Browsing by Author "Bandara, AMDC"

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item: Thesis-Full-text
Development of a sensor system to investigate the arching action of soil
(2019) Bandara, AMDC; De Silva LIN; Amarasinghe YWR
This research focused on introducing a new mechanism to measure the effective earth pressure and total earth pressure in one degree of freedom sensor system. To identify the structural deformation with respect to the earth pressure (in other words sense the earth pressure) strain gauge based cross beam structure is introduced as the sensing structure. This study was focussed on measuring 150 kN/m2 maximum earth pressure however, it is capable of customizing the system according to the measuring requirement. A novel mechanism is developed to measure the effective earth pressure directly by allowing infiltration of water into the sensor and there by cancelling the outside pore water pressure. Finite element analysis was carried out to identify and optimize the sensing cross-beam structure dimensions. Dimensions and the shape of the sensor were finalized after referring to the literature. Aluminium material was used to manufacture this sensor considering different geotechnical, mechanical and environmental factors. Precision marching methods were used to manufacture a highquality sensor minimizing the manufacturing errors. For that CNC milling machine and CNC lathe machine in the Die and Mould laboratory were used. After that a complete data acquisition system was developed to collect, visualize and store the data. Cloud database based remote sensing mechanism was also introduced to monitor the earth pressure in real time via a web portal. Laboratory testing and validation were done using sand material. Sensitivity, zero load drift and thermal characteristic of the sensor was also identified. Finally using the developed sensor system, arching effect of sand was studied. Initially the active and passive arching effect behaviour of dry sand due to the settlement of clay soils was investigated. After that research was carried out to investigate the arching effect of dry sand and saturated sand with the known settlement. Special apparatus was developed to create a known settlement inside a sand fill .
item: Conference-Full-text
Development of an earth pressure cell to evaluate the total and effective stresses of soil
(IEEE, 2018-05) Bandara, AMDC; De Silva, LIN; Amarasinghe, YWR; Chathuranga, D
This study focuses on development of an earth pressure cell to identify the effective soil pressure and pore water pressure in a single degree of freedom sensor system. A strain gauge based four cross-beam metal structural element is used to identify the maximum earth pressure of 150 kN/m2. For that, pressure transferring mechanisms are developed to transfer the earth loads to sensing elements via deformation of cross-beam structure as a total load and as an effective load. Finite element analysis is done to select the optimum dimension for the sensor element. Other dimensions and the shape of the sensor are selected by referring the literature. Accuracy of the system will be verified by using methods which are currently available for measuring soil pressure and pore water pressure under laboratory and field conditions.
item: Conference-Abstract
Study on development of arching action of sand using an earth pressure cell
Havisanth, E; De Silva, LIN; Bandara, AMDC; Amarasinghe, YWR
Stress transformation from yielding part of soil on to adjacent rigid part is known as the arching action of soil. Terzaghi’s trapdoor test was an important milestone in development of theories on soil arching, soil arching has both active and passive effects. Stresses acting on underground structures need to be estimated correctly for economical design and evaluation of the performance of those structures accounting the effect of soil arching. An experimental approach in measuring real-time stress variation on buried structures due to arching effect of soil is discussed in this paper. Experimental study was done to study the effect of both active and passive soil arching in dry and saturated sandy soil using effective and total earth pressure cells and the stress variation on underground structures was analyzed. The test results were compared with Terzaghi’s arching theory. Results conclude that in passive soil arching stress transform to structures increase with stress increment where, as the stress transform to structures reduce with settlement of the structure. In addition, settling of surrounding soil causes increase in the stress transform to structures.