Underground » Environment - Subsidence and Mine Water
Original research work has been underway since March 2003, in order to gain a better understanding of the impacts of underground coal mining on building structures.
The major aims of this research project were to develop improved methods of assessing the likely damage to building structures and to more clearly define what constitutes a 'safe, serviceable and repairable' level of damage. It was anticipated that such methods would avoid the sterilisation of valuable coal resources.
The research work was based upon measured impacts on building structures, which were recorded as longwalls were mined at Tahmoor Colliery and historical claims data provided by the Mine Subsidence Board for the Newcastle and Southern Coalfields.
It was originally intended that the research project would continue for a period of eighteen months, but the project was extended for a number of reasons and the research was not completed until October 2008. The extension of the project, however, allowed the research team to capture a greater quantity of data as Longwalls 22,23A, 23B, 24B and 24A were mined at Tahmoor Colliery. The original proposal was to study a sample of 260 building structures and 200 historical records. The study actually included observed data from 1210 buildings and 542 historical records.
Prior to commencing this research project, increased pressure from the regulatory authorities had resulted in conditions being applied to development consents and mining leases, which severely restricted the permissible impacts of subsidence on building structures. The permissible level of impact, adopted by the authorities was that which would, after mining, leave a building in a condition considered to be 'safe, serviceable and repairable', taking into account any mitigatory measures that might be undertaken.
If it was assessed that a mining development would cause damage to a building structure greater than this permissible level, the mining company was obliged to enter into a compensation agreement with the owner of the building or to purchase the building before mining could occur.
The research project involved:
- A state-of-the-art review.
- Collection of historical claims data from the records of the Mine Subsidence Board.
- Initial surveys of the ground above and around longwall panels.
- Initial surveys of building foundations above longwall panels.
- Pre-mining condition surveys and structural assessments of building structures.
- Recording of building movements and conditions during the mining period.
- Recording of ground movements during the mining period.
- Study and analysis of ground movements.
- Study and analysis of building movements.
- Review and statistical analysis of historical claims data.
- Correlation of building movements and levels of damage with NCB damage assessment curves.
- Development of improved methods for the prediction of building movements.
- Development of improved methods for the assessment of subsidence impacts.
- Study of available methods for the rectification of tilt.
- Review of 'safe, serviceable and repairable' criteria.
The final output from the research project is this detailed report on the findings of the research work, which includes new methods for the assessment of mining subsidence impacts on building structures.
It is hoped that this will assist coal mining companies that are planning to mine beneath urban or rural residential areas, and also to provide the general public with a better understanding of the potential impacts of mining on building structures.
The report includes an electronic copy of the subsidence impact database collected by the Researcher, which forms the basis of the findings discussed in this report.
Whilst significant knowledge has been gained, as a result of this research project, the importance of ongoing research in this field cannot be overemphasised.