Study on the migration law of aggregate sediment in the water inrush channel of coal rock mass

Grouting after pouring aggregate can effectively control water inrush from coal and rock mass. The study on the deposition and migration law of aggregate in the water inrush channel from coal and rock mass is an important prerequisite to determine the aggregate particle size, aggregate grouting volume and the spacing of aggregate grouting holes. However, there are few theoretical and experimental studies in this area at present, and the actual construction mainly depends on experience, which is blind. In view of this, based on the slurry pipeline transportation theory and sediment movement mechanics, combined with Newton’s second law, the whole movement process of aggregate from the pouring hole to the water inrush channel is divided into three movement stages: free fall, similar horizontal throwing and sliding, and their stress analysis is carried out respectively. A sedimentation, migration and diffusion model from single aggregate to aggregate particle group is established, and the sedimentation and migration rules characterizing the aggregate particle group in the horizontal direction are obtained; A model test platform for visualization of aggregate deposition and movement in water inrush channel of coal and rock mass is designed by ourselves. With the help of this platform, aggregate deposition and movement model tests are carried out under the influence of various factors such as different hydrodynamic velocity, aggregate particle size, pouring height, et al, to analyze the deposition and movement rules of aggregates in water inrush channel, and to obtain the total length of aggregate deposition and movement area under different test schemes. The experimental results show that the actual migration process of aggregate is consistent with the assumption of three movement stages in theory, and the average error between the experimental value and the theoretical calculation value of the sediment migration distance of aggregate is 7.34%; On the premise that the injection height is controlled to be consistent with the dynamic water conditions, the theoretical formula is more applicable to coarse aggregate (particle size > 5 mm) than to fine aggregate (particle size ≤ 5 mm); When solving the problem of water inrush from coal and rock mass in engineering, if the aggregate particle size is greater than 5 mm, the migration distance of aggregate particle group in the horizontal direction can be calculated by using the theoretical formula in this paper, so as to determine the spacing of aggregate grouting holes and reduce the blindness in the actual construction process.