Browsing by Author "Kurukulasuriya, LC"

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item: Conference-Full-text
Characteristics of municipal solid wastes from selected plots located at up-slope and down-slope of the dumping site: a case study in Udapalatha/Gampola
(2013-11-13) Wijewardane, NK; Takahiro, K; Mowjood, MIM; Ken, K; Kurukulasuriya, LC
Open dumpsite has become the most widely used and common practices in most of the developing countries in waste management due to their lack of will, technology, capital and virtuous attitudes. This has elevated the risk to the ecosystem and humans derived by the improper dumping of waste in bare lands, sloping lands (valleys, river banks), wet lands etc. Characterization of waste is an important primary stage in studying dumpsites in sloping lands to identify its effects and potential remedial actions, and to develop new technologies to reduce their adverse effects on the environment and society. In this research, waste characteristics of some selected plots located at up and down slope of a dumpsite were studied to identify the possible difference and their relationships with the slope. The results revealed that waste characteristics such as ash content, combustible content, ignition loss and aggregated soil content vary in the plots located at up and down slope, suggesting that the rolling and sliding of larger particles in high sloping dumpsites has a profound effect in varying waste characteristics. This was further confirmed by the particle size distribution of both plots.
item: Conference-Full-text
Consolidation characracteristics for Sri Lankan and Japanese clays: void index in relation to stress states and sedimentation environment
(2013-11-19) Yanase, Y; Tsuboi, H; Hamamoto, S; Kawamoto, K; Takemura, T; Kurukulasuriya, LC; Oda, M
It is well known that cementation/aging and sedimentation environment affect significantly a compressibility of natural clays. In this study, one-dimensional consolidation curves (e-log p) have been measured using a standard oedometer test for several Sri Lankan and Japanese clays with different sedimentation environment (i.e., freshwater and marine sediments). The void index proposed by Burland (1990) was used to analyze the measured cosnsolidation curves. As a result, void index of marine sediments is higher than that of freshwater sediments and drastically decrease after consolidation yield stress. On the other hand, void index of Sri Lankan clays is quite low and gently narrow as increase consolidation stress. That indicates the Burland’s void index well characterized the effects of sedimentation enviroments on the consolidation characteristics of clays.
item: Conference-Full-text
Development of a capping material for an Engineered Landfill in Wet zone of Sri Lanka
(2016-01-06) Niruthshanan, P; Loganathan, FD; Premarathne, HMWAP; Kurukulasuriya, LC
Capillary Barriers (CB) which consist of coarse sand overlain by a low permeable fine soil are low cost alternatives used in capping system for controlling the infiltration in a Landfill. In wet region, the durability of capping layer is questionable as due to high precipitation, capillary effect can reduce making the layer highly permeable. A potential solution is to alter the soil grains by mixing with a Hydrophobic Agent (HA) such as Oleic Acid (OA), so that the water repellent characteristics are introduced into the sand layer. In this study, the hydrophobicity (water repellency) of CBs containing coarse sand mixed with OA was investigated. Hydrophobicity was evaluated by measuring the time taken for a water droplet to penetrate the surface of a compacted sand sample which is identified as the Water Drop Penetration Time (WDPT). Initially, dry coarse sand particles were hydrophobized by mixing-in coating method with different OA contents. In addition, the effect of moisture content of coarse sand particles on its hydrophobicity was also studied. The results show that WDPT for dry samples increased sharply with increasing HA content and reached a peak value of 4080 s at 3gkg-1 of sand and thereafter decreased. Irrespective of the OA content, an increase in moisture content decreased the water repellency. However, this decrease is less significant for the optimum value of OA content of 3gkg-1 within the range of moisture content tested. The impact of the slope angle on the water repellancy was also investigated by increasing the slope upto 1V:3H. Results showed a decrease in water repellency when the slope angle was increased. It was observed that water drop was spreading due to the effect of weight acting along the slope and as a result the WDPT time decreased due to less surface tension.
item: Conference-Abstract
Numerical analysis of GEOMAT reinforced vertical earth embankments using plaxis software
Yasotharan, G; Kugaruban, S; Kurukulasuriya, LC
The design procedure of reinforced earth retaining structures considers the safety against tensile failure and pull out failure as the internal stability criteria. However, evaluation of the lateral deformation also needs to be considered as an important criterion to satisfy serviceability limit states. It is imperative that the designer limits the lateral deformation of reinforced earth walls under service loads. In a reported number of previous studies, extensive laboratory experiments have been carried out to investigate the lateral deformation characteristic of embankments reinforced with coir mats. For this purpose, ordinary coir mats and those coated with polyethylene to improve their durability under acidic and alkaline environments have been used. The above studies, also investigated the effect of wetting on the lateral deformation as well. In this study, numerical analyses of the above laboratory experiments are carried out using Plaxis 2D software to determine lateral deformation characteristics and the results are compared with the experimental results. The analyses was carried for uncoated and coated geomats used to reinforce a vertical embankment prepared to 95% of maximum dry density and that subjected to soaked conditions which simulates exposure to rainy weather. The results show that the variations of lateral deformation obtained from the numerical analyses under various conditions are similar to those observed in the experimental studies. However, quantitatively, the lateral deformation obtained from the numerical analyses show less value in magnitude than those observed in the experimental work.
