| Budget Amount *help |
¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 2001: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Research Abstract |
1. An elastoplastic model for geomaterials in three-dimensional stresses. For applying a three-dimensional criterion the Extended SMP criterion to elastoplastic models for cohesive-frictional materials, a transformed stress based on the criterion is proposed, which is determined by making the criterion become a cone having the axis as the space diagonal in the transformed principal stress space. Furthermore, an elastoplastic model for geomaterials is presented, which takes the following three characteristics of goematerials into consideration. The first is the strength and deformation characteristics of geomaterials in three-dimensional stress; the second is the dilatancy characteristics of geomaterials; the third is the confining-pressure dependency of strength and deformation. The proposed model is capable of predicting the stress versus strain relations of geomaterials including cohesive-factional materials and granular materials in three-dimensional stress and a wide range of the c
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onfining pressure.
2. Application of the proposed model to numerical analysis of rock-fill dam. In order to apply the model to practical engineering by using FEM, the elastoplastic constitutive tensor is derived. An example of the existing rock-fill dam was selected to demonstrate the usefiilness of the model in the finite element analysis for predicting deformation of geomaterials under embankment loading. The settlement and the lateral displacement of foundation computed by the proposed model fairly agree with the observed results.
3. A three-dimensional elasto-plastic model for unsaturated soil. Using a transformed stress tensor based on the Extended SMP criterion, an elasto-plastic model was proposed for unsaturated soil. The influences of suction on the mechanical behavior ofunsaturated soil are taken into account in the model by using a parameter named as suction stress, which is added to net stress to form an effective stress, and associating a yield stress and model parameters with it. The proposed model needs few material parameters, which can be easily determined from the results of the ordinary tests, for example, oedometer and direct shear tests or biaxial test. It can predict the stress-strain-strength behavior of unsaturated soil under the conditions of three-dimensional stresses and constant or variable suction. A considerable number of triaxial compression and extension tests on unsaturated compacted clay were performed by using a suction controllable triaxial apparatus, to measure the stress-strain behavior under different stress paths with constant and decreasing suction. The prediction by the proposed model shows good agreement with the measured behavior of unsaturated soil not only in triaxial compression but also in triaxial extension under the conditions of constant suction and reduction in suction, which may induce an irrecoverable volumetric compression (collapse). Less
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