In recent years, ground columns, such as vibro-concrete columns and geosynthetic-reinforced stone columns, have been increasingly used to support superstructures and embankments when they are constructed on soft foundations. Several new column technologies have emerged, including different shapes of concrete columns and composite columns. The column technologies have also been combined with other technologies to create more effective and/or economic solutions. However, the composite columns and the combined technologies have presented complicated geotechnical problems in design and construction. This paper summarises different types of column technologies and their functions, installation and applications, addresses design issues, and reviews recent research and development related to the column technologies to improve soft foundations, including failure modes, load transfer mechanisms, bearing capacity, settlement, consolidation and stability. Recent research has indicated that lateral deformation and yi...

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Recent research and development of ground column technologies

Experimental study on vibration reduction by using soilbags

Design method for geotextile tubes considering strain – Formulation and verification by laboratory tests using photogrammetry

Earth reinforcement using soilbags

Innovative methods for dike construction – An overview

Use of an apron to stabilize geomembrane tubes for fighting floods

Recent changes and consolidation in building codes across the U.S. have put a larger emphasis on the need for cost-effective foundation support of both bearing and uplift foundation loads resulting from wind and seismic forces. The Rammed Aggregate Pier (RAP) system is a commonly-accepted soil reinforcement method that results in highly-densified aggregate columns for liquefaction mitigation, bearing capacity enhancement, and uniform settlement control for conventional shallow foundations. The RAP system provides a cost beneficial alternative to deep foundations such as pre-cast driven piles, auger-cast piles, or concrete piers and to mass excavation and replacement for shallow foundations. In high seismic and wind areas, uplift loads created by overturning forces on foundations are resisted with uplift RAPs that are equipped with a structurally designed steel anchor assembly. Typical uplift capacities in California range from 178 to 445 kN (40 to 100 kips) for 762 to 838 mm (30 to 33 inch), 3.6 to 7.0 m (12 to 23 feet) meter long RAP elements using ASD (allowable stress design) and incorporating a minimum factor of safety of 2. Full scale load tests on uplift RAPs show repeatable tangent stiffness after multiple overstress load cycles. This paper presents the first published results of psuedo-cyclic uplift load tests on uplift RAPs installed on projects in California.

Uplift Testing of Rammed Aggregate Pier® Systems

Highway construction often requires the placement of embankments and earth retaining walls to facilitate grade separations. Instability and settlement occur when these structures are placed on top of weak and compressible soils. Historically, the severity of these problems have been reduced using toe berms and surcharging. More recently, Rammed Aggregate Piers have been used to avoid the need for extending large right-of-ways required for toe berm construction or for time-consuming surcharging. The installation of Rammed Aggregate Piers reinforces weak and compressible foundation soils prior to construction of earth embankments and walls. The installation of Rammed Aggregate Piers increases the factor of safety against slope stability as a result of the high angle of internal friction (48 to 52 degrees) achieved during ramming and reduces the magnitude and time of settlement by increasing the overall stiffness of the foundation soils and providing a drainage pathway for dissipation of excess pore water pressure. This paper presents analytical methods used to design Rammed Aggregate Piers to reinforce weak soils and control settlements below highway and railroad retaining walls and embankments. The analytical methods are illustrated by a case history for a Mechanically Stabilized Earth (MSE) wall support project near Houston, Texas. This work is of particular significance because it presents design methodologies and a case history for an effective ground reinforcement technique increasingly used to support highway embankments and walls.

Brendan FitzPatrick

Papers

Use of an apron to stabilize geomembrane tubes for fighting floods

Uplift Testing of Rammed Aggregate Pier® Systems

Stabilization of Retaining Walls and Embankments using Rammed Aggregate Piers TM

Design and Construction of Intermediate Foundation Solutions for Wind Turbines