Computation of Seismic Active Earth Thrust on Retaining Wall for c-Φ Backfill

摘要

The concept of seismic active earth thrust is essential for the safe design of earth retaining walls in the seismic zone. In the proposed method, reaction along the planar failure surface is obtained using Kotter's (1903) equation. Further, limit equilibrium method is effectively used to compute active earth thrust considering pseudo-static condition with both horizontal and vertical seismic coefficient. An attempt is made to locate point of application of active thrust using moment equilibrium condition in c-Φ backfill. This study is further extended to compute active earth thrust considering pseudo-dynamic condition which is more realistic in representing time and phase difference within the soil backfill. Effect of various parameters such as angle of internal friction, wall friction angle, angle of backfill inclination, horizontal and vertical seismic co-efficient, shear wave, compression wave etc. are discussed. It is seen that seismic active earth thrust decreases with increase in both friction angle and cohesion. Further active earth thrust increases with increase in horizontal seismic co-efficient and surcharge angle. The results obtained by trial and error method are underestimated by 2% than the results obtained from pseudo-static and pseudo-dynamic analytical approach suggested by Sharma and Ghosh (2010). Similarly, predictions made in case of static approach are in good agreement with results obtained from analytical approach suggested by Sharma and Ghosh (2010).