Abstract
The evolution of mining-induced stress field in longwall panel is closely related to the fracture field and the breaking characteristics of strata. Few laboratory experiments have been conducted to investigate the stress field. This study investigated its evolution by constructing a large-scale physical model according to the in situ conditions of the longwall panel. Theoretical analysis was used to reveal the mechanism of stress distribution in the overburden. The modelling results showed that: (1) The major principal stress field is arch-shaped, and the strata overlying both the solid zones and gob constitute a series of coordinated load-bearing structures. The stress increasing zone is like a macro stress arch. High stress is especially concentrated on both shoulders of the arch-shaped structure. The stress concentration of the solid zone in front of the gob is higher than the rear solid zone. (2) The characteristics of the vertical stress field in different regions are significantly different. Stress decreases in the zone above the gob and increases in solid zones on both sides of it. The mechanical analysis show that for a given stratum, the trajectories of principal stress are arch-shaped or inversely-arched, referred to as the “principal stress arch”, irrespective of its initial breaking or periodic breaking, and determines the fracture morphology. That is, the trajectories of tensile principal stress are inversely arched before the first breaking of the strata, and cause the breaking lines to resemble an inverted funnel. In case of periodic breaking, the breaking line forms an obtuse angle with the advancing direction of the panel. Good agreement was obtained between the results of physical modeling and the theoretical analysis.
Highlights
Longwall mining has been widely used in China for nearly half a century (Kang et al 2019b; Wang 2018; Xu et al 2004)
This study investigated its evolution by constructing a large-scale physical model according to the in situ conditions of the longwall panel
This study proposed a system of physical modeling to carry out the real-time monitoring of mininginduced stress during model excavation to examine its distribution and evolution
Summary
Longwall mining has been widely used in China for nearly half a century (Kang et al 2019b; Wang 2018; Xu et al 2004). With the widespread application of the fully mechanized mining technologies, such as LHM and TCC, both the cutting height and the advancing velocity have increased rapidly, which implies an increase in the intensity of excavation of the longwall panel (Bai and Tu 2019; Bandyopadhyay et al 2020) This can lead to such strata behaviors as coal wall spalling (Bai et al 2016; Wang and Pang 2017), hydraulic support crushing disasters(Ju et al 2015), and other accidents that endanger the safety of workers (Li et al 2007; Qi et al 2019). As an indispensable approach to longwall mining, physical modeling has played a critical role in determining the movement and breaking of the strata as well as ground subsidence (Bai et al 2019; Ghabraie et al 2015b; Kang et al 2018). Mechanical analysis was used to reveal the mechanism of stress distribution as well as the correlation between the distribution of principal stress and the breaking of the strata
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
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 call
