Laserfiche WebLink
•~ <br />s a: ~ ~„ <br />Memo to Dave Berry <br />Bowie No. 2 Geotech Study <br />page 4 <br /> <br />cut and fill proposed for some bench and road locations, it will be <br />important to monitor the performance of the slope. Because of the <br />unfortunate fact that clay soils and bedrock, once failed, can rarely be <br />returned to the "peak" strength exhibited prior to failure, but rather <br />exhibit a lower "ultimate" plastic regime strength; it is important to <br />identify and treat impending failure as evidenced by accelerated creep. <br />anticipate that strategically placed and frequently monitored <br />inclinometers will be one component of an appropriately comprehensive <br />slope monitoring scheme at the Bowie No. 2 Mine site. <br />Page 10 <br />The author reports that several soils exhibited volumetric expansion <br />(under 500 psf fixed loads) of up to 13 percent, correctly termed "highly <br />expansive. Further, the author appropriately comments; "Clearly, most of <br />the clays on this site would be considered sensitive to loss of strength <br />and/or volume change upon increases in moisture content or pore pressure. <br />However, where the soils are dry of saturation, they have considerable <br />strength via high internal stresses and negative pore pressures." Mine <br />sites tend to be challenging in terms of their engineering maintenance. <br />Management of surface water is significantly more challenging than in a <br />urban commercial subdivision setting. Specific methodology for the <br />control of surface water to prevent the deleterious effects of <br />moisturizing potentially problematic materials will need to extensively <br />addressed within the designs of the surface facilities at the Bowie No. 2 <br />Mine. <br />Further, upon reclamation of the surface facilities extensive soil <br />materials will be unavoidably exposed to the elements. In their reclaimed <br />configuration, swelling and low-strength soils will be unconfined and <br />exposed to extensive moisture. In this configuration materials will <br />exhibit their swollen, deteriorated "ultimate" plastic regime strengths. <br />Reclaimed facilities will have to be designed and analyzed with this fact <br />