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2006 Subsidence and Geola~~c Field Observations <br />Box Canyon• Nest Flatiron, Apache Rocks, and South of Divide Mming Areae <br />l'he tr:utsvcrse crocks th^t :uc I,,calrel above the lung,vall ttunnr~ face have a dymm~ic htst,~r~ <br />They open tahcn the lungwall Face moves beneath a particular crack area, and then close again <br />when the lungwall litre moves out of the area of mining influence in this area. <br />Longitudinal cracks occur above, and ntughly parallel to• the edge; of the lung,vall mining panel <br />above the gate road pillar. (Figure I b Longitudinal cracks commonly remain open, particularly <br />in areas ahavc gate roads with a ngid-pillar conliguratiun. Fhc cracks may he open or closed m <br />areas above gate roads with a combination rigid-pillaryirld-pillar cunfiguranun. <br />~M~ <br />_ - • <br />l - ~_ ` <br />('untpression tcatun+s (bulges and ,varps) also occur uhuce the Inngw:dl mining panels in :trca. <br />where the ground surCacc undergoes compression in the subsidence process. Chc rompressmn <br />fcatuns. which occur toward the center of the mining panel in cones u(maximum compression, <br />arc usually more ditlicult h, r~rugnizc. 'fhuy uficn arc nriskcd, ur absorbed, by soil and <br />t:ulluaiunt, or arc holden in the htvsh and grass. l hey also may he indistinguishable from sutural <br />humps ;utd ntnunds in the soil and cullu~ tom. <br />2.2 Construction Cracks <br />('racks caused by ctanstrucuun activities arc camnu,n nn the h:mks of newly constructed n,ud> <br />:md doll pads (f=igure ?1. fhcse cracks arc often caused by thr hulldutrr during construction <br />detirtitcs. fhev are mull noticc;thlr where fractured tool weatlured bedrock is eneuwttercal <br />P31-032.?.50 Wdghl Weter Engineers, Inc. Paye A <br />December 2006 <br />