Performance Improvement of Ballasted Railway Tracks for High-Speed Rail Operations

The high-speed rail (HSR) is one of the most significant technological advancements in the field of transportation, which is continuously gaining popularity worldwide. A major challenge to the development of HSR in any country is the selection of an appropriate railway track. Although ballastless/slab tracks are especially dedicated for the HSR operations, they have a few shortcomings such as, high initial construction costs, inability to align itself according to the ground movement, generation of higher levels of noise and vibration than the ballasted tracks. An alternative strategy is to strengthen the existing tracks to accommodate high-speed traffic. The present article investigates the adequacy of using geosynthetics and recycled concrete aggregates to improve the performance of the ballasted rail tracks for HSR operations. Two-dimensional finite element analysis is employed to examine the effectiveness of using geogrids, geocells, and recycled concrete aggregates in the ballasted railway tracks. The efficacy is evaluated in terms of the track settlement. The results indicate that the use of recycled aggregates and geosynthetics significantly reduce the track settlement and may permit a higher train speed for same allowable settlement. The maximum reduction in track settlement is observed with geocell reinforced capping followed by the capping layer composed of recycled aggregates and the geogrid reinforced capping. Thus, the present study shows that the geosynthetics and recycled concrete aggregates may offer cost-effective alternatives to improve the performance of ballasted railway tracks for high-speed rail operations

Biogeochemical processes and geotechnical applications: progress, opportunities and challenges

Consideration of soil as a living ecosystem offers the potential for innovative and sustainable solutions to geotechnical problems. This is a new paradigm for many in geotechnical engineering. Realising the potential of this paradigm requires a multidisciplinary approach that embraces biology and geochemistry to develop techniques for beneficial ground modification. This paper assesses the progress, opportunities, and challenges in this emerging field. Biomediated geochemical processes, which consist of a geochemical reaction regulated by subsurface microbiology, currently being explored include mineral precipitation, gas generation, biofilm formation and biopolymer generation. For each of these processes, subsurface microbial processes are employed to create an environment conducive to the desired geochemical reactions among the minerals, organic matter, pore fluids, and gases that constitute soil. Geotechnical applications currently being explored include cementation of sands to enhance bearing capacity and liquefaction resistance, sequestration of carbon, soil erosion control, groundwater flow control, and remediation of soil and groundwater impacted by metals and radionuclides. Challenges in biomediated ground modification include upscaling processes from the laboratory to the field, in situ monitoring of reactions, reaction products and properties, developing integrated biogeochemical and geotechnical models, management of treatment by-products, establishing the durability and longevity/reversibility of the process, and education of engineers and researchers