Key Strata Inducing Dynamic Disasters Based on Energy Condition: Criterion and Application

Chao Xu,Haoshi Sun,Zhijie Wen,Gang Yang,Bo Ren,Liangliang Qin,Kai Wang,Chuangzhou Wu

doi:10.1155/2021/6672020

Abstract

The thick and hard rock strata (THRS) exist widely in coal measure strata, which control the movements of overlying rock strata in stopes. When THRS break, great energy is released, which could aggravate the risks of coal and gas outburst, rock burst, and other dynamic disasters. Therefore, the foundation and key of preventing dynamic disasters are to distinguish the THRS that could induce coal-rock dynamic disasters and to analyze the laws of rock stratum breaking and energy releasing. The paper proposed the theoretical calculation methods of the energy accumulation and attenuation of rock breaking which is greatly affected by the hanging length of rock strata and the spreading distance. One or more roof strata that play a leading role in inducing dynamic disasters of the underlying coal mass are defined as the key disaster-inducing strata (KDIS). The disaster-inducing coefficient (DIC) is defined and used as the criterion of KDIS. The greater the source energy, the shorter the spreading distance, and the smaller the attenuation coefficient are, the easier the roof strata are to become KDIS. The disaster-inducing ability of the main THRS was analyzed, and the igneous sill was judged as KDIS, taking the Yangliu Coal Mine as project background. The breaking laws of the igneous sill were obtained by the methods of UDEC numerical simulation and microseismic monitoring, which verified the criterion of KDIS.

Highlights

With the huge demand of economic development for energy and the gradual exhaustion of shallow coal resources, the depth of coal mining is increasing by 10-25 m per year in China [1, 2]
Afterwards, the key disasterinducing strata (KDIS) in Yangliu Coal Mine, Huaibei Coalfield, China, was distinguished, in which results were verified by the numerical simulations and microseismic monitoring
The main conclusions are as follows: (1) The total of the accumulated energy is composed of the bending elastic energy, the volumetric strain energy, and the kinetic energy generated by rock strata movement, which is positively correlated with the hanging length, overburden load, and kinematic velocity

Summary

Introduction

With the huge demand of economic development for energy and the gradual exhaustion of shallow coal resources, the depth of coal mining is increasing by 10-25 m per year in China [1, 2]. In case of THRS failure and instability, huge elastic energy is released and transmitted to the stopes, which aggravates the risk of coal and rock dynamic disasters (Figure 1) [9, 10]. Bed-splitting space under the 43.6 m-thick igneous rock stratum in the Yangliu coal mine on July 17, 2011 [13] These examples highlight the need to investigate the effects of the THRS failure on the coal-rock dynamic disasters. The concept of key strata in immediate roof (KSIR) was put forward, and the dynamic effect and control mechanism of KSIR were studied [18]. The laws of energy accumulation, spreading, and attenuation for the THRS instability was studied theoretically, the sensitivity of those influencing factors was analyzed, and the concept and criterion of key disasterinducing strata (KDIS) were put forward. Afterwards, the KDIS in Yangliu Coal Mine, Huaibei Coalfield, China, was distinguished, in which results were verified by the numerical simulations and microseismic monitoring

Energy Spreading Laws of THRS Instability

Concept and Criterion of KDIS

Figure 6

Engineering Application

Conclusions