Influence of Loading Rate on Deformability and Compressive Strength of Three Thai Sandstones

Abstract

Uniaxial and triaxial compressive strength tests have been performed using a polyaxial load frame to assess the influence of loading rate on the strength and deformability of three Thai sandstones. The applied axial stresses are controlled at constant rates of 0.001, 0.01, 0.1, 1.0 and 10 MPa/s. The confining pressures are maintained constant at 0, 3, 7 and 12 MPa. The sandstone strengths and elastic moduli tend to increase exponentially with the loading rates. The effects seem to be independent of the confining pressures. An empirical loading rate dependent formulation of both deformability and shear strength is developed for the elastic and isotropic rocks. It is based on the assumption of constant distortional strain energy of the rock at failure under a given mean normal stress. The proposed multiaxial criterion well describes the sandstone strengths within the range of the loading rates used here. It seems reasonable that the derived loading rate dependent equations for deformability and shear strength are transferable to similar brittle isotropic intact rocks.

Effects of Displacement Velocity on Rock Fracture Shear Strengths under Large Confinements

“…A polyaxial load frame (Fuenkajorn & Kenkhunthod, 2010) is used to apply constant and uniform lateral stresses (confining pressures, σ 2= σ 3 ) and vertical (axial -σ 1 ) stress to the block specimen. Figure 2 shows the directions of the applied stresses with respect to fracture orientation.…”

Characterization of three Himalayan rocks using a split Hopkinson pressure bar

“…Dynamic compression tests of rocks at different strain rates have been performed by several researchers using the split Hopkinson pressure bar (SHPB) and dynamic triaxial tests. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] Dynamic uniaxial compression tests were performed on three rocks by 3 using SHPB at strain rates from 10 À 4 /sec to 10 4 /sec at varying temperatures and the SHPB test data for rocks were reported for the first time in the literature. They observed that the rocks exhibited increased stiffness and higher stress with increasing strain rate and decreasing temperature.…”

Failure mechanisms in coal: Dependence on strain rate and microstructure

“…[], Ray et al . [], Li and Xia [], Kohmura and Inada [], Fuenkajorn and Kenkhunthod [], and Wang et al . [] conclude from experimental observations that the uniaxial compressive strength of rock increases with an increase in strain and loading rates.…”

“…Apart from the microstructure itself, the strength and failure mechanisms of coal are also affected by the loading rate . Okubo et al [1992], Ishizuka et al [1993], Ray et al [1999], Li and Xia [2000], Kohmura and Inada [2006], Fuenkajorn and Kenkhunthod [2010], and Wang et al [2013] conclude from experimental observations that the uniaxial compressive strength of rock increases with an increase in strain and loading rates. However, it remains unanswered how the combined effects of microheterogeneity and loading/strain rates influence the strength and failure behavior of coal.…”