Robust design of braced excavations using multiobjective optimization-focusing on prevention of damage to adjacent buildings

This paper presents a new geotechnical design methodology, referred to herein as robust geotechnical design (RGD), and its application in the braced excavation design in clays. The RGD approach is aimed at optimally selecting the design parameters so that the system response (e.g., the damage probability of the adjacent building caused by excavation) is insensitive to, or robust against, uncertainty in statistics of noise factors. In this paper, the uncertainty in the estimated statistics of noise factors is evaluated using the bootstrapping method, and the variation in the probability of damage is evaluated using the point-estimated method integrated with first-order reliability method. The RGD is realized through a multiobjective optimization, in which all the requirements such as safety, robustness, and cost are explicitly considered. A design example of braced excavation is used to demonstrate the effectiveness and significance of the RGD approach.