| The rock mass with cracks is very common in underground engineering.The mechanical properties of rock are often greatly changed due to the influence of cracks and other factors,which brings many uncontrollable risks to the actual engineering.In this paper,based on the principle of similarity test,a rock like specimen with parallel double cracks is poured,and a static test is carried out to analyze the influence of the thickness and spacing of parallel double cracks on the mechanical properties and creep properties of rock like specimens.The main research is as follows:(1)The uniaxial compression test is carried out on the rock specimen with parallel double cracks.The results show that the prefabricated parallel double cracks have a certain deterioration effect on the compressive strength of the specimen.When the crack spacing is 20 mm,the compressive strength of the specimen is greatly affected by the crack thickness,which decreases with the increase of the crack thickness.When the crack spacing is increased,the compressive strength of the specimen shows a trend of first increasing and then decreasing;When the crack thickness remains unchanged,the compressive strength of each group of specimens shows a trend of increasing with the increase of crack spacing;According to the development trend of macro cracks,the tensile failure is the main failure,and the shear failure is the auxiliary failure.(2)Triaxial compression tests were carried out on rock specimens with parallel double cracks under confining pressures of 4Mpa and 8Mpa.It was found that the compressive strength of the specimens increased significantly after the application of4 Mpa confining pressure.After the confining pressure continued to increase,the growth range of the compressive strength of the specimens decreased;Under the confining pressure of 8Mpa,the compressive strength of double main cracks with crack thickness of 1.0mm increases first and then decreases with the increase of crack spacing,and the compressive strength of other groups of specimens increases with the increase of crack spacing;The cohesion of the specimens(Group B,Group E)with the thickness of 1.0mm of double main cracks and secondary cracks increases gradually with the increase of crack spacing,and the cohesion of the specimens in other groups changes with the increase of crack spacing,but the overall cohesion is relatively uniform;The internal friction angle of B and E groups decreased with the increase of crack spacing.(3)The staged loading creep test was carried out on rock specimens with parallel double cracks.It was found that the instantaneous strain of each group of specimens was the largest at the first stage of creep loading,and then decreased rapidly.The strain of specimens at the stable creep stage showed a gradual increase trend,and the average stable creep rate also showed a gradual increase trend with the progress of the creep test.In the first three stages of creep loading,The average steady creep rate of each group of specimens shows a trend of increasing with the increase of crack spacing.(4)The uniaxial compression test is carried out on the creep specimens.The results show that the compressive strength of several groups of specimens is improved after the creep action,and the strength of some groups of specimens decreases after the creep action.The overall crushing degree of the specimens is relatively more serious during the compression process.The macro cracks are mainly tensile cracks,supplemented by shear cracks.Some groups of specimens produce some longitudinal cracks on the surface of the specimens when they are damaged.Figure 43 Table 10 Reference 81... |
