LiDAR for Mine Subsidence Management
The Springvale Colliery located near Lithgow, NSW Australia, has a local surface terrain that is rugged and complex in shape. It contains clifflines and rock ledges, and extensive vegetation coverage. While the Springvale Colliery itself is an underground mine, surface terrain monitoring above the mine is required for subsidence management in the Newnes State Forest and the Coxs River Catchment. Coal from Springvale is supplied, via dedicated conveyors, to the nearby Mt Piper and Wallerawang Power Stations, and the Port Kembla coal-loader to international markets.
A LiDAR approach was determined by the Springvale Colliery Surveyor, as the most cost effective method to capture the necessary Digital Terrain Model (DTM) data in this difficult environment. Mining approvals, in New South Wales, are granted by the Director General – Department of Primary Industries, and as part of the approval process, underground mines are required to submit a Subsidence Management Plan (SMP) to the Department. The Mine operates via Longwall extraction and continuous miner.* Any SMP must consider the impacts on constructed features such as roads, buildings, bridges etc. In addition, the SMP must consider the impacts on natural features such as streams, rivers, lakes, clifflines, rock formations and archaeological sites. During the process of developing the Springvale SMP, and the life of mine planning, AAM was commissioned to capture a DTM by LiDAR.
The definition of the clifflines was an important part of the process in order to allow the design of the underground longwall panels with due reference to these significant surface features. The aerial mission was planned with East-West plus North-South scanning swathes, ensuring that all aspects of the clifflines were comprehensively covered. Approximately 1,133,000 thinned ground points were supplied, over an area of approximately 3800ha from which 1m contours were generated for the subsidence management plan.
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| Springvale Colliery and surrounds, near Lithgow, NSW. | Springvale Colliery, typical ground cover |
*In longwall mining, large rectangular blocks of coal are defined during the development stage of a mine and are then extracted in a single continuous operation. Generally each defined block of coal, known as a panel, is created by driving a set of headings from main or trunk roadways in the mine, some distance into the panel. These roadways are then joined to form the starting face of longwall face. Coal is extracted mechanically from all the longwall faces. As the coal is cut the longwall face is supported with hydraulically operated supports. The function of these supports is to provide a safe working environment by supporting the roof as coal is extracted as well as advancing the longwall equipment. As the face advances the immediate roof above the coal is allowed to collapse behind the line of supports forming the goaf.
Acknowledgement to Wollongong University
