This paper explores the ultimate bearing capacity of two closely spaced interfering strip footings resting on a reinforced cohesionless soil bed using upper-bound limit analysis. The soil is assumed to follow the Mohr-Coulomb failure criteria along with the associated flow rule. A kinematically admissible multi-block failure mechanism is adopted in the analysis. The effect of interaction is studied with respect to angle of internal friction of soil (ϕ), clear spacing between the footings (s) and the number of reinforcement layers (p). The interference effect in terms of efficiency and influence factor is found to increase with the increase in s and becomes maximum at a critical spacing (scr) followed by a reduction with further increase in s. However, the interference effect is seen to decrease with increase in the number of reinforcement layers. The present theoretical observations are generally found to be in good agreement with the results reported in literature for the same class of problem.

Utilization of 100% recycled asphalt pavement (RAP) material in the base layer of road construction can provide a cost-effective and sustainable solution. However, excessive permanent deformation of RAP reduces its applicability for such projects. In this study, the effectiveness of geocell reinforced RAP base (GRRB) layers for the flexible pavement sections constructed over the expansive subgrade is investigated. Furthermore, the mechanism involved in the improvement of material stiffness because of the development of additional confining stress in the reinforced base layer is also presented in this paper. During the initial monitoring period, the average vertical compressive stresses over the pavement subgrade for the reinforced sections were observed to be significantly lower in comparison with the corresponding unreinforced sections. The preliminary results indicate that GRRB layers can significantly improve the performance of the pavement by controlling the subgrade deformation.

A research study was designed and conducted to evaluate the applicability of using crystalline silica-rich material as a co-additive with calcium-based stabilisers to treat sulfate-rich expansive soils. Extensive laboratory tests were conducted on lime-treated sulfate-rich soils, with and without crystalline silica admixture, to evaluate the improvements in engineering properties, including swell strain, unconfined compressive strength and resilient moduli properties. The influence of co-additive dosage, curing period and duration of moisture exposure was studied to gain insights into the behaviour of treated soils. Supplementary mineralogical and microstructural studies including X-ray diffraction, scanning electron microscope imaging and differential scanning calorimetry studies were performed on the treated soils to detect the formation of ettringite mineral and cementitious gel compounds. Test results indicated that the use of crystalline silica facilitated enhancement of both the strength before and after capillary soaking, and the resilient moduli properties, while suppressing ettringite mineral formation and associated free swell strains in the treated soils. Mineralogical and engineering studies showed the dominance of pozzolanic activity between lime and crystalline silica over ettringite formation and hence contributed to the effective stabilisation of sulfate-rich soils. Overall, the paper provides a comprehensive understanding of the role of crystalline silica admixture for mitigating deleterious sulfate heaving in lime-treated soils.

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The longevity and performance of a pavement section depend on the characteristics of the subgrade soil. A majority of the pavements in North Texas, U.S., are constructed on expansive soils. The deterioration of the pavement performance because of rutting, cracking, and differential heaving is a regular phenomenon in the regions predominantly distributed with expansive soils. The pavements, particularly those built for low-volume traffic conditions, experience distress because of the high swelling and shrinkage characteristics of the underlying problematic soils. Geosynthetics have been traditionally used to improve such poor subgrades because of their many benefits, such as ease of installation, and ample mechanical and hydraulic properties. In the last decade, a newly available wicking geotextile, with a moisture redistribution capacity, has been developed to improve the performance of pavements constructed over expansive and frozen soils. In this study, small-scale laboratory and full-scale field studies were conducted to comprehend the wicking ability of this innovative geotextile in an expansive soil environment. Full-scale test sections were constructed with reclaimed asphalt pavement aggregate and traditional crushed stone aggregates in the base layer near North Texas. Details of the construction and instrumentation procedure are discussed in this paper. A comparative study between the performance of the pavement sections subjected to traffic loads and moisture intrusion was also performed. Furthermore, the rutting life of the sections, estimated using a linear elastic model, was compared and validated using the in situ data. The observations during the initial phase indicated that the wicking geotextile has the potential to improve the long-term pavement performance.