Surya Sarat Chandra Congress

Infrastructure in the U.S.A. was graded with a “C–” in the 2021 ASCE report card. Frequent monitoring of infrastructure assets is key to ensuring the serviceability of the assets and safety of public users. Advancements in aerial technologies, compact sensors, computer processing, and image analysis software have given rise to various engineering applications of sensor-mounted unmanned aerial vehicle (UAV) platforms. Several contactless sensors are being mounted on UAVs to conduct a comprehensive assessment of infrastructure conditions compared to a qualitative visual examination by an experienced inspector. Many transportation agencies in the U.S.A. have been using UAVs for applications ranging from the research stage to regular inspection activities. These applications are mainly focused on inspecting infrastructure assets such as pavements, bridges, substructures, railways, and other assets. The current research discussed the approaches followed to conduct aerial condition monitoring of transportation infrastructure assets using optical sensors mounted on UAVs. Qualitative and quantitative inspections of pavement, bridge, and substructure infrastructure case studies were performed. Pavement distress extents were measured in three dimensions and a 360° inspection of bridges was conducted by accessing hard-to-reach areas. Scaled views of the four sides of a bridge were developed and the challenges in data collection and processing were outlined. Further, a localized inspection was also demonstrated to show the feasibility of using photogrammetry for remote condition assessments post-disaster/emergency. Overall, the rich visualization, safety, flexibility, and ease of handling offered by these technologies are expected to transform the method of conducting infrastructure performance monitoring inspections in the future.

The current pavement design guidelines, for example, Mechanistic-Empirical Pavement Design Guide (MEPDG), heavily rely on the resilient moduli of pavement materials. Some locally available pavement materials may not meet the design requirements and often require the application of efficient stabilizers. Therefore, the characterization of natural and treated subgrade soils using resilient modulus is important for the design of durable flexible pavements. A research study was designed and conducted to investigate the effect of polymer emulsion treatment on the resilient characteristics of sandy soil, which is used in constructing highways and airport surfaces. A commercially available polymer emulsion was used to stabilize cohesionless soil, and an attempt was made to understand the influence of polymer emulsion dosage and curing time on the strength and resilient characteristics of treated soil mixtures. Several laboratory tests were conducted on mixtures prepared with different dosages and curing times to evaluate the improvement in unconfined compressive strength and resilient moduli properties of treated sandy soil. Multiple regression analyses were conducted on resilient moduli test results using two- and three-parameter models and identified the best model exhibiting a good fit with the experimental data. A case study was demonstrated using the resilient moduli of untreated and polymer emulsion-treated soil to determine the thickness of airfield pavement. Overall, the outcome of the study is expected to assist the state and federal agencies in stabilizing and using problematic sandy soils for constructing various pavement structures.