Grouting is an important method to reinforce soft coal roadway, and the presence of primary cracks in the coal body has an important influence on the grouting effect. With the discrete element simulation method, the grouting process of the soft coal seam was simulated. The mechanism of primary cracks on grouting was revealed, while the influence of fracture characteristics and grouting pressure on the grouting effect was analyzed. The results demonstrated that grouting in the soft coal seam involves the stages of seepage, rapid splitting, slow splitting, and stability. Due to the presence of primary cracks, the grouting diffusion radius increased significantly. Under the slurry pressure, the tensile stress concentration was formed at the crack tip, and the slurry split the coal once the splitting pressure was reached. In addition, the distribution characteristics of fractures are found to have a great influence on the grouting effect. It is observed that smaller fracture spacing is associated with a larger slurry diffusion radius and thus easier penetration of the primary crack tips. The fracture angle affects the direction of fracture propagation. The secondary fracture formed by splitting is a tensile fracture, which is more likely to extend along the direction parallel to the maximum principal stress. Overall, these simulation results have guiding significance for the setting of reasonable spacing of grouting holes in the practice of grouting engineering.

注浆是加固软煤巷道的重要方法，煤体中初生裂缝的存在对注浆效果有重要影响。采用离散元模拟方法，对软煤层注浆过程进行了模拟。揭示了初次裂缝对灌浆的作用机理，同时分析了断裂特性和灌浆压力对灌浆效果的影响。结果表明，软煤层注浆涉及渗漏，快速劈裂，缓慢劈裂和稳定等阶段。由于存在初级裂纹，注浆扩散半径显着增加。在泥浆压力下，裂纹尖端处形成了张应力集中，一旦达到分裂压力，泥浆就将煤分解。此外，发现裂缝的分布特征对注浆效果有很大影响。可以看出，较小的裂缝间距与较大的浆液扩散半径有关，因此较容易穿透初级裂纹尖端。断裂角影响断裂传播的方向。通过分裂形成的二次断裂是拉伸断裂，其更可能沿着平行于最大主应力的方向延伸。总体而言，这些模拟结果对于灌浆工程实践中合理设置灌浆孔间距具有指导意义。可以看出，较小的裂缝间距与较大的浆液扩散半径有关，因此较容易穿透初级裂纹尖端。断裂角影响断裂传播的方向。通过分裂形成的二次断裂是拉伸断裂，其更可能沿着平行于最大主应力的方向延伸。总体而言，这些模拟结果对于灌浆工程实践中合理设置灌浆孔间距具有指导意义。可以看出，较小的裂缝间距与较大的浆液扩散半径有关，因此较容易穿透初级裂纹尖端。断裂角影响断裂传播的方向。通过分裂形成的二次断裂是拉伸断裂，其更可能沿着平行于最大主应力的方向延伸。总体而言，这些模拟结果对于灌浆工程实践中合理设置灌浆孔间距具有指导意义。