Monitoring and analysis of results for two strutted deep excavations using vibrating wire strain gauges

Abstract

As part of the North East Line Mass Rapid Transit Project in Singapore, Contract 704 included the construction of two underground station structures. The excavation for Serangoon Station was in the residual Bukit Timah granite and the excavation for Woodleigh Station was in the residual Old Alluvium material. The temporary retaining structures for both excavations consisted of driven soldier piles and timber lagging supported by steel struts. The excavation for the construction of both stations was monitored in part using vibrating wire strain gauges on the struts. This paper presents the strut monitoring results. A comparison is made with the apparent earth pressure envelopes recommended by Peck. The need to balance continued development with the land constraints in Singapore means that underground structures will continue to be used. The results presented in this paper are relevant in determining the geotechnical parameters for deep excavation retaining walls constructed in these types of materials. It is concluded that the measured earth pressures relate reasonably well to the apparent earth pressure envelopes recommended by Peck.