The increasing environmental concerns associated with conventional soil stabilization materials, particularly cement, have driven the exploration of sustainable alternatives such as biopolymers. However, the practical application of biopolymer-treated soils remains questionable due to their susceptibility to biodegradation and hydrolysis under fluctuating environmental conditions. This study investigates the durability of clay soil treated with carboxyl methyl cellulose (CMC) biopolymer under cyclic wetting and drying conditions, aiming to evaluate the progressive strength degradation and potential serviceability of such treated soils for temporary or medium-term geotechnical applications. The experimental program employed soft silty clay obtained from southeast Baghdad, Iraq, treated with 5% CMC biopolymer by dry weight of soil. Specimens were prepared at optimum moisture content and subjected to up to five cycles of controlled wetting (submersion in water for 24 hours) and drying (oven drying at 45°C for 24 hours), with unconfined compressive strength (UCS) measurements taken at each drying and wetting phase. The results revealed a progressive reduction in UCS from an initial dry strength of 2050 kN/m² after the first drying cycle to 460 kN/m² after the fifth drying cycle, while wet strengths decreased from 270 kN/m² to 49.5 kN/m² over the same period. Despite this substantial strength loss, partial strength recovery was observed during each re-drying phase, attributed to the re-establishment of polymer-soil bonds upon moisture removal. The study demonstrates that while biopolymer-treated clay exhibits significant vulnerability to cyclic moisture fluctuations due to the hydrophilic nature of CMC and irreversible polymer dissociation, the gradual rather than catastrophic strength degradation suggests potential viability for temporary geotechnical applications where long-term durability is not critical.
Intersections are among the most critical elements of highway networks because they directly influence traffic efficiency, capacity, and safety. This study evaluates improvement alternatives for Al-Kansaa's three-leg intersection in Iraq, which currently experiences severe traffic congestion and operates at Level of Service (LOS) F. Traffic volume surveys and geometric data were collected and analyzed using Highway Capacity Software (HCS2010), while Autodesk Civil 3D was employed to develop and evaluate four geometric improvement alternatives. The existing intersection analysis indicated an average control delay of 398.66 s/veh, corresponding to LOS F. The first improvement proposal, which involved adding a lane to the southbound approach, reduced the average delay to 165.67 s/veh; however, the intersection continued to operate at LOS F, indicating that geometric widening alone was insufficient. Therefore, three grade-separated interchange alternatives were developed and assessed based on operational performance, geometric feasibility, land-acquisition requirements, and constructability. Among the proposed alternatives, the interchange incorporating two bridges and a roundabout was identified as the most suitable solution because it provides smoother traffic operations, minimizes land acquisition, reduces construction constraints, and preserves the operational performance of the major roadway. The findings demonstrate that comprehensive geometric redesign is more effective than minor geometric modifications for improving heavily congested three-leg intersections and may serve as a practical reference for similar intersections in developing countries. The novelty of this study lies in the integrated evaluation of four alternative intersection improvement proposals by combining traffic operational performance, geometric design, constructability, and land-acquisition considerations within a single decision framework for a real-world three-leg intersection.
Skirted foundations are an appropriate ground improvement method for improving the performance of shallow foundations built in sandy soils. This paper reports an experimental study on the effect of the skirt length and foundation size on the performance of circular foundations under vertical loading on medium-dense dry sand. Six laboratory model tests were made, of which two were unskirted and four skirted foundations. Two (2) different diameters of circular footings, 60 mm and 90 mm, were tested with two different lengths of the footing skirts (L/D), 0.5 and 1.0. Terzaghi's criterion, in which the settlement is 10% of the footing diameter, has been used to determine the ultimate bearing capacity. The results showed that the use of skirts was significantly helpful to improve the load–settlement response, increase the foundation stiffness, and increase the ultimate bearing capacity. The ultimate load for the footing of diameter 60 mm was increased from 0.167 kN to 0.304 kN, which is about 82% increase when the footing is skirted with L/D = 1.0. The same trend applied to the 90 mm diameter footing, where the ultimate load went from 0.343 kN to 0.677 kN, which is about 97% improvement. The bearing capacity of foundations with L/D = 0.5 increased by 29% and 43% for footing diameters of 60 mm and 90 mm, respectively. The experimental results also showed that as the skirt increased in length, the settlement decreased, and the failure mechanisms were more stable and deeper due to the increased soil confinement and passive resistance along the walls of the skirts. Further, all skirts yielded higher failure loads with larger foundation diameters. The study has verified that the length of skirts and foundation size are important parameters that control the performance of circular skirted foundations on sandy soils. The application of skirts is an effective and cost-efficient way to increase bearing capacities, decrease settlement, and enhance shallow foundation stability.