Browsing by Author "Hamamoto, S"

Now showing 1 - 9 of 9

item: Conference-Full-text
Characterization of geotechnical properties as affected by sediment environment in Kanto lowland clays in Japan
(2013-11-11) Tsuboi, H; Yanase, Y; Hamamoto, S; Kawamoto, K; Takemura, T; Oda, M
The purpose of this study is to investigate effects of sedimentary environment (freshwater and marine deposits) on geotechnical properties for Kanto lowland clays. Freshwater and marine sediments were used to perform standard consolidation tests, undrained triaxial compression tests, and unconfined compression test. Pore-water compositions were also measured for the sediments. As results, higher compression index, higher sensitivity, and lower shear strength ratio were observed for the marine sediments as compared to those for the freshwater sediments. In addition, the measurements of pore-water compositions revealed that the sensitivity values were well related to the proportion of monovalent cations, especially for the sediments with plastic index of less than 30.
item: Conference-Full-text
Characterization of landfill leach ate from municipal solid wastes landfills in Sri Lanka
(2013-11-13) Sewwandi, BGN; Takahiro, K; Kawamoto, K; Hamamoto, S; Asamoto, S; Sato, H
Open dumping of municipal solid waste (MSW) is the most common way of handling solid waste in Sri Lanka due to high cost involved with advanced technologies for landfilling, lack of technical capacity, lack of know-how to manage landfill sites, and so on. Landfill leachate generated from the MSW landfill sites must be treated before dispose into the environment as it creates many social and environmental problems. Characterization of landfill leachate is important to identify the most critical pollutants present in the leachate and thereby to introduce suitable and applicable treatment technologies such as in-situ permeable reactive barrier technologies for contaminant remediation. Therefore, the objective of this research is to characterize landfill leachate collected from several MSW landfills in Sri Lanka. The leachate samples were collected from 12 landfill sites located in Matale, Hambantota, Kataragama, Bandaragama, Kolonnawa, Gampola, Gohagoda, Wennappuwa, Rathnapura, Negombo, Galle, and Matara. For the collected samples, general water quality parameters (pH, EC, DO, ORP, and SS), organic pollutants (BOD5, COD, TOC, IC, TN, TP), typical anions and cations (Cl-, SO42-, NH4+, K+, Mg2+, Ca2+, etc), and heavy metals (Cr, Mn, Fe, Se, Pb, etc) were measured. The results showed that most of the pollutants (F-, Cl-, PO43-, NH4+, Fe, Se, Pb, BOD5, and COD) exceeded the maximum tolerance limits in Sri Lankan Standards. It was found that the BOD5/COD ratio ranged from 0.01 to 0.6 for the most samples and the highest value of 0.6 was observed in the Kolonnawa sample. Measured EC values for all samples were high and varied ranging from 4.5 to 38.3 mS/cm, indicating the biological treatment system alone would not be effective in reducing the pollutants especially for heavy metals. The results of this study will be used in developing site specific remediation technologies in landfill leachate treatment.
item: Conference-Full-text
Compressibility of Japanese landfilled/buried waste samples: measurement of compaction curves and consolidation test for compacted waste samples at different compaction levels
(2013-11-13) Nandika, HLD; Hamamoto, S; Koide, T; Kawamoto, K; Endo, K
Compressibility characteristics of landfilling and buried waste samples are highly heterogeneous, depending on various waste compositions, degree of organic matters, decomposition, and so on. Measured data presented in this paper are the results from laboratory tests for different types of landfilling and buried waste such as incineration ash, industrial waste (plastics, rubbers, etc.) and un-burnable domestic waste (glasses, ceramics, etc.) and buried industrial solid waste fully mixed with soil from an industrial waste landfill at Saitama Prefecture in Japan, respectively. Prior to the compaction and consolidation tests, each sample was dried and the waste composition and particle size distribution were determined. Standard proctor compaction tests were carried out to discuss the compaction properties. For the buried industrial solid waste fully mixed with soil (two sample fractions: < 2 mm and < 9.5 mm) and incineration ash samples, optimized water contents (wopt) which gave the maximum dry bulk densities can be measured similar to typical soil samples. On the other hand, for the industrial and domestic waste samples mainly composed of plastics and glasses, the values of wopt could not be clearly observed and measured dry bulk densities were not controlled by the initial water content of samples. Consolidation tests for compacted samples at different compaction levels were carried out by using a specially designed oedometer in the laboratory. Based on the results from consolidation tests, the compressibility characteristics will be discussed based on the consolidation indices such as compression and consolidation coefficient, and their dependency of waste composition and fraction and surrounding environment (e.g., temperature).
