| It is a difficult problem in rock mechanics that the process of rock fracture propagation.The experiment is the foundation of theoretical analysis and numerical simulation of rock engineering.The inherent mechanism of rock fracture and failure can be deeply understood by doing experiments to study the process of crack propagation in rock.Aiming at the crack propagation problem of rock,the paper carried out experiments of type ? and type ?-? rock fracture.The digital speckle correlation method was adopted for studying the propagation process of rock crack and related mechanical parameters.The experimental systems for type ? and type ?-?rock fractures were built.The calculation principles of digital speckle-related methods and the experimental system and were introduced.And the calculation methods of fracture parameters such as crack tip opening displacement,crack propagation rate and stress intensity factor of crack tip were described.The experimental investigation on the evolution characteristics of the type I crack propagation in rock was carried out by using the prefabricated crack three-point bending test method.Indexes such as the displacement field in the vicinity of the crack and the crack tip opening displacement,crack growth rate,stress intensity factor of crack tip during crack propagation are analyzed,and the influence characteristics of loading speed on these indexes are studied.The evolution process of the displacement field and the crack growth rate during the type I crack growth process of rock,as well as the influence of the loading speed on these indexes are obtained,and the crack growth mechanism under tensile stress is revealed.The experimental investigation on the evolution characteristics of type ?-? crack propagation in rock under the action of tensile stress and shear stress was carried out,by using the three-point bending test method of crack with offset prefabricated.The specimen displacement field,crack tip opening displacement and stress intensity factor of crack tip during crack propagation were analyzed,and the influence of the offset distance of crack from the force application point on these indexes was studied.Some results are obtained,such as: the evolution of the displacement field during the type ?-? crack growth process of rock,the relationship between the direction of crack growth and the offset distance,the influence of the offset distance on crack tip opening displacement and stress intensity factor of crack tip.The crack propagation mechanism under the combined action of tensile and shear stress is revealed.The experimental investigation on the evolution characteristics of type ?-? crack propagation under the action of compressive stress and shear stress was carried out by using the bilateral crack compression-shear test method.The displacement field of the specimen,the sliding between crack interface,and the stress intensity factor of crack tip during the crack propagation process are analyzed.Some evolution law are obtained that rock surface displacement field,the frictional sliding between crack interface,and the stress intensity factor at crack tip during the application of horizontal shear load under vertical confining pressure. |
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