Axial Bearing Performance of Helix Stiffened Cement Mixing Piles in Sandy Soils

The Helix Stiffened Cement Mixing (HSCM) piles are a type of composite pile with peripile hydraulic soil formed by simultaneous grouting during the installation of helical piles. Combining the grouting process with the helical pile increases pile stiffness, improves axial bearing capacity, addresses buckling and corrosion issues of the pile body, and enhances pile skin friction, thereby increasing its bearing capacity. Currently, there has been extensive research on the bearing capacity of HSCM piles in clay soil, but less on their bearing performance in sandy soil. This study investigated the effects of the number of helix plates, grouting pressure, and the location of grouting holes on the axial bearing performance of HSCM piles through laboratory model tests. The pile formation process, load–displacement curve, variation in pile diameter, and load transfer mechanism of each test pile were analyzed. Using a parametric analysis of numerical simulations, the influence of a sandy soil foundation on the bearing capacity of HSCM piles under varying internal friction angles was examined. The results indicated that grouting holes positioned below the first layer of helix plates enhanced the axial bearing performance of HSCM piles; additionally, increasing the number of helix plates and grouting pressure appropriately also enhanced the axial bearing performance and increased the pile body diameter, positively affecting the pile formation. Additionally, HSCM piles functioned as friction end-bearing piles in sandy soil, with the vertical load at the top of the pile primarily borne by pile end resistance at the limit state of bearing capacity. With increasing internal friction angles and dilation angle, the bearing capacity of the pile foundation exhibited a rising trend.