Effect of sample preparation on the behaviour of fibre reinforced sands

The concept of reinforcing soils by introducing tension resisting elements such as flexible, discrete fibres is becoming widely accepted by geotechnical engineers. The effectiveness of fibre inclusion is largely dependent on their spatial orientation which, in turn, depends on the fabrication procedure. The most common fabrication method used so far is the moist tamping technique but recent research has shown that this preparation procedure leads to preferred near-horizontal orientation of the fibres. A new specimen fabrication procedure using vibration is proposed here and the uniformity of the spatial orientation distribution of fibres is assessed. While the uniformity of distribution of vibrated fibre reinforced specimens improves, the fibre orientation pattern was found to remain highly anisotropic with a nearly-horizontal distribution. Triaxial compression and extension test results show and confirm the importance of fibre orientation as a key parameter which has to be considered for the design of the fibre reinforced geotechnical structures.