Numerical Simulation of CFRA Pile Subgrade Reinforcement Based on Recycled Aggregate of Demolition Waste

There is a large quantity of construction waste with low utilization in China. The construction and demolition (C&D) waste can be manufactured into recycled aggregate instead of natural aggregate, made into cement fly-ash recycled aggregate (CFRA) pile for foundation reinforcement. This study investigated the building demolition waste and construction waste production in Suzhou. The laboratory test was conducted to explore the unconfined compressive strength of CRFA pile samples with different condition, and the strength of samples met the design strength. The CFRA pile composite foundation is simulated to explore the relationship between influence factors (pile length, pile spacing, pile diameter, pile modulus) and settlement. The results indicate that the building demolition waste and construction waste production increases year by year, and waste concrete accounts for over 50% of building demolition waste. The length of pile has a great influence on the surface settlement of subgrade and foundation, and the settlement reduces effectively due to the strong bearing capacity of the pile in the soft soil layer. When the pile spacing is 3 times diameter of pile, the surface settlement at the center of the foundation is minimum. The increase of pile diameter and elastic modulus of pile yield to the decrease of the surface settlement of subgrade. The settlement of CFRA pile composite foundation meets the general control requirements (the post-construction settlement in the first-grade highway should be less than 300 mm).