively. This paper summarizes the existing related research results at home and abroad firstly. Then numerical simulations are conducted based on the modified Cambridge model, considering the porosity-depth relationship and the effect of dewatering in actual situation. Corresponding subroutines are compiled in ABAQUS. The effects of excavation on adjacent buildings pile are studied in numerical analysis.The numerical simulation method has been verified. The verification results show that the ground settlement is larger when the porosity-depth relationship and the effect of dewatering are considered, which is about1.6times of that the dewatering is not considered. Numerical simulation results obtained in the paper are close to the settlement prediction curve proposed by Hsieh. Numerical simulations are conducted to study the influences from excavation to adjacent piles at different excavation step and different space between pile and foundation pit. The following conclusions are obtained:(1) The displacement of pile decreases gradually with the increase of pile diameter, and this decrease is much more obvious when pile diameter increases from0.8m to1.4m.(2) The horizontal displacement of pile decreases with the increase of thickness of underground continuous wall. The maximum horizontal displacement of pile decreases by12%with a thickness of0.9m.(3) The horizontal displacement of pile decreases with the increase of support stiffness, while its variation keeps descending. At last, the effects of soil reinforcement technology on adjacent piles are studied. Results indicate that good project benefits may be achieved when the elastic modulus of reinforce is1.0GPa, the thickness of reinforce at passive area is0.5-0.64H, the width of reinforce at passive area is0.57-0.86H, and the thickness of reinforce at active area is0.86～1.1H.