巷道层状顶板三向承载梁承载能力弱化机理研究

Bearing and weakening mechanism of triaxial beam structure in roadway laminated roof

为了研究影响煤巷安全和稳定性的层状顶板结构承载能力衰减问题,采用理论推导、数字试验和相似模拟方法,建立了巷道层状顶板三向承载梁结构的物理和力学模型,依据Drucker-Prager强度准则提出了巷道层状顶板三向承载梁结构的弹塑性分析方法,基于三向承载梁结构的承载机理和极限平衡理论,以淮南张集矿17246工作面轨道巷顶板为分析对象,通过Matlab等数值计算软件,推导出了特定工程地质条件下三向承载梁结构峰后软化阶段和残余承载阶段的极限承载应力及其影响规律。结果表明:巷道层状顶板呈现层状分布、相互作用、分区承载的三维长板结构;基于应力通过岩层逐层传递特性,可求解出岩层当中任意岩层上的作用应力;巷道顶板三向承载梁结构的压剪破坏判断值f<0表示该点进入压剪破坏状态,f=0表示该点达到压剪破坏的临界状态,f>0表示该点仍处于弹性承载状态;煤巷顶板在峰后残余阶段依然具有一定的承载能力,计算得到试验巷道层状顶板的极限承载应力约为5.1MPa,残余承载应力约为2.9 MPa;煤巷开挖后顶板经历弹性承载、弹塑性承载、塑性承载,当顶板处于峰后残余承载时,顶板结构受到外界应力扰动可能发生大变形灾害;随着围压的增加,岩体的峰值抗压强度、残余抗压强度均呈增加趋势。该研究结果揭示了顶板结构承载能力弱化的本质。

In order to solve the problem about attenuation of bearing capacity of roof structure which affects safety and stability of roadway,theoretical derivation,digital experiments and analog simulation method were undertaken to establish a physical and mechanical model of triaxial beam structure of roadway laminated roof.Based on the strength criterion of the Drucker-Prager type,an elastic-plastic analysis method of the triaxial board and bend structure of roadway laminated roof was proposed.The roadway roof of the No.17246 working face in Zhangji Coal Mine in Huainan was analyzed as the object.Based on bearing mechanism and limit equilibrium theory of triaxial beam structure,the ultimate bearing capacity of triaxial beam structure and its influence rule at the post-peak strain-softening stage and residual carrying stage under the special engineering geological condition was deduced with numerical computation software such as Matlab.The results showed that the roadway laminated roof had a long plate structure with lamellar distribution,interaction and partial weight bearing.Based on the characteristic that stress transfers layer by layer through a rock formation,the applied stresses on any rocks in the rock formation could be figured out.The value f was used to determine if shear and compression failure in the triaxial beam structure of roadway roof occur: while f < 0,it was at a shear and compression failure state;while f = 0,it was at the critical state of shear and compression failure;while f > 0,it was at an elastic bearing state and coal roadway roof still had a certain carrying capacity at the post-peak residual stage.The calculation results were obtained that the ultimate load bearing capacity of the roadway roof was about 5.1 MPa and the residual load bearing stress was about 2.9 MPa.Once the excavation of coal roadway begins,roof would undergo elastic bearing,elastic-plastic bearing and plastic bearing.When roof was at the post-peak residual bearing stage and roof structure was perturbated by external stress,a large deformation disaster would probably occur.As confining pressure increases,there are a rising tendency in the rock peak compression strength and the residual compressive strength.The study results revealed the essence of loading capacity weakening of roof structure.