金川集团龙首矿西二采区上部中段充填采场发生失稳事故后，采矿方法由下向分层进路式胶结充填法转为无底柱分段崩落法时，面临着软破矿岩条件下覆盖层形成和采场稳定性问题。采用数值计算和现场试验等方法，对这2个关键技术问题进行了研究。数值模拟结果表明，随着崩落法首采分段回采工作的进行，采场复合顶板经历了破坏裂纹萌生、零星散块冒落、拱形批量冒落和柱塞状整体冒落等阶段，当首采分段回采结束时，顶板复合岩层冒落能够为崩落法采场提供足够厚度的覆盖层，且在崩落法采动地压下软破矿岩采场能够保持稳定。现场工业试验表明，在崩落法采场首采分段采用“阶梯式退采均匀扩展采空区+总量控制出矿”的技术方案，能够安全、高效地形成覆盖层，并通过增补“钢拱架+钢筋网+锚杆”的技术方案，解决在崩落法采动地压下维持破碎矿岩采场稳定性的问题，为无底柱分段崩落法在西二采区的扩大应用奠定了技术基础。

Following the instability incident in the upper middle section of the filling stope at the West No.2 mining area of Longshou mine in Jinchuan，the original downward-layered consolidated filling method was replaced with the non-pillar sublevel caving method.To investigate critical technical challenges，such as cover layer formation and stope stability associated with the practical application of this method，numerical simulation techniques were employed for the research.The research findings suggest that as the sublevel stope area within a caving stope expands，the composite roof experiences a sequence of progressive failure stages.These stages include the initiation of failure cracks，dispersed bulk caving，arch batch caving，and plunger integral caving.By the conclusion of the first sublevel mining，the height of the roof collapse is expected to exceed 30 meters，thereby forming a sufficiently thick cover layer for the caving method stope.Concurrently，during the mining process，plastic zones are generated on the surface of the roof along the mining approach.The support structure serves a critical function in anchoring and stabilizing the majority of the plastic zones，thereby contributing to the overall stability of the mining approach.Despite the minimal displacement observed in the access roof，there is a pronounced stress concentration within 5 meters behind the working face，necessitating continued attention.An industrial experiment was subsequently conducted on-site，employing the non-pillar sublevel caving method and utilizing induced caving technology to establish a cover layer.To mitigate the risk of large-scale collapse of the composite roof，a technical strategy involving“stepped mining and uniform expansion of goaf combined with total ore extraction control”was implemented on-site.Microseismic monitoring and on-site tracking data revealed that during the initial sublevel mining phase，the actual caving height of the roof in the mining area surpassed 20 meters，resulting in the formation of a thick cover layer approximately 30 meters thick，inclusive of the reserved ore layer.Throughout the entire mining process，the stope remained in a stable condition.To address the issue of significant damage to the access road in the fractured ore and rock zone，a comprehensive technical scheme incorporating multiple support structures was proposed.For the problem of medium and deep hole damage，a systematic approach involving hole inspection，hole dredging，and hole filling was established.Additionally，relevant equipment was promptly introduced to mitigate operational intensity and enhance the applicability of the non-pillar sublevel caving method under the soft，fractured ore and rock conditions prevalent in the Jinchuan mining area.