采动过程中底板岩层变形破坏与损伤机理分析

底板岩层在采动过程中的变形破坏取决于底板的应力场和原生缺陷分布。为了研究底板岩层破坏的细观机理,描述底板岩层的裂隙演化,在分析煤层底板应力环境的基础上,基于岩石工程破坏准则,采用连续介质损伤力学和几何损伤理论的研究方法将损伤、渗流及孔隙率演化等相互耦合的有效应力概念引入莫尔-库仑(Mohr-Coulomb)破坏准则,建立了煤层底板脆性裂隙岩体介质在孔隙水压力作用下受采动影响的脆性动力损伤发展和孔隙率演变模型。并应用该模型对谢桥矿8#煤层开采过程中的底板变形破坏特征和裂隙水的迁移活动规律进行了脆性动力损伤分析。该损伤力学模型可用于煤层底板稳定性分析。

Damage Mechanism Analysis of Deformation Failure Characteristics in Floor Strata

The failure of the floor rock mass depends on the floor stress field and distributions of the primary fissure.On the basis of analyzing the rock engineering failure criteria and the stress situation of the floor strata, the author analyzed the interaction of coupled seepage and stress fields in cracked rock mass,described the microscopic mechanism and evolution of crack in floor strata.In this paper,A brittle dynamic damage model for cracked floor strata subject to coal mining is adopted for the analysis of dynamic responses of damaged rock mass based on the continuum damage mechanics and geometry damage theory.In the developed model,the concept of effective net stresses in the damaged zone,which involve the coupling affects of damage,seepage characteristic of cracked rock mass,pore pressure and porosity evolution in floor strata has been introduced into the modified Mohr-Coulomb failure criterion in order to express the brittle dynamic damage growth and propagation phenomenon.The developed dynamic damage theoretical model for cracked rock mass is utilized to analyze stability of the floor strata of No.8 coal seam in Xieqiao Coal Mine as an engineering example of the application.The results of the brittle dynamic damage analysis for the floor strata show that the significant damage growth starts in the position where a high shear stress concentration area exists.