Comparative Study On Size Effect Of Rock Tensile And Compressive Strength Under Different Strain Rates

As two important parameters of rock,compressive and tensile strength has been a research focus of Rock Mechanics and Engineering.At present,the rock strength obtained mainly through laboratory tests,and laboratory test sample size is much smaller than the actual project size of the rock,it should be considered such size differences affect their strength.Meanwhile,rock strength affected by strain rate,rock strength under static and dynamic loads showed a greater difference.Therefore,studying the size eff-ect of rock tensile and compressive strength under different strain rate(or loading rate)have great theoretical and practical significance.We selected two kinds of rock(sandstone,Zigong Sichuan and granite Gansu Beishan),experimented uniaxial compression test and Brazilian test with different size rock samples under static,quasi-static and dynamic conditions,the main results obtained are as follows:1.Under static and quasi-static conditions,sandstone uniaxial compressive strength decreases with increasing size,and the higher the strain rate,the size effect is more obvious;However,under dynamic conditions,the uniaxial compressive strength increases with increasing size,but also the higher the strain rate,the size effect is more obvious.2.Sandstone uniaxial compressive strength with increasing strain rate increases;Under static and quasi-static conditions,the relationship between the strength and strain rate performances linear,while the smaller the sample size,strength with strain rate increasing trend more obvious.3.Under different loading rate(static,quasi-static and dynamic)conditions,sandstone and granite Brazil splitting tensile strength decreases with the increase in size,and the higher loading rate,the size effect is more obvious.4.Sandstone and granite Brazil splitting tensile strength increased with increasing loading rate.Under static and quasi-static conditions,the Brazilian splitting tensile strength with the logarithm of loading rate increasing increased linearly.But under dynamic conditions,Its strength and loading rate showed a power function;At the same time different loading rate(static,quasi-static and dynamic)conditions,the smaller the sample size,strength increases with loading rate trend more obvious.5.Under the same loading conditions,the ratio of sandstone tensile and compressive strength increases with decreasing size.Under static and quasi-static conditions,the tension and compression ratio of the same size rock samples is changed not obvious with loading rate increasing,but under dynamic condition,it increased with loading rate increasing...