The construction of embankments or retaining walls over soft foundation soils is a common challenge for geotechnical engineers. Problems associated with it include poor bearing capacity, excessive differential settlements and lateral sliding instability. This led to the development of several ground improvement techniques. However, when settlements need to be controlled, rigid intrusions are commonly installed to provide support and settlement control by transferring the load to a stiffer foundation. To effectively transfer the load from the soil structure to the piles and develop soil arching between rigid intrusions, piles spacing and cap size need to properly designed. To optimize the design and reduce the number of piles needed, geosynthetic reinforcement can be used to transfer the vertical load from the soil structure to the piles while maintaining the settlement control. In literature several design methods are available to calculate the vertical stresses and the strain mobilized in the geosynthetic reinforcement. However, two major design approaches are currently used in the USA and Europe: the beam method (FHWA-NH1-16-028, 2017) and the catenary method (BS 8006:2010). The first one considers multiple layers of low strength geosynthetic reinforcement equally spaced within a select granular structural fill that act as a single rigid beam. The second approach considers high strength geosynthetic that acts as a catenary single layer at the interface between the columns and the soil structure. This paper presents an overview and comparisons between these two design approaches, design examples, and cost analysis.
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