Study on bearing capacity characteristics of Cement-Flyash-Gravel piles and cement-soil compacted piles in composite foundations

Abstract To investigate the mechanical performance of Cement-Flyash-Gravel (CFG) piles and Cement-Soil Compacted (CSC) piles in composite foundations (CF), this study uses numerical simulation methods combined with field tests to examine the bearing capacity characteristics and behavior patterns of CFG and CSC pile composite foundations in the collapsible loess area of the Yinxi high-speed railway. The results indicate that the stress ratio between the CFG piles and the surrounding soil follows a trend of ‘steady-sharp rise-steady transition-sharp drop. Additionally, the side friction resistance of the CFG pile reaches its maximum negative value at 2/3 of the pile length and its maximum positive value at 7/8 of the pile length. These findings provide important insights and practical guidance for the design and construction of composite foundations in collapsible loess regions.