doi:10.3850/GI183

ABSTRACT

The Gautrain Rail Link will connect the cities of Johannesburg and Pretoria with a branch connecting both cities to the OR Tambo International Airport along approximately 80 km of alignment with 10 stations and a depot. Approximately 15 km of the railway alignment is underlain by dolomite with nearly 6 km elevated on a viaduct close to Centurion. The dolomites underlying the viaduct alignment present a sinkhole risk for the project. In order to mitigate against the effect of sinkhole formation a modified compaction grouting procedure was developed and implemented based upon two full scale trials. The methodology adopted is based on an attritive approach with stages of grouting and depth related pressure and volume criteria. Drilling and grout injection by upstage grouting comprise the two main components of the work. High resolution techniques were implemented for the works to characterise the ground and monitor the grout works which facilitated a thorough validation process. Fifty five pier locations and a railway station site were grouted by six grouting teams in 24 months. The design and results are presented to show how challenges in difficult ground conditions were successfully overcome.

Keywords: Pressure grouting; dolomite; Gautrain; ground improvement; sinkhole; doline.

© 2010 by Geotechnical Society of Singapore (GeoSS)