Insights into the mechanics of multi seam subsidence from Ashton Underground Mine - Ken Mills - Steve WilsonPublished Feb, 2017Examples of subsidence monitoring of multi-seam mining in Australian conditions are relatively limited compared to the extensive database of monitoring from single seam mining. The subsidence monitoring data now available from the mining of longwall panels in two seams at the Ashton Underground Mine (Ashton) provides an opportunity to significantly advance the understanding of subsidence behaviour in response to multi-seam mining in a regular offset geometry. This paper presents an analysis and interpretation of the multi-seam subsidence monitoring data from the first five panels in the second seam at the Ashton Underground Mine. The methods used to estimate subsidence effects for the planned third seam of mining are also presented.
Observations of the characteristics of multi-seam subsidence indicate that although more complex than single seam mining, the subsidence movements are regular and reasonably predictable. Movements are constrained within the general footprint of the active panel. They are however sensitive to the relative panel geometries in each seam and to the direction of mining. In an offset geometry, tilt and strain levels are observed to remain at single seam levels despite the greater vertical displacement. At stacked goaf edges tilt and strain levels are up to four times greater. Latent subsidence recovered from the overlying seam has been identified as a key contributor to the subsidence outcomes. Some conventional single seam concepts such as angle of draw and subcritical/supercritical behaviour are less meaningful in a multi-seam environment. Insights-into-the-mechanics-of-multi-seam-subsidence-from-Ashton-Underground-Mine-K.Mills-S.Wilson-2017.pdf2.5 MB