According to the classification of water conservation mining in shallow coal seams in China, when the ratio of the impermeable layer thickness to the mining height is less than 18, the mining belongs to the category of special water conservation, and the strip backfilling mining method is employed. This study is based on the geological conditions in northern Shaanxi. By analyzing the stability of the impermeable layer, the stability criterion of the impermeable layer was developed. The study also investigated the compositions and properties of the backfilling materials. The results show that reasonable subsidence of the impermeable layer is allowed during mining under the basic precondition (upward cracks and downward cracks are not connected). A lower strength and lower cost backfilling method is called flexible strip backfilling. After the impermeable layer mechanical model of strip backfilling mining was established, the development height of upward cracks and depth of downward cracks were determined. From these data, the stability criterion of the impermeable layer was determined. In addition, the high-sand backfilling materials made with aeolian sand, cement, coal ash. additive, and water were studied, and the strength of the backfilling body was analyzed. According to the physical simulation, the backfilling ratio of 10% can decrease 75% of the surface subsidence. This study provides a basis for strip backfilling water conservation mining in shallow coal seams.
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