Reliability-based design optimization of geosynthetic-reinforced soil walls

Structural design optimization usually aims to extract more function from less material. This can result in more failure modes designed against their limits, thus reducing safety. The compromise between cost reduction and safety is particularly relevant for geotechnical structures, as they are subject to significant scatter and uncertainties in their properties. In this context, this paper presents an application of Reliability-Based Design Optimization (RBDO) for the problem of geosynthetic-reinforced soil retaining walls. Design variables include the mean strength of the geosynthetic, spacing between reinforcements, and the length of the geosynthetic. Random variables include soil angle of friction, soil unit weight, the strength of the geosynthetic and the friction angle between the reinforcement and soil mass. The solution procedure proposed herein combines the ant colony optimization (ACO) algorithm with the First Order Reliability Method (FORM) algorithm, which results in nested optimization loops. Results show that significant savings can be achieved in structural design without hindering structural safety.