Hills, Christopher William Walter (1994) The examination and prediction of opencast backfill settlement. PhD thesis, University of Nottingham. Access from the University of Nottingham repository: http://eprints.nottingham.ac.uk/11501/1/260774.pdf Copyright and reuse: The Nottingham ePrints service makes this work by researchers of the University of Nottingham available open access under the following conditions. · Copyright and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. · To the extent reasonable and practicable the material made available in Nottingham ePrints has been checked for eligibility before being made available. · Copies of full items can be used for personal research or study, educational, or not- for-profit purposes without prior permission or charge provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. · Quotations or similar reproductions must be sufficiently acknowledged. Please see our full end user licence at: http://eprints.nottingham.ac.uk/end_user_agreement.pdf A note on versions: The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher’s version. Please see the repository url above for details on accessing the published version and note that access may require a subscription. For more information, please contact [email protected] THE UNIVERSITY OF NOTTINGHAM DEPARTMENT OF MINERAL RESOURCES ENGINEERING H ..; 1it Ci' THE EXAMINATION AND PREDICTION OF OPENCAST BACKFILL SETTLEMENT by Christopher W. W. Hills Bsc., Msc. Thesissubmitted to the University of Nottingham for the degreeof Doctor of Philosophy November 1994 ABSTRACT With ever increasingdemands on land use large areasof land are being consideredfor developmentwhich due to past or presentmining activities are covered by substantial depthsof fill materials.The problem faced with the developmentof land infilled with opencastmining backfidlis in predictingthe behaviourof the fill upon development.To be able to design foundations suitable to withstand the movement%that occur within opencastbackfill. or design a backfilling operation that produces land suitable for a proposedafter development,a meansof predictingbackfill settlementis required. From the analysisof a considerablequantity of data collected from the monitoring of backfilling operations and backfill movementat a range of opencastcoal sites located within the UK, the behaviour of opencast backfill has been examined and better understood.Ibis information has enableda method of predicting backfill settlementto No,developed which has been subsequentlyimplemented as a computer program runningunder the Windows operatingsystem. Factors taken into consideration during the prediction process are the timing of backfffling operations, the compactive state of the backfill, the inundation of the backfill and the influence of surroundingmaterial and a meansof predictingdifferential settlementdue to backfill heterogeneityis proposed.Examples are given demonstrating the significanceof these factors upon settlement predictions made at a hypothetical site. Finally, a comparisonis madebetween predicted settlements and those monitored at an actualsite to demonstratethe validity of the method proposed. AFFIRMATION The work submitted in this thesis is my own work and has not been previously submittedfor any other degree. The following publicationhas beenbased in this research: Hills C. W. W. & Denby B. (1995) The prediction of opencastbackfill settlement. In Preperafion. It is anticipated that other publications will be shortly forthcoming based on the researchcovered in this thesis. ii CONTENTS Abstract i ...................................................................................................................... Affirnwtion fi ................................................................................................................. Contents ifi ...................................................................................................................... List Figures ix of ............................................................................................................. List Tables of ..............................................................................................................xv AcAnowledgements ......................................................................................................xviii CHAPTER1 INTRODUCTION 1:1 ...................................................................................................... 1.1 General Introduction 1:1 .................................................................................. 1.2 ResearchObjectives 1:2 ................................................................................... 1.3 Synopsis Thesis 1:3 of ...................................................................................... CHAPTER2 OPENCAST BACKFILL BEHAVIOUR AND PROPERTIES 2: 1 .................................... 2.1 Introduction 2: 1 ............................................................................................... 2.2 Typical UK Opencast Backfill 2: 1 .................................................................... 2.3 Movements in'Opencast Backfil] ................................. 2.3.1 Creep 2: 2 .......................................................................................... 2.3.2 Collapse 2:6 ...................................................................................... 2.3.3 Heave 2: 10 .......................................................................................... 2.3.4 Differential Settlement 2: 11 ................................................................. 2.3.5 Lateral Movements 2: 13 ...................................................................... 2.3.6 Imposed Loads 2: 16 ............................................................................ 2.4 Factors Influencing Movement Behaviour 2: 17 .................................................. 2.4.1 Fill Material Properties 2: 17 ................................................................. 2.4.2 Mining Method Restoration Procedure 2: 19 and .................................. 2.4.3 Mine Features 2: 21 .............................................................................. 2.4.4 Groundwater Recovery 2: 22 ................................................................ 2.4.5 Surface Water Infiltration 2: 26 ............................................................ 2.5 Conclusion 2: 26 ................................................................................................. hi Contents CHAPTER3 ANALYSIS OF STUDY SITE DATA 3: 1 ........................................................................ 3.1 Introduction 3: 1 ............................................................................................... 3.2 Barnabas Opencast Coal Site 3: 2 ...................................................................... 3.2.1 Compaction Monitoring 3: 5 ............................................................... 3.2.2 Instrumentation 3: 5 ........................................................................... 3.2.2.1 GroundwaterRecovery 3:5 ................................................. 3.2.2.2 Creep Strain 3:5 .................................................................. 3.2.2.3 Collapse Strain 3: 6 .............................................................. 3.3 Bilston Opencast Coal Site 3: 7 ......................................................................... 3.3.1 Compaction Monitoring 3: 8 ............................................................... 3.3.2 Instrumentation 3: 8 ........................................................................... 3.3.2.1 GroundwaterRecovery 3:8 ................................................. 3.3.2.2 Creep Strain 3:8 .................................................................. 3.3.2.3Collapse Strain 3:9 .............................................................. 3.3.2.4 Heave 3:9 ........................................................................... 3.3.2.5Differential Settlements 3:9 ................................................. 3.4 BlindweUs Opencast Coal Site 3: 10 .................................................................... 3.4.1 Compaction Monitoring 3: 11 ............................................................... 3.4.2 Instrumentation 3: 11 ........................................................................... 3.4.2.1 GroundwaterRecovery 3: .................................................. 11 3.4.2.2 Creep Strain ..................................................................3: 11 3.4.2.3 CollapseStrain 3: .............................................................. 13 3.5 Dixon Opencast Coal Site 3: 14 .......................................................................... 3.5.1 Compaction Monitoring * 3: 15 ................ ............................................... 3.5.2 Instrumentation 3: 15 ........................................................................... 3.5.2.1 Groundwater Recovery 3: 15 ................................................. 3.5.2.2 Creep Strain 3: 15 .................................................................. 3.5.2.3 Collapse Strain 3: 15 .............................................................