Experimental Study on the Vertical Bearing Capacity of Stiffened Deep Cement Mixing Piles

A stiffened deep cement mixing (SDCM) pile is a type of composite pile that has a rigid pile at the core that reinforces the deep cement mixing (DCM) pile. An SDCM pile combines the advantages of both a DCM pile (i.e., high lateral friction resistance) and a rigid pile (i.e., high stiffness and strength). This work presents four sets of laboratory model tests that were aimed at investigating the vertical bearing capacity of SDCM piles with different cement contents by monitoring the pile top load, the axial force, the pile settlement, and the pile end resistance. Two failure modes of the SDCM piles were observed during the tests––pile failure (the pile ruptured at the section below the core pile) and punching failure (the pile penetrated into the underlying soil). It was found that the vertical bearing capacity of the SDCM piles increased with cement content, up to the point of punching failure. The pile end resistance increased with the pile top load. When the ultimate bearing capacities of the SDCM piles were reached in the model tests, the ratio between pile end resistance and pile top load ranged from 19.4% to 54.2%, indicating that pile end resistance cannot be ignored.