Research On The Soil Pressure Of Piles In Row In Chengdu Area

The piles in row supporting structure is widely applied in Chengdu, however, large number of engineering practices have found that the actual stress on the pile body is less than that of designed, which shows lower soil pressure is acting on the supporting structure. To know the reasons and to provide reasonable design theory, the finite element method is applied to research into the influence factor and law of the soil pressure behind the piles in row supporting structure.The following work has been done:(1) The excavation process is simulated using the ABAQUS software. To probe into the law of influence the different factors have on the strain of the supporting structure and the soil pressure behind the piles, the following factors:the strength and stiffness of the soil, the diameter of the shaft, the pile spacing, and the prestressed anchor cable, are regarded as variable factors. A reduction factor of the soil pressure over the excavation face is proposed, and the reason for a less actual soil pressure than the active soil pressure is studied.(2) The model is made according to the practical engineering. The simulation of the excavation of the foundation pit is based on the displacement of the pile body determined by inversion of the horizontal displacement of the pile body, and a comparison with the measured data is made to verify the accuracy of the model.The following conclusions are made:(1) The drilling process of the supporting piles may bring about some release of the soil pressure, which would make the displacement of the supporting structure and the bending moment of the pile body less than the theoretical value and reducing the role of the excavation soil pressure on retaining structures..(2) The strength and the stiffness of the soil have great influence on the stress and strain of the supporting piles. The better property of the soil would bring about strong self-stability, lower soil pressure would act on the supporting piles, and smaller the strain of the supporting piles. Internal friction angle of the soil has a large effect on the value of internal force and displacement.(3) In most cases, when the excavation is completed, the soil pressure acting on the supporting piles is lower than the active soil pressure. During calculation, the value of the soil pressure over the excavation face should adopt the reduced active soil pressure.(4) The alternative arrangement of the piles in row structure would bring about soil arch effect. Properly taking advantage of the soil arch effect would effectively develop the self stability of the soil, and then a proper spacing of the piles could be determined.(5) Using the on-site measurements to get the soil pressure behind pile and the bending moment which indicates that the pile is less than the design value of internal forces, and houtu pile pressure is less than the active soil pressure, and verify the conclusions.