doi:10.3850/GI184


Large Scale Dynamic Compaction for Gautrain Rapid Rail Link, South Africa


R. B. Storry1, R. Tosen2, A. Guilloux3 and K. Diemont4

1Bouygues TP (Seconded to Bombela Civil Joint Venture), Chief Geotechnical Manager, South Africa.

2Bombela Civil Joint Venture, Deputy Geotechnical Manager, Johannesburg, South Africa.

3Terrasol, Director, France.

4Bombela Civil Joint Venture, Geologist, Johannesburg, South Africa.

ABSTRACT

The Gautrain Rapid Rail Link project will connect the cities of Johannesburg and Pretoria with an extension to the OR Tambo International Airport. Approximately 15 km of the railway alignment is underlain by dolomite with highly heterogeneous residual and transported soils overlying a highly irregular bedrock found at the surface and to depths of more than 100 m below ground level. The soil profile is complex and the result of variable karst development affected by the proportion of chert in the Malmani Dolomite rock formations, presence of igneous intrusions and paleo variation in groundwater level. Soils with a high potential for collapse were identified along the alignment underlain by dolomite and ground treatment by dynamic compaction (DC) was nominated for residual dolomite soils, residual syenite and colluvium along approximately 2.5 km of the alignment. Trials were carried out at the start of the project. A systematic DC ground treatment methodology was developed comprising primary and secondary prints and phases (passes) of treatment for each print. The results of the DC carried out concurrently by four teams over an area of 95 000 m2 are presented.

Keywords: Dynamic compaction; dolomite; Gautrain; ground improvement.

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