In this article, synthetic fibres in the presence of lime stabilisation are proposed as an alternative to overcome the issues related to shrink-swell distress in expansive soils. Two types of synthetic fibres, Fiber Cast® (FC) and Fiber Mesh® (FM), were studied by conducting one-dimensional fixed ring Oedometer swell-consolidation and bar linear shrinkage tests. Three dosages (0.2, 0.4 and 0.6% by weight of soil) and two lengths of the fibres (6 and 12 mm) were evaluated with and without lime treatments. The results indicated that FC fibres had better swell restricting performance in the absence of lime treatment, while in the presence of lime both fibres had similar performance in reducing swelling. Shrinkage tests results showed that irrespective of dosage levels, both the fibres had pronounced effect in reducing the linear shrinkage strains up on lime treatment. Non-linear best fit equations have been proposed to relate compression index (C _c ) and recompression index (C _r ) of expansive clay deposits with and without lime treatment to amount and dosage of FC and FM reinforcements. The proposed non-linear fit provides a mean for recognising, more efficiently, the patterns in the experimental data and predicting the compression indices, C _c and C _r reliably.

Soil reinforcement using synthetic fibers is a proven technique for enhancing engineering properties to meet the requirements of subgrade materials for pavement projects. The safe and economical design of fiber-reinforced pavement layers requires better insights into their unsaturated behavior. The soil–water characteristic curve (SWCC) is a measure of the water content inside soil pores at a given suction and is considered an essential property to better understand or predict the behavior of unsaturated fiber-reinforced soils. This paper centers on investigating the soil–water characteristic curves for typical expansive clay reinforced with two different types of polypropylene fibers having different surface morphological properties. The effect of an increase in the fiber dosage (0.2% and 0.6% by dry weight of soil) and fiber lengths (6 and 12 mm) on the resultant SWCC patterns is investigated. The addition of lime is considered to enhance the bonding between clay particles and fiber elements to ensure better friction mobilization levels. SWCCs were determined for all experimental mixtures using a combination of axis translation and filter paper techniques that cover the entire matric suction range during measurements. Volume changes undergone during suction measurements have been duly highlighted and discussed. Furthermore, the one-dimensional deformation (swelling/consolidation) characteristics of these lime-blended fiber-reinforced mixtures at different levels of initial matric suction are studied, and the correlations between initial matric suction with both compression index (${\mathrm{C}}_{\mathrm{c}}$ ) and swell index (${\mathrm{C}}_{\mathrm{s}}$ ) are established. The results indicate a significant change in the shape of the SWCC for lime-blended fiber-reinforced mixtures compared with the shape of the SWCC for natural clay. The contribution of fiber inclination to altering the shape of the SWCC curve is observed as slight regardless of the type, length, and dosage of fiber. Compression and swell indices for tested mixtures increased proportionately with an increase in initial matric suction levels. Doubling the length of the fiber also induced an increase in the compression index. Under no stress conditions did both fiber type and fiber length have a marginal effect on the swell potential and SWCCs.

Proper understanding of the field performance of lime-treated expansive soils requires the evaluation of their unsaturated properties under stress conditions similar to that in the field. This paper studied the influence of net vertical stress on the soil-water characteristic curves (SWCC) of lime-treated expansive clay. The first phase of this study investigated the influence of lime content and curing period under low net vertical stress (7 kPa) using axis translation and filter paper techniques with simultaneous measurements of sample volume change. The second phase evaluated the SWCCs of untreated and lime-treated clays under vertical stresses of 100 and 600 kPa. Different representations of SWCCs were considered in the interpretation of test results. Test results indicated that lime content had a significant effect on the shape and air entry value of SWCCs because of changes in soil microstructure, whereas curing period had a far less significant effect. Furthermore, the application of net ve...

Rapid industrialization in developed countries has led to a continuous release of heavy metals into the environment. When these effluents are discharged directly into natural surrounding soils, not only is the geotechnical behavior altered but the natural surface and subsurface waters become contaminated. In this study, experiments are conducted to examine the unconfined compressive strength (UCS) and compressibility behavior for two semiarid soils exhibiting different mineralogy spiked with selected heavy metals (As³⁺, Cr⁶⁺, Cu²⁺, Hg²⁺, Pb²⁺, and Zn²⁺) and their relative immobilization levels in the presence of a binder. Removal efficiencies of selected metal ions were estimated by performing desorption tests using different extractants [acetic acid (H₃COOH), nitric acid (HNO₃), ethylenediaminetetraacetic acid (EDTA), and diethylenetriaminepentaacetic acid (DTPA)]. Analytical grade lime was used as a binder and the concentrations of spiked metal ions were maintained at 50 and 100 ppm respectively. The variations in electrical conductivity and pH for both soils spiked with selected metal ions were evaluated for the control case (absence of lime) and lime treated case and have been related to the compression behavior. Results from this study reveal that the UCS values of both soils increased for the control and lime treated cases. The compression behavior of the selected soils exhibited contrasting behavior with an increase in compression index (Cc) values for soil A and a decrement for soil B when spiked with selected metal ions. The desorption studies revealed higher removal efficiencies for EDTA compared with other extractants.

The main objective of this study is to evaluate the hysteresis of soil–water characteristic curves (SWCC) of highly expansive clay subjected to wetting and drying cycles. Variables considered included hysteresis suction range (i.e. low and high suction ranges), suction determination technique (vapour equilibrium technique, axis translation technique and contact filter paper technique) and initial specimen condition. Experimental results revealed that the degree of SWCC hysteresis was higher in the low hysteresis suction range (less than 1.5 MPa) than the high hysteresis suction range (greater than 1.5 MPa). The results further revealed notable difference between matric and total SWCCs of this expansive clay. Furthermore, a hysteresis was observed that is inherent to suction determination technique and is independent of soil characteristics. Also, it was concluded that initial specimen condition (i.e. as-compacted and saturated) had a significant impact on degree of hysteresis, especially in the low suction range. Plausible explanations of observed trends in view of soil–water retention mechanism were provided. Finally, volumetric strains during drying and wetting paths were evaluated and its impact on SWCC was assessed.