Mechanical Behaviour of a Compacted Residual Soil of Gneiss from Brazil under Constant Water Content Condition

Abstract

Compacted fine-grained soils are widely used in the construction of geotechnical infrastructures such as the embankments, retaining walls and pavements. These infrastructures are typically constructed at a relatively fast rate such that the pore-water phase is not allowed to drain, or under constant water content (CW) condition. The mechanical behaviour of compacted fine-grained soils under CW condition should be well understood in addition to various other loading conditions for rational design of geotechnical infrastructures. In this study, compacted soil specimens of a residual gneiss from Brazil were tested using a conventional triaxial testing equipment under CW condition. A high capacity tensiometer was used to measure the matric suction in the compacted soil specimens. Three groups of soil specimens compacted at different initial water contents representing dry of optimum, optimum and wet of optimum conditions were tested to study the influence of soil structure on the matric suction development in the soil specimens during testing. The test results suggest that the matric suction changes in the soil under CW condition depend mainly on the volume change behavior, which is influenced by the level of confining pressure, the degree of saturation and the soil structure. The simple conventional triaxial testing equipment has been found to be useful for determining the mechanical behavior of compacted fine-grained soils under CW condition with the aid of a high capacity tensiometer.