Data:

Depth factor $=(1+0\mathrm{.}2(\frac{D}{B}))upto$ a $limitof1\mathrm{.}5$

Shape factor $=(1+0\mathrm{.}2(\frac{B}{L}))$

$K_g=\frac{1+sin{}^{\text{'}}}{1-sin{}^{\text{'}}}$

and the foundation has width $B,$ length $L$ and depth $D.$

Comment briefly on the assumptions: ${}_h^{\text{'}}=(1-sin{}^{\text{'}}){}_v^{\text{'}}$ and $=0\mathrm{.}67{}^{\text{'}}.$ Why in reality might it be necessary to reduce the allowable load per pile?Question $2(25$ Marks$)$

Figure $1$ shows a soil profile in which it is proposed to install a foundation made up of a

number of circular concrete piles of $1\mathrm{.}5m$ diameter and $10m$ depth. Estimate the long$-$

term design vertical load $($acting downward$)$ for a single pile, if minimum partial

factors on resistances of $2\mathrm{.}24$ on base bearing, $1\mathrm{.}82$ on skin friction and $2\mathrm{.}1$ on the total

are required. $($Assume that the horizontal effective stress at any depth is equal to $(1-$sin

$\{$:${}^{\text{'}})$ times the vertical effective stress at the same depth, that the angle of friction $$

between the concrete and the soil is equal to $0\mathrm{.}67{}^{\text{'}},$ and that the long$-$term pore water

pressures are hydrostatic below the indicated water table. Take the unit weight of water

as $10k\frac{N}{m^3},$ and the unit weight of concrete as $24k\frac{N}{m^3}.$