Effects and influence factors of rapid impact compaction (RIC) application on silt foundation for highway

Rapid impact compaction (RIC) has been applied to deal with clay or sandy ground reinforcement. However, its application effect and construction parameters for silt foundations remains unclear, which impeding its widespread adoption. To address this issue, a serial of field tests and numerical simulations were conducted. Field test results demonstrated that the RIC could reinforce silt foundation effectively around 6 m depth. And tamping energy and tamping times are the key parameters to improve reinforcement effect. Thereinto, for every 40 kJ increase in tamping energy, the cumulative settlement increases by 11-16%. And the recommended total tamping energy are from 5600-7500 kJ. Meanwhile, the lateral displacement of soil increases in a parabolic pattern with the ground depth, and the peak value occurs from 3 to 4 m. To further analyze the reinforcement effect and influencing factors of RIC in detail, numerical simulation analysis was conducted by adopting ABAQUS. The results showed that RIC force could induce stress concentration within 6m, which is similar to field test result. However, soil modulus increase by 40% could reduce cumulative settlement by 3-15% and influence depth by 2-4% respectively. Meanwhile, the reinforcement indexes above showed increase-decrease pattern following with anvil diameter increasing. Then the optimum anvil diameter could be determined as 1.25 m.