1、翻译部分Ground Movement Due to Longwall Mining in High Relief Areas in New South Wales, AustraliaL.HollaAbstractThe theoretical pattern of ground movement observed in flat terrains was modified by surface topography and geological structures. In high relief areas, e.g. creeks and gullies, the observed p
2、attern of movement was asymmetrical about the centre of the extraction panel. The lateral movement of both sides of the valley caused large compressive strains and a hump at the creek bed. The strains were three-four times those normally observed in flat or fairly gentle topographies. The hump was d
3、ue to the rock mass in the creek bed being pushed up by the lateral forces from the valley sides. A major geological fault caused both sides of the valley to move laterally away from the fault plane. The magnitude of the maximum horizontal movement was as large as 40% of the observed vertical moveme
4、nt. Outside the goaf, the horizontal movements were generally larger than the corresponding vertical movements. However, the horizontal movements outside the goaf appeared to be rigid body type movements with small deformations which may only have insignificant surface consequences. Keywords: Longwa
5、ll mining; High relief area; Ground movements1.INTRODUCTION A number of empirical methods exist for predicting ground movement due to longwall mining. Most of these methods deal with vertical subsidence and horizontal ground strains. Even though ground strains result from horizontal ground movements
6、, there has been little study in Australia of horizontal movements and their relations to vertical movements. All of the past studies appear to assume that the limit of vertical movements is also the limit of horizontal movements. In addition, the studies apply to either flat, low or mild relief top
7、ographical areas. The pattern of movement is believed to be modified in rugged surface terrains with high reliefs. However, studies of ground movement in high relief areas are very few and their findings inconclusive .In this paper, the pattern of ground movement due to longwall mining is a flat ter
8、rain was compared with the theoretical pattern. The effect of surface topography on ground movement was then examined by monitoring the ground movement in high relief areas.2.NATURE OF GROUND MOVEMENT IN FLAT TERRAIN The general ground movement pattern associated with a wide underground extraction s
9、uch as a longwall panel is shown in Fig. 1. Both the horizontal and vertical movement distributions across the extraction panel are symmetrical about the panel centreline. The movement within the undermined rock mass is directed towards the extraction void and that of the ground beneath the mining h
10、orizon, upwards. The maximum vertical movement occurs at the panel centre and the maximum horizontal movement at the inflection point of the ground strain curve, where subsidence is half the maximum subsidence. Figures 2 and 3 show, respectively, the vertical and horizontal movement profiles monitor
11、ed in a flat terrain in the Cooranbong Colliery in the Newcastle Coalfield of New South Wales. The panel was 135.7 m wide between centrelines of gate roads of 4.7 m width. The average mining thickness was 2.43 m and the mining depth was 80 m. The immediate roof of the extracted seam was up to 2 m of
12、 mudstone with most of the overlying strata comprising mudstones and sandstones. The floor of the seam was the claystone of “Awaba TulT”. The overlying surface was almost level, with the ground slope along the survey line not exceeding 1%. The profiles in Figs 2 and 3 were obtained by plotting the o
13、bserved movements across a longwall panel. Both profiles conformed to the generally accepted conven- tional ground movement patterns. The profiles were almost symmetrical to the centre of the panel. The maximum ground slope occurred at the point of half maximum subsidence, where the ground strain wa
14、s zero.In addition to monitoring the change in the distance between survey pegs, the horizontal movement of pegs was also monitored in two orthogonal directions as northings and eastings . The movement of pegs was then resolved into two components, one perpendicular to and the other along the direct
15、ion of mining (along the survey line and perpendicular to it, respectively, as the survey line is laid across the longwall panel). The former was towards the centre of the goaf for all pegs except for the peg at the centre of the panel, which remained in its horizontal position all the time (Fig. 3)
16、. The movement increased progressively, as the vertical subsidence did and reached its maximum value after the completion of mining. As the face approached and went past a point, the cantilever strata at the point deflected progressively over the longitudinal rib which was the source of horizontal movement and tensile strains. The maximum movement was 350 mm which was approximately 15% of the extracted seam thickness and 28% of the maximum subsidence.Fig. 1. General
