Investigation into the dynamic compaction reinforcement characteristics and particle crushing effects of construction and demolition waste

This paper conducted laboratory scaled-down testing and studied the dynamic compaction effects and particle crushing issues of construction and demolition waste (CDW) by combining the discrete element method (DEM). The findings of testing revealed that during the dynamic compaction process, the internal dynamic stress within the CDW propagated irregularly from the surface to deeper layers due to the combined effects of increasing density, particle rearrangement, and particle crushing. This propagation was characterized by a rapid decay of peak dynamic stress and significant energy dissipation. Specifically, under commonly used compaction energies of 2000 kN·m, 4000 kN·m, 6000 kN·m, and 8000 kN·m, the corresponding recommended stopping compaction counts were 9, 6, 4, and 4 times, respectively. After reaching these stopping counts, the compaction settlements account for 98%, 90%, 80%, and 82% of the total compaction settlement. Therefore, it was suggested to re-evaluate the stopping criteria based on trial compaction results. The DEM simulation results, considering the particle crushing effect, indicated that the initial dense state was achieved when the cumulative tamping energy reached 20,000 kN·m. Following this, the sensitivity of the relative crushing rate ( B r ) of the fill material to the cumulative tamping energy increased with the increase in single tamping energy. Furthermore, a strong correlation was observed between the B r of the CDW and the compaction settlement under fixed tamping energy. A predictive model for estimating the B r of the fill material considering different compaction energies was proposed, with estimation errors was effective.