The role of powered support in ensuring the proper longwall working cross-section area in rockburst-prone seams

Abstract

In Poland, for underground hard coal seam extraction, the longwall method is used. Retreat longwalls with natural roof caving in the gob are the most common. Currently it is estimated that about a half of the hard coal output in Poland originates from seams located in areas of rock burst hazard. The article shows information about 18 rock bursts, and 14 other seismic events which occurred between 2003 and 2012 in underground mines belonging to one of coal companies in Poland. In addition, negative consequences of those dynamic phenomena in the longwall workings are described. In the next part of paper, the most common types of damage to powered supports after the rock mass tremors and other dynamic phenomena in longwall workings are shown. In order to avoid damage of powered supports, in geo-mining conditions where dynamic phenomena occur, different types of protective means are applied. In the paper the methodology of assessing the powered support yield ability is described. At the end, an example of the assessed yield ability of a powered support in given geo-mining conditions of a longwall face affected by the seismic events is presented.

Monitoring the Geometry of Powered Roof Supports—Determination of Measurement Accuracy

“…The powered roof support selected depends on the mining geological parameters of a given longwall [1][2][3][4][5]. Prior to the commissioning of a powered roof support, it is tested in an accredited laboratory [1,6].…”

A Novel Coal Burst Criterion of Anchored Roadway Surrounding Rock under Dynamic Disturbance

“…(2) The hazard degree of coal burst increases gradually after entering deep mining, while the buried depth of roadway cannot be changed. Thus, it is necessary to take measures in advance from reducing static and dynamic loads of surrounding rocks and improving supporting performances [2]. (3) In order to reduce the strength and bursting liability of coal-rock masses and transfer high static stresses to deep surrounding rocks, the pressure-relief measures should be reasonably carried out outside the roadway support structure, such as pressure-relief blasting [39], large diameter pressure-relief drilling, water-infusion softening, etc.…”

“…Coal burst is one of the most serious dynamic disasters in underground coal mining [1]. With the increase in mining depth, coal burst disasters have been widely reported worldwide, including in Poland [2,3], Russia [4], the United States [5], Canada [6], France [7], China [8,9], and Australia [10,11]. Coal bursts have both occurred in working face and mining roadway, but mainly in the latter, accounting for 91% of the total times of coal bursts [12].…”

Energy release induced rockbursts based on butterfly-shaped plastic zones in roadways of coal reservoirs

“…In Fig 2, a refers to the radius of the roadway, (r, θ) denote the polar coordinates, and P z and P x represent stresses at the vertical and horizontal directions, respectively [21]. Suppose that P z and P x both refer to constant principal stresses, P x = λP z ; in that case, the stress on a…”