Application Of Support Theory For Excavation Damaged Zone In Deep Layered Rock Mass

Due to wide distribution of layered rock mass in nature, plus the tendency of the engineering construction to a peak period in recent years, stability problems of those engineering in layered rock mass are becoming increasingly important. For underground engineering, the stability considerations are focused on the reasonable support method of the surrounding rock mass. As a complex rock mass, the strength and deformation properties of layered rock mass are usually transversely isotropic or orthotropic, and its failure mode and mechanism are different from other rock mass significantly. Therefore, its failure mechanism should be studied sufficiently before designing the supporting method of stratified surrounding rock mass. Subsequently, the support theory based on excavation damaged zone is introduced. Several valuable conclusions are obtained by means of theoretical analysis, numerical simulation and field measurement. The main contents and conclusive results are as follows:(1)The stress distribution in the surrounding rock mass of the circular roadway excavated in non-layered rock mass is analyzed, and its radiuses of plastic zone and relaxation zone are obtained respectively, then the laws of roadway depth, radius, shear parameters of the surrounding rock mass and the relaxation zone are discussed. On this basis, the effects of the bedding plane of stratified surrounding rock mass on the relaxation zone are analyzed qualitatively. It is found that the strength and deformation properties are influenced by dip of the bedding plane remarkably, and their magnitudes depend on the degree of anisotropy of rock mass.(2)The loose and failure conditions in the surrounding rock mass of the cicular roadway and semicicular arch roadway excavated in non-layered rock mass and layered rock mass are studied by a mechanical calculation software——RFPA2D-SRM. The applicability of the software is verified. In addition, the whole process from cracks initiation, expansion and transfixion to roadway failure in layered rock mass with different dips of the bedding plane and lateral stress ratios are explored and finally the engineering stability of layered rock mass is analyzed qualitatively.(3)On basis of the support theory based on excavation damaged zone, the main supporting objects of surrounding rock mass, classification methods of excavation damaged zone and supporting mechanism of bolts are explored. Under the guidence of the theory, the destructions of deep roadways in Shabatu Mine are investigated in detail, the physical and mechanical properties of red shale are tested, the laws of deformation and failure of roadway surface and internal rock mass are measured in site, a deformation-coordinated and energy absorption bolt is designed. And finally a new supporting type and construction technology are proposed. It is indicated that the new ones can have better technical and economic effects through the in-site tests.