Papers by Author: Bo Han

Abstract: This paper mainly concerns the non-linear strength characteristics of the loess. A series of consolidated undrained triaxial tests(CU test) and consolidated drained triaxial tests (CD test) of normal consolidation and over consolidation loess specimens are carried out by using the normal triaxial apparatus of strain control. The stress-strain relationship curves and strength characteristics of loess are investigated and analyzed. The results show that the stress-strain relationship obtained by CU tests appears strain softening, while the stress-strain relationship for CD tests appears strain hardening. Different failure modes have different stress-strain relationships. Furthermore, the results also show that the peak strength, residual strength and residual strength ratio change with the different confining pressure. Based on the triaxial shear tests of normal consolidated loess, the influences of over-consolidated loess on the stress-strain relationships and strength characteristic are discussed. Several conclusions obtained in this paper can be referenced for the loess experimental study.

Abstract: This paper is mainly concerned with the saturated-unsaturated seepage analysis of earth dams based on unsaturated soil theory and the stability analysis of earth dams based on conception of slices. At first, beginning basic seepage theory, thesis introduce the saturated-unsaturated and steady-unsteady seepage differential equation of porous media and the FEM regarding hydraulic pressure head as basic unknown quantity. Then considering the shear strength of unsaturated soil, the method of analysis of general limit equilibrium has been approved and it can be used in the analysis of the stability of saturated-unsaturated slopes. Through an example it is respectively discussed effects of seepage flow when water head is changed in earth dam and the effects of percolation in the stability of the earth dam slope. Some helpful conclusions are gained. This can be making the best of the tow methods and the results can be used in engineering for reference.

Abstract: This paper is mainly concerned with the saturated-unsaturated seepage analysis of embankment dams based on unsaturated soil theory and the reliability analysis of embankment dam based on conception of reliability. The transient seepage due to change of the water level is calculated using the finite element method based on unifying saturated-unsaturated seepage governing equations. The transient pore water pressures are then used for stability analyses of embankment dam considering the effects of suction on shear strength of unsaturated soils. Meanwhile, combined with reliability computation, the Monte-Carlo stimulation method is used to calculate the corresponding reliability index dealing with the stochastic features of soil parameters. The reliability of different water level condition of embankment dams has been analyzed. The effects of different reservoir water level drawdown and raise speeds on reliability of embankment dam are discussed.