Operational reliability of shale gas pipelines is critically compromised by solid particle erosion, and the effect of particle interactions on the erosion mechanism under high concentration conditions has not been fully investigated. In this study, a numerical model of liquid-solid direct jet erosion considering particle interactions is established, and the fluid flow characteristics, particle trajectories and erosion damage patterns are analyzed by comparing the discrete phase model (DPM) with the dense discrete phase model (DDPM). A systematic investigation into the influence of particle concentration, flow velocity and particle size on erosion mechanisms was conducted employing the Realizable k-ε turbulence model, the Zhang erosion model, and an experimentally verified computational mesh. The results show that increased particle concentrations lead to lower erosion rates, and DDPM predictions are about 2.5 % lower than those of two-way DPM, which overestimates erosion by ignoring particle-fluid interactions. DDPM is more effective at high concentrations, and the distribution of particle collision velocities it captures shows that particle collision velocities are greater in the center region, but DDPM predicts higher values at the radial peak, leading to an overestimation in the severely eroded zone. This study develops a more accurate numerical modeling approach for predicting erosion in high concentration liquid-solid two-phase jets.