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Gob-side entry retaining (GER) is a popular non-pillar mining technique regarding how to reserve a gateroad for the use of next panel mining. When used in thick coal seams, the conventional entry retaining method requires a huge amount of filling materials and may cause entry (gateroad) accidents. Thus, an innovative non-pillar longwall mining approach is introduced. First, structural and mechanical models were built to explore the mechanism of the new approach. The modeling results indicate that effective bulking of the gob roof and reasonable support of the entry roof were key governing factors in improving entry stabilities and reducing roof deformations. Accordingly, a directional roof fracturing technique was proposed to contribute to gob roof caving, and a constant resistance and large deformation anchor (CRLDA) cable was used to stabilize the entry roof. Subsequently, the evolutionary laws of the roof structure and stresses were explored using numerical simulation. It was found that the structure of the surrounding rocks around the retained entry changed significantly after roof fracturing. The stress-bearing center was transferred to the gob area, and the entry roof was in a low stress environment after adopting the approach. Finally, the approach was tested on a thick coal seam longwall mining panel. Field monitoring indicates that the retained entry was in a stable state and the index of the retained entry met the requirement of the next mining panel. This work provides an effective and economical approach to non-pillar longwall mining in thick coal seams.

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Male sterility is an essential trait in hybrid seed production, especially for monoclinous and autogamous food crops. Soybean male-sterile ms1 mutant has been known for more than 50 years and could be instrumental in making hybrid seeds. However, the gene responsible for the male-sterile phenotype has remained unknown. Here, we report the map-based cloning and characterization of the MS1 gene in soybean. MS1 encodes a kinesin protein and localizes to the nucleus, where it is required for the male meiotic cytokinesis after telophase II. We further substantiated that MS1 colocalizes with microtubules and is essential for cell plate formation in soybean male gametogenesis through immunostaining. Both ms1 and CRISPR/Cas9 knockout mutants show complete male sterility but are otherwise phenotypically normal, making them perfect tools for producing hybrid seeds. The identification of MS1 has the practical potential for assembling the sterility system and speeding up hybrid soybean breeding.