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- 13 - <br />1 <br />1 <br /> <br /> <br /> <br />1 <br />1 <br /> <br />1 <br /> <br /> <br /> <br />1 <br /> <br /> <br />eliminated and replaced by a cut slope 2 : 1; at the same time, <br />the potential for saturation should be eliminated to achieve <br />long-term stability. <br />The following conclusions can be made and recommendations <br />formulated for the proposed construction: <br />1. It is evident that any unsupported excavation at ,the <br />steep slopes such as the one above the entry 5 would result <br />in a slope failure if the soils are saturated. In dry con- <br />ditions, the excavation may be temporarily stable; saturation <br />at some later date would cause a failure. In order to avoid <br />the risk of failure, any excavations in steep slopes should be <br />carefully dewatered prior to the excavation. <br />2. Excavations at flatter slopes such as the slopes above <br />the entries 1, 2, 3, and 4 might be temporarily stable even if <br />saturated. For long-term stability, the potential for saturation <br />should be avoided. <br />3. It is impractical to design any retaining structure to <br />resist a potential slide; retaining structures could be designed <br />using conventional design methods only if effective drainage is <br />implemented in the slope portion behind the structure. 4Ie <br />recommend that an effective underground drainage system be <br />utilized to prevent the saturation of the surficial layer; thick- <br />ness of the same should equal at least the height of the struc- <br />ture (including the below ground portion). The thickness should <br />be at least 10 feet. For a slope configuration and height <br />of the retaining wall such as indicated on Plate 8, the drainage <br />should be effective at some 100 - 120 feet behind the structure; <br />it could be proportionally shorter for a lower structure. <br />4. The analysis of the entry 3 shows that the retaining <br />wall could be eliminated and replaced by a cut. Factors of <br />oea«.o.o cwa~unu, Nc <br />