item: Conference-Abstract
Shear strength characteristics of ballast subjected to particle breakage and mud pumping using parallel gradation technique
Shihana, AM; Vasan, V; Kurukulasuriya, LC
Ballasted rail tracks are most commonly used in rail track structure and are designed to provide a stable, safe and economic foundation. Main components of ballasted rail track structure can be grouped as track superstructure and track substructure. The cyclic loading by the train will be distributed from the superstructure to substructure. Sri Lanka currently uses the Indian standard gradation for almost all the tracks. Most of the ballast material used in Sri Lanka is obtained from biotite gneiss rock which is available in abundance. However, ballast is constantly subjected to degradation throughout its service due mainly to ballast breakage and migration of fine particles from the subgrade into the ballast layer, which is known as mud pumping. In this study, the effect of ballast particle breakage and mud pumping on the shear strength characteristics of ballast is investigated. Parallel gradation technique was used to model the sample as it is difficult to handle large size ballast in the conventional direct shear box. Sample was collected from Elugoda quarry (in the Kandy District) from where the ballast material is supplied to upcountry railway construction. Scaled down sample was sieved and test sample was prepared according to Indian standard gradations using the parallel gradation technique and the direct shear test was carried out under three normal pressures of 15 kPa, 30 kPa and 90 kPa. The study revealed that the shear strength of ballast is decreased for lower degrees of fouling due to ballast breakage and mud pumping and starts to increase with increased degree of fouling, but not as much as that of fresh ballast.
item: Conference-Full-text
SHEAR STRENGTH CHARACTERISTICS OF DIFFERENT GRADATIONS OF BALLAST USING PARALLEL GRADATION TECHNIQUE
(2016-01-06) Pakalavan, V; Nirvekala, B; Kurukulasuriya, LC
Ballasted rail tracks are most commonly used rail track structure and to be designed to provide a stable, safe and economical foundation. Main components of ballasted rail track structure could be subdivided as track superstructure and track substructure. The loading from the train will be distributed from the superstructure to substructure. The main structural component of substructure is considered as track ballast which is generally crushed hard stones. Railway authorities specify gradation specifications for selection of ballast for rail tracks. Sri Lanka railways also specified a gradation limits in the selection of ballast for rail tracks. Current standard is closely resembled to the Indian rail track ballast specifications. Commonly, the ballast used in Sri Lanka is crushed gneiss rocks which are in abundance. It is well understood that granular materials derive its strength by resistance to shearing. However, there is no examination conducted to evaluate the performance of rail track ballast used in Sri Lanka considering the shear behaviour. The objective of this preliminary study is to investigate the shear strength characteristics of ballast gradation used in Sri Lanka and compare with selected other ballast gradation specifications. Parallel gradation technique was used to model the sample as it is difficult to handle large size ballast in the conventional direct shear box. Direct shear tests were conducted under three normal pressures of 15 kPa, 45 kPa and 90 kPa on different ballast gradations including current Sri Lankan specification. The results showed that the Current Sri Lankan ballast gradation specification which is the same as Indian standard gradation has the highest shear strength compared to other ballast gradations tested.
item: Conference-Abstract
Stability analysis of a compost-biochar mixed capping soil on Hydrophobised capillary barrier in an engineered landfill
Jaiprakash, T; Vijeeth, U; Kurukulasuriya, LC
Engineered landfill is a final municipal waste disposal method. A capping system is the final component in the construction of an engineered landfill. In addition to permeability criteria that need to be satisfied, stability is also an important aspect in its design. In this study, the slope stability of the capping layer interfaces and waste interfaces was analyzed. A low permeable soil with or without mixing with biochar and compost can be used as a capping layer. In addition, a hydrophobized sand (using Oleic acid) can under lie the above layer for improved performance. The shear strength parameters between interfaces and of the waste were determined using the direct shear tests. Analyses were carried out for waste – capillary barrier interface and capillary barrier – top soil (with or without biochar and compost mixture) interface, for different side slopes of the capping. Numerical analyses were carried out using SLOPE/W software. A comparative analytical study was also carried out using infinite slope theory. It was found that circular type of slip surface developed within the capping is more critical than the slip surface develop along the interfaces and introducing compost and biochar into the topsoil infact has improved the stability of the slopes of the capping layer.
item: Conference-Full-text
Stability of an open dumpsite with ageing
(2016-01-06) Sayilacksha, G; Venuja, T; Kurukulasuriya, LC
Open dumping is the most commonly used method adopted in Sri Lanka as solid waste management. However, slope failures of open dump sites lead to environmental pollution as most of the open dumps are located near water bodies. Therefore, analysing the stability of open dumps is important in implementing mitigatory measures where required. Abandoned Udapalatha open dump site which is located near Gampola, Sri Lanka was considered as a case study to analyse the stability of its slopes consisting of old and new waste representing different degrees of decomposition. Shear strength parameters of the waste samples of the old and new waste sites were determined using box samples at different depths with particle size less than 9.5 mm. Specific gravity test, Oedometer test and Standard Proctor compaction test were performed to obtain Gs, primary and secondary consolidation parameters, maximum dry density and the optimum moisture content. In addition, direct shear test was carried out to determine the shear strength parameters of the fill. Slope stability analysis was carried out using Slope/W and Plaxis-2D software considering Mohr Coulomb and soft soil creep models respectively for waste material. Consideration of primary and secondary consolidation settlement within the landfill in the Plaxis-2D analysis resulted in an increase in the Factor of safety (FOS). Therefore, FOS values obtained from the slope stability analysis of the old site, was higher than that in the new waste site.