ISERME - 2017
http://dl.lib.uom.lk/handle/123/14733
2024-03-28T12:51:34ZInternational Symposium on Earth Resources Management & Environment 2017 [Pre Text]
http://dl.lib.uom.lk/handle/123/18909
International Symposium on Earth Resources Management & Environment 2017 [Pre Text]
2017-01-01T00:00:00ZKey factors of metastable phase formation for strength development in steel slag and dredged soil mixtures
http://dl.lib.uom.lk/handle/123/12850
Key factors of metastable phase formation for strength development in steel slag and dredged soil mixtures
Toda, K; Otake, T; Sato, T; Sato, H; Weerakoon, N; Nishimura, S
Abeysinghe, AMKB; Dassanayake, ABN; Elakneswaran, Y.;
The usage of by-products from industrial activities, as construction resources is awaited in Japan to decrease the environmental impacts. Steel slag from ironworks and dredged soil extracted beneath the ports are examples for such resources. Recently, it is discovered that mixtures of steel slag with dredged soil are hardened. This discovery may expand their application into building materials for undersea construction which may solve the problem. Nonetheless, different combinations of a type of steel slag and dredged soil from various areas show gaps in strength development. The relationship between mixing condition and strength development is not clarified, making the mixture difficult to be utilized for the above application. Understanding of the hardening mechanism of the steel slag-dredged soil mixture would enable the prediction of the strength with a particular combination of steel slag and dredged soil. To achieve it, clarifying the secondary mineral formation that contributes to hardening is essential. Previous studies suggested that the strength development was related to the pozzolanic reaction, which results in cementation by the formation of calcium silicate hydrates (C-S-H). Key factors in the pozzolanic reaction are the increase in pH of the pore water and the supply of calcium and silica ions to pore water. While calcium supply is determined to be Ca(OH)2 in steel slag which also increases pH by its hydration, silica supply is only suggested to be originated in dredged soils. The objective of this study is set to understand the effects of silica-bearing phases in dredged soil on the strength development of steel slag-dredged soil mixture. In this study, dredged soils from various sampling locations (A, B, C and D) and steel slag from ironworks-1 were mixed for the investigation. The unconfined compressive strength showed mixtures with soil-A exhibits the highest strength, followed by those with B, C and D. Firstly, the silica ion which is most likely to be supplied from dredged soils was investigated. The biogenic silica content and inorganic amorphous silica such as volcanic glass content were quantified. XRD analysis showed no significant difference between the mineralogical compositions of all the dredged soils including clay minerals. Then, the effect of humic acid which may limit the supply of soluble calcium is quantified and its functional groups are analysed to see the effect on strength development of the mixtures. Through geochemical modeling for estimation of C-S-H formed from above silica supply, we suggest that the silica supply from each silica-bearing phase of dredged soils may be the driving force for the pozzolanic reaction for the strength development.
Applicability of ground penetration radar (GPR) technique to optimize soil Nail Wall designs
http://dl.lib.uom.lk/handle/123/12849
Applicability of ground penetration radar (GPR) technique to optimize soil Nail Wall designs
Lasan, HLI; Weerasekara, MN; Prashanth, S; Abeysinghe, AMKB; Premasiri, HMR; Samaradivakara, GVI
Abeysinghe, AMKB; Dassanayake, ABN; Elakneswaran, Y
Soil nailing is used to stabilize existing natural slopes or excavations using soil reinforcement technique. Due to lack of information on ground profiles and thickness of soil layers, the required soil nail lengths cannot be determined in advance, for most of the steep slopes. Furthermore, the cost of drilling in fresh rock is much higher than the cost of drilling in soft soil and weathered rock. Without proper information on the depth at which the fresh rock is found, a cost-effective soil nail wall design cannot be finalized. This research was focused on studying the methods that can be used for soil nail wall design optimization by applying Ground Penetration Radar (GPR). The study was carried out on an unstable slope near Nursing Training School located in Kandy in the central part of Sri Lanka.The physical properties of soil were determined by direct shear tests, and stability analysis was done by means of “Slope-W” software. GPR techniques were also used in this study. The investigation results showed that the existing slope is unstable, and necessary to be protected. Further, it was identified that the basement rock
cannot be encountered at already designed depths of the soil nails, which was
subcequently proven as correctbased on data from ongoing drilling for soil nail installations. With the precise knowledge about the underground geological
structure using GPR technique, the drilling cost, nail transporting cost, nail off cutting time to complete the total work can be reduced.
Geochemical aspects of Calcite and Dolomite deposits around Rajawaka off Balangoda, Sri Lanka, and suitability for industry
http://dl.lib.uom.lk/handle/123/12847
Geochemical aspects of Calcite and Dolomite deposits around Rajawaka off Balangoda, Sri Lanka, and suitability for industry
Liyanage, WLDNK; Ranasinghe, GHPGKM; Yapa, SKSP; Weerawarnakula, S; Premasiri, HMR; Abeysinghe, AMKB
Abeysinghe, AMKB; Dassanayake, ABN; Elakneswaran, Y
Major calcite and dolomite occurrences are found in Rajawaka off Balangoda in Sri
Lanka. The area is undertaken by Precambrian marble rock which is one of the most common sources of calcite and dolomite in Sri Lanka. Field investigation, locating sample points, analytical work using AAS, ETDA titration, colorimetric methods
and microscopic analysis were carried out in different phases to obtain chemical and mineralogical composition of calcite and dolomite. Results revealed that the marble
samples contain major proportion of calcite mineral, calcitic marble with minor
amount of dolomite. Quartz, graphite, pyrite, diopside, apatite, muscovite, phlogopite and biotite occur as accessory minerals. Also, analytical data showed an average acid insoluble of 5.73% and SiO2 of 4.71%, moderately high CaO content` of 81.71%, with low MgO content of 4.91% and very low iron oxide content of 0.37% and aluminum oxide content of 1.62%. These characteristics make this deposit suitable for major industrial uses especially the production of high quality lime and fertilizer manufacturing industries, and it is not suitable for the high-quality glass industry due to high content of silica and other accessories.