Investigation into Abnormal Increased Subsidence above Longwall Panels at Tahmoor Colliery NSW - Winton GaleTahmoor Colliery, located in the Southern Coalfield of NSW, has been in operation for over 30 years. Longwall extraction of 23 successive longwall panels has occurred with subsidence occurring within predictions and resultant impacts to natural and built environments occurring to expectations.
Subsidence over a recent longwall panel of approximately twice that previously measured occurred at Tahmoor Colliery. An investigation of the potential causes was conducted using computer modelling together with hydrological characterisation and detailed geotechnical characterisation of the strata.
The abnormal subsidence was found to be consistent with localised weathering of joint and bedding planes above a depressed water table adjacent to an incised gorge. The study showed that other factors such as variation in stress field, joint zones, variation in rock strength and topographic factors did not sufficiently induce the abnormal subsidence.
The results have significant implications to subsidence prediction in areas which may be prone to the phenomenon found at Tahmoor. Key indicators of the potential for this form of abnormal subsidence are presented. Investigation-into-Abnormal-Increased-Subsidence-above-Longwall-Panels-at-Tahmoor-Colliery-NSW-W.Gale.pdf2.4 MB