Mine Subsidence and Strata Control in the Newcastle District of the Northern Coalfield Ewn South Wales William Arthur Kapp University of Wollongong
Total Page：16
File Type：pdf, Size：1020Kb
University of Wollongong Research Online University of Wollongong Thesis Collection University of Wollongong Thesis Collections 1984 Mine subsidence and strata control in the Newcastle district of the northern coalfield ewN South Wales William Arthur Kapp University of Wollongong Recommended Citation Kapp, William Arthur, Mine subsidence and strata control in the Newcastle district of the northern coalfield New South Wales, Doctor of Philosophy thesis, Department of Civil and Mining Engineering, University of Wollongong, 1984. http://ro.uow.edu.au/theses/ 1250 Research Online is the open access institutional repository for the University of Wollongong. For further information contact Manager Repository Services: [email protected]. MINE SUBSIDENCE AND STRATA CONTROL IN THE NEWCASTLE DISTRICT OF THE NORTHERN COALFIELD NEW SOOTH WALES APPENDIX A AND APPENDIX B to accompany a thesis for the degree of DOCTOR OF PHILOSOPHY from THE UNIVERSITY OF WOLLONGONG by WILLIAM ARTHUR KAPP, B.E. (Civil), M.E. (Mining) DEPARTMENT OF CIVIL AND MINING ENGINEERING 1984 APPENDIX A BACKGROUND TO THE STUDY OF SUBSIDENCE IN THE NEWCASTLE DISTRICT APPENDIX A CONTENTS Page No 1 Geographical setting ..... A- 1 l.l Introduction A x 1.2 Physiography 1.3 Land use A A- 5 2 Geological setting " 2.1 History of coal formation A~ 5 2.2 Structure J _ 2.3 Stratigraphy J_ c 2.4 Conglomerate units A A- 9 3 Coal resources ** 3.1 Wallarah Seam A" 9 3.2 Great Northern Seam A j" 3.3 Seams of minor significance A io 3.4 Australasian Seam A io 3.5 Victoria Tunnel Seam A X1 3.6 Dudley Seam A \2 3.7 Yard Seam A-\I 3.8 Borehole Seam A " 3.9 Reserves and coal use 4 Mining and subsidence A_1 4.1 General historical review A~*-j 4.2 Early subsidence events a-17 4.3 Mining methods A _] 4.4 Current subsidence studies ^ iy 4.5 Application of subsidence studies A A-21 5 Survey procedures 5.1 Introduction A"^ 5.2 Layout of grids A 5.3 Levelling and distance measuring Zlil 5.4 Data processing Page A-ii FIGURES Fig. A. 1 Coalfields of the Main Coal Province Fig. A. 2 Coastal strip of the Newcastle Coal District Fig. A. 3 Locations of collieries, Newcastle District Fig. A. 4 Production graph of N.S.W. coal districts Fig. A. 5 Geology of Newcastle District Fig. A. 6 Upper Permian and Triassic stratigraphic units Fig. A. 7 Views of South Belmont and Redhead Beaches Fig. A. 8 Views of the Central Coast lakes and the Hawkesbury River Fig. A. 9 Environment of coal formation, Borehole Seam Fig. A. 10 Structures in the northern part of the coal measures Fig. A.11 Base of the Newcastle coal measures Fig. A.12 North east part of geological cross section Fig. A.13 South west part of geological cross section Fig. A.14 Areas affected by Belmont and Charlestown Conglomerates Fig. A.15 Isopachs of the Charlestown Conglomerate Fig. A.16 Seam sections and areas of investigation Fig. A.17 Seam sections and areas of investigation Fig. A.18 Seam sections and areas of investigation Fig. A.19 Isoash map showing combinations of the Dudley Seam Fig. A.20 Early coal mines in Newcastle Fig. A.21 Burwood Colliery workings, 1886 Fig. A.22 Newcastle collieries, 1887 Fig. A.23 Bord and pillar mining operations Fig. A.24 Examples of recent mining layouts Fig. A.25 Computer printout of calculated subsidence Fig. A.26 Computer printout of calculated strain Fig. A.27 Computer printout of calculated strain triangle results APPENDIX A BACKGROUND TO THE STUDY OF SUBSIDENCE IN THE NEWCASTLE DISTRICT A.l GEOGRAPHICAL SETTING l.l Introduction There are about thirty large sedimentary basins in Australia ranging in age from Devonian through to Recent and coal has been located in most of these basins. The coals are from Carboniferous to Tertiary age. Most of the black coal production in Australia has come from the Permian coal measures of the Sydney Basin, which forms the major part of the Main Coal Province and occupies an area of 60,000 sq. km. The various coalfields which make up the Main Coal Province are shown in Fig. A.l (Stuntz, 1975). The Northern Coalfield is subdivided into five Coal Districts, with the Newcastle Coal District extending 90 km from the City of Newcastle to the Hawkesbury River, and inland for 3 0 km as shown in Fig. 1.2. The coal seams extend beyond the coast but knowledge of the seams under the Pacific Ocean is limited to the strip near the shore line which is shown in Fig. A.2. There are 26 operating collieries in the Newcastle District, all located to the north of Tuggerah Lake, around Lake Macquarie and north to Newcastle (Fig. A.3). The Newcastle