Laserfiche WebLink
Subsidence and Geologic Field Observations <br />Apache Rocks and Box Canyon Mining Areas <br />July 12-15. 2004 <br />Figure 23. Eastward view of part of the same rockfall/landslide area shown in Figure 21. This Image was <br />taken in July 2003 before any longwall mining. Recent movement can be seen in the upper scary area in <br />Fgure 22, compared with this image. This image is a cropped enlargement of Figure 20 0l the 2003 <br />repoR. <br />• Thr rockfall-landslide area shown in Figure 22, which consists of at least two separate <br />fallyslidcs, is locatul above the approximate midpoint of mined longwall panel 22 (Map 2). <br />• Mining apparently accelerated the natural rockfall process because of the timing of the <br />nwvrmrnts and of being in the areas of mining influence of the mined panel, <br />• Subsidence tilt and strain most likely accelerated the natural rockfall process to a grwter <br />extent than did any seismic effects produced during the mining of longwall panel 22. <br />However earth tremors related to stress rradjustmrnu and releases of strain energy in the <br />longwall mining, particularly under thick overburden of Wrst Flatiron (up to 2,250 fret), may <br />have contributed to some minor extent. <br />• 'fhe overburden depth of the rockfalUlandslide area to the B Scam ranges tiom about 1,000 <br />feet ut the base (toe area) to about 2,200 feet at the top of the head scarp. <br />831-032,640 Wnght Water Englneera. Inc. Pape 40 <br />Septembar2004 <br />