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TABLE OF CONTENTS <br />DEFINITION OF SYMBOLS ............................................................................................... IV <br />DEFINITION OF TERMS ..................................................................................................... V <br />1.0 INTRODUCTION ....................................................................................................................1 <br />2.0 MINING METHOD ..................................................................................................................2 <br />3.0 FACTORS INFLUENCING SUBSIDENCE ............................................................................3 <br />4.0 FIELD RECOGNITION OF SUBSIDENCE AND NON-SUBSIDENCE FEATURES IN <br />THE WEST ELK MINING AREA .........................................................................................4 <br />4.1 Subsidence Cracks and Compression Features ......................................................4 <br />4.2 Construction Cracks ................................................................................................. 4 <br />4.3 Desiccation Cracks ...................................................................................................5 <br />4.4 Pseudo Subsidence Features (Gravity-Induced Tension Cracks) ............................5 <br />5.0 SUBSIDENCE PREDICTION BASED ON LONGWALL MINING AT WEST ELK <br />MINE ....................................................................................................................................6 <br />5.1 ' Caved Zone ..............................................................................................................6 <br />• 5.2 Fractured Zone .........................................................................................................6 <br />5.3 Continuous Deformation Zone and Near Surface Zone ...........................................7 <br />5.3.1 Vertical and Horizontal Displacement, Tilt, and Horizontal Strain .............................. 8 <br />5.3.2 Maximum Projected Depths of Surface Cracks ........................................................11 <br />5.4 Angle of Draw .........................................................................................................12 <br />5.5 Break Angle ............................................................................................................12 <br />5.6 Angle of Major Influence .........................................................................................13 <br />5.7 Relation Between Dynamic and Final Subsidence Deformations ..........................13 <br />5.8 Critical Extraction Width of Mining Panels ..............................................................13 <br />5.9 Results of Computer Modeling ...............................................................................13 <br />6.0 RATE AND DURATION OF SUBSIDENCE .........................................................................15 <br />7.0 EFFECTS OF TOPOGRAPHY AND STRUCTURE ON SUBSIDENCE <br />PROCESSES .....................................................................................................................16 <br />7.1 Effects of Topography on Subsidence Cracks .......................................................16 <br />7.2 Effects of Rugged Topography on Subsidence and Mine Stresses .......................16 <br />8.0 FRACTURE-CONTROLLED DRAINAGES .........................................................................17 <br />9.0 WATER AND METHANE .....................................................................................................18 <br />9.1 Potential Impact of Water on Subsidence in Wet Mining Areas .............................18 <br />10.0 POTENTIAL IMPACTS OF SUBSIDENCE AND MINE-INDUCED SEISMIC <br />• ACTIVITY ON LANDSLIDES AND ROCKFALLS ............................................................ 19 <br />10.1 Landslides ..............................................................................................................19 <br />10.1.1 Effects of Subsidence and Mine-induced Seismic Activity on Landslides ................ 20 <br />10.2 Rockfalls .................................................................................................................21 <br />Tetra Tech - 0907171P ii.