Comparative Study on the Test Method for Tensile Elastic Modulus of Rock Materials

Abstract

Rock material has different mechanical behaviors under compressive and tensile loading. Correspondingly, there are two types of elastic modulus: compressive elastic modulus Ec and tensile elastic modulus Et, respectively. To distinguish which indirect test methodology, including three-points bending test and Brazilian disc test, is more suitable to measure the tensile elastic modulus Et of rock materials, a series of uniaxial compressive test (UCT), direct tensile test (DTT), three-points bending test, and Brazilian disc test are performed for three typical types of rock: marble, granite, and sandstone. Comparative investigation on the reliability of measurement results of tensile elastic modulus Et is systematically conducted. Finally, it is found that Brazilian disc test could be a suitable method to measure tensile elastic modulus of rock materials, due to the excellent agreement with that measured by DTT and the simplicity of sample preparation, as well as test operation.

Predicting the Mechanical and Fracture Properties of Mars Analog Sedimentary Lithologies

“…In computational fracture models, however, the use of E C alone is invalid, as the elements in the cohesive zone can experience both tensile and compressive stress at varying times during crack growth. It has been demonstrated that elastic moduli of rock may differ considerably in compression versus tension (Zhang & Yu, 2019). We were unable to derive the E T of rock specimens from our experimental test efforts, so we utilized common sandstone values (~3.5 GPa) from the literature in G IC determinations, with the recognition that doing so introduced a layer of error into our analysis (Zhang & Yu, 2019).…”

“…To determine the mechanical properties needed to predict rock fracture in our analog lithologies (Missoula mudstone and silt and sandstone of the Cutler, Clinch, and Chapman Ridge formations), three types of experimental testing were performed to characterize UCS, TS, and plane strain fracture toughness ( K IC ) (Figure 5). Compressive elastic modulus ( E C ) and fracture energy ( G IC ) were then derived via standard relationships (American Society for Testing and Materials (ASTM) 7012, 2014; Zhang & Yu, 2019) from UCS and K IC test results, respectively. Additional properties needed for computational model input included the tensile elastic modulus ( E T ) and Poisson's ratio ( v ).…”

“…For modeling efforts, we held v constant and selected a standard value for sandstone rocks (0.25; Gercek, 2007). Values for E T were derived from previously published studies that analyzed similar sedimentary rock types (e.g., Zhang & Yu, 2019).…”

“…Since E T was not available from our test data, we utilized values reported in the literature for sandstone (i.e., ~3.5 GPa; Zhang & Yu, 2019).…”

“…To simulate the scenario in which only UCS values would be available from Curiosity rover data, we used published correlation equations (Table 1) to predict the properties of TS and G IC from UCS values for Chapman Ridge, Clinch, Cutler, and Missoula specimens. Other required inputs, including E T (~3.5 GPa; Zhang & Yu, 2019) and v (~0.25; Gercek, 2007), were estimated from the literature, whereas E C was acquired from experimental testing. Using these five properties, we evaluated the effects of the uncertainty in these properties on the force‐displacement curve of the three‐point bend simulation throughout crack propagation.…”