Study On Contact Zone Composite Rock Mass Incompatible Deformation And Control In Underground Mining

In underground mining, contact zone composite rock mass non-compatibledeformation caused widely shear failure and local roof falling. Meanwhile, waste rockcould easily collapse from soft and broken contact zone roof stopes, which not onlyformed significant safety hidden dangers but also reduced mining efficiency greatly.Non-compatible deformation failure of contact zone composite rock mass could not beinterpreted and cotrolled effectively by the existing control theory and technology, whichseriously restricted large-scale efficient exploitation of underground mines. In order tofind efficient treatment methods of contact zone composite rock mass, and realize safeand highly efficient operation of contact zone tunnels and stopes, by rock mechanics tests,theoretical analysis, similarity experiments, numerical simulation and field test, themechanical properties and underground mining engineering stablity problems of contactzone composite rock mass were studied in this paper.(1) The failure and strength characteristics of contact zone composite rock sampleswith different contact angle were obtained by the uniaxial compression tests.Microscopically, the strain coordination and transverse constraint stress on the contactface in rock materials with different deformation characteristics was analyzed. Thestrength model of contact zone composite rock mass with macroscopic non-compatibledeformation was constucted, which could explain strength change characteristics ofcontact zone composite rock samples in the uniaxial compression tests. A rock creepconstitutive model considering the initial damage and creep damage was constucted, onthe basis of which, the relation between secondary stress caused by contact zonecomposite rock mass non-compatible creep deformation and rock mechanical parameters,load, time. The secondary stress and strength of composite rock mass has been revealed.(2) By numerical simulation and similarity test, influence of contact zonemechanical properties, contaet zone occurrence and ground stress on distribution ofnon-compatible deformation and secondary shear stress was systematically analyzed.Based on plastoelasticity theory, the influence of contact zone rock non-compatibledeformation on the tunnel plastic loosened zone was studied. Strength decrease,secondary shear stress concentration and plastic loosened zone extension resulting from contact rock non-compatible deformation was concluded to be the main cause of contacttunnels failure.(3) Based on fracture mechanics theory, extension criteria, extension direction andextension depth function of single fracture in the secondary shear stress environmentresulting from contact zone rock non-compatible deformation was constructed. Themechanical dynamic process from fracture extension to roof falling in the surroundingrock of contact zone tunnels was simulated, which could reveal mechanism of contactzone tunnels non-compatible deformation failur and effectively interpret the failurecharacteristics of typical contact zone tunnels.(4) Contact zone tunnels control idea based on “coordinating deformation” wasproposed. On this basis, a contact zone tunnels non-uniform transition support methodwas formed, with support pattern of “X” shear resistance support, asymmetric supportand non-uniform distribution prestressed support. Furthermore, non-uniform supportparameters adapt to the distribution of stress and deformation in surrounding rock wasbuilt. Depending on this support method, non-compatible deformation and secondaryshear stress concentration in contact zone tunnels could be relieved, meanwhile, thesurrounding rock failure caused by shear slip extension of original fracture could becontrolled effectively.(5) A mining method of continuous strip mining with roof cutting in advance, wasterock and tailings filling suitable for soft contact zone roof deposit was developed.Determination method of safety mining strip width with maximum productive capacitywas formed, meanwhile, composite backfill unloading technology of tailings flexibleroof-contact was proposed. With this mining method and roof cotrol measures, rooftreatment, mining and filling in soft contact zone roof deposit could be efficiently andcollaboratively conducted.Through the above researchs, the mechanical properties of contact zone compositerock mass with non-compatible deformation has been revealed, and the highly efficientmethods of contact zone tunnels and stopes stablity control has been formed, whichcould provide contact zone rock mass treatment during underground mining with basictheory and application technology support.