Culmann's Graphical Method to find Active Earth Pressure

Culmann's Graphical Method

          Culmann's Curve is the curve use to find Active and Passive Earth Pressure in Retaning wall. Culmann's curve is drawn using Culmann's Graphical Method.

In this article we describe the step by step procedure how to draw culmann's curve and how to find Active Earth Pressure Using Culmann's curve.

Procedure:

1) Draw Ground Line , Failure Line & Earth Pressure Line with β, 丫, ψ angle respectively.

2) Consider any trial wedge ABC1 and measure length AC1 as a L1

3) Calculate the weight of wedge ABC1 and plot it at point E i.e. BE1=L1

4) Consider all such lines BC2, BC3, BC4, and corresponding points E1, E2, E3, E4.

5) Through E1 draw a line parallel to ψ line which cut's BC1 at point F1.

6) Draw similar lines F2E2, F3E3, F4E4.

7) Draw a smooth curve which passes through B, F1, F2, F3, F4. This curve is called as 

    Culmann's Curve.

8) Draw a tangent to the Culmann's curve which cuts the curve at pt F.

9) Drwa FE line parallel to ψ lines.

    Hence  Active Earth Pressure is calculated as Pa= 1/2 (丫) (H) (E.F.)

    Where 丫 = unit weight of soil.

    So in this way we can find active earth pressure using Culmann's curve.