The reliability of a pillar increases with pillar width but decreases with depth of cover, pillar height and entry width.
This evaluation was intended to reinforce the influence of topographic changes, depth of cover, multiple-seam interactions, geological conditions, and mining geometry.
This paper addresses geotechnical considerations for concurrent pillar recovery in two coal seams with 21 m of interburden under about 305 m of depth of cover.
The model predicts pillar length and width using depth of cover, mining height, panel width, roof strength rating and loading conditions.
In regard to the primary rib support database, it is evident from the current database that the primary factors affecting the capacity of rib support required for a successful design are roadway height and depth of cover.
The significance of the model is the potential to maximise both reserve recovery and mining efficiencies without any discernible increase in geotechnical risk, particularly in thick seams and higher depth of cover mining situations.
The results of the analysis allow for prediction of roof collapse and to determine whether the failure surface that develops in the rock mass remains localised or extends through the full depth of cover.
That could only be a good thing for Fulham who, despite their generally accomplished displays over the last two years, do have scope for improvement and not only in terms of the depth of cover (notably for the centre-backs and Danny Murphy).
After briefly examining differences and similarities between the support design philosophies applied in these circumstances and those prevailing in most civil engineering tunnels, the paper goes on to suggest concepts that might prove useful in civil works under great depth of cover.
Based on the results, the laboratory column provides an effective way to estimate the H2S adsorption coefficient, which can then be incorporated into the developed model to predict the depth of cover soil required to reduce emitted H2S concentrations below a desired level.
However, a minimum depth of cover of 0.6 m must always be maintained. .
