Real Time Monitoring at the Olive 8 Excavation

Abstract

The real time monitoring for the Olive 8 project in Seattle is described. This project involved construction of a 39 story structure with 5 levels of below grade parking. The 76 ft deep excavation next to an adjacent building required a hybrid support system consisting of large soldier piles with tightly spaced soil nails in the upper portion and steeply inclined tieback anchors in the lower portion. Because the City of Seattle limited lateral movements to 1 inch, engineers implemented a detailed monitoring system. Conventional inclinometers and optical survey points were supplemented by real time monitoring consisting of a web camera and an automated total station. This paper summarizes the philosophy behind the real-time instrumentation and shows how the total station data complemented the conventional inclinometer data. Data reduction techniques are described and performance data are presented. Finite element simulations of the excavation process showed the critical observation was the cantilever movements at the top of the support walls. Survey prisms were mounted at three such locations along the west wall to provide real time performance data. A project web site allowed all interested parties access to the data. The paper illustrates how real time monitoring and careful design can be used to great effect.

Maximizing the Benefits of Real Time Monitoring of Geotechnical Construction

“…The Olive 8 high-rise development in Seattle involved construction of a 39 story structure with 5 levels of below grade parking (Finno and Langousis 2007). The excavation was 70 ft deep, and was supported by a soldier pile wall supported by both soil nails and ground anchors.…”