Master of Engineering in Foundation Engineering & Earth Retaining Systems

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Browsing Master of Engineering in Foundation Engineering & Earth Retaining Systems by Subject "CIVIL ENGINEERING"

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    Optimization of uplift capacity of transmission tower foundations
    Gunasena, UPP; Thilakasiri, HS
    Transmission tower lines using lattice towers and concrete foundations are the common practice in most of the countries all over the world. A significant amount of the cost of the transmission tower line is spent for the tower foundation construction. Uplift capacity of transmission tower foundation is determined based on the assumption that, the uplift force is resisted by the weight of the footing and the weight of the soil inside the volume of inverted frustum. Hence, the uplift capacity of the foundation is a major aspect of determining the dimensions of the tower foundation. However, the values of the frustum angle seem to be arbitrary and the failure pattern is more likely to be varied from the assumed pattern. Apart from that, the frustum angle is unsymmetrical for the inclined loadings. Further, the estimated uplift capacity shall also be reassessed according to the failure plane variations. As the first step of this study, a research survey was conducted on the available empirical methods of estimating the uplift capacity. Data were collected on transmission tower types and their foundation types based on different soil categories. This report will use PLAXIS; a finite element software to analyze the uplift capacity of transmission tower foundation. A comparison between the results from the software analysis and the capacities given by empirical methods is included in the report. An evaluation on the assumptions made on frustum angle, composition of uplift capacity to determine the uplift capacity of the transmission tower foundations is also given in the report. This analysis also includes the failure patterns, uplift capacity, composition variation of uplift capacity for different types of foundations used for transmission towers. Conclusively, this will evaluate and make a recommendation on determination the uplift capacity of transmission tower foundation, assumption of the frustum angle and the composition of the uplift capacity.
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    Study of pullout resistance of soil nails in tropical residual soil
    Ranjan, KWEP; Kulathilaka, SAS
    As a norm, most design engineers typically resort to theoretical and empirical approaches in order to determine the pullout resistance of soils while designing soil nailed retaining walls. The tendency to design based on actual field tests are minimal due to the time and cost involved while implementing such tests. Though results obtained through pull out tests done within the laboratory have been used to perform design calculations, the outcome of such test results are questionable, as such tests do not replicate precise site conditions. This research primarily juxtaposes and establishes a relationship between the theoretical and on field practical pullout resistance of soil nails in unsaturated conditions with the use of information extracted from an extensive literature review and data obtained through an actual pull out test conducted on a set of soil nails installed in predetermined locations of a 25ft high embankment spanning 70ft. This research also attempts to explore the effects of over burden pressure on the pull out resistance of the soil nails and the behavior of the actual failure surface of the soil nail, which has also been mentioned as the effective diameter in this report.
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    Study on the effect of dredging on existing sheet pile retaining structures
    Senarathne, DEN; De Silva, LIN
    Sheet pile retaining structures are widely used in many purposes in engineering designs. Most common applications are shoring, stabilize excavations, harbor quay wall structures, canal bank protection structures.. etc. This research is mainly focused on the issue of stability of harbor quay wall structure when deepening the harbor basin to cater larger vessels. Most of the quay wall structures in Srilanka are anchored sheet pile walls. So the effect of dredging on the sheet pile structure is studied. If the same method can be applied for the cantilever sheet pile walls which could be used in drainage improving projects. The study is extended to both anchored and cantilever sheet pile structures to increase the stability while reducing the depth of embedment. Another improvement sheet pile wall is proposed from the passive side of the existing sheet pile structure to provide an additional support to the main structure. The finite element analysis is used to estimate the effect of the improvement wall on the stability and the deflection of the wall in cohesion less soils. The effect of the distance between the existing structure and the improvement wall and the effect of increasing the depth of embedment of the improvement structure are analyzed through the finite element models. The models are tested for 22 to 38 degrees wide range of friction angles of cohesion less soils The results of the finite element model are verified by a physical model conducted in a laboratory. The results of the analysis shows that the improvement wall can significantly increase the stability of the existing structure. Compared to anchored sheet pile walls higher improvement can be achieved for cantilever sheet pile walls from this method. Rather than replacing the entire structure , applying a this sort of improvement method will be highly economical as well as less damages to the other structures close to the existing sheet pile wall.
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    Study on utilization of building debris in road construction in northern province of Sri Lanka
    Shankar, P; Nawagamuwa, UP
    Due to rapid development and population growth, construction industry has emerged with few new problems. The major problem faced by the industry is the scarcity of construction material and disposal of construction waste because of high disposal cost and inadequate land fill area. Northern region of Sri Lanka is undergoing a massive infrastructure development within a shorter period especially in the road sector development. Roads are major consumers of aggregate and soil and the influence of aggregate cost is more in total construction cost of the roads. The aggregates for these road construction projects are transported from Medawachchiya due to scarcity of local material and the approximated transport distance from Medawachchiya is more than 150 km. Hence, transport cost is approximately 70% of the project cost. In order to curtail the cost of construction of roads and reduce the industrial waste disposal, the possibility of using building waste as road construction material has been studied. Building debris such as concrete, random rubble masonry, concrete block and plaster were selected for this research. Experimental studies were carried out to determine the engineering properties of the recycled construction material and compared with conventional road construction material. Aggregate Impact Value Test, Aggregate Crushing Value Test, Los Angeles Abrasion Test and California Bearing Ratio Test were carried on selected building debris to find out the suitability for road base construction. Crushed samples of selected debris were tested to determine the suitability for replacement of soil in road construction. It has been observed that the Random Rubble Masonry debris can be directly used for road base construction however, crushed debris of block masonry, plaster and concrete can replace the soil for construction of sub base, shoulder, embankment and for surface of ā€˜Dā€™ & ā€˜Eā€™ class roads after adding suitable percentage of plastic clay.