Loading rate effects on anisotropy and crack propagation of weak bedding plane-rich rocks. (1st May 2020)

• Record Type: Journal Article
• Authors: Ju, Minghe; Li, Jianchun; Li, Jing; Zhao, Jian
• Is Part Of: Engineering fracture mechanics. Volume 230(2020)
• Publication Date: 2020-05-01
• Subjects: Bedding plane -- Crack deflection -- Dynamic loading -- Rock fracture -- Anisotropy; Fracture mechanics -- Periodicals; Rupture, Mécanique de la -- Périodiques; Fracture mechanics; Periodicals; 620.112605
• DOI: 10.1016/j.engfracmech.2020.106983
• Languages: English
• ISSNs: 0013-7944

Abstract

Highlights: The mechanism of fracture pattern transition of heterogeneous rock was experimentally and theoretically revealed. The rate-dependent fracture patterns of bedding plane-rich rock were quantitatively derived. Rate effect on anisotropic behaviour of heterogeneous rock was systematically analysed. Abstract: Weak bedding planes and joints predominate the anisotropic behaviours of rock mass under external static or dynamic loads. In this article, the rate-dependent fracture performance of a bedding plane-rich rock was experimentally investigated via a split Hopkinson pressure bar (SHPB) system. Based on the dynamic loading of notched semi-circular bending rock specimens at various intersection angles between the notch and bending planes (from 0° to 90°), a couple of outcomes were obtained. It is found that the deflection distance into the bedding plane linearly decreases with bedding angle, indicating the failure pattern of such stratified rock changes from bedding-dominated to rock matrix-dominated. With increasing the loading rate, the trajectory of the propagating crack converted from deflection along the bedding plane to direct penetration into the rock matrix. A factor, anisotropy index η ai, was used to determine the rate-dependent fracture toughness transition at various bedding angles. This anisotropy index exponentially decreases approaching the extreme isotropic value ( η ai = 1) with loading rate. The mechanism of bedding plane-dominated rock fracture was analysed in terms of an energy criterion where the theory was verified by the experimental results. This article is helpful for the deep understanding of fracture behaviour in stratified and grain-based heterogeneous rock structures under dynamic loads.