Retaining Walls Under Seismic Loading

The design of retaining walls in seismic areas poses a complex problem. The traditional design approach usually consists of calculation of a factor of safety against sliding, overturning and bearing capacity failure. This is generally enough for static loads. During seismic loading, the retaining walls tend to get displaced from their original position. The performance of quay walls during the past earthquakes emphasizes this fact. For safe design of retaining walls in seismic areas, the calculation of static and dynamic earth pressure behind the retaining walls is the first requirement. Realistic calculation of displacement of the retaining wall is an equally important aspect. The paper presents a simple method for calculation of static and dynamic active force on the rigid retaining wall. The method follows the pseudo-static approach of analysis and includes the effects of cohesion of the backfill and the friction between the backfill and the wall face. The resultant earth pressure obtained by this method has been compared with the experimentally observed values during small scale tests on retaining walls by other investigators. The displacement must not exceed specified allowable values. A brief discussion of calculation of displacement of rigid retaining walls is also included