Effect of Polypropylene Fibers on the Shear Strength–Dilation Behavior of Compacted Lateritic Soils

The stress–dilatancy relationship for fiber-reinforced soils has been the focus of recent studies. This relationship can be used as a foundation for the development of constitutive models for fiber-reinforced soils. The present study aims to investigate the effect of recycled polypropylene fibers on the shear strength–dilation behavior of two lateritic soils using the stress–dilatancy relationship for direct shear tests. Results show that fibers improved the shear strength behavior of the composites, observed by increases in the friction angle. Fibers’ orientation at the sheared interface could be observed. The volumetric change during shearing was altered by the presence of fibers in both soils. Overall, results indicate that the stress–dilatancy relationship is affected by inclusions in the soil mix. Results can be used to implement constitutive modeling for fiber-reinforced soils.

Influence of Plant Roots On Slope Stabilization: A Geotechnical Investigation

Direct shear tests conducted on soil samples reveal that soils with plant roots show an increase in cohesive factor but increase in frictional angle is insignificant. Displacement and shear strength graphs, however, indicate that soil with plant roots can withstand more shear stresses. Among the three plant species selected for the present study, Chimonobambusa sp. has the highest shear strength increment, ∆C = 5.0 KN/m2 followed by Cymbopogon sp., and Pseudosasa japonica with 4.5KN/m2 and 1.0KN/m2 shear strength increments respectively. An increase in shear strength is also observed in the reinforced soils with increase in number of roots of these plant species. Cymbopogon sp. has higher root density near the surface but decreases with increasing depth and absent at 320mm depth, Pseudosasa japonica has the lowest root density but penetrates deeper up to 530mm while Chimonobambusa sp. penetrates deepest at 700mm with lateral branches extending up to 650mm. Cymbopogon sp., and Pseudosasa japonica may be useful as a bioengineering tool to mitigate soil erosion while Chimonobambusa sp. to mitigate both erosion and shallow landslides.

Improvement in CBR value of soil reinforced with nonwoven geotextile sheets

Geosynthetics are human made material used to reinforce soils to improve the bearing capacity and permeability of the soil, reducing soil settlement. Geosynthetics application plays a vital role in the highways constructions with no additive layers, such as cement concrete, asphalt concrete, or in a subgrade layer that affects the bearing capacity of unbounded layers. This paper presents the geosynthetics as a tensional material that has been used for reinforcement of clayey soil. Laboratory California bearing ratio (CBR) test samples were prepared with clayey soils. Clayey soil containing unreinforced soil and reinforced soil. The sample comprised thermally bonded nonwoven geotextiles (NW) and superior needle-punched nonwoven geotextiles (SNW) with different characteristics (NW 8, 10, 21, 30 and SNW 14, 25, 62, 75) with three-layered, based on the sample materials to perform defined tests. These tests show that, bearing ratio of reinforced soils with thermally bonded nonwoven geotextiles increases.