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ABSTRACT: A new type of mechanically stabilised earth structure composed of geosynthetic tubes filled with expanded clay lightweight aggregate and backfill with geosynthetic reinforcement is introduced. The results of the study demonstrate that alternative solutions such as expanded clay lightweight aggregates can be used in interaction with geosynthetics in comparison to classical soil. The new type of geosynthetic tubes filled dynamically with expanded clay lightweight aggregate was tested in situ under compressive loading. The geosynthetic tube was instrumented with load cell transducers and the characteristic cross-section was obtained from three-dimensional scanner measurements after loading. Next, a simplified engineering formulation for geosynthetic tubes under compressive loading and unloading was evaluated including the influence of volume variation of the tube. It is based on the classical approach from soil mechanics and it produces the required design tensile force of the tube dependent on geosynthetic stiffness. The experimental results of compressive loading tests were compared with analytical equations. The results are discussed and show the influence of the geosynthetic stiffness on the behaviour of the tube in terms of loading capacity, volume variation and cross-section of the tube. The agreement between theoretical analyses and experimental results was reasonably good and can be formally accepted for a given volume variation of the geosynthetic tube.

The reinforcing capability of high strength geotextile and geogrid in residual soil has been studied recently, using pullout tests and wide width tensile tests. However, the drainage behaviour of these geosynthetics products in reinforcement applications has not been well addressed so far. This paper presents experimental evaluation of the drainage performance of a high strength composite permeable geotextile and a HDPE geogrid in a poorly draining Singapore residual soil. The drainage behaviour of these geosynthetics products embedded in poorly draining Singapore residual soil was evaluated with large-scale drainage behaviour tests. Pore pressure transducers were installed at strategic locations in the soil mass to evaluate the development and dissipation of excess pore pressure. The test results showed that with the placement of permeable geosynthetics materials, the rate of pore pressure dissipation was faster than without any geosynthetics product or with a non-permeable geosynthetics product.

Geotextiles have been extensively used in hydraulic structures as revetment filters subjected to wave loads. The alternating flow through the geotextile creates a flow regime very different from the unidirectional flow condition that has been extensively studied. The stability of the revetment system depends on many factors, such as the hydraulic properties of geotextile, the initial placement condition and particle size distribution of the subsoil, and the intensity of the wave loads. A new laboratory apparatus has been used to investigate the influence of the hydraulic conditions on the behavior of soil-geotextile interaction and the stability of the revetment system. One series of tests has been conducted simulating cyclic flow conditions normal to the soil-geotextile interface. Preliminary test results are presented and discussed in this paper.

The principle of retaining structures consisting of a reinforced soil mass has led to routine applications primarily through the work of la Terre Armee (TA). From this viewpoint, geotextile-reinforced structures may be compared to TA reinforced-earth structures.