Experimental study on the development of surrounding soil stress during XCC pile installation in sand

A series of small-scale 1 g model tests were conducted using a self-designed pile driving loading model test system to investigate the effect of relative density and cross-section geometry on the development of soil stress around the pile during the penetration of X-section Cast-in-place Concrete (XCC) pile in sand. It is found that the variations of the radial stress Delta sigma'(r)/sigma'(v0) in the surrounding soil presented a significant "h/R effect" during the penetration of the XCC pile, indicating that the "h/R effect", which was found for circular pile during the penetration of piles, was also observed for the XCC pile. The radial stress distribution along the axial direction of the pile could be divided into three zones, i.e., the pile body region, the pile tip region, and the soil region below the pile tip. The development trend of the radial stress along with soil depth is different in each region. Additionally, the peaks of the radial stresses in the pile tip region were very sensitive to the variations of the relative density of the surrounding soils and the cross-section geometry of the piles, which increased significantly with increasing the relative density and cross-section geometry. The radial stresses Delta sigma'(r)/sigma'(v0) decreased exponentially as the radial distance r/R increased. The decay rates decreased with increasing the relative densities of the surrounding soils, while increased with decreasing the cross-section geometry parameter of the piles.