ABSTRACT
Passive Earth Pressure Coefficient Coulomb developed an analytical solution for determining Kp based on a plane surface of failure and this is given in Eq. (11.57). Figure 11.24(b) gives curves for obtaining Coulomb's values of Kp for various values of 8 and C/J for plane surfaces of failure. with a horizontal backfill. They indicate that for a given value of C/J the value of Kp increases rapidly with increasing values of 8. The limitations of plane surfaces of failure are given in Section 11.9. Curved surfaces of failure are normally used for computing Pp or Kp when the angle of wall friction 8 exceeds C/J/3. Experience indicates that the curved surface of failure may be taken either as a part of a logarithmic spiral or a circular arc. Caquot and Kerisel (1948) computed K~ by making use of curved surfaces of failure for various values of C/J, 8, eand {3. Caquot and Kerisel's calculations for determining K~ for curved surfaces of failure are available in the form of graphs.
