Static and cyclic performance of polyurethane foam adhesive bound soil–rubber mixtures under drained conditions

Abstract

The major drawbacks of a railway track include noise, vibration, and aggravated track degradation. Resilient mats and asphalt have been increasingly used in recent years to mitigate this noise and vibration. However, these materials are quite expensive. Conventional asphalt is very stiff and brittle, making it more prone to cracking. The present work aims to develop a novel material that can be used as a base layer in ballasted and slab tracks. The current research proposes a sustainable and resilient base course layer comprising ground rubber (GR) and polyurethane foam adhesive (PFA). In this study, the performance of GR embedded in the sand is investigated. The use of PFA-treated sand with and without GR is then explored. The optimum dosage of PFA for soil and GR for treated and untreated soil is recommended based on static direct simple shear (SDSS) and cyclic direct simple shear (CDSS) tests. SDSS tests were performed to evaluate the monotonic performance of all mixtures. CDSS tests were performed to assess the long-term performance of these different mixes under repeated cyclic loading (50,000 load cycles) and varying cyclic shear stress amplitude. It is shown that PFA helps reduce the settlement and enhance soil shear strength, while GR increases the damping ratio of the soil. The optimum dosage of PFA is recommended 10%. The optimum GR content for untreated and PFA-treated soil is recommended 5 and 10%, respectively.

Experimental and Computational Analyses of Sustainable Approaches in Railways

“…The two soil types are classified as well-graded gravel (GW) and well-graded sand (SW), following the ASTM D2487 standard [41]. More details on the material description can be found elsewhere [24,42,43].…”

“…The two soil types are classified as well-graded gravel (GW) and well-graded sand (SW), following the ASTM D2487 standard [41]. More details on the material description can be found elsewhere [24,42,43]. Static direct simple shear (SDSS) tests were conducted using a direct simple shear apparatus (Figure 4a) to determine the optimum dosage of scrap rubber granules and PFA.…”

“…It must be noted that the treated Figure 3. Particle size distribution of soil and rubber adopted in this study (data sourced from [24,[38][39][40]42]).…”

“…Both SDSS and cyclic triaxial tests were conducted under drained conditions. A detailed description of the testing methodology for SDSS and cyclic triaxial tests can be found elsewhere [24,42].…”

Monotonic and cyclic triaxial testing of untreated and polyurethane-treated soil and soil–rubber mixtures

“…Some studies [19,47] report reduced settlement, while others [14] observed an increase in settlement due to scrap rubber addition. Recently, a rigorous laboratory investigation was performed by Farooq and Nimbalkar [15] to investigate the influence of scrap rubber on the performance of granular soil. They observed that at low rubber content (5-10%), a reduction in the settlement is observed, while the settlement increases at higher rubber dosages.…”