5- An anchor supports a retaining wall. The backfill

is a silty clay with the following properties:

c' = 10kPa

$' = 20°

Yt. = 18kN/m³

Ko = 0.4

The silty clay is well drained so no pore pressures

are expected. One mode of anchor failure is by very

slowly pulling the square prism of soil indicated by

the dotted lines. What force would need to be

generated in the anchor to cause this failure?