District is a major producer of coal in the Sydney Basin. In the 1982-83 year 120 million tonnes of raw coal were produced in Australia. The N.S.W. contribution was 67 million tonnes. The Newcastle District has been a consistently high production area (Fig. A.4) with 18 million tonnes being mined in 1982-83 (Joint Coal Board, 1983). Both steaming coal for electricity generation and coking coal for use in the steel industry are mined, and both coals are exported. The large urban area of Newcastle is located in a scenically attractive area along the coast of the Pacific Ocean and around Lake Macquarie. The area has warm to hot summers and mild winters and the coastal areas are popular for residential and tourist development. A significant part of this area is closely associated with the exploitation of the local coal deposits and with the associated BHP steelworks in Newcastle. Many of the operating collieries are in or border areas of population and are Page A-2 near the coastline of the Pacific Ocean, or near the large tidal lakes of the Central Coast. The subsidence work has had a large influence in determining the maximum safe recovery of coal from beneath residential areas, other surface features, the Ocean and tidal lakes, and will continue to be of vital importance in the planning of longwall operations in areas where the effects of surface subsidence must be considered. 1.2 Physiography The landscape and natural environments are determined by such characteristics as climate, geology and topography which affect the drainage pattern, soil types and vegetation. The topography of the Newcastle District varies from the rugged mountain topography in the west where the elevations are as much as 500 m above sea level to the flat coastal plains to the east. In the areas around the operating collieries, and in particular where subsidence investigations have been and are being carried out to the east of Lake Macquarie the topography is flat to gently undulating. There are several creeks in the area which flow east into the tidal waters of Lake Macquarie, Lake Budgewoi and Tuggerah Lake, and south into the Hawkesbury River. The land surface features are to some degree conditioned by the nature of the rock formations. Although the geology will not be discussed at this stage, it is convenient to note that the base of the outcropping Newcastle Coal Measures defines the northern boundary of the Newcastle Coal District; the strata dipping generally to the south. The Newcastle Coal Measures are of Permian age and above these lie the Triassic Narrabeen and Hawkesbury Groups which influence the topography in the Northern Coalfield. A geological plan and section are given in Fig. A.5 (Crapp and Nolan, 1975). The stratigraphic units are set out in Fig. A.6. The topography and drainage patterns vary considerably in the Newcastle District, and are related to the different weathering characteristics of the main outcropping geological formations. The lowest part of the Newcastle Coal Measures at the northern boundary of the Newcastle District are generally soft and form an undulating landscape. The Lower Hunter River winds from Maitland to Newcastle through large open flood plains which are poorly drained. To the south of this flood plain the land rises to the belt of hills which enclose Lake Macquarie. Along the coastline south of Newcastle, the resistant sandstone and conglomerate of the Coal Measures form rocky headlands and sea cliffs up to 100 m above sea level. In the same area the wind blown sands along the coast surround the large attractive tidal lakes and Ocean beaches which extend further south to form the scenic resorts of the Central Coast. Page A-3 In the central and western part of the Newcastle District, the shales, claystones and sandstones of the Triassic Narrabeen group form the steep hillsides, broad valleys and coastal and estuarine flats. Drainage from the hills is into a series of coastal lakes and lagoons. The strata above the Newcastle Coal Measures, known as the Clifton Sub-Group of the Narrabeen Group consist of shale, sandstone and conglomerate and is exposed over much of the study area west and north of Tuggerah Lake. It is generally easily weathered and forms the broad gently sloping valleys of the coastal plain. The lakes and coastal lagoons are shallow and brackish. Although they are open to the Ocean they rely largely on the flow of flow of fresh water from the hills for flushing. The sandstone and shale of the upper part of the Narrabeen Group, known as the Gosford Formation compose the surface geology of the coastal hills south of Tuggerah Lake. This formation is heavily dissected and the weathered material forms the alluvium of the flat valley floors.