Study on the Disturbance Test Mechanism and Uplift Bearing Capacity of Constrained Grouting-expansion Piles

Steel pipe piles have stable uplift bearing capacity and quick construction speed, but their lateral resistance and tip resistance are insufficient in clayey soil with a high groundwater table. Hence, by combining pre-drilling and bag-type grouting technology, the Steel Pipe Pile with Constrained Grouting (SPPCG) was designed. Taking the clayey soil in Shanghai as the research objective, the laboratory scaled model test was conducted to study the disturbance influence of different construction techniques on the uplift resistance performance of the SPPCG. A simplified calculation method was proposed to calculate the ultimate uplift bearing capacity of the SPPCG, and its effectiveness and applicability were verified in the field test. The results show that the in-situ scaled model test reveals the influence of drilling excavation on the uplift resistance performance, and drilling excavation weakens the lateral resistance of the soil and affects the mechanics performance of the pile-soil interface. Based on Rankine's theory, a simplified calculation method for the uplift bearing capacity of the SPPCG was modified, providing a precise and simple preliminary estimation tool for engineering design.