Geoscience Reference
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Normal stress around the fiber body
Soil matrix
Hard particles
such as sands
Tensile
stress
Fiber
Pore in soil
Figure 7.21 Sketch of mechanical behaviour at the interface between fibre surface and soil matrix ( after
Tang et al ., 2007).
Table 7.4 Polypropylene fibres specifications ( after
Sika Fibres 2005; Brown et al. , 2002).
Property
Specification
Colour
Natural
Specific gravity
0.91 g cm 3
Fibre length
12mm
Fibre diameter
18 micron (nominal)
Tensile strength
25-33MPa
Elastic modulus
6,000-9,000Nmm 2
Flexural modulus
1.2-1.5 GPa
Elongation at break
150-300%
Water absorption
None
Softening point
160 C
axial strain of about 1.5-2.5%, following which they collapsed. However, the fibre-
reinforced specimens exhibited highly ductile behaviour (Kaniraj and Gayathri, 2003).
Also, from the experiments on field test sections in which a sandy soil was stabilized
with polypropylene fibres, Santoni and Webster (2001) concluded that the technique
showed great potential for military airfield and road applications and that a 203mm
thick sand fibre layer was sufficient to support substantial amounts of military truck
traffic.
According to Tang et al . (2007), in fibre-reinforced soils the fibre surface is attached
by many soil particles which make a contribution to the bond strength and friction
between the fibre and the soil matrix. The distributed discrete fibres act as a spatial
three-dimensional network to interlock soil grains, help the grains to form a unitary
coherent matrix and restrict their displacement. Consequently, the stretching resistance
between soil particles and strength behaviour are improved. Because of the interfacial
force, the fibres in the matrix are difficult to slide and they can bear tensile stress, as
shown in Figure 7.21.
 
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