The Influences of Key Strata Compound Breakage on the Overlying Strata Movement and Strata Pressure Behavior in Fully Mechanized Caving Mining of Shallow and Extremely Thick Seams: A Case Study

Abstract

In order to analyze the impact of compound breakage of key strata on overlying strata movement and strata pressure behavior during the fully mechanized caving mining in shallow and extremely thick seams, this paper took the 1322 fully mechanized caving face in Jindi Coal Mine in Xing County as the engineering background. Under the special mining and geological condition mentioned above, UDEC numerical simulation software was applied to research the engineering problems, and results of numerical simulation were verified through the in-site measurement. The research results showed that during the fully mechanized caving mining in shallow and extremely thick seams, the inferior key strata affected by mining movement behaved in the mode of sliding instability and could not form the stable structure of the voussoir beam after breaking and caving. In addition, the main key strata behaved in the mode of rotary instability, and the caving rocks behind the goaf were gradually compacted because of the periodic instability of the main key strata. With the continuous advance of the working face, the abutment pressure of the working face was affected by the compound breakage and periodic instability of both the inferior key strata and the main key strata, and the peaks of the abutment pressure presented small-big-small-big periodical change characteristics. Meanwhile, the risk of rib spalling ahead of the working face presented different levels of acute or slowing trends. The actual measurement results of ground pressure in the working face showed that, in the working process, the first weighting interval of the inferior key strata was about 51 m and its average periodic weighting interval was about 12.6 m, both of which were basically consistent with the results of numerical simulation. The research has great significance in providing theoretical guidance and practical experience for predicting and controlling the ground pressure under the similar mining and geological conditions.

Study on the movement characteristics of the overlying stratum and surrounding rock control in ultraclose coal seams: A case study

“…Mining activity at a single longwall face in the UCS will cause destruction of the old roof stratum following a vertical "O-X" pattern, after which a "masonry beam" structure will form in the overlying stratum. [26][27][28][29][30][31] As demonstrated by a considerable number of studies, [31][32][33][34][35][36][37] the mining activities at multiple longwall faces will enlarge the fracture zone of the overlying stratum when the coal seam is deeply buried. In this case, the key layers located in the upper middle part of the fracture zone far away from the coal seam may experience rotation or fracturing and become unstable.…”

Influence Characteristics of Double-Stratum Hard Roof Movement in a Fully Mechanized Top Coal Caving on the Working Resistance of Supports

“…To deeply understand the influence laws of fracture and caving of such multi-stratum hard roofs in relation to the support resistance of a working face, many scholars have adopted the calculation method of support resistance for the working face under the multi-stratum hard rock strata condition. Li [20], Bai [21], and Guo et al [22] analyzed the stope stresses of compound hard roofs with large mining heights based on key strata theory and obtained reasonable hydraulic support types and their working resistance on the working faces of multi-stratum hard roofs. By using onsite measurement data, Mangal [23] established a calculation model for a cantilever beam at the compound key strata and proposed a calculation method for the working resistance of supports on a working face of a multistratum hard roof.…”

Prediction of the First Weighting from the Working Face Roof in a Coal Mine Based on a GA-BP Neural Network

“…The geological conditions mainly include the lithology and thickness of the direct roof and basic roof of the working face, the inclination, and the depth of coal seam and other parameters. The mining technological parameters mainly include the support pattern, the length, width, and mining height of the working face, and the advance speed [22][23][24][25][26].…”