Study On Structure And Mechanical Properties And Constitutive Model Of Very Weakly Cemented Rock

Very weakly cemented rock is a special kind of soft rock which is widely distributed inJurassic and Cretaceous strata of China western mining area. Its physical and mechanicalcharacteristics were formed due to the special diagenetic environment and sedimentaryprocess. Due to a series of problems in the study of very weakly cemented rock, there arelittle relevant research in the basic physical-mechanical properties and constitutive model ofvery weakly cemented rock test. With the large-scale construction of China west mine, controlproblem of very weakly cemented rock formation roadway is gradually outstanding. It isnecessary to carry out physical-mechanical properties and constitutive model research of veryweakly cemented rock which with important practical significance and engineeringapplication value of construction and safety production to China western mining area.In this paper, technical means such as rock test, theoretical analysis and numericalsimulation are comprehensively used to the research object of very weakly cemented rock.Physical and mechanical properties of very weakly cemented rock under different stressconditions and water content were studied. The rock regenerative structure formation process,surrounding rock displacement, plastic zone and stress distribution and evolution wererevealed. Dilation and large deformation constitutive model of very weakly cemented rockwere constructed. The failure mechanism of large dilation deformation of very weaklycemented rock mass was analyzed and roadway surrounding rock control technology of veryweakly cemented formations was put forward.The main achievements and progresses:(1) Regenerative structure test device of very weakly cemented rock was independentlydeveloped. The regenerative structure rock loading and consolidation method weredetermined. Regenerative structure rock specimen with different moisture of very weaklycemented rock was formed. The forming process, structure and mechanical properties ofregenerative structure specimen were revealed.(2) Based on crack volumetric strain model, large dilation deformation failuremechanism of very weakly cemented rock mass was analyzed. Stress-strain curvecharacteristics of very weakly cemented rock were studied under different stress state andwater content. The rock mass strength and dilation parameters evolution regularity withdifferent equivalent plastic strain and moisture content were revealed.(3) The pre peak damage dilation and post peak fracture dilation yield criterion wereestablished. The shear and tensile failure regional division conditions of Mohr-Coulomb criterion were modified. The constitutive model of very weakly cemented rock large dilationdeformation was constructed. The post peak strain softening and dilation characteristics ofvery weakly cemented rock were revealed.(4) The incremental iterative format of constitutive model of very weakly cemented rockmass was determined. The secondary development of constitutive model of very weaklycemented rock mass large dilation deformation was realized. Roadway surrounding rockdisplacement, plastic zone and stress distribution and evolution law under the conditions ofdifferent depth, lateral pressure coefficient and dilation angle were revealed.(5) The circle arch section and double anchoring equilibrium arch structure wereproposed. Based on the buried depth effect of roadway and coal seam thickness, classifiedroadway supporting technology scheme of very weakly cemented strata was put forward. Thesurrounding rock deformation and the supporting structure stress evolution law were revealedand successfully applied to engineering practice.