Abstract:Peat has several unfavourable characteristics such as low bearing capacity, high compressibility, high content of natural water and difficulty of access and thus is not suitable for Civil Engineering constructions. One of the widely used techniques for its improvement is its chemical stabilization through the addition of chemical admixtures such as ordinary Portland cement, lime, fly ash, natural fillers etc. This research was focused on stabilizing peat using low Ca fly ash (ASTM Class F) combined with well graded sand. An experimentally based approach was followed to analyse the stabilization of peat samples with different proportions of fly ash (10, 20 and 30 % by weight) and 125 kg/m 3 of well graded sand. With the increase in the fly ash content, the Maximum Dry Density (MDD) increased while the Optimum Moisture Content (OMC) decreased. The Unconfined Compressive Strength (UCS) increased with the addition of fly ash up to 10 % by weight and thereafter it began to reduce as more and more fly ash was added. The UCS increase with curing period for all of the stabilized samples. Rowe cell test results showed that there was an improvement in the compressibility of peat after stabilization. On the whole, it was found that the geotechnical engineering properties of peat can be improved by stabilizing it using fly ash and well graded sand.
The shear resistance at the sleeper–ballast interface of a ballasted track is an important contributor in maintaining track stability under faster and heavier axle loads where the ballast undergoes significant lateral sliding. Different types of sleeper–ballast interfaces based on the type of sleeper arrangements, such as concrete sleepers, timber sleepers, and under sleeper pads (USPs) attached to the concrete sleepers influence the lateral stability of railway tracks. Therefore, in this study the shear and degradation behaviour of ballast at concrete–ballast, timber–ballast, and USP–ballast interfaces were examined in the laboratory using large-scale direct shear tests under 60 kPa normal stress. The use of waste materials in the construction of civil infrastructure is gaining a lot of interest in the engineering community. Therefore, in addition to commercial USPs manufactured using raw materials, recycled USPs manufactured from granulates of end-of-life rubber tyres were also tested in this study. The discrete element modelling (DEM) approach was used to predict the shear behaviour of ballast at 30, 90, 120, 150, and 180 kPa normal stresses. The bonded particle model (BPM) was adopted in the DEM to simulate the effects of particle breakage during shearing. The results exhibited that both commercial and recycled USPs significantly improve the shear resistance at the sleeper–ballast interface while reducing particle degradation compared to concrete and timber sleeper interfaces.
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