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i TABLE OF CONTENTS <br />r1 <br />U <br />• <br />DEFINITION OF SYMBOLS ........................................................................................................................iv <br />DEFINITION OF TERMS ...............................................................................................................................v <br />1.0 INTRODUCTION ...........................................................................................................................................1 <br />2.0 MINING METHOD ........................................................................................................................................1 <br />3.0 GEOLOGIC FACTORS INFLUENCING SUBSIDENCE ..........................................................................2 <br />4.0 FIELD RECOGNTITON OF SUBSIDENCE AND NON-SUBSIDENCE FEATURES IN THE WEST <br />ELK MINING AREA ........................................................._.......................................................................................2 <br />4.1 SUBSIDENCE CRACKS AND COMPRESSION FEATURES ............................................................................................3 <br />4.2 CGNSTRUCTIGNCRACKS ........................................................................................................................................3 <br />4.3 DESICCATION CRACKS ............................................................................................................................................4 <br />4.4 PSEUDO SUBSIDENCE FEATORES (GRAVITY-1NDiICED TENSIGN CRACKS) .............................................................4 <br />5.0 SUBSIDENCE PREDICTION BASED ON LONGWALL MINING AT WEST ELK MINE .................5 <br />5.1 <br />5.2 <br />5.3 <br />5.3. <br />5.3. <br />5.4 <br />5.5 <br />5.6 <br />5.7 <br />5.8 <br />5.9 <br />CAVED ZONE ....................................................................................................................... ...............................5 <br />FRACTURED ZONE ............................................................................................................... ...............................5 <br />CONTINUOUS DEFORMATION ZONE AND NEAR SURFACE ZONE .......................................... ...............................7 <br />Vertical and Horizontal Displacement, Tilt, and Horizontal Strain ........................... ...............................7 <br />Maximum Projected Depths of Surface Cracks ........................................................... ............................10 <br />ANGLE OF DRAW ................................................................................................................. I <br />2 <br />.............................12 <br />ANGLE OF MAJOR IFIFLUINCE ................................................................... <br />RELATION BETWEEN DYNAMIC AND FINAL SUBSIDENCE DEFORMATIONS <br />CRICICAL EXTRACTION WIDTH OF MINING PANELS ................................... <br />RESULTS OF COMPUTER MODELING ......................................................... <br />6.0 RATE AND DURATION OF SUBSIDENCE <br />12 <br />13 <br />13 <br />14 <br />14 <br />15 <br />7.0 EFFECTS OF TOPOGRAPHY AND STRUCTURE ON SUBSIDENCE PROCESSES .......................15 <br />7.1 EFFECTS OF TOPOGRAPHY ON SUBSIDENCE CRACKS ........................................................................................ 16 <br />7.2 EFFECTS OF RUGGED TOPOGRAPHY ON SUBSIDENCE AND MINE STRESSES ......................................................16 <br />1 <br />