oa Civil Engineering = Siviele Ingenieurswese - Port Louis Ring Road - design approach for post-failure stabilisation : geotechnical engineering



Over the past six years Mauritius embarked on major road and traffic infrastructure upgrade projects as part of solutions to improve road user safety, alleviate traffic congestion, boost the industry and facilitate economic growth, with added social and environmental benefits. Positive population growth and an increasing number of road users required construction of dual-carriageway roads capable of accommodating high volumes of traffic. Massive capital investments and acquisition of land were required for these projects, ultimately leading to the planning and alignment of these roads over very challenging topographical, hydrological and geological terrain and environments. The Ring Road Phase 1 project was constructed during 2010-2013, and comprises a 4.9 km dual-carriageway, and one large bridge over the St Louis River, with access roads to industrial and retail areas and the National Convention Centre. Terrain elevation and road alignment required the construction of several large cuts and fills. Space restrictions justified the implementation of large mechanically stabilised earth walls (MSEWs) in lieu of traditional fills.

In early 2014, cracks appeared on the northbound carriageway, followed by the collapse of a 15 m high MSEW portion of the fill (Photos 1 and 2). Observations pointed to a textbook slope failure with "slip at the lip" and "bulge at the toe", indicating that deep-seated movement had occurred. This article summarises the geotechnical investigation conducted to identify the failure mechanisms, the design of remedial measures, and the knowledge and understanding gained for use in future projects.


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