QUESTION $3$

$[23$ MARKS$]$

A gravity retaining wall of trapezoidal section with a vertical face on the earth side is Im wide at the top, $3m$ wide at the bottom and $5m$ high as shown below. The unit weight of the soil retained is $17000\frac{N}{m^3}$ for the upper $2\mathrm{.}5m$ and $19000\frac{N}{m^3}$ for the lower $2\mathrm{.}5m.$

$3\mathrm{.}1.$ Find the total horizontal force on the wall

$(7)$

$3\mathrm{.}2.$ The maximum and the minimum stress intensities under the base it the angle of internal friction is $30$ for both sois and the unit weight of concrete is $23k\frac{N}{m^3}$

$(16)$