English：

The entrance section of the Xianyueshan Tunnel project on the Louli Expressway passesthrough complex and loose accumulation strata, posing significant challenges to construction safety. Thispaper, based on ray casting algorithm and particle discrete element method, randomly simulates theplacement of boulders to construct a computational model for the excavation of the Xianyueshanaccumulation strata tunnel and proposes effective reinforcement measures. The results show that,compared to the lower rock mass, the surrounding rock stability of the accumulation strata is poorer. Asthe excavation ratio increases, the deformation zone of the surrounding rock expands, and asymmetrichorizontal displacements occur in the left and right sidewalls,with an asymmetric distribution of theplastic zones as well. Particularly,when crossing the interface of different strata, stress concentrationcauses an increase in sidewall stress,while the stress at the crown and bottom decreases. With anincrease in the excavation ratio, the settlement of the crown and the heave of the bottom plate aremitigated, and the sidewall displacement increases before decreasing with the increase of the excavationratio. In response to the failure characteristics of the accumulation strata, surface grouting reinforcementmeasures are proposed. After reinforcement of the strata, the cohesion between soil and rock particles isgood, and the support is stable, producing favorable results.