| In the construction of water rich bedrock shaft sinking,the artificial underground ice formed by freezing method and the near area of the rock mass bonding surface are also affected by the dynamic impact.Therefore,the study of the strength and deformation characteristics of the frozen rock wall of the ice rock combination plays an important role in the safety of the freezing project.Based on the difference of impact strength and the non-uniformity of temperature around the frozen wall,the thesis adopts experimental research and numerical simulation to analyze the dynamic mechanical characteristics of the ice rock combination bonded by ice and frozen red sandstone,and studies the influence of different impact pressure and freezing temperature on the energy dissipation and compression deformation failure of the ice rock combination,and compares them with two single medium specimens.The main research contents and achievements are as follows:(1)Static uniaxial compression tests were carried out on columnar ice,saturated frozen red sandstone and ice rock combination under different freezing temperatures.The compression strength and deformation failure characteristics of three specimens were studied.The effects of water and water ice phase transition on the corresponding rock strength properties were analyzed.The microscopic parameters of PFC numerical simulation were calibrated.The results showed that the failure modes of columnar ice specimens mainly included brittle splitting failure and ductile bulging failure,The failure form of brittle ductile transition has not occurred,and the components of the rock of the ice rock combination have not been damaged,while the ice rock combination has produced a large number of cracks.Therefore,the strength of the ice rock combination should be paid more attention to during the freezing method construction,so as to avoid water inrush and other accidents.(2)Based on SHPB dynamic impact test,the influence of different impact pressure and freezing temperature on energy dissipation and compression deformation failure of ice,frozen red sandstone and ice rock combination is studied,and the dynamic mechanical properties of the three specimens are compared.The results show that the bonding effect restricts the lateral deformation of ice and frozen sandstone,and the lateral restraint effect of the bonding interface is strengthened with the increasing strength of impact load,The dynamic compressive strength of the specimen is improved.The bonding interface of ice rock combination is affected by the bonding between ice body and frozen sandstone and the strength of ice crystals.The frozen sandstone has the function of preventing crack growth.The closer to the frozen rock,the greater the compressive strength of ice body.(3)The energy time density EV(tm)with time intensity is introduced to study the relationship between impact pressure and freezing temperature and energy absorption per unit time,respectively.Through crushing screening test and fractal dimension calculation,the impact fracture fractal characteristics of frozen sandstone are analyzed,and a functional relationship model between energy time density and fracture fractal dimension is established.The results show that the fragment distribution of frozen red sandstone specimen in SHPB test has fractal characteristics,The fractal dimension can be used as a quantitative indicator of rock damage.The energy time density and fractal dimension of frozen sandstone specimen conform to the power function relationship.(4)Based on the PFC-FLAC coupling SHPB simulation method,the two-dimensional dynamic impact process of the ice rock combination under different combination modes is simulated,the dynamic mechanical properties of the ice rock combination under different combination modes are studied,and the dynamic crack propagation law of the ice rock combination under impact load is revealed from the mesoscopic perspective.The results show that the dynamic elastic modulus combination angle of the specimen is independent,and with the increase of the combination angle of the ice rock combination,The peak stress decreases first and then increases.Some cracks in the sandstone of the combination specimen continuously extend from the incident end to the ice rock interface,and finally form a through main crack in the direction of parallel loading.The propagation of microcracks plays a "guiding" role in the damage of the combination. |
