Numerical Analysis of Creep Effects on the Settlement of PHC Pipe Pile in Soft Clay Treated by Deep Mixing Method

Creep effect has a significant influence on the long-term settlement of foundations in the soft soil ground. Deep cement mixing (DCM) method is commonly used to treat soft soil to against the development of the foundation settlement. However, the long-term creep settlement of foundations reinforced by DCM columns is rarely considered in the industry. In this study, numerical investigations are conducted to analyze the settlement characteristics of PHC pipe pile foundations in soft clay treated by DCM column. The responses of pile long-term settlements and distribution of failure soil under vertical loads are examined. The numerical results show that the modified creep index mu* has a visible effect on the long-term settlement and stability of pile foundation. When mu* exceeds 0.01, there is a large risk of pile failure under long-term loading. The deep mixing method exhibits well in controlling long-term settlements of PHC pipe pile foundation, and improve the stability of the pile foundation effectively. From the economic consideration, the reasonable volume of soil reinforcement area is about 15 m3-20 m3. Finally, based on the numerical results, two prediction equations for the long-term settlement of PHC pipe pile foundations under two typical reinforcement radii are proposed in this study.