Experimental study on granite and the determination of its true strain-rate effect

Abstract

To accurately determine the true strain-rate effect of granite in split Hopkinson pressure bar (SHPB) tests, systematic experimental studies from quasi-static to dynamic loading on the same batch of granite samples is required. Therefore, firstly, splitting, uniaxial and triaxial compression tests were used to study the mechanical response of granite under different static stress conditions with the MTS rock mechanics test system, and the impact compression tests were performed at different strain-rates by the split Hopkinson pressure bar (SHPB). The test results show that the compressive strength increases with the increase of confinement, but the increase rate decreases as the confinement gets larger. The axial failure strain also increases with the increase of confinement. Failure is related to the composition and structure of granite, as well as the stress state. With increasing confinement, the sample is more constrained, the elastic limit strain becomes smaller, and the elastic modulus becomes larger accordingly. In addition, shear slip failure takes place under triaxial compression. In the dynamic compression tests, the strain-rate affects not only the strength of granite, but also the degree of fragmentation and the breaking pattern. Also, it has been found that the dynamic compressive strength enhancement of rocks under impact loading is due to the combined effects of the material strain-rate, lateral inertia and end friction; however, in SHPB tests they are coupled together and could not be separated from each other. To determine the material strain-rate effect of rocks in the SHPB tests, the dynamic compressive strength enhancement caused by the lateral inertial effect and end friction effect needs to be removed. Assuming that the effect of the material strain-rate, lateral inertia and end friction is uncoupled, the numerical simulation method has been employed to simulate the SHPB tests on granite. The true strain-rate effect of granite in SHPB tests is thus determined.

Further Investigation on the Real Rate Effect of Dynamic Tensile Strength for Concrete-Like Materials

“…The dynamic performance of mortar under compressive and tensile loading was studied by Yang et al (2015) based on splitting tests, and the results show that mortar is of rate sensitive. Cai et al (2015) systematically conducted quasi-static and dynamic compressive tests to analyze the rate effect of granite, and numerical simulation method is employed to determine the true rate effect of granite through the uncoupled assumption of the rate effect, lateral inertia and end friction effect in SHPB tests. Lu et al (2014) investigated the dynamic compressive behavior of recycled aggregate concrete specimens prepared with five different amount of recycled coarse aggregate [i.e.…”

Energy Evolution Law and Fractal Characteristics of Different Rock Specimen Sizes on Dynamic Compression

“…Cai et al [21] studied that the lateral inertia effect has few influence on test results when the strain rate is lower than some certain value. e test strain rates are all less than 200 s −1 , so the consumed energy of transverse movement can be ignored.…”

“…e test strain rates are all less than 200 s −1 , so the consumed energy of transverse movement can be ignored. Combined the one-dimensional elastic stress wave theory and the stress uniform assumption, the energy is performed by the following equation [21]:…”

Derivation of the True Strain Rate Effect of Roller Compacted Concrete (RCC) from Impact-Induced Fragmentation

“…Finally, the true strain-rate effect can be obtained numerically and analytically. The above traditional decoupling method has been employed in the determination of brittle materials, such as limestone (Yu et al 2013), granite (Cai et al 2015), and normal concrete (Cui et al 2018). Nevertheless, this traditional decoupling method largely depends on the input parameters of numerical analysis, which is generally the mean value of material properties despite the variability in experiments.…”