Research and practice on key technologies for coordinated green mining of shallowly buried multi-coal seam groups

The multi-seam occurrence conditions in the western mining area have brought forth prominent and common issues such as "contradictions in mining face layout, variable overburden structure, and superimposed surface migration". Exploring the coordinated green mining technology suitable for high-intensity mining of multiple coal seams is the key to the safe and efficient mining of multiple coal seams in the western mining area. In response to the main technical challenges faced in the high-intensity mining of shallow-buried thick coal seam groups, several key technologies for the coordinated green mining of shallow-buried multi-seam groups have been systematically expounded from aspects such as the spatio-temporal layout of multi-seam mining, the stability control of the rock strata in the working face, and the surface subsidence under repeated disturbances. The following research results have been obtained: ① The interlayer interaction mechanism of high-intensity mining of multiple coal seams in the western region has been revealed. A quantitative criterion and evaluation method for repeated mining disturbances of multiple coal seams have been constructed. An innovative coordinated mining technology with the staggered distribution of “thin, medium, and thick” coal seams aiming at minimizing inter layer disturbances has been proposed. ② The stability control technology of the rock strata in the multi-seam working face has been put forward. The full overburden structure failure model has been established, and the interaction law between the support and the surrounding rock under the condition of full overburden structure failure has been revealed. On this basis, in response to the demand of using different support strategies at different positions of the multi-seam mining working face, an anti-impact double telescopic column for the working face support and a monitoring system for the support state of the advanced roadway have been developed to achieve safe, efficient and stable support in multiple areas of the working face. ③ By revealing the dynamic movement characteristics of the surface and the development law of surface fractures under the oblique superimposed mining of shallow-buried multi-seam coal seams, the determination method of the surface subsidence coefficient has been given. The key treatment technology combining "soil reconstruction – in-situ filling – micro-topography modification" for fractures in the subsidence area has been developed, effectively preventing the surface subsidence of coal mining in the loess gully area. The above core technologies have been successfully applied in more than 20 large-scale coal mines such as Zhangjiamao, Ningtiaota, and Hongliulin, providing technical support for the high-quality and sustainable development of the western mining area in China.