Grouting diffusion law and reinforcement technology of fully mechanized caving working face in extra-thick coal seam under irregular goaf

In order to solve the problem of mine pressure and surrounding rock control in the process of fully-mechanized caving mining in extra-thick coal seam under irregular goaf, taking 5106 fully-mechanized caving face of Shanxi Ningwu Yushupo Coal Mine as the engineering background, the characteristics of mine pressure in fully-mechanized caving face of extra-thick coal seam under irregular goaf are studied by means of field monitoring. On this basis, the numerical simulation method is used to analyze the slurry plume diffusion law of characteristic parameters of different cracks, and the mechanism of triangular sawtooth dynamic cyclic pulse grouting is revealed. The triangular sawtooth dynamic cyclic pulse grouting reinforcement technology is formed, and the implementation scheme of surrounding rock grouting reinforcement technology is formulated and applied in engineering. The results show that during the mining period, the support resistance of the working face shows a trend of “small at both ends and large in the middle”, and there are obvious differences in the distribution characteristics of the working resistance of the working face in different advancing distances. The diffusion shape of grouting is affected by the distribution of cracks. With the increase of the number of cracks, the diffusion shape of grouting changes from the initial circle to the irregular plume guided by cracks. After the implementation of pulse grouting reinforcement technology, it is found that the diffusion rate of pulse grouting is increased by about 25%, and the cracks of coal body in fully-mechanized caving face are fully filled. The reinforcement effect of surrounding rock is remarkable and the implementation effect is good.