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G <br /> <br />Table ]. -Soil Proaerties <br />Description Max dry density <br />c Saturated Density <br />(c Cohesion <br />s Direct Shear <br />Friction an le <br />Siltstone Cla stone 128 140 300 45 <br />Embankment I15 128 200 18 <br />Alluvium 126 138 0 32 <br />EMBANKMENT DESIGN <br />Based on the results of the geotechnical site investigation, it was decide that the <br />embankment would be constructed of a mixture of the siltstone (claystone bedrock and <br />the sandy lean clay overburden located on the site. The embankment will not extend <br />above the ground surface and will extend down into bedrock. A keyway trench will be <br />used to insure proper cutoff between the embankment and foundation. <br />DESIGN ANALYSIS AND CRITERIA <br />The proposed reservoir embankment was analyzed using the XSTABLE v5.105a <br />computer program. XSTABLE was designed to analyze the slope stability of earth <br />embankments subjected to several critical situations that may occur during the life of the <br />embankment. For this project, four situations were identified as critical. <br />Case I -Mining Conditions. The site will be mined with near vertical <br />` highwalls. There are several public roads that are within 200 feet of the proposed <br />highwall. A 35.0 foot setback leas been proposed from all public R.O.W. for this <br />site. An H.S. 24 highway loading with a 1.3 impact loading factor has been added <br />to the stability model <br />Case 2 -Mining Conditions. The Box Elder Ditch currently runs North to <br />South across the site. A 25' foot mining limit setback from the top of the ditch <br />has been proposed. <br />Case 3 -Full Reservoir. The reservoir is full for an extended period of time <br />causing the embankment to become completely saturated.. An H.S. 24 highway <br />loading with a 1.3 impact loading factor has been added to the stability model for <br />this case. <br />Case 4 -Rapid Drawdown. The reservoir is evacuated in a short enough time <br />period to leave the embankment saturated. An H.S. 24 highway loading with a 1.3 <br />impact loading factor has been added to the stability model for this case. <br />The attached cross-sections show the estimated phreatic surface associated with each <br />case. <br />4 <br />