Research On Characteristics Of The Cracked Media Under Static And Dynamic Shear Conditions

Aimed at the intermittent jointed rock mass(not intact rock sample ) and the dynamic shear loading conditions, the failure modes and the mechanical properties of the cracked media are studied systematically through lots of experiment in meso-scope.In this paper, through the model tests under direct shear conditions, the deformation and strength and their corresponding varying law of rock containing close cracks and rock bridge under 7 regimes with different combinations of crack continuity, crack arranging modes and normal stress are studied. The deformation and failure mechanism of crack and rock bridge are discussed. The normal pressure influences directly the shear resistance of rock mass. There is no definite instruction on the selection of normal force in current rock shear resistance tests, as leads to the extremely easy appearance of different testing results with different operators. In according with this situation this paper has proposed some suggestions of normal pressure in direct shearing test separately for whole rock mass and the cracked media.In this paper, the mechanics characteristics of rock mass with one set of intermittent crack under the dynamic shear cyclic load are systematically studied by means of gypsum laboratory model test for the first time. Based on the idea of using the prefabricated cracks in the gypsum samples to simulate the actual rock mass, the failure mode and the mechanism of rock samples with the intermittent cracks are studied by means of dynamic shear cyclic load and the static load. Then, the frequency effect and the fatigue damage behavior in the cracked gypsum samples are compared and studied further in the paper. The influence of the loading frequency, the crack angle and the crack density to the deformation and strength characteristics of intermittently cracked rock mass are mainly studied, and compared with the study of the non-cracked rock mass. The influence of loading form and the behavior of the simulating materials to the mechanics responses of intermittently cracked rock mass are also researched.