A Design Method of Deep Excavation in Cohesive Soil Based on the Reliability Theory

Abstract

ABSTRACT The recent excavation has become wider and deeper and in addition, the excavation works of poor ground have steadily increased. In design and construction of large-sized excavation works, the following two points are specifically important. One is the quantitative evaluation of various uncertainties which occur in design and construction. The other is the optimization of design and construction under consideration from the mechanical and economical aspects. In order to satisfy the two points, a design method based on the reliability theory is applied to the design of large-sized excavation works. In the first half of the present paper, the optimization of the prior design before construction is described. That is, the method to decide the optimal action in the prior design is discussed based on the statistical properties of soils and the analytical error of the conventional design equations. The obtained optimal solutions are compared with the actual results of the past construction fields. In the second half of this paper, the dynamic design procedure in which the results of the prior design are modified by new information obtained during construction is applied to the excavation problem. The dynamic design procedure which was firstly formulated for the embankment problem is modified so as to be applied to the excavation problem and the results obtained from the numerical studies are also compared with those actually obtained hitherto through the course of excavation works.