Active Earth Thrust on a Wall
Active Earth Thrust on a Wall
Integrating the triangular active pressure over the wall height gives the total thrust used to check sliding and overturning.
The active thrust is P_a = ½·K_a·γ·H². where K_a is the active coefficient, γ the soil unit weight and H the wall height.
Inputs
K_a := 0.333=0.33
gamma := 18 kN/m^3=18000 kg/m^2/s^2
H := 4 m=4 m
Integrate the triangular pressure over the height.
P_a := 0.5·K_a·gamma·H^2=47952 kg/s^2
Results
The thrust grows with the square of height and acts at one-third height, producing a large overturning moment — the governing action for retaining-wall stability.
Assumptions & limitations
- Cohesionless backfill, active state.
- No surcharge or water pressure.
- Per metre run of wall.