A retaining wall 3.6 m high supports a dry cohesion less backfill with a plane ground surface sloping upwards at a surcharge angle of 20° from the top of the wall. The back of the wall is inclined to the vertical at a positive batter angle of 9°. The unit weight of the backfill is 18.9 kN/m3 and φ = 20°. Suppose a wall friction angle of 12°, verify the total active thrust by Rebhann's method.