Mechanism of Hard-Roof Rock Burst Control by the Deep-Hole Blasting: Numerical Study Based on Particle Flow

Anliang Lu,Jiliang Kan,Jinzheng Bai,Kunyou Zhou,Jinrong Cao,Yanjiang Chai,Linming Dou,Shikang Song,Fan Deyuan

doi:10.1155/2021/9527956

Abstract

In underground coal mines, the deep-hole blasting (DHB) technology is generally adopted for thick hard-roof control. This technology uses the energy released by explosives to weaken the energy storage capacity of hard roof so as to prevent hard-roof rock burst disasters. In this paper, a numerical simulation model of roof DHB was established based on particle flow and the damage range of single-hole blasting with concentrated cylindrical charge was studied. The temporal and spatial evolutions of overlying strata, the distribution of the force chain structure, and the working resistance of hydraulic pressure in the mining process before and after the application of DHB were contrastively analyzed. The following beneficial conclusions were drawn. The blasting-induced single-hole damage range is generally characterized by annular zoning. After the application of DHB, overall the collapse morphology of the key strata in the mining process changes from long-distance instantaneous slipping instability to stratified short-arm stepped synergistic subsidence. The density and strength of force chains in the overburden are notably reduced; the peak value of compressive force chain strength in the key strata in the mining process falls by 17.85% as a result of DHB. The monitoring results of the working resistance of hydraulic support reveal that the DHB technology can effectively shorten the step distance of periodic weighting and reduce the variation amplitude of overburden load during weighting. In summary, the mechanism of hard-roof rock burst control by DHB is reflected by both static load reduction and dynamic load reaction.

Highlights

Rock burst, characterized by the sudden and violent release of massive elastic strain energy accumulated in coal rock, poses a major threat to the health and safety of workers in coal mining [1,2,3]
A numerical simulation model of roof deep-hole blasting (DHB) was established through Particle Flow Code (PFC), and the damage range of single-hole blasting with concentrated cylindrical charge was studied
To quantitatively characterize the strength evolution characteristics of compressive force chain of strata in the mining process, this study proposes for the first time to define the compressive force chain strength (CFCS) to be the ratio of the sum of contact forces of compressive force chains between rock particles to the total number of compressive force chains

Summary

Introduction

Rock burst, characterized by the sudden and violent release of massive elastic strain energy accumulated in coal rock, poses a major threat to the health and safety of workers in coal mining [1,2,3]. Ick hard roof can control rock burst from two aspects. According to the theory of dynamic load and static load superposition [4,5,6], when the static load and dynamic load in coal rock around the mining space overlap and exceed the critical load, rock burst will occur. It can form hanging roof at the edge of the gob due to its good mechanical properties, which transfers the overlying load to the coal rock around the gob and leads to the formation of locally high-static-load stress concentration. In the hope of effectively controlling the hard-roof rock burst, active pressure relief measures are required to reduce the high static load and dynamic load around the mining space. The commonly adopted methods include deep-hole blasting [9] and hydraulic fracturing [10]

Results

Discussion

Conclusion