On the load capacity and fracture mechanism of hard rocks at indentation loading

On the Inelastic Mechanical Behavior of Granite: Study Based on Quasi-oedometric and Indentation Tests

“…In percussive drilling, both rate and size effects on the tensile strength play an important role in the fragmentation response and the combination of them is needed to explain these phenomena. However, considering the small values of the effective volume during indentation testing (Weddfelt et al 2017), the rate dependence of Bohus granite based on previous studies performed by the authors and also the range of strain rates occurring in percussive drilling (Saadati et al 2016), the rate effect should be less critical than the size effect (Weddfelt et al 2017). It should also be mentioned that any size effect in the compressive behavior was excluded in that study.…”

“…The fragmentation response of quasi-brittle materials subjected to quasi-static (Q-S) or dynamic loadings has been widely studied in the literature (Price and Farmer 1979;Cook et al 1984;Vermeer and De Borst 1984;Detournay 1986;Pang and Goldsmith 1990;Liu et al 2002;Saksala 2011Saksala , 2013Zhao and Cai 2010;Saksala 2010;Wang et al 2011;Arzúa and Alejano 2013;Saadati et al 2014Saadati et al , 2016Saadati et al , 2018Tkalich et al 2016;Weddfelt et al 2017). Cook et al (Cook et al 1984) investigated the fracture process by performing Q-S indentation tests on rock samples using circular flat-bottomed indenters with different sizes.…”

“…Further, the size effect on the tensile strength of Bohus granite was investigated by performing three-point bend tests on specimens of different sizes and using the Weibull size effect and the concept of effective volume (Weibull 1952;Davies 1973;Hild and Marquis 1992), namely, the portion of the total volume that is subjected to a positive equivalent stress (Saadati et al 2018). Furthermore in indentation applications the effective volume was calculated for a semi-infinite medium loaded by a cylindrical indenter and using a probabilistic approach (Weddfelt et al 2017). In percussive drilling, both rate and size effects on the tensile strength play an important role in the fragmentation response and the combination of them is needed to explain these phenomena.…”

“…One of the other interests of the present work is to investigate the Q-S force-penetration (P-h ) response of Bohus granite loaded by a spherical indenter, and thereby also validating the employed material model. The attention is primarily put on the loading range up to the first main load drop, corresponding to the load capacity of the material (Weddfelt et al 2017), in order to avoid effects due to cracking in the constitutive modelling.…”

Numerical Study on the Elastic Deformation and the Stress Field of Brittle Rocks under Harmonic Dynamic Load

“…At present, a large number of studies on the indenter intrusion process have been proposed for different geometries of indenters such as spherical, pyramidal, conical and flat-ended cylindrical 2 of 16 indenters through theoretical, numerical and experimental methods [20][21][22][23]. Elastic mechanics is the most common theoretical approach for studying the deformation and stress field of rocks [24][25][26][27]. The finite element method (FEM), the boundary element method (BEM) and the discrete element method (DEM) are three widely used methods to simulate the indenter intrusion process [28][29][30][31][32].…”