Reclaimed asphalt pavement (RAP) materials have been considered as one of the most sustainable options in the pavement industry. However, the low shear strength and high permanent deformation behaviour of RAP materials often limit their application in road bases. Stabilisation of RAP bases using high-density polyethylene (HDPE) geocell was hence attempted in this study to assess the efficacy of three-dimensional geosynthetic reinforcements in improving the resilient properties of RAP materials and mitigating permanent deformation of them. The present paper discusses the results from a series of large-scale repeated load box tests conducted to study the effectiveness of HDPE geocell-reinforced RAP bases (GRRB). The performance of the geocell reinforcement was evaluated based on various parameters including resilient deformation, cumulative permanent deformation, resilient modulus, traffic benefit ratio (TBR), and rut depth reduction (RDR) factors. Test results show that HDPE geocell layer increased the resilient modulus of the RAP base layer by 2.5–3.3 times and reduced the permanent deformation of RAP base by 70–80% when compared to the unreinforced RAP bases. Test results were then used to perform pavement design to quantify the base thickness reduction with geocell reinforcement.

Calcium-based stabilizers such as lime and cement control swell and shrinkage behavior and enhance strength properties for expansive soils through the formation of pozzolanic components. However, sulfate-bearing subgrade soils stabilized with calcium-based stabilizers might cause excessive swelling and shrinkage due to the formation of highly expansive minerals like ettringite and thaumasite. In this paper, one liquid ionic soil stabilizer (LISS) was evaluated as an alternative stabilizer used to control swelling and shrinkage behavior of expansive soils. A comprehensive laboratory experiment program including a linear shrinkage test, a one-dimensional swell test, and an unconfined compressive strength test, was designed and carried out on soils from Dallas, Texas before and after treatment. Three dosage levels of stabilizer and four different curing periods were investigated. Test results indicate that LISS is an effective stabilizing agent, which not only reduces swelling and soil plasticity but also increases soil strength. Furthermore, a similar type of LISS is utilized to treat the soil in Dallas via deep injection using a hydraulic pump. Field emission scanning electron microscopy results on the test soil showed that the stabilizing program is likely to work through clay flocculation and morphological variations in the clay particles.

Design of flexible pavements over fine-grained soils requires determination of subgrade resilient modulus over a wide range of degree of saturation and suction for different soils. A novel experimental setup was developed by integrating a cyclic triaxial apparatus with capability to control suction using axis-translation and automated vapor pressure control to the specimen gas phase. System performance was evaluated through repeated load triaxial (RLT) tests for suction ranging from 0 kPa at saturation to 600 MPa at drier conditions. Replicate tests performed on a silty soil and a high-plasticity clayey soil indicated excellent repeatability. Resilient modulus of the materials is essentially unaffected with drying at low-suction range near the air-entry value and the optimum moisture content condition. This property then increases rapidly with subsequent drying until reaching a residual state after which the rate of increase in resilient modulus with respect to suction decreases to a low value. Limitations of a recent prediction model in capturing this trend demonstrated the need to determine resilient moduli over a wider range of suction for developing robust resilient moduli prediction model.

Assessing the stability of rock slopes is essential to ensuring the typical performance of adjacent transportation infrastructures but simulating the existing field topography and boundary conditions for stability analysis is challenging. This paper describes a case study in which highly weathered rock slopes adjacent to a railroad track in Texas were analyzed using close-range photogrammetry data obtained from an unmanned aerial vehicle with close-range photogrammetry (UAV-CRP). A highly weathered rock mass with low intact strength was considered as a single continuum that undergoes circular failure and was analyzed using Spencer’s two-dimensional (2D) and three-dimensional (3D) limit equilibrium method (LEM) analyses. A 3D critical slip surface was obtained to identify the critical sections on which to conduct the individual 2D stability analysis and obtain a safe resloping angle. These angles were further used to reslope the whole rock slopes and conduct a 3D analysis to arrive at a safe and economic slope angle for each side of the rock-cut. The realistic geometrical slopes developed from the aerial imagery were used to develop a framework for comprehensively analyzing the stability of a rock slope undergoing circular failure.

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.