Behavior of retaining walls and adjacent structures during braced excavation

The construction work described in this paper is braced excavation adjacent to existing subway structure. Because a subway structure is hardly allowed to move for the safe service, influence of excavation is required to be held down to a minimum. In this work, measuring devices were placed on the retaining walls, surrounding ground, and the subway structure in order to monitor their behaviors. In addition, a set of back analysis and prediction analysis, based on the observed data, was conducted at every steps of excavation, which made confirmed the safety of excavation and subway operation in advance. The excavation phase was concluded in a safe manner. The observed data showed that rebound, as well as settlement, had to be accounted for influence that excavation had on adjacent structures. And the predicted movement of the subway structure appeared to agree quite well with those measured. The arrangement of instruments and the executed prediction procedure were so effective it can be applied to other projects with the similar conditions. This paper focuses on the observed data and outline of the prediction procedure.