Case Study on Dynamic Identification of Overburden Fracture and Strong Mine Pressure Mechanism of Isolated Working Face Based on Microseismic Clustering

Abstract

Strong mine pressure has a great impact upon the safety production of coal mines. Microseismic information provides a more advanced technical means for overburden fracture dynamic identification and mine pressure mechanism research, since it contains rich information on rock fracture sources. In this study, the isolated LW8102 working face in Tongxin Mine was investigated in order to propose a spatio-temporal microseismic event data analysis method based on the k-means clustering algorithm. This algorithm can handle dynamic identification of overburden fractures constrained by spatiotemporally discrete distributions of microseismic events. This provided the dynamic extension process and the fracture distribution pattern of the overburden: eight fracture extensions were formed in the overburden. In each extension, vertical fractures connected the low and high rock layers in the LW8102 and LW8103 goafs, and through fractures connected the LW8102 and LW8103 goafs in their high, middle, and low levels. Some extensions had fractures that were connected to form a closed loop structure. In the vertical fracture, there was a tendency for one or two layers of the stratum to fail first, and then extend to one or both sides. The process of through and vertical fracture propagation followed a certain temporal sequence, reflected primarily in two forms: firstly, as the vertical fracture extended to a certain layer, it provided the initial rupture space for through fracture spreading; secondly, the through fracture first broke, and then extended to the vertical fracture until it intersected with the vertical fracture or provided the initial rupture space for the expansion of the vertical fracture. By matching the overburden fracture to the mine pressure that responded to the support resistance, we analyzed the mechanism of mine pressure at the working face. Through fracture at the high level was found to be the primary cause of the occurrence of mining pressure. It was precisely placed that the formation of multiple adjacent high through fractures 110 m from the floor, triggering simultaneous instability motion of the lower multi-layer level rock; this was the main reason for the phenomenon of strong mine pressure at the working face. Meanwhile, high through fracture at 80 m from the floor was the main reason for the phenomenon of large mine pressure at the working face.

A Prediction Approach Based on Clustering Reconstruction for Abnormal Mining Pressure of Longwall Face under Residual Coal Pillars

“…According to formulas ( 16) to (20), the reasonable support resistance can be deter- The masonry beam rock block M 1 and the overburden self-weight P 0 are determined by the following formula:…”

“…According to Formulas ( 16)- (20), the reasonable support resistance can be determined. After the calculation, the additional concentrated static force caused by the remaining coal pillar is 960 kN, the impact force is 7500 kN, and the additional concentrated resultant force is 8460 kN, and after being absorbed and reduced by the lower rock layer, the pressure acting on the hydraulic support of the working face is 1946 kN.…”

“…The clustering analysis method is also applied in the field of impact pressure prevention and control. Chen took the LW8102 working face of Tongxin Mine as the research object, used the k-means clustering algorithm to analyze the microseismic event data, and identified the relationship between the microseismic event and the dynamic change of the overlying layer fracture [20].…”

Change Characteristics of the Advance Stress and Strata Fracture Structure of Spatial Isolated Island Formed by Roof Drainage

“…The working face of an isolated island in an underground coal mine is an area of great importance for the prevention and control of rock bursts. A conventional island working face may include two, three, or four goafs [3][4][5]. Several scholars have studied the occurrence of dynamic disasters at the conventional isolated island working face.…”