Study On Mechanical And Creep Properties Of Fractured Rocks With Different Thickness And Distribution

Fractured rock mass is very common in engineering,and its mechanical and creep properties are obviously different from those of intact rock mass.Many scholars have carried out research on this and achieved fruitful results.In this paper,a variety of similar materials are used to prepare rock like specimens with through cracks,carry out indoor experimental research,and analyze the effects of crack thickness and distribution position on the total stress-strain curve,mechanical and creep characteristics of rock like specimens.(1)Through the uniaxial compression test of rock like specimens with different prefabricated through cracks,the results show that the through cracks greatly weaken the compressive strength and elastic modulus,in which the compressive strength decreases in a cliff like manner due to the existence of through cracks,with a decrease of about 55%;Compared with other crack distribution positions,when the crack is distributed near the end of the specimen,it has a certain degree of strengthening effect on the compressive strength,while when the crack is distributed near the center of the specimen,the greater the crack thickness,the lower the strength;When the crack is 0mm,20mm and 30mm away from the center of the specimen,0.6mm is the most unfavorable thickness,but when the crack is 10mm away from the center of the specimen,the change trend of elastic modulus with thickness of the crack specimen is completely opposite to that of other groups.(2)Triaxial compression tests with confining pressures of 4MPa and 8Mpa were carried out on rock like specimens with different prefabricated through cracks.The results show that the application of confining pressure can not effectively inhibit the weakening effect of through cracks on strength;With the increase of confining pressure,the sensitivity of compressive strength of fracture specimens to confining pressure gradually decreases,which is not a linear positive correlation;The variation trend of internal friction angle of each group of crack specimens is similar to that of compressive strength increment when the confining pressure is 4MPa.When the crack distribution is 10mm from the center of the specimen,the cohesion has the lowest sensitivity to the crack thickness,and the end of the specimen has a certain enhancement effect on the cohesion.When the thickness is 1.0mm and the distribution position is 20mm,the cross influence of crack thickness and distribution position is the most obvious.(3)Through the uniaxial graded creep test of rock like specimens with different prefabricated through cracks,the results show that the instantaneous strain produced in the process of stress level loading of the same specimen first decreases in the form of a cliff,and then decreases slowly.On the contrary,the steady-state creep rate increases slowly;The instantaneous strain at each distribution position first increases and then decreases with the increase of crack thickness.When the crack thickness is 0.6mm and 1mm,the specimen is most sensitive to stress loading and is more likely to produce large instantaneous strain;When the crack distribution is close to the center and end of the specimen,it can promote the steady-state creep rate,and the greater the crack thickness is,the more obvious the effect is.(4)The results show that the compressive strength of most crack specimens increases in varying degrees after uniaxial creep,but some specimens produce new cracks during creep,resulting in a slight decrease in uniaxial compressive strength,The compressive strength of intact specimens decreased most significantly.When the cracks are distributed near the end of the specimen,the effect of thickness on the compressive strength after creep is obviously weakened.Figure 32 Table 10 Reference 81...