Recently, artificial blanketing earth dams founded on pervious stratum have been projected in our country.
The authors had a chance of model tests on such a blanketing dam, and obtained some knowledges about its character and design procedure on blankets.
The resume of our study is as follow;
1. The calculations by theoretical formula on uniform thickness blankets developed by P.T. BENNETT showed good concurrence with the results of sand model tests.
2. Founding on BENNETT theory. the authors derived formulas on the trapezoid blanket (Formulas. 16-18).
3. The triangular blanket has the smallest sectional area for a definite effective resistance, and the trapezoidal one follows. The rectangular (uniform thickness) blanket has the largest sectional area. But the triangular one seemed to be eroded at the upstream end having very thin thickness, therefor the trapezoidal section is desirable for the artificial blanket.
4. In the design of the artificial blanket, its length should be decided considering the limitation of controlling underseepage quantity in pervious foundation.
Such viewpoint leads to. preventing the design of exceedingly large length, and to increasing the ratio of blanket's effective length to blanket's length, and more economical section will be gained.
5. In sand model test, the underseepage quantity was controlled by the upstream blanket to about 50% of the quantity for no blanketing case. And by the blanket with infinite length the control was calculated to be about 26% for the ultimate seepage.
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