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Earthworks Design and Control
Designing of earthworks for schemes of various sizes under a variety of ground conditions, and in ensuring that these are implemented under proper construction control, is another of CGL’s capabilities. Our senior staff have substantial experience in the design of major highway and rail schemes, some of which have necessitated detailed engineering analysis to overcome difficult ground conditions and ensure long term stability and serviceability. Our capabilities include assessment of sources to identify material suitability, the effective re-use of materials, and minimisation of the cost of imported fill. Our approach uses the principle of ‘relationship testing’ where complex engineering parameters can be correlated to routine on-site test procedures; a simplified but robust approach to compliance testing resulting in confidence in the construction and savings in earthworks programmes.
Specialising in the design of earthworks over soft alluvial soils, CGL has expertise in the design of ground improvement methods to enhance settlement rates beneath embankments. Typically these permit settlements that would ordinarily take 12 or 18 months under normal conditions to be completed within as little as 3 to 6 months, substantially reducing construction programmes and associated costs.
In addition, careful design of earthworks with geotextile reinforcement can lead to the creation of vertical walls and development platforms that can allow highly constrained sites to become developable. We have been involved in a number of schemes in which levelling of sloping sites has been recommended to allow the construction of residential development. Similarly, the judicious use of test data and detailed specifications can be used to allow placed fill to support structural foundations.
Where earthworks necessitate the removal of contaminated materials, CGL’s in-house waste experts are able to refine disposal classifications to substantially reduce off-site disposal costs. Our contribution often leads to substantial savings which make otherwise marginal schemes financially viable. An example of this is our recent involvement with the Wandsworth project. Our clients often seek our independent advice during early tender evaluation to enhance their competitive position and, ultimately, their success rate.
Supporting our design, we provide construction quality assurance services to monitor and validate the formation of different types of earthworks ranging from simple capping layers to large reinforced earth structures. This independent validation and certification offers confidence to clients that their asset conforms to the relevant design codes, providing posterity for the future.