The engineering properties and mechanical behaviour of fibre reinforced clay

Abstract

Embankment slope failure due to insufficient strength, weak bearing capacity, excessive deformation and desiccation cracking of problematic soils is commonly observed on the UK road network, and this leads to huge expenditure in the maintenance and repair of highway projects every year. It is necessary to reduce these engineering problems and economic losses through environmentally and economically friendly methods.
Previous studies have shown that randomly distributed fibres can significantly improve various soil properties. However, there is a lack of comprehensive study on the engineering properties of fibre reinforced high plasticity clay. Also, limited mechanical models have been proposed for predicting the shear strength behaviour of fibre reinforced clay.
In order to investigate these problems, a series of laboratory investigations including compaction, bearing capacity, one-dimensional consolidation, linear shrinkage, desiccation cracking, direct tensile strength, triaxial compression tests were conducted on unreinforced and polypropylene fibre reinforced London Clay. A mechanical model was proposed for predicting the shear strength of fibre reinforced clay.
The experimental results showed that fibres can significantly improve the engineering properties of London Clay. As fibre inclusion ratio increased, the bearing capacity, coefficient of consolidation, tensile strength and shear strength of the soil increased; the compression index, swelling index, linear shrinkage and desiccation cracking area of the soil decreased. As fibre length increased, the bearing capacity and desiccation cracking area of the soil decreased; the tensile strength and shear strength of the soil increased. The mechanical model was proposed based on the conception of equivalent confining stress and the predicted stress-strain-pore water pressure response and stress path behaviour of fibre reinforced soil were compared with the experimental results. The comparisons showed that the model was capable of predicting the shear strength behaviour of fibre reinforced clay.