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• Therefore, an undrained shear strength of 750 psf was assumed for these subgrade materials. In addition, <br />Tensar geogrid reinforcement will be placed a[ the base of the imported till materials and an angle of <br />internal friction of 25 degrees was assumed for this material placed and compacted [o at least 95 90 of the <br />maximum modified Proctor density in accordance with ASTM D1557. In accordance with the geogrid <br />manufacturer's ruommenda[ions, anincrease in undrained soil shear strength of Z.0 is assumed in the <br />analysis for the underlying subgrade soils. <br />Based on the available information and the assumptions stated above, it appears that the roadway should <br />have a mutimum factor of safety on the order of 2.0 for shallow failures within the embankment fill <br />materials. For deeper seated failures within the subgrade soils, it appears [hat the roadway should have a <br />minimum factor of safety on the order of 1.7. Results of the stability analyses is shown in Appendix A. <br />These values are based on the proposed construction and the assumptions given above. Variations in the <br />loading conditions (static versus dynamic), soil profile and corresponding strength values may change <br />with time or be different from [hose assumed. We do not guarantee the stability of [he embankment, <br />only that our work meets the standard of care in our profession. If you have any questions regarding [his <br />letter or stability analysis, or if we may be of further service, please contact this office. <br />Sin <br />NO <br />• <br />Hai <br />Rey <br />u <br />APPROVED NOV 2 4 1997 <br />lob No. 97-3325 Nonhwesr Colorado Consul~enu, Inc. page 2 <br />