Influence of Drainage Trenches on Slope Stability

An unfavorable groundwater condition is a frequent cause of slope sliding. Pore pressure decreases the effective stress level and consequently the shear existance of the soil on the slip surface is decreased. Thus the slope safety against sliding is reduced. A change in the groundwater condition is achieved by drainage systems. The drains introduce a lower potential to the pore water which reduces the pore pressures in the sliding mass. Drainage trenches are suitable for stabilizing shallow translational slides. This paper examines the determination of the necessary spacing of trenches for a required increase in factor of safety. The factor of safety obtained represents the long‐term value for the steady state condition.