| Budget Amount *help |
¥4,000,000 (Direct Cost: ¥4,000,000)
Fiscal Year 1999: ¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1998: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Research Abstract |
(1) Modifications of apparatus: First, existing triaxial apparatus was modified for accurate and smooth cyclic loading test. To conduct large deformation test, new pedestal and cap facilitated with end-friction free mechanism were also manufactured. Second, pressure system and measurement-control system of the existing hollow cylinder torsional apparatus was renewed. Torsional shear driving system was also manufactured so that simultaneous monotonic and cyclic loading with large deformation. Further more, pedestal and cap of the torsional apparatus were modified for larger specimen.
(2) Developing of measurement system: Personal computer programs were developed for the experiments. This program enabled real-time display of external forces on the specimen and stress and strain components of the specimen. It also enabled fast-speed sampling of the measurements. The feature of this program is the calibration system that directly related the strain of the gauges on the sensors and the outpu
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t of AD converter.
(3) Triaxial tests: First, a series of undrained monotonic loading tests were conducted on sand and the effect of loading direction (i.e. triaxial compression vs. extension) was examined. Especially, the effects of initial shear loading was studied with attention to the anisotropy of the specimen. Second, numerous undrained cyclic tests were conducted and the strength of sand to liquefaction with initial shear stress conditions were closely examined. From these test results, it was concluded that the triaxial compression in initial shear and subsequent undrained shear deformation, those are the common testing procedure for liquefaction tests for sand, overestimate the resistance of sand deposit to liquefaction failure.
(4) Hollow cylinder torsional shear tests: In the view point of the importance of the anisotropic nature of sand, undrained shear tests in genera stress and strain conditions such as simple shear tests were conducted. It was found that the undrained behavior of sand in simple shear was the intermediate of those from triaxial compression and extension the test results indicated that it was possible to estimate the undrained shear deformation in general stress and strain conditions from triaxial compression and extension tests. In addition to these laboratory tests, case study from past failures in fields was conducted and it was shown that the laboratory test results in simple shear condition were well consistent with the field observations. Less
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