Laserfiche WebLink
M03106GE <br />Suring the gob pile poundation preparation, an additional drain <br />system should be installed at that location to intercept, collect <br />and discharge water from seepages or springs. We should be con- <br />tacted to observe the foundation preparation and provide additional <br />geotechnical engineering recommendations for drainage of springs or <br />seepages if exposed during gob pile foundation preparation. <br />4.3 Slope Stability <br />The stability of any slope is dependent on many factors. Typi- <br />ca11y the stability of a slope is analyzed by calculating the <br />anticipated gravitational forces that tend to drive the mass of <br />soil downhill and the anticipated internal strength of the soil <br />along the expected plane of failure that will resist the downhill <br />movements. If the driving forces are equal to or greater than the <br />resisting forces then failure is imminent. A theoretical calculat- <br />ed factor of safety of 1.5 is considered by the geotechnical <br />engineering industry as a minimum factor of safety for a slope to <br />be considered as stable. A calculated factor of safety of 1.0 or <br />less indicates that slope movement is imminent or in process. <br />Failure can occur as slow deformation, creep, or as a somewhat <br />spontaneous failure. <br />Factors that have an adverse influence on slope stability can <br />generally be classified as those that increase the stress (driving <br />force) on the system or decrease the strength (resisting forces) of <br />the soil. <br />Our stability analyses of the site slope soil material was based <br />on th6 Bishops method of slices. This method is based on the <br />assumption that the slope soil mass will fail in a rotation mode on <br />a circular arc plane. In this method-of analysis the mass of soil <br />is divided into vertical slices. The forces acting on each slice <br />are evaluated from the equilibrium of the slices; that is, the <br />forces that tend to drive the slice downhill and the forces that <br />tend to resist the movement of the slice. The equilibrium of the <br />entire mass is determined by summing the driving and summing the <br />resisting forces acting on all slices and comparing these forces. <br />Our slope stability analysis was performed using "Slope Stability <br />Analysis" by Geosoft computer software. Our slope stability <br />analysis considered three (3) different cross sections with a total <br />of about 10,000 separate possible failure surface iterations to <br />help identify the potential theoretical slope stability. Our <br />discussions and data presentation is based only on the calculated <br />critical circle which presented the lowest factor of safety against <br />failure. Our presentation does not include the results of all of <br />the iterations which resulted in a theoretical factor of safety <br />greater than the lowest factor of safety and therefore were not <br />critical. <br />~~ <br />5. <br />~Lam6ert anD ~,s~,~ueiarea <br />CONSULTING GEOTEOM NICAL ENGINEERS ANG <br />YATERUL TESTING <br />