Abstract
In situ stress is one of the most important factors affecting rock dynamic fractures during blasting excavation of deep rock mass that generally is hard rock. In this research, crater blasting experiments on hard rock under different uniaxial static stresses were conducted to investigate the initiation and propagation process of crack networks that were induced by coupled dynamic and static loads. Furthermore, the effects of anisotropic static stress fields on the initiation and propagation of crack networks during hard rock blasting, and the crack network morphological characteristics were analyzed and elucidated. The experimental results showed that the static stress field changed the process of crack network initiation and propagation during hard rock blasting, and then control the crack network morphology. Under uniaxial static stress, the crack network was elliptical with the long axis parallel to the static stress. In addition, the larger the anisotropic static stress is, the more obvious the elliptical morphology of the crack network. Moreover, the static stress lead to the delay of crack formation which indicates that the delay time during millisecond blasting excavation of deep rock mass should be adjusted appropriately according to the in situ stress. A stress-strength ratio (SSR) of 0.15 is the threshold value where static stress may have a significant effect on the initiation and propagation of a crack network. Meanwhile, the strain field prior to crack initiation during rock blasting controlled the morphological characteristics of the crack network. Finally, the mechanism of static stress affecting propagation and morphology of crack network was revealed theoretically.
Highlights
The development and utilization of deep underground mineral resources and underground space will become an inescapable trend in the future [1,2,3,4,5]
The result of a geo-stress survey in the Jinping II Hydropower Station, China, showed that the geo-stress increases with an increasing burial depth and that this geo-stress changes from a horizontal stress state to a vertical stress state with the increasing of the burial depth from 600 to 3000 m
(1) Uniaxial static stress changes the type of initial cracks during rock blasting and leads to the delay of the initial cracks’ formation and propagation
Summary
The development and utilization of deep underground mineral resources and underground space will become an inescapable trend in the future [1,2,3,4,5]. There are few methodologies that have been developed for underground production blasting, and the few that have been developed do not adequately consider in situ stress [6,7,8]. The maximum in situ stress that was obtained from the survey reached up to 42.11 MPa [11,12]. Owing to the deep in situ stress, the blasting excavation of deep rock mass is completed under the coupling of dynamic and static loads [13,14,15]. In situ stress causes many problems for rock blasting such as boulder yield, serious over and under excavation, and rock burst [11,12,16,17,18]. Rock blasting where the stresses are high has attracted considerable attention from researchers around the world [19,20]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
