Browsing by Author "Admassu, Tirualem"

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    Effect of Strain Rate on The Stress- Strain Relationship And Shear Strength of Addis Ababa Red Clay Soil
    (Addis Ababa University, 2011-07) Admassu, Tirualem; Hadush, Seged (PhD)
    This research work tries to see the effect of strain rate on stress-strain relationship and shear strength of red clay of Addis Ababa. It is tried to identify the effect of strain rate by conducting a series of triaxial compression test on remolded soil samples. All the specimens were compacted at OMC with standard compaction apparatus. Besides basic tests have been done to identify the soil type. The triaxial tests were done on samples of 38mm and height of twice the diameter. The type of triaxial test employed was Consolidated Undrained/CU/ with pore pressure measurement and with the effective consolidation pressure of 250 kPa, 350 kPa and 450 kPa. After saturation and consolidation stage, the specimen were axially loaded at a rate of strain varying from 0.001mm/ min to 1mm/min. A total of twelve triaxial CU tests were run. Data presented includes consolidation data, pore pressure observation, stress-strain relationship and modified Mohr failure envelop diagram. The results of triaxial tests were used to examine the stress-strain relationship and shear strength parameters. The results show that strain rate affects both the stress-strain relationship and strength of soil. As the strain rate increases the strength of soil also increases, but the strain rate has more pronounced effect on the cohesion and little effect on angle of internal friction of the soil. The values of cohesion obtained from modified failure envelope for strain rate 0.001mm/min, 0.01mm/min, 0.1mm/min, and 1mm/min are 40.82kPa, 44.76kPa, 52.80kPa and 102.51kPa for total stress and 31.21kPa, 36.95kPa, 41.87kPa and 78.6kPa for effective stress. The values of angle of internal friction obtained from modified failure envelope for strain rate 0.001mm/min, 0.01mm/min, 0.1mm/min, and 1mm/min are 14.17 o , 14.35 o , 14.11 for total stress and 22.4 o , 22.07 o , 21.54 o , and 21.19 for effective stress.