Comparative Study On Rocks In Different Tensile And Compressive Tests

Rocks are typical brittle materials, the tensile strength which can withstand is far less than the compressive strength, this makes the tensile state the important degree of the rock rising greatly.To obtain all kinds of mechanical parameters of rocks under tensile state, including the tensile strength, elastic modulus and Poisson’s ratio, etc. To obtain mechanical parameters of rocks under tensile state by indoor rock mechanics test is the most direct method to measure.Based on the existing literature review, it is not difficult to found that the tensile test of the rock is not like rock compression test only have uniaxial compression test, but there is a direct tensile, the Brazilian splitting, and three point bending, broken ring and hydraulic fracturing test a variety of ways, and especially in the most widely used for the Brazilian splitting testing.Because of the lack of high strength glue and the backwardness of test instrument there are so many kinds of tensile test methods. Scientists try to calculate the tensile strength of the rocks with other methods to avoid the difficult of the direct tensile test.But at the same time we also noticed that, with the development of rock mechanics test method, there has been a lot of scholars realize the direct tensile test of rocks successfully, through the study of their test methods, combined with the existing test instrument, some reasonable improvements have been made, we can also succeed in this study for the direct tensile test of the rocks, and the test result is satisfactory.This method provides a guarantee in order to obtain the most reliable mechanical parameters of rock tensile. But we also found that in many cases because of the limitation of test instrument, to realize the direct tensile test of the rock is still not easy, but if make comparative study of mechanical parameters of rock tensile with both the rock direct tensile test and indirect tensile test and find their similarities and differences, This research can be reference for other rocks indirect tensile test.Chose four more typical rock (QuYang granite, marble, Beishan granite and limestone), meet the test requirements of standard sample, respectively were carried out under uniaxial compression, direct tensile, the Brazilian splitting and three point bending test, get in the drawing (including direct tensile and indirect tensile and compression strength under deformation parameters.Through the analysis of tensile and compression strength and deformation parameters, first by three big strength criterion, this paper derived the Brazilian splitting the indirect tensile test tensile strength and direct tensile test of tensile strength of the cause of the difference.Also found that the deformation of rock under the condition of the two stress parameters (elastic modulus, Poisson’s ratio), the difference is very big, this according to the test results using FLAC3D numerical analysis software, comparing the thinking of rock under tension and compression, under the premise of different nature, the Brazilian splitting test method for the difference between the results of numerical simulation and theoretical calculation.