A Comparative Study on Various Codes and Current Practices for Design of Caissons

Abstract

Caissons are among the less frequently used but among the most important type of foundations as they support lifeline structures like bridges. In the present study, different codes of practice adopted in different countries and the progress made by various researchers has been reviewed. One of the important parts of design of caissons is the determination of scour depth, which is given by different methods for different types of strata. In alluvium, Lacey’s theory is a well-accepted theory which is adopted globally. However, for other types of soil, different codes recommend different methods of analysis, which has been reviewed in the current study. The computation of lateral stability of caissons was previously based on Terzaghi’s (1943) analysis for a free, rigid bulkhead. Pender (1947) (see [8]) analyzed the situation by considering soil around the pier to behave as linear springs with their stiffness increasing with depth. Banerjee and Gangopadhyay (1960) derived equations for lateral stability of well foundations using Pender’s plastic flow concepts along with Terzaghi’s rigid bulkhead stress distribution and subgrade modulus concepts. In this study, caisson has been designed for a given set of site conditions using recommendations of different codes and comparisons have been drawn between recommendations of different codes. Upon review of all the codal practices and methodologies available for design of caissons, it was concluded that there is significant scope for improvement and amendment in the codes to keep up with the advancement in technology with time.