Development of knowledge-based system for the preliminary design of cantilever retaining walls

This paper describes an application of knowledge-based expert systems (KBES) in the domain of geotechnical engineering design. The KBES, named TWALL, performs the preliminary design of cantilever retaining walls, including the proportioning of wall dimensions to ensure external stability (i.e., wall stability against overturning, sliding and bearing failures) and provision of sufficient steel to ensure internal stability of the wall. TWALL is structured to design for either external stability only or both external stability and internal stability. In TWALL, a hierarchical decomposition of the task of wall design is used as a basis for system organization. The knowledge base of TWALL is developed in Production Rule Language (PRL) provided by the LEVELS expert system shell. There are a total of 297 rules used in the knowledge base. The developed system is semi-automated with a user-friendly interface and contains proportioning algorithms developed to obtain a design with only few trials. An external graphic program coded in Microsoft FORTRAN draws the final design sketch of the wall.