A Deep Retaining System Construction with Soil Nailing in Soft Rocks in Istanbul, Turkey

摘要

In-situ reinforcement of ground by a series of inclusions is an effective technique for improving the stability of slopes and excavations. During the past fifteen years, significant development has taken place in the techniques of in-situ ground reinforcement using nails and anchors. Especially, soil nailing has gained world-wide acceptance in both theory and practice due to its economy, technical advantages and construction speed. In this paper, application of a soil nailing system for a new commercial center in the city of Istanbul is documented as a detailed case study. The application is in greywacke formation where the total excavation height reaches approximately 27m with an angle close to the vertical. During the construction of the retaining system, the deformations and the behavior of the system are monitored systematically with fourteen inclinometers installed within the site. The retaining system is numerically modeled using the software FLAC and the displacement patterns together with nail loads are determined for every step of the excavation. It is shown that the measured and calculated displacement patterns and their values are very closely comparable. It is also shown for the first time that the estimation of lateral displacements as a certain percentage of excavation height according to the present state-of-the art may lead to considerable underestimation of lateral displacements, especially beyond a certain depth of excavation.