Design Example:

An earth dam has to be constructed at a place where soils have the following characteristics:

i$.$ Sand mixed with gravel

a$.$ Saturated unit weight $2\frac{t}{m^3}$

b$.$ Specific gravity $2\mathrm{.}65$

c$.$ Angle of internal friction $33$

d$.$ Cohesion nil

e$.$ Dry unit weight $,1\mathrm{.}65\frac{t}{m^3}$

This material constitutes the foundation to a depth of $15m,$ below the base of a dam after which rock available.

ii$.$ Silty clay

a$.$ Saturated unit weight $,1\mathrm{.}76\frac{t}{m^3}$

b$.$ Specific gravity $2\mathrm{.}55$

c$.$ Angle of internal friction $12$

d$.$ Cohesion $3k\frac{g}{c}{m}^2$

The material has to be obtained from an average distance of $1\mathrm{.}5km.$

iii. Levels

a$.$ River bed level $103m$

b$.$ Dead storage level $123m$

c$.$ F$.$S$.$L$.155m$

d$.$ H$.$F$.$L$.158m$

Assume the material above phreatic surface to be $40\%$ saturated.

iv$.$ Earthquake factor

a$.$ For sudden drawdown $,=0\mathrm{.}15$

b$.$ For steady seepage $,=0\mathrm{.}10$

c$.$ For just after construction $=0\mathrm{.}05$

wind velocitys $150kPh,F_{5}20km$

Design a suitable section of the earth dam and indicate the position of seepage line.