Treatment of soft ground by Fibredrain and high-energy impact in highway embankment construction

Abstract

The economic growth of a country depends significantly on its transportation system. The highways that form part of this system sometimes pass over compressible soft soil deposits. Two major geotechnical problems associated with the construction of road embankments on these soil deposits are stability during construction and long-term settlement. If the latter problem is not addressed adequately, excessive post-construction settlement will have serious consequences for the maintenance of road pavement, in addition to the unwarranted downdrag force (negative skin friction) and lateral pressure on the piles supporting the bridge abutments and ancillary structures. To mitigate these adverse effects, deep-seated saturated clays are pre-consolidated with Fibredrain, a vertical drain manufactured with biodegradable jute and coir fibre, and surcharge, and surface deposits of granular, clayey or peaty materials are treated by high-energy impact (HEI) application to enforce settlement and improve their bearing capacity. If post-construction secondary compression is significant it can be reduced by placing a higher surcharge than required for primary consolidation. Because of their cost-effectiveness these techniques have been and are being used in several soil improvement projects in the Southeast Asian region. Details of the treatment, the properties of and design procedure for Fibredrains, and the application of HEI are discussed.