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Port Louis Ring Road – Construction of a post-failure stabilisation design for a mechanically stabilised earth wall

By Marie Basson, Geotechnical Director: ARQ Mauritius (Pty) Ltd; Coert van Dyk, Geotechnical Engineer, ARQ Geotech (Pty) Ltd; Alan Parrock, Specialist Geotechnical Engineer, ARQ Geotech (Pty) Ltd.

For Phase 1 of the Ring Road, steep natural topology necessitated the construction of several large cuts and fills. Space restrictions justified implementation of large mechanically stabilised earth (MSE) walls instead of traditional fills.

In early 2014, cracks appeared on the northbound carriageway, followed by the collapse of a 15 m high MSE wall portion of the fill. Observations pointed to a textbook circular slope failure with “slip at the lip” and “bulge at the toe”, indicating that deep-seated movement had occurred. ARQ (Pty) Ltd was appointed to identify the mechanism of failure, design remedial measures and oversee implementation of these solutions. These remedial measures consisted, inter alia, of a vertical secant piled wall supported by seven-strand, three-level, high-strength ground anchors, coupled with a geosynthetically reinforced fill section behind the reconstructed MSE wall. An article discussing the investigation and design aspects of this remedial work was published in the April 2016 edition of Civil Engineering, and this article now summarises the construction of the remedial solutions. The successful completion of Phase 1 of this project was therefore paramount to the implementation of Phase 2.

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