无煤柱切顶留巷开采核心工艺为超前工作面采用预裂爆破技术切断巷道顶板与采空区顶板力学联系。基本顶预裂爆破期间是动静耦合作用过程，动静耦合作用下既要保证基本顶炮孔连线间形成贯通裂缝，达到切顶效果，同时还要保证巷道基本顶稳定，装药长度与炮孔间距是决定性因素。以祁东煤矿7135工作面为工程背景，基于岩层中应力波衰减公式，分析了基本顶预裂爆破成缝机理，并以此建立基于抗拉强度的成缝判据，确定基本顶成缝时装药长度及炮孔间距的最小量化关系。基于预裂爆破过程基本顶受力特征，建立基本顶动静耦合作用力学模型，获得耦合作用下基本顶应力计算公式，分析了动载作用下基本顶不同时间应力分布规律，揭示了爆破应力波在基本顶内呈拉、压交替变换且巷道基本顶同一位置持续受到拉、压应力脉冲作用的传播规律;分析了静载作用下基本顶拉应力分布与不同侧向应力集中系数关系，揭示极限平衡区应力集中系数仅对巷道基本顶局部拉应力分布有影响(0<x<30 m)，而对远处的巷道基本顶应力分布无影响(x>30m)的规律;分析了巷道基本顶稳定机理，并以此获得巷道基本顶稳定判据，确定巷道基本顶稳定时装药长度及炮孔间距的最大量化关系。根据编制的VB计算平台，得到祁东煤矿7135工作面回风巷预裂爆破装药长度为4 m，炮孔间距为600 mm。通过对炮孔进行窥视及顶板收敛观测，验证了理论计算模型的合理性。

The core technology of non pillar gob side entry retaining by roof cutting is to adopt presplitting blasting technology to cut off the mechanical connection between roadway and goaf roof.Presplitting blasting implies a coupled static dynamic loading of the main roof.Dynamic static coupling load is intended to cut the roof by the crack initiation and propagation between the blast holes along the roadway while ensuring that the roof above the roadway remains undamaged.This process,controlled by the spacing between the blast holes (SBH) and the load application length (LAL),was studied for the particular case of the tailgate at the 7135 working face in the Qidong Coal Mine,China.Based on the attenuation formula of the stress wave in the rock strata,the fracture mechanism of main roof presplitting blasting was analyzed,and the fracture criterion based on tensile strength was established to determine the smallest quantitative relationship between SBH and LAL during the crack formation.Based on the characteristics of the main roof stress in the process of presplitting blasting,the mechanical model of the dynamic static coupling action of the main roof mechanics is established.The calculation formula of the main roof stress under the coupling action is obtained.The stress distribution law of the main roof at different time under dynamic load is analyzed.The propagation law of the blasting stress wave in the main roof is revealed,which is the alternating transformation of tension and pressure,and the same position of the main roof of the roadway is continuously affected by the tension stress and pressure dynamic pulse.The relationship between the main roof tensile stress distribution and different lateral stress concentration factors under static load is analyzed.The results show that the stress concentration coefficient in the limit equilibrium zone only affects the local tensile stress distribution of the main roof of the roadway (0<x< 3.0 m),but has no effect on the main roof stress distribution in the distance (x>3.0 m).The main roof stability of the roadway is analyzed and the stability criterion of the main roof is obtained,and the maximum quantitative relationship between SBH and LAL is determined.According to the VB calculation platform,the length of presplitting blasting charge at the 7135 working face of Qidong Coal Mine is 4 m,and the spacing between blastholes is 600 mm.These predictions are experimentally verified by the visual observation of the roof convergence through the blast holes.

1 无煤柱切顶留巷基本顶受力特征

    1.1 无煤柱切顶留巷工程概况

    1.2 无煤柱切顶留巷基本顶预裂爆破受力特征

2 基本顶成缝机理

    2.1 成缝机理分析

    2.2 成缝与炮孔间距及装药长度量化关系

3 巷道基本顶稳定机理

    3.1 动载作用下基本顶应力分布

    3.2 静载作用下巷道基本顶应力分布

    3.3 稳定与炮孔间距及装药长度量化关系

4 工程验证

5 结论