Waveform features and failure patterns of hollow cylindrical sandstone specimens under repetitive impact and triaxial confinements

Abstract

In underground engineering practice, the surrounding rocks are subjected to a nonuniform stress field with various radial gradients. In this study, a series of conventional triaxial repetitive impact tests using hollow cylindrical sandstone (HOS) specimens were conducted to reveal the impact waveform features and failure properties of rocks under nonuniform stress conditions. The tests were conducted using a modified large diameter split Hopkinson pressure bar (SHPB) testing system. The confining pressure was set as 5, 10 and 12 MPa. The data of specimens under equilibrium stress states were chosen and analyzed, and the results showed that more applied numbers of cyclic impact loads were needed to break rocks with the increase of confining pressure. Three types of cracks, i.e., ring-shaped cracks around the hole in the center of specimens, axial cracks located in the outer cylindrical surface, and lateral cracks fracturing rock fragments into small pieces appeared in HOS specimens. The failure degrees of HOS specimens could be judged by the waveform features of the reflected wave, and the waveform features of reflected wave are similar in the same failure mode, regardless of the impact velocity and the number of impacts, which only affect the failure degree.

Acoustic emission and computed tomography investigation on fatigue failure of fissure‐contained hollow‐cylinder granite: Cavity diameter effect

“…The excavation stability in shaft sinking or tunnel and drifting engineering and bore-hole stability of oil and gas engineering are closely related to cavity-contained rock. Previously, a lot of attempts have been made to reveal the mechanical responses of cavity-contained rock by numerical test, 11,12 uniaxial or triaxal compression test, [13][14][15][16] multi-axis hollow column test, 17 Brazilian disk test, 18 uniaxial dynamic impacting test, [19][20][21] triaxial repetitive impact test, 22 and hydraulic fracturing test. 23 The strength, crack damage behavior, damage evolution, energy dissipation, hole spalling pattern, and failure modes were systemically investigated for hollow rock exposed to static to dynamic loading conditions.…”

Mechanical properties and failure modes of CRCB specimen under impact loading

“…There are multiple in-depth studies on the mechanical properties 8 – 15 , energy evolution behaviour 16 – 18 , deformation and failure characteristics 19 – 26 , constitutive models 27 , 28 and destruction criteria 29 – 31 of multiphase coal and rock layered composite structures via laboratory tests, theoretical analysis, numerical simulation, etc. For example, Chen et al 2 analysed the evolution of deformation and strength parameters of roof-coal pillar structures with different height ratios based on uniaxial compression tests of roof sandstone-coal pillar structures, which revealed the progressive failure mechanism of the coal–rock structure.…”

Stochastic assessment of hard rock pillar stability based on the geological strength index system

“…On the other hand, many hard rock mechanics experiments show that the information of rock mass quality (such as frequency and feature of fractures, etc.) has very closely relations with rock strength, which affects the stability of rock mass (Li et al 2018;Li et al 2020a, b;Gong et al 2018;Xiong et al 2018;Wang et al 2020aWang et al , b, 2021Yang et al 2020). In specific large underground opening, it is stated that the quality of rocks is directly related to stability of pillars.…”