Key technologies and equipment for a fully mechanized top-coal caving operation with a large mining height at ultra-thick coal seams

Abstract

Thick and ultra-thick coal seams are main coal seams for high production rate and high efficiency in Chinese coal mines, which accounts for 44 % of the total minable coal reserve. A fully mechanized top-coal caving mining method is a main underground coal extraction method for ultra-thick coal seams. The coal extraction technologies for coal seams less than 14 m thick were extensively used in China. However, for coal seams with thickness greater than 14 m, there have been no reported cases in the world for underground mechanical extraction with safe performance, high efficiency and high coal recovery ratio. To deal with this case, China Coal Technology & Engineering Group, Datong Coal Mine Group, and other 15 organizations in China launched a fundamental and big project to develop coal mining technologies and equipment for coal seams with thicknesses greater than 14 m. After the completion of the project, a coal extraction method was developed for top-coal caving with a large mining height, as well as a ground control theory for ultra-thick coal seams. In addition, the mining technology for top-coal caving with a large mining height, the ground support technology for roadway in coal seams with a large cross-section, and the prevention and control technology for gas and fire hazards were developed and applied. Furthermore, a hydraulic support with a mining height of 5.2 m, a shearer with high reliability, and auxiliary equipment were developed and manufactured. Practical implication on the technologies and equipment developed was successfully completed at the No. 8105 coal face in the Tashan coal mine, Datong, China. The major achievements of the project are summarized as follows: 1. A top-coal caving method for ultra-thick coal seams is proposed with a cutting height of 5 m and a top-coal caving height of 15 m. A structural mechanical model of overlying strata called cantilever beam-articulated rock beam is established. Based on the model, the load resistance of the hydraulic support with a large mining height for top-coal caving method is determined. With the analysis, the movement characteristics of the top coal and above strata are evaluated during top-coal caving operation at the coal face with a large mining height. Furthermore, there is successful development of comprehensive technologies for preventing and controlling spalling of the coal wall, and the top-coal caving technology with high efficiency and high recovery at the top-coal caving face with a large mining height. This means that the technologies developed have overcome the difficulties in strata control, top-coal caving with high efficiency and high coal recovery, and enabled to achieve a production rate of more than 10 Mtpa at a single top-coal caving face with a large mining height in ultra-thick coal seams; 2. A hydraulic support with 5.2 m supporting height and anti-rockburst capacity, a shearer with high reliability, a scraper conveyor with a large power at the back of face, and a large load and long distance headgate belt conveyor ...

Mechanism and Prevention of a Chock Support Failure in the Longwall Top-Coal Caving Faces: A Case Study in Datong Coalfield, China

“…This is the reason why the strata behavior is intense in LTCC faces with hard coal seams, while the strata behavior is moderate in LTCC faces with soft coal seams. In order to judge whether there is overhanging of top-coal or not, field measurements in LTCC-8105 in the Tashan mine were conducted [23]. Two groups of drill holes were drilled in the air-return roadway against the mining direction of the working face.…”

“…Based on the above-mentioned analysis and measured results, it can be concluded that the top-coal is too hard to collapse in time and the top-coal overhanging that formed behind the support is also a main reason for the intense strata behavior and chock support failure accidents in working faces. In order to judge whether there is overhanging of top-coal or not, field measurements in LTCC-8105 in the Tashan mine were conducted [23]. Two groups of drill holes were drilled in the air-return roadway against the mining direction of the working face.…”

Field and simulation study of the rational coal pillar width in extra‐thick coal seams

“…A coal seam with a thickness greater than 8 m is called extra‐thick coal seam in China. Extra‐thick coal seams account for ~1/4 of China's annual coal production capacity of 3.394 billion tons . In the past, studies of the coal pillar width mostly focused on thin (thickness ≤ 1.3 m), medium (1.3 m < thickness ≤ 3.5 m), and normal (3.5 m < thickness ≤ 8 m) coal seams .…”

Multi-Body Dynamics and Vibration Analysis of Chain Assembly in Armoured Face Conveyor

“…Statistical data on malfunctions in mining face show that AFC malfunctions account for a large proportion, most of which involving chain assembly malfunctions [3]. In chain assembly failures in the AFC, most malfunctions mainly involve jam and fracture of the chain.…”