In order to study the velocity characteristics of grouting diffusion in a single fracture,a three-dimensional single-fracture model consistent with the real fracture is constructed according to the fractal dimension characteristics of the fractured rock mass.Different fractal dimensions are used to construct different single fracture models.The COMSOL Multiphysics is used to simulate the flow velocity characteristics of grout with different water-cement ratio in a single fracture.The results show that the three-dimensional shape of single fracture and the water-cement ratio of grout are important factors affecting the flow velocity of slurry when the head is constant.When the fractal dimension is fixed,the larger the water-cement ratio of the grouting body is,the faster the diffusion velocity is,and the non-linear increase occurs.With the increase of diffusion distance,the flow velocity decreases nonlinearly and the descent rate decreases gradually.When the diffusion reaches a certain distance,the flow velocity tends to a stable value.The larger the water-cement ratio is,the smaller the decline rate of flow velocity is.With the increase of fractal dimension,the smoother the fracture surface of the three-dimensional single-fracture model is,the higher the slurry flow velocity is.