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358                   CHAPTER TWELVE

             Case II. When I < 2U,
                              Q     hk    2U    1   1 3
                                       I
                                         2      L             (12.213)

             Figure 12.33 gives 10 formulas for seepage through the embankment of an
           earth dam with an impervious foundation.
           Slope Protection. The slopes of earth embankments must be protected against
           erosion by wave action, rainwash, frost, and wind action. Protection cannot


             20.0


                                                                  L
                                                        Q = 0.05kh t
             10.0
              8.0
              7.0
              6.0                                        Q = 0.10kh L
              5.0                                                t
              4.0
              3.0
                                                         Q = 0.20kh L
                                                                 t
              2.0
                                                         Q = 0.30kh L
                                                                 t
           d
           h t       0.33-m-flat slopes                  Q = 0.40kh L
                                                                 t
              1.0    0.25-m-medium slopes
              0.8    0.10-m-steep slopes                 Q = 0.50kh L
                                                                 t
              0.7
              0.6      m                                 Q = 0.60kh t  L
              0.5
              0.4                                        Q = 0.70kh t  L
              0.3  h t
                                      α                  Q = 0.80kh L
                                                                 t
              0.2                  d

                                                         Q = 0.90kh L
                                                                 t
              0.1
               10°          20°    30°   40° 50° 60°  80°        100°
                                            α
           FIGURE 12.33 Seepage through embankment on impervious foundation. (Davis—Handbook
           of Hydraulics, McGraw-Hill.)
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