Masato Bando

Modulus of deformation and its measuring technique in anisotropically consolidated cohesive soil

Supervisor Hirofumi TOYOTA

Strain appeared in real ground extends to dozens of % when considering failure state. On the other hand, deformation modulus and damping constant in small strain level of 10-6 to 10-3 are necessary for seismic response analysis or precise deformation analysis. In addition, it is known that the ground usually exists under not isotropic but anisotropic stress state.
Therefore, the modulus of deformation in small strain level was examined using anisotropically consolidated cohesive soil. The measuring technique of the deformation modulus was also discussed comparing the local strain measurement and the bender element method in this study.
The results obtained from the study are shown as follows:
1)It is proper for anisotropic consolidation that the axial strain rate is 0.005%/min and 24 hours, which corresponds to the 12t, is necessary after reaching final consolidation stress state.
2)One sinusoidal wave with 10, 15, 20 kHz frequency, which is also recommended in sandy soil, can be applied as the input wave condition in cohesive soil.
3)The modulus of deformation increases with consolidation time in spite of drainage and consolidation conditions. This effect appears more greatly in the local strain measurement than in the bender element method.
4)The secant Young's modulus and the elastic shear modulus become small as the K-value becomes large under constant p�f conditions. The influence of the K-value is small in the bender element method comparing with the local strain measurement.
5)When K-value is large, the elastic shear modulus obtained from the bender element method becomes larger than that from the local strain measurement.
�@For a future examination problem, more tests should be conducted under different effective confining stress to establish the measuring technique for deformation modulus.