复杂围岩条件下巷道底板反拱支护失效机制及控制

Mechanism of floor failure of roadway supported by inverted arch under complicated surrounding rocks and its control

为探索巷道底板反拱支护结构失效机制,以刘园子煤矿+1100 m轨道石门为工程背景,采用现场勘察、理论分析、数值计算和工程实施相综合的研究方法,阐明底板反拱结构失稳的原因,揭示反拱结构失稳的力学机制,提出反拱结构失稳的'滑转梁'力学模型,并基于Lamé公式、弹塑性理论及力学原理给出'滑转梁'的平衡方程,以该方程分析摩擦因数、岩体内聚力、'锚护岩'深度和'滑转梁'厚度对反拱结构的稳定性及支护强度的影响。结果表明:1)底板反拱结构与U型支架连接处刚度不足是其失稳的关键;2)摩擦因数和底板岩体强度对反拱结构的稳定性有较大影响,而'锚护岩'深度和'滑转梁'厚度对其影响则不明显;3)'滑转梁'的力学状态决定底板的稳定性,当底板支护强度小于临界值时,反拱结构会发生'滑移上升''旋转上升''滑转上升'3种不同的失稳,每种失稳方式的判式及临界值亦不同;4)在巷道及其应力分布对称条件下,3种失稳判式可写成一个程式;5)通过增加反底拱结构与U型钢支架接触处的约束力,或增大底板岩体内聚力可有效控制底鼓;采用底板锚杆支护和增大反拱结构厚度亦能在一定程度上抑制底鼓。基于以上研究,采用底角锚杆+喷浇筑混凝土+36U型圆棚联合支护方案来提高巷道底角刚度及岩体强度,数值分析及现场实施结果均表明该方法能有效控制石门底鼓。

To investigate the failure mechanism of roadway floor supported by inverted arch,the mining level+1100 m track cross-cut in Liuyuanzi coalmine was selected as the experimental mine.By means of field investigation,theoretical analysis,numerical simulation and engineering practice,the instability mechanism of inverted arch structure were clarified.Meanwhile,the mechanical principles of instability in inverted arch structure was revealed.The'sliding-rotating beam'mechanical model for inverted arch structure instability was put forward.Finally,based on Lamé’s formula,elastoplastic theory and mechanics principles,the equilibrium equation of'sliding-rotating beam'was derived.The effects of friction coefficient,cohesion of rock mass,depth of'bolting support rock'and thickness of'sliding-rotating beam'on the stability and support strength of inverted arch structure were analyzed.Results show that:1)The insufficient joint stiffness between inverted arch structure and U-shaped steel support is key to the floor instability.2)The friction coefficient and floor rock mass strength largely affect the stability of inverted arch structure,while the depth of'bolting support rock'and thickness of'sliding-rotating beam'have little effect.3)The mechanical state of'sliding-rotating beam'determines the floor stability.When the floor support strength being less than the critical value,three instability types may occur in the inverted arch structure,i.e.'sliding upward','rotating upward'and'sliding-rotating upward'.The instability and critical value of each mode is also different.4)For the symmetrical roadway and its stress distribution,above three instability formula could be written as one equation.5)The floor heave could be effectively controlled by increasing the restraint force at contact between the inverted arch structure and U-shaped steel support,or by increasing floor rock cohesion.To a certain extent,the floor bolting support and big thickness of inverted arch structure could also restrain the floor heave.Finally,the combined support method with bolt-mesh-shotcrete and 36 U-shaped steel is applied to improve the floor corner stiffness and rock mass strength.Outcomes of numerical analysis and field practice both show that above combined support method could effectively control the cross-cut floor heave.