Subsidence Management Plan - Quetools

3 SUBSIDENCE PREDICTIONSDetailed subsidence predictions are provided in Section 7 of the SMPApplication – Written Report.In summary, full subsidence is likely to develop at any point only after severaladjacent longwall panels have been mined. Subsidence in the final subsidenceprofile is likely to vary locally across each panel, being greater in the centre ofeach panel and less over the chain pillars. This variation across individuallongwall panels is expected to decrease in the later longwalls because of theincreasing overburden depth.The maximum vertical subsidence predicted over Longwalls 10 to 16 is 1.6mand 0.8m over Longwall 17. The 1.6m maximum subsidence value isdetermined from 65% of the assumed 2.4m seam section mined. Assubsidence data becomes available from Longwalls 7 to 9, the predictions ofmaximum subsidence and other subsidence parameters over the remaininglongwall panels will be able to be refined (SCT, 2006).Systematic ground tilt and strain is likely to be fairly regular and may increasewith maximum subsidence. The overburden depth ranges fromapproximately 380m to 500m over Longwalls 10 to 17 with an averageoverburden depth estimated to be about 460m. A value of 380m is used toprovide an upper limit on the maximum values of tilt and strain. On thisbasis, a maximum tilt of 12mm/m is predicted (SCT, 2006). The actualmaximum tilt measured to date over Longwalls 1 to 5 is 5mm/m (SCT, 2006).On the basis of previous measurements at Glennies Creek, the maximumstrains expected are up to 6mm/m in tension and 9mm/m in compression(SCT, 2006).4 SUBSIDENCE IMPACTSDetails of the potential subsidence impacts on surface and sub-surface featuresare provided in Section 10 of the SMP Application – Written Report.ENVIRONMENTAL RESOURCES MANAGEMENT AUSTRALIA 0038321/FINAL/3 JANUARY 20073