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
Effects of moisture content and shrinkage on soil-thermal properties for peat soils in Japan
(2013-11-19) Hamamoto, S; Dissanayaka, S; Kawamoto, K; Komatsu, T
Wetland is known as a source of atmospheric methane, typically produced by microbiological and chemical processes under anaerobic conditions. Soil temperature in the wetlands is a key factor to control the processes. Peat soils can be found in many types of wetlands. Peat soils contain high organic matter content and thus shows unique physical properties such as high total porosity and shrinkage. This study aims to study the heat transport of peat soils at variably saturated conditions and effects of volume shrinkage on thermal properties of peat soils. Study area of this research is Bibai marsh, Hokkaido in Japan. Undisturbed peat samples were obtained from two different peat profiles at different depths. In general, the thermal conductivity (TC) and the heat capacity (HC) of peat soils linearly increased with increasing volumetric water content, and simple two-phase (solid and water phases) models for TC and HC could generally express TC and HC behaviors, respectively, for most of peat soils. In addition, the observed volume-shrinkage of the peat soils under dry conditions did not affect the TC and HC behaviors for the studied samples.
item: Conference-Full-text
Gas and Heat transport in variably-compacted landfill cover at variably-saturated condition
(2013-11-11) Hamamoto, S; Kawamoto, K; Komatsu, T
Understandings of gas and heat transport in the landfill covers are essential for enhancing the landfill site stabilization and reducing the greenhouse and toxic gas emissions. Gas diffusion and thermal conduction are main mechanisms for gas and heat transport in soils. Gas diffusion coefficient and thermal conductivity govern gas diffusion and thermal conduction, respectively. In this study, we developed a unified predictive model for gas diffusion coefficient and thermal conductivity considering soil compaction level. Numerical simulations of gas (methane, carbon dioxide, and oxygen) and heat transport in a landfill cover were performed using the developed predictive model. Increase of compaction level enhanced not only heat transport in the landfill cover but also methane gas emissions due to reduced methane gas oxidation nearby soil surface.
item: Article-Abstract
Gas transport parameters for compacted reddish - brown soil in Sri Lankan landfill final cover
Wickramarachchi, P; Ranasinghe, K; Hamamoto, S; Kawamoto, K; Nawagamuwa, UP; Moldrup, P; Komatsu, T
Gas exchange through (he compacted final cover soil at landfill sites plays a vital role for emission, fate, and transport of toxic landfill f,ases. This study involved measuring the soil-gas diffusivity tDp/Du, the ratio of gas diffusion coefficients in soil and free air) and air permeability (k,J for differently compacted soil samples (reddish-brown soil) from the final cover at the Maharagama landfill in Sri Lanka. The samples were prepared by either standard Proctor compaction or hand compaction to dry bulk densities of 1.60-1.94 g cm='. Existing and modified models for predicting Dp/ Do and k" were tested against the measured data. The simple, single-parameter Buckingham model predicted measured Dp/ Do values across compaction levels equally well or better than a dry bulk density (DBD) dependent model and a soilwater retention (SWR) dependent model. The measured ku values for differently compacted samples were highly affected by the compactionlevel and the sample moisture preparation method. Also, for air permeability, a single-parameter Buckingham-type k" model was most accurate in predicting k" in the differently compacted soil samples. Equivalent air-filled pore diameters
item: Conference-Full-text
Heat and gas transport characteristics in differently-decomposed peaty soils at variably-saturated conditions
(2013-11-12) Dissanayaka, SH; Hamamoto, S; Kawamoto, K; Komatsu, T
Knowledge of heat and gas transport properties of the peat soils is important to simulate greenhouse gas behaviour and changes of soil-temperature in the wetlands. In this study, the heat and gas transport properties for differently-decomposed and variably saturated peat soils were measured in order to investigate the general analogies and differences between transport properties of the peat soils. As results, changes in liquid-phase tortuosity under different moisture conditions and volume shrinkage under dry conditions did not significantly affect the thermal conductivity, showing linear increase of thermal conductivity with moisture content. On the other hand, marked effects of soil-water blockage and volume shrinkage on the soil-gas diffusion coefficient under wet and dry conditions, respectively, were observed.
item: Conference-Full-text
Locally available expansive soils as a liner material for municipal landfills
(2013-11-13) Wanigarathna, D; Kurukulasuriya, C; Hamamoto, S; Kawamoto, K
The bottom liners in the municipal landfill sites are expected to prevent the migration of pollutants (leachate) to the groundwater. Different types of liner materials are being used in the construction of liners of municipal landfills over the world. Compared to the liner materials such as Geosynthetic Clay Liners (GCL) and High Density Polyethythene (HDPE), Compacted Clay Liners (CCL) are more economical, if materials are locally available. Different types of clay have been experimented for their suitability as liner materials in many countries. An expansive soil however, having a high plasticity index can be expected to absorb more volume of water emanating from the leachate and as a result it can withstand longer dry periods before cracks develop. Further, even if cracks do develop during a prolonged dry period, the cracks may self heal with the subsequent exposure to a rainy period as the shrink-swell behavior of expansive soils is reversible. Therefore, in this study, the suitability of a locally available expansive soils in which the major clay mineral is montmorillonite was investigated for use in landfill liners. For this purpose expansive soils obtained from Digana and Moragahakanda areas of Sri Lanka were chosen as candidate soils. The Rowe Cell apparatus was used to measure the hydraulic conductivity of the consolidated soil sample using de-aired water as the permeant liquid. The results showed that for all the test specimens hydraulic conductivity was less than 1x 10-9 m/s conforming to the requirements of maximum hydraulic conductivity recommended for liner materials. Similar tests were performed on expansive soils obtained from Moragahakanda amended by the addition of 5% bentonite (Sodium Bentonite). Addition of bentonite resulted in a decrease of hydraulic conductivity by a significant amount. Therefore, it can be concluded that subjected to the satisfaction of durability criteria the expansive soils of Digana and Moragahakanda are suitable as liner materials and have the potential to be incorporated into a relatively thin liner by amending with bentonite.