Engineering Behaviour of Fibre-Reinforced Soil
Over the past 30–35 years, the effects of inclusion of synthetic, natural and waste fibres on the engineering behaviour of soils have been investigated worldwide. Most studies are based on the laboratory and small-scale tests, such as direct shear tests,
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Engineering Behaviour of FibreReinforced Soil
3.1
Introduction
In the early days of soil reinforcement practice, most experimental and mathematical studies considered reinforcing the soil with continuous metal and geosynthetic reinforcement elements, such as strips, bars, discs and meshes, in a definite pattern (e.g. horizontal, vertical and inclined orientations) for investigating the behaviour of systematically reinforced soils. McGown et al. (1985) investigated the strengthening of a granular soil using randomly distributed polymeric mesh elements and observed the improvement in strength of the soil at all strain levels, even at very small strains. The action of randomly distributed polymeric mesh elements is to interlock particles and groups of particles together to form a unitary, coherent matrix. Because of the limited practical scope of random distribution of continuous metal and geosynthetic reinforcement elements, these elements have not been used widely for reinforcing the soils randomly, and hence the studies of such reinforced soil systems have not been given much attention. Over the past 30–35 years, the engineering behaviour of randomly distributed, discrete, flexible, fibre-reinforced soils has been studied in significant details by many researchers worldwide. Most studies are based on the laboratory and smallscale tests, such as direct shear tests, triaxial compression tests, unconfined compression tests, compaction tests, California bearing ratio (CBR) tests, plate load tests, etc. This chapter presents the engineering behaviour of randomly distributed, discrete, flexible, fibre-reinforced soils as investigated through these tests by focusing on the key factors that govern the behaviour and test observations and their critical analysis in view of their field applications.
© Springer Nature Singapore Pte Ltd. 2017 S.K. Shukla, Fundamentals of Fibre-Reinforced Soil Engineering, Developments in Geotechnical Engineering, DOI 10.1007/978-981-10-3063-5_3
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3.2
3 Engineering Behaviour of Fibre-Reinforced Soil
Factors Affecting the Engineering Behaviour
Improvement in the engineering properties (strength, stiffness/modulus, permeability, etc.) of soil by inclusion of discrete flexible fibres within the soil mass depends on several factors relating soil characteristics; fibre characteristics; fibre concentration; distribution and orientation; type of admixtures, if any; mixing and compaction methods; and test/field conditions, as listed below: • Soil characteristics: types (cohesionless/cohesive/cohesive-frictional); particle shape and size; gradation, generally expressed in terms of mean particle size (D50) and coefficient of uniformity (Cu); unit weight of soil solids; total unit weight; water content; and shear strength • Fibre characteristics: fibre types and materials (natural/synthetic/waste); shapes (monofilament, fibrillated, tape, mesh, etc.); fibre diameter, fibre length and aspect ratio (length to diameter ratio); specific surface; specific gravity of fibre solids; tensile strength
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