Residual soil from the Passo Fundo region (Brazil), presents natural cementation, responsible for a peculiar behaviour that is clearly distinguishable from that of soils with other origins. Understanding this behaviour and the effects of the fabric, with an influence on the cementation bonding, is essential to characterise these materials. Therefore, the aim of the present study is the mechanical characterisation of this soil, mainly by analysis and testing of remoulded and undisturbed samples. The experimental programme included uniaxial compressive strength tests, oedometer tests, consolidated drained monotonic triaxial tests and consolidated undrained cyclic triaxial tests. Based on the data collected, a clear influence of interparticle bonding, provided by the natural cementation, was detected on the soil's intrinsic behaviour; the undisturbed material showed a higher stiffness modulus than the remoulded material, mainly due to the bond breakage to which the latter was submitted, losing its natural cementation. A uniaxial confining stress of 89.4 kPa was obtained for the undisturbed material, assumed to be its yield stress. This value was corroborated by the oedometric (87.5 kPa), isotropic (80 kPa) and triaxial compression (90 kPa). The natural cementation was influential in every type of loading and should be considered during the design process.
Sulfate-rich dispersive soils are a major concern due to their high susceptibility to erosion and heave, related to high amounts of adsorbed Na+ ions and the formation of expansive minerals derived from reactions involving sulfates and calcium, respectively. In this sense, the development of alternative treatments to overcome such problems must be sought, since the application of lime and/or Portland cement by themselves has proven to be ineffective. Thus, the present paper proposes a binder composed of carbide lime and ground glass waste combined with fiberglass reinforcement to stabilize such soils. The efficiency of the proposed alternative towards reduction of swelling was assessed through 3-D volumetric swell tests carried out on compacted soil-binder-fiberglass blends molded with multiple different dosages. The results have shown that the porosity and the amount of carbide lime influenced the volumetric strain (εv) of the tested specimens greatly. The influence of porosity was inversely proportional, while the influence of the amount of carbide lime was directly proportional. The addition of fiberglass was shown to be ineffective. Thus, the εv was successfully correlated to the adjusted porosity/lime index (η/Liv), proving the innovative character of the approach applied herein and enabling the prediction of the εv for different dosage options.
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