THE PREDICTION OF OPENCAST BACKFILL SETTLEMENT

With ever-increasing demands on land use, large areas of land are bein g considered for development, which owing to past mining activities ar e covered by substantial depths of fill materials, This paper examines the problem faced, with the development of land infilled with opencas t mining backfill, in predicting the behaviour of the fill upon develo pment, To be able to design foundations suitable to withstand the move ments that occur within opencast backfill or to design a backfilling o peration that produces land suitable for development, a means of predi cting backfill settlement is required, The information required to mak e accurate predictions includes the timing of backfilling operations, the compactive state and type of backfill, and the inundation of the b ackfill, This information will be available in most cases where develo pment is planned, as a scheme of controlled backfilling will generally be undertaken, The resultant monitoring scheme, carried out to ensure controls are being met during backfilling, will provide the informati on necessary to enable settlement predictions to be made, From the ana lysis of a considerable quantity of data collected from the monitoring of backfilling operations and backfill movement at a range of opencas t coal sites located within the UK, a computer program has been develo ped, enabling opencast backfill settlement predictions to be made taki ng into consideration the factors mentioned above, To demonstrate the validity of the approach, a case study is carried out from a real site from which a comparison between predicted and actual settlements can be made.