The Design and Construction of a Reinforced Embankment on Soft Compressible Soil

The paper centres on the design and construction of a leachate lagoon at a landfill site located in Essex, United Kingdom (UK). The lagoon is to be used for the storage of between 150,000m3 and 200,000m3 of leachate generated by the adjacent landfill site as part of its treatment process. The location of the lagoon is on the southern boundary of the site, and is bounded to the north by the landfill itself, to the east by an existing leachate treatment lagoon and to the south and west by a flood defence bund for an adjacent creek and the Thames estuary beyond. Due to the proposed capacity and size of the lagoon, it qualifies in the UK as a reservoir under the 1975 Reservoirs Act and the design and construction is therefore constrained by this legislation. The area proposed for the lagoon is generally level, but with groundwater levels close to, or at, the ground surface. Waste dating from the 1950’s underlies the site and this overlies a generally soft stratum of alluvial clays and sands. A similar, but earlier, lagoon encountered significant difficulties during construction associated with the high groundwater levels and the trafficability of the waste and the soft alluvial materials. A discussion of the geotechnical and environmental issues considered during the design process is presented and the need for responsive design during the construction phase of a project is highlighted. The benefits of value engineering in civil engineering are also discussed in the context of design and construction projects. By their very nature, civil engineering projects such as this require imaginative and innovative design solutions, coupled with the use of non-traditional geomaterials. A discussion of the geosynthetics employed at this site is provided, in the context of their primary and secondary applications