Experimental Study On The Influence Of Cracks At Different Angles On The Mechanical Properties Of Sandstone Under Dynamic And Static Loads

As a kind of complex geological body, rock experienced a variety of complex and uneven geological effects in the geological history of its formation and change. It usually contains irregular defects such as joints, fissures and so on. With the geotechnical engineering excavation, unloading and other disturbances, defects in rock will be further extended, through and lead the rock damaged. In recent years, research on mechanical properties of the rock has become a focus in the field of rock mechanics and engineering. The topic has become one of the hottest topics.In this paper, firstly, the influence of fracture on rock mechanical properties is analyzed from the theoretical point of view. Then the test specimens were prepared and tested in the laboratory. The test results are analyzed under the conditions of static and dynamic loading respectively. The following conclusions are obtained through comparative study.(1)The mechanical properties of the specimens can be changed by the angle of the prefabricated cracks under dynamic and static loads. The sliding surface is influenced by the internal crack formation, expansion and transfer. The strength of test piece is reduced and cracks occur closure in varying degrees.(2)Two kinds of dynamic and static conditions.The failure mode of the complete test piece,0 degree crack specimen and 90 degree fracture specimen is mainly the crack through the bottom of the top of the specimen that splitting tensile failure. The fracture surface and the loading direction of the 45 degree crack specimen have certain dip angle which shear failure and tensile failure occurred at the same time.(3)The breaking degree and ultimate strength of the dynamic load are higher than the static load. It is because of the increase of strain rate of specimen under dynamic load and Increase cracks involved in the expansion. Under the two test conditions, the strength of the crack specimens is lower than that of the complete specimens. When the crack angle is the same, the failure mode of the specimen is the same.In this paper, the samples of pre fabricated rock samples with different angles are studied. The observation of crack evolution under dynamic and static loads and the mechanical properties of specimens are analyzed. The effect of fracture on rock mechanical properties is discussed. Provide theoretical basis for related geotechnical engineering,which provide theoretical basis for related geotechnical engineering.