软岩巷道锚喷支护破坏分析与对策

软岩巷道锚喷支护破坏原因主要有:巷道底板无支护或支护的强度不够,底板流变极易发展,形成了围岩体的流变通道;大部分锚杆支护为低工作阻力值,支护作用没有得到有效发挥;混凝土喷层和围岩体变形不匹配,导致喷层体离层、剪切破坏;钢笆网抵抗破坏和变形的能力弱,降低了网喷层的强度和抗变形能力.采取的支护对策有:底板反拱加强支护,避免局部围岩体的整体移动,实现巷道周边岩体的均匀收敛变形;选用长锚杆,更好地控制巷道围岩的变形;初喷混凝土为厚度20 mm薄喷层,实现初喷层与巷道围岩体的同步变形;用直径4 mm冷拔钢丝编织金属网替代钢笆网,提高网喷层支护体的强度与抗变形能力;二次锚杆支护在复喷混凝土后进行,防止网喷层与围岩体离层现象的发生.

Failure analysis and countermeasure of bolt shotcrete support for soft rock roadway

The failure causes of bolt net shotcrete support for soft rock roadway are mainly include unsupported roadway floor, insufficient support strength, the floor viscous deformation easily, and viscous deformation passage of rock mass is formed. The most bolts have lower work resistance value, can not realize effective effect. The shotcrete deformation is not in correspondence with the surrounding rock mass, and the shotcrete produces absciss layer and shear failure occured. The resistance of deformation and failure for steel bar net is low for reducing strength and deformation capability of net shotcrete layer. The adopted countermeasures are that the floor support is reinforced with opposite arc, to avoid a whole movement of part rock mass, and realize well - distributed convergence of roadway surrounding rock by using long bolts better controls roadway deformation. The first original shotcrete is 20 mm thin layer, to realize a consistent deformation between the original layer and roadway surrounding rock. The knitted 4 diameter cold - drawing steel net replaces steel bar net, to heighten the strength and displacement capacity of net shotcrete. The second bolts are constructed after the second shotcrete, to prevent absciss layer between net shotcrete and rock mass.