Mechanism of rock bursts in a large inclined extra-thick coal seam under the condition of upper slice mining: a case study

Abstract

With the increase of mining depth and mining intensity of the large inclined extra-thick coal seam (LIETCS), the number of rock bursts increases significantly. In this paper, based on a rock burst during upper roadway driving of the LIETCS, the distribution characteristics and fracture mechanism of microseismic (MS) events are analyzed using data statistics and seismic moment tensor inversion. By means of mechanical analysis and numerical simulation, this paper studies the static load distribution characteristics and dynamic load action effect of the LIETCS under upper slice mining condition. Based on the theory of dynamic and static combined load, the mechanism of rock bursts is proposed. The results show that the coal and rock mass of the LIETCS are mainly destroyed by shearing. The “shear-clamping” stress produced by the joint action of the roof and floor is the static load source. In upper slice mining, the shear stress and energy of the coal pillar behind the slice and the coal body below the coal pillar always remain high. Under the superposition of floor dynamic load, the regional stress environment changes, which induces rock bursts. This study provides a theoretical basis for rock burst prevention under similar conditions.

Key Policy Highlights

• By means of data statistics and seismic moment tensor inversion, the paper analyzes the distribution characteristics and focal mechanism of MS events in the rock burst area of the LIETCS, and indicates that the coal and rock mass around the rock burst area and the floor rock stratum are mainly destroyed by shearing.

• By means of theoretical formula and numerical simulation, this paper explores the static load evolution law and dynamic load effect of the LIETCS during the upper slice mining. The results show that the joint action of the roof and floor produces “shear-clamping” stress and dynamic load is the force source of rock bursts.

• Based on the theory of dynamic and static combined load, the paper reveals the process of rock bursts induced by the high-stress area of the coal and rock mass below during the upper slicing mining of the LIETCS and the dynamic load of the floor.

Keywords:

• The large inclined coal seam
• microseismic monitoring
• focal mechanism
• shear stress
• mechanism of rock bursts

Code availability

Not applicable.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability

The data that support the findings of this study are available from the first author, [Songwei Wang], upon reasonable request.

Additional information

Funding

This research is supported by National Natural Science Foundation of China under Grant Nos. 52274098, U21A20110 and 51734009, and Major Science and Technology Innovation Program of Shandong Province under Grant No. 2019SDZY02.