Browsing by Author "Kulathilaka, A"

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item: Conference-Full-text
Effect of dynamic compaction on the compressibility characteristics of municipal solid waste, under the saturated and unsaturated conditions
(IEEE, 2022-07) Rathnayaka, A; Ragavan, P; Kulathilaka, A; Rathnayake, M; Adhikariwatte, V; Hemachandra, K
The scarcity of land suitable for new developments in urban areas is a growing problem in many countries. In Sri Lanka, open dumping has caused unsanitary landfills within major cities, and it is economically, socially, and environmentally desirable to rehabilitate them. Ground improvement is a significant step in the rehabilitation of landfills, and dynamic compaction (DC) is a commonly used method in treating heterogeneous fill materials such as municipal solid waste (MSW). In this study, MSW samples obtained from the Meethotamulla landfill site, Sri Lanka, subjected to DC under both saturated and unsaturated conditions, were tested using the Rowe cell apparatus. Their compressibility characteristics were established under four conditions: saturated-compacted, saturated-noncompacted, unsaturated-compacted, and unsaturated-noncompacted. The results of the analysis indicated that the improvement of density and compressibility characteristics of MSW due to DC is greater under the unsaturated condition. In addition, the results were compared with that of preloading. It was found that preloading is more effective in improving the compressibility of MSW under both saturated and unsaturated conditions.
item: Conference-Full-text
Effect of dynamic compaction on the compressibility characteristics of municipal solid waste, under the saturated and unsaturated conditions
(IEEE, 2022-07) Rathnayaka, A; Ragavan, P; Kulathilaka, A; Rathnayake, M; Adhikariwatte, V; Hemachandra, K
The scarcity of land suitable for new developments in urban areas is a growing problem in many countries. In Sri Lanka, open dumping has caused unsanitary landfills within major cities, and it is economically, socially, and environmentally desirable to rehabilitate them. Ground improvement is a significant step in the rehabilitation of landfills, and dynamic compaction (DC) is a commonly used method in treating heterogeneous fill materials such as municipal solid waste (MSW). In this study, MSW samples obtained from the Meethotamulla landfill site, Sri Lanka, subjected to DC under both saturated and unsaturated conditions, were tested using the Rowe cell apparatus. Their compressibility characteristics were established under four conditions: saturated-compacted, saturated-noncompacted, unsaturated-compacted, and unsaturated-noncompacted. The results of the analysis indicated that the improvement of density and compressibility characteristics of MSW due to DC is greater under the unsaturated condition. In addition, the results were compared with that of preloading. It was found that preloading is more effective in improving the compressibility of MSW under both saturated and unsaturated conditions.
item: Conference-Extended-Abstract
Evaluation of electro kinetic properties of Sri Lankan peaty clays
(2006) Kulathilaka, A
Finding economical and speedy methods for the improvement of extremely soft peaty clays is a major challenge ahead of the Sri Lankan geotechnical engineers involved in new infrastructure development projects. Peaty clays are with very high water contents and found in low lying areas in several parts of the country. Major Geotechnical problems are associated with constructions done on peaty clays due to very high primary and secondary consolidation settlements and very low shear strengths. Extremely soft consistency of soils encountered in some sites makes it impossible to place any fill without the use of reinforcements and separation layers. Even then the construction will have to be done in several stages to prevent shear failures. In this context the possibility of consolidating the extremely soft peaty clays by electro osmosis - without application of a physical load was studied.
item: Thesis-Abstract
Improvement of peaty clays by deep mixing and preloading
(2014-08-19) Saputhantiri, DR; Kulathilaka, A
One major problem related to construction on peaty clay deposit is the low shear strength of the soil. However previous researches have shown that the shear strength could increase significantly by mixing with cement and various stabilizers. Hence some improvement methods have been developed to increase the bearing capacity of the peaty clay deposit by mixing with stabilizers and cement. The aim of this project is to evaluate the increase of shear strength of peaty clays due to mixing with cement and the application of preloading pressure during the curing period. The initial undrained shear strength was obtained from untreated remoulded peaty clay subject to preloading pressures. For this study, samples were prepared for untreated peaty clay samples and treated peaty clay by mixing with 15% and 20% cement by wet weight and keeping under two preloading pressures of; 20kN/m2 and 40kN/m2 . The shear strength of the samples was obtained by triaxial compression test under unconsolidated undrained condition. The results proved that there is an increase in the range of 150% to 240% in shear strength due to mixing with cement and application of preloading pressure during the curing process. The other major problem related to construction on peaty clay deposit is the high settlement of the soil. The previous researches have proven that the settlement of soft soil has decreases significantly with the addition of stabilizers and cement. For the analysis of compressibility characteristics, peaty clay samples were mixed with 0%, 15% and 20% cement by wet weight and keeping under two preloading pressures of; 20kN/m2 and 40kN/m2. Consolidation characteristics of the untreated and treated peaty clay are determined through the series of laboratory consolidation testing. From the consolidation test results, coefficient of volume compressibility (mv) and the coefficient of secondary consolidation (Ca ) were evaluated in all the loading and reloading increments. The values of compression index (Cc) and recompression index (Cr) were also evaluated using the e Vs log a plot. The improvement of the stiffness is assessed and compared by the measurement of compressibility characteristics of the treated peaty clay with untreated peaty clay.
item: Conference-Full-text
Use of the concept of capillary barriers to optimize the support systems of deep vertical excavations in unsaturated soils
(IEEE, 2022-07) Ragavan, P; Rathnayaka, A; Kulathilaka, A; Rathnayake, M; Adhikariwatte, V; Hemachandra, K
In deep excavations, it is necessary to guarantee stability against catastrophic failure and to ensure that the deformations in the surrounding are within acceptable limits. Excavations done above the groundwater table can be supported with simple structures such as soldier pile walls. But the stability of the structure is affected by the infiltration of rainwater. If the infiltration of rainwater can be reduced the construction of a deep vertical excavation support system can be optimized. A Capillary Barrier (CB) which consists of a fine layer lying on top of a coarse layer at the ground level can cut off the infiltration into the lower layers. In this research study, initially, attempts were made to establish the critical parameters through parametric studies. A laboratory model of a Capillary Barrier was constructed with instrumentation and a rainfall pattern was applied. Experimental results were verified with GeoStudio, 2012 SEEP/W software and there was a very good agreement. A deep excavation supported by a soldier pile wall in an unsaturated soil was modelled thereafter with Midas GTS NX 3D software and the effectiveness of the capillary barrier in optimizing the design of the support system during a prolonged rainfall was illustrated.