Study Of Ultimate Vertical Bearing Capacity Of A Single Pile Due To Pit Excavation

According to a project of excavation pile static load test results in Dezhou, its compressive bearing capacity of single pile of the same found buried deep pile reduces a lot than before excavation (approximately42.47%). Research methods of this paper are the phenomenon theoretical analysis and numerical simulation method of combining research.By finite difference software FLAC3D modeling for practical engineering analysis, determine a reasonable argument. Its force and deformation and other aspects of the law change by Analysis of test piles in excavation. Simulation results show that after excavation, pile-soil stress decreases a lot, causing soil interface and ultimate friction resistance decreases and resulting in compression of single pile bearing capacity declined, making excavation works exist security risks; excavation pit bottom during and after the completion of soil have been happening rebound. Rebound displacement is greater than the soil pile rebound displacement relative displacement between pile and soil, land uplift effect produced on the pile, the pile lower friction to balance the pit down there on the pile of soil on the upper pulling force generated by the impact load transfer; excavation and soil resilience after pile-soil interface between pile and soil parameters on the contact surface has a certain impact, shear stiffness decreased, thereby affecting their capacity. In the final analysis, when the other conditions are the same, the excavation depth increased more, the actual pile bearing capacity and the gradual increase in the gap between the calculated value, the greater the depth of excavation on the pile capacity reduction will be greater; with increasing excavation width, vertical bearing capacity in constant decreases, on the pile capacity reduction effect becomes larger; pile longer pile capacity due excavation will decrease as the length of the pile decreases; soil cohesion larger value greater pile bearing capacity, reduced by the impact is smaller.The Final conclusion:After excavation, compressive bearing capacity of single pile reduced compared with before excavation, bottom test pile bearing capacity does not meet the design requirements and even threaten the safety of buildings. Sowing the pile capacity calculated vertical bearing capacity is unsafe. According to the overburden conditions under static load test to determine pile capacity, not only to less within the scope of the excavation of soil pile friction, taking into account also the foundation pit excavation unloading pile friction.