9701467 Yamamuro This action is to support an integrated research and educational-enhancement project submitted under the NSF Faculty Early Career Development (CAREER) Program. Most research into liquefaction of soils has been performed on clean sands, while most of the documented historic cases of earthquake-induced liquefaction have occurred in alluvial silty sands. The current view of the effect of fines (particles smaller than 0.074 mm) on the liquefaction behavior of soils is that it either inhibits liquefaction or that it has little effect. However this is not necessarily correct. The behavior of silty sands has also been observed to be highly unconventional. The four major tasks and objectives of the research program are: (1) To investigate the unconventional behavior of silty sands by performing drained and undrained testing using monotonic and cyclic loading. The objective is to explore the bounds of the observed unconventional behavior. (2) To evaluate, using scanning electron microscope and thin- sections analysis, the soil fabric of silty sands formed by the different depositional methods used to create test specimens. This will be followed by a study of soil fabric created by water depositional processes in a fabricated cylindrical vertical sedimentation chamber. The objective is to ensure that the fabric created by alluvial deposition is incorporated accurately into test specimens. The soil fabric will then be modeled using Discrete Element Methods (DEM), the objective being to verify possible 'collapse' mechanisms of 'meta-stable' structures created in silty sands during alluvial deposition. (3) To perform model cone penetrometer tests (CPT) in a fabricated double-walled calibration chamber on silty sands. The objective is to evaluate existing insitu liquefaction assessment methods and the effect of grain size. (4) To modify an elasto-plastic, non-associated flow constitutive soil model to capture the unconventional behavior pattern. The objective is to enable predictions of liquefaction in alluvial silty sand. The three main educational objectives are: (l) To improve students' electronic communications skills when acting as 'disassociated' project team members connected only by networking technology. (2) To improve undergraduate soil mechanics education by providing undergraduate students with greater exposure to advanced soil mechanics testing by developing interactive videos. Videos will be developed for tests such as monotonic and cyclic triaxial testing, torsion shear, CPT, and pressuremeter. This will supplement the basic undergraduate laboratory experience. (3) To encourage minority participation into the geotechnical engineering program at Clarkson University. This will be best accomplished by participation in the McNair Program which funds qualified minority students to participate in undergraduate research during summers.
