4.1.3 Water is filled in discontinuities

When water is filled in the discontinuity, it exerts a water pressure that will reduce the normal stress on the discontinuity. Due to this, the shear strength of joint reduces which increases the chance of slope failure. The effect of water pressure can be estimated by determining the effective normal stress. The effective normal stress due to present of water in the joint, is given as


It is assumed that water is discharge from point A, therefore the water pressure is equal to atmospheric pressure  at point A and C.


μ = water pressure, MPa

σ = effective normal stress, MPa

σ = normal stress, MPa

ρ = density of water, kg/m3

h= height of water column, m




Figure 2a: Geometry of a slope for plane failure with filled water