Q$1(40$ marks$)$

$($i$)$ Refer to Fig $1\mathrm{.}1$; plot the stress distribution diagram $(10$ marks$)$

$($ii$)$ Calculate the resultant forces $(5$ marks$)$

$($iii$)$ Check all stability factors $(25$ marks$)$

$($iv$)$ Discuss effect of change of Q from $200$kPa to $500$kPa $(10$ marks$)$

Given

Back fill: Clayey soil

Cohesion: $40$kPa

Unit weight: $12\mathrm{.}5k\frac{N}{m^3}$

$Q=200$kPa

Backfill $15$ degree toward the wall

Figure $1\mathrm{.}1$