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M98168GE • <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 slope stability analysis was perfoz~ned using "Slope Stability <br />Analysis" by Geosoft computer software and was based on the Bishops <br />method of slices. This method is based on the assumption that the <br />slope soil mass will fail in a rotation mode on a circular arc <br />plane. In this method of analysis the mass of soil is divided into <br />vertical slices. The forces acting on each slice are evaluated <br />from the equilibrium of the slices; that is, the forces that tend <br />to drive the slice downhil'_ and the forces that tend to resist the <br />movement of the slice. The eq',~ilibrium of the entire mass is <br />determined by summing the driving and summing the resisting forces <br />acting on all slices and comparing these forces. <br />Our analysis was based on soil strength characteristics obtained <br />from laboratory triaxial shear strength testa of samples of soil <br />-:material encountered in our test borings obtained during our field <br />study. The soil strength values used in our analysis included: <br />Site soil material: <br />an internal angle of friction of twenty (20) degrees, <br />cohesion of two-hundred-fifty (250) pounds per square foot <br />and <br />a moist unit weight of one-hundred-twenty-five (125) pounds <br />per cubic foot, and <br />Site formational material: <br />an internal angle of friction of twenty-five (25) degrees, <br />a cohesion of one-thousand (1,0003 pounds per square foot, <br />and <br />a moist unit weight of one-hundred-forty (140) pounds <br />per cubic foot. <br />5 <br />~tam6ert anD ~~~nciate~ <br />CAMNILTIMO OEOT[CMYIC~I [MOOI![A HMO <br />Y~T[11,~1 1[[TIMO <br />