Depends on the soil. A stiff clay would stand on its own with the slope you have shown (about 60[sup]o[/sup]). For a more accurate assessment, perhaps the Geo technical forum would be better able to provide an answer.
Earth pressure acting against a battered wall is covered in all of the soil mechanics and geotechnical engineering books. Ask the project geotech about the effect of battering. The more a wall is battered back toward the retained soil, the less earth pressure there is pushing on the wall. The batter of the wall reduces the active earth pressure coefficient. Eventually, with increasing wall batter, the wall could become battered enough that you could have a stable, unsupported slope where a wall is not needed.
Thank you for the documents, the angle between the horizontal and the wall is less than 90 deg. On the reference it’s higher than 90. On the second reference it’s a flexible walls.
Hasna - Segmental retaining walls are inclined the same as your drainage channel. See pages 5 and 6 of the Allan Block Engineering Manual for calcs suitable for the desired angle. The equation shown is for the active pressure coefficient (K[sub]a[/sub]). Using that value, force on the wall is determined the same way as a vertical wall.
In the equation, "csc" is the cosecant of the angle of inclination, equal to the reciprocal of the sine of the angle.
φ[sub]w[/sub] is assumed to be (0.66)φ
Back slope at the top of the retaining wall (i) is zero degrees (0[sup]o[/sup]) for your sketch.
As a quick check on this equation, notice that if β = φ, then K[sub]a[/sub] = 0... exactly what it should be for that situation.
