Measurement of explosively induced movement and spalling of granite model blocks

Fracture Initiation, Gas Ejection, and Strain Waves Measured on Specimen Surfaces in Model Rock Blasting

“…For example, Johansson and Ouchterlony (2013) measured a wavelength of less than 400 µs in smallscale bench blasting, and Liu et al 2018presented a wavelength of approximately 30 µs in a confined mortar model blasting. Sun (2013) showed that the measured waves were longer than 400 µs, but he did not present complete wave, i.e., the waves did not have ends. Interestingly, we found that the length of the strain wave of a cubic granite specimen S6 in Chi et al (2019a) was approximately 1500 µs, which is much greater than the length measured by other researchers mentioned above.…”

“…Another reason for the unsatisfactory blast results is that many basic parameters in rock blasting have not been well determined such as crack propagation velocity, gas penetration speed, and characteristics of stress waves induced in the rock. To understand the mechanism better and improve blast results, various model blasts have been carried out, dealing with stress waves, gas pressure, and fragmentation (e.g., Field and Ladegaard-Pedersen 1971;Bergmann et al 1973;Fourney et al 1974Fourney et al , 1981Dally et al 1975Dally et al , 1993Dally et al , 2006Katsabanis et al 2006Katsabanis et al , 2014Tilert et al 2007;Johansson and Ouchterlony 2013;Onederra et al 2013;Sun 2013;Fourney 2015;Liu et al 2018;Chi et al 2019a, b, c;Yang et al 2019;Zhang et al 2020a, b;Mao et al 2020;Jeong et al 2020). In a number of the previous model blasts, a high-speed camera was used to monitor the blasting process (Chi et al 2019a, b, c;Zhang et al 2020a, b;Jeong et al 2020) and the initiation times of the earliest cracks and gas ejection of a few specimens were approximately determined (Chi et al 2019a, c).…”

“…In a number of the previous model blasts, a high-speed camera was used to monitor the blasting process (Chi et al 2019a, b, c;Zhang et al 2020a, b;Jeong et al 2020) and the initiation times of the earliest cracks and gas ejection of a few specimens were approximately determined (Chi et al 2019a, c). In many other experimental studies using rock, concrete, mortar, and rock-like specimens, strain waves were measured either on the free surfaces of models or within the mortar or concrete models during blasting (e.g., Dally et al 1975;Johansson and Ouchterlony 2013;Sun 2013;Liu et al 2018;He et al 2018;Chi et al 2019a, c;Mao et al 2020). However, the studies combining the determination of fracture initiation and gas ejection with the strain wave measurement are few.…”

Plate impact experiments to investigate shock-induced inelasticity in Westerly granite

“…Shock-induced response of geological materials has been the focus of attention for last several decades due to its applications in planetary impact, explosive crater formations, response of geomaterials to blast/explosive loading, rock fragmentation research [1][2][3][4][5][6][7][8][9], to name a few. In these applications strain rates of the order of 10 5 s À 1 and higher are common and the loading process is usually adiabatic.…”

“…They found the shock-wave front to split into a leading elastic precursor followed by a plastic (in-elastic) compressive wave; the amplitude of the elastic precursor is observed to decrease with increasing propagation distance in the samples. Tilert et al [9] studied explosively-induced movement as well as spall due to buried detonation charges in granite blocks with thicknesses in the range 60-300 mm. Their results suggest a critical spall distance of around 210 mm for buried charges of 1 g high explosives, beyond which no spalling was observed.…”