1、翻译部分 英文原文 Design of backfilled thin-seam coal pillars usingearth pressure theory 1. Introduction The Self-Advancing Miner has been designed to extract coal from seams less than 90centimeters thick. The SAM allows for extraction of the fullseam height while minimizing waste rock, and utilizes remote
2、operation that allowsthe miner to advance up to 180m (600ft) into the seam. However, the coal seams areso thin that the recovery rates of this mining method will be fairly low and willdecrease rapidly with the depth of mining. In order to increase the recovery fromthin-seam mines, pillars must be de
3、signed as small as possible withoutcompromising the stability of the mine. Backfill can provide the support necessaryto maintain the integrity of the underground workings while allowing for increasedextraction. The placing of backfill underground has predominantly been a practice employedin cut-and-
4、fill mines (Thomas, 1979). Backfill material is introduced undergroundinto previously mined stopes to provide a working platform and localized support,reducing the volume of open space which could potentially be filled by a collapseof the surrounding pillars (Barret et al., 1978). The presence of fi
5、ll in an openingprevents large-scale movements and collapse of openings merely by occupying voidsleft by mining (Aitchison et al.1973).Therefore, the placement of fill in open spacesunderground tends to prevent the unraveling/spalling of the surrounding rock massinto the mined-out space, effectively
6、 increasing the strength, or load bearingcapacity, of the surrounding rock mass. This type of support mechanism not onlyhelps provide support to pillars and walls, but also helps to prevent caving and rooffalls, minimize surface subsidence, and enhance pillar recovery (Coates, 1981). Although the su
7、pport capability of backfill is well known it still remains fairlydifficult to quantify. Models and equations for the determination of backfill supporthave been proposed (Cai, 1983； Guang-Xu and Mao-Yuan, 1983) and pillar-backfillsystems have been modeled using laboratory set-ups in order to correla
8、te the actualsupport behavior of fill with proposed models (Yamaguchi and Yamatomi, 1989；Blight and Clarke, 1983； Swan and Board, 1989； Aitchison et al., 1973). But ingeneral these models and lab tests are dependent on local experience and empiricallyderived relationships between backfill support, m
9、aterial properties, and minegeometry. Since the SAM is still in development there is a need for a simple andreliable method of estimating the magnitude of support provided by backfill basedon existing knowledge. It is proposed that classical earth pressure theory can be usedto estimate the lateral e
10、arth pressure applied by backfill. The anticipated behaviorand response of fill to deformations of the surrounding pillars and roof are analyzedhere. The supporting effect of backfill is incorporated into the original pillar design(unsupported) so that new pillar widths can be calculated and the inc
11、rease inrecovery can be determined. 2. The thin-seam coal mine A thin-seam coal mine, employing the SAM technology, can be thought of as an underground highwall mine. Figure 1 depicts the simplified panel geometry createdby the development of entries and cross-cuts, and the system of pillars left be
12、hind afterpanel extraction. It is probable that the cuts and cross-cuts will be angledat approximately 60so as to decrease the turning radius of mining equipment, butthis will not effect pillar design. The length of each panel is 1200m (4000ft).The width of each panel varies with depth in order to a
13、ccommodate a barrier pillarthat runs through the center of each panel. However, the panel width will be at leastGreaterthantwicethedistancerequiredforoneSAMcut,inthiscase300m(1000ft).Upon extraction of the panels, the barrier pillar and a series of pillars left betweencuts remain in every panel. Lar
14、ge barrier pillars are also left at the ends of the panelsto protect the cross-cuts. Figure 2 is a cross-sectional view of the cutting face. The face evokes the highwallmine comparison； the coal seam runs through the middle of the panel and a portionof the panel material is left above and below each
15、 cut. The cut width is 3m (10ft)and the cut height is equivalent to the seam height (less than 90cm (36in). It isintended that as the SAM retreats from each cut, backfill will be either hydraulicallyor pneumatically placed in the mined-out void. 3. Application of earth pressure theory The idea that
16、the backfill support mechanism described in the previous section canbe quantified using principles taken from soil mechanics is not new. A broadunderstanding of fill behavior has always been dependent on knowledge of earthpressures. However, earth pressure theories and concepts have not generally be
17、enconsidered adequate in properly quantifying the magnitude of fill support inunderground mines. Limited understanding about the transfer of loads from thesurrounding rock to the fill and frictional effects, along with mine geometry, havemade it difficult to apply the concepts of earth pressure theo
18、ry to backfill support(Thomas, 1979). What makes the case of the SAM operating in a thin-seam coal mine different isthe concept of designed failure of the pillars so that deformations capable ofmobilizing the passive resistance of the backfill will occur. From civil engineeringdesign of retaining wa
19、lls it has been shown that the movement required to reachmaximum passive earth pressure within in a loose sandy soil is 4% of the wall height(Clough and Duncan, 1971). The denser the soil, the less movement required.Applying this guideline to the thin-seam coal mine； for a pillar height of 90cmlateral deformation of the pillar must be at least 3.6cm for a loose, sandy backfillto reach maximum passive earth pressure conditions. The initial stages of pillar failuremay not
