Influence Of Stress Path On Strength And Deformation And Pore Pressure Of Saturated Loess

The loess is mainly distributed in arid and semi-arid areas in central & western China, which is a typical structured soil. Its characteristic presents considerably the distributional characteristics of the soil particle which is different in sizes and content in the soil: their properties will be significantly different when the volume of pores in soil is equal with uniform small pores and mainly uneven large pores separately. A lot of research results present that the strength and distortion characteristics of soil are not only related to the stress state, but also influenced by generation, stress history, stress path, and other factors. The peculiar impracticable structure with macropore of loess makes the mechanical characteristics of loess greatly different under different stress path.Based on the analysis and summary of the former mechanical characteristics of loess, this paper takes the loess in Yangling Shaanxi area as research subject, carries out experiments with the selected loess samples of different dry density, consolidation conditions and stress path, compares and analyses all the affecting factors, especially the influence of factors ,such as consolidation conditions, loading method, and dry density,etc. on the mechanical properties and characteristics of pore pressure quantitatively and qualitatively .Moreover this paper studies total stress path and the effective stress path of saturated loess under different stress path. Finally proposes an equation of pore water pressure of saturated reshaped loess through the normalized pore pressure curve.The results show that stress-strain curves of saturated reshaped loess presents weak-hardening and principal stress difference increases with the increased consolidation pressure and the dry density under the same stress path through carrying out triaxial compression tests on saturated reshaped loess under different consolidation conditions and different stress paths (values for k are different). The influence of the stress paths on curves is more complex, which is different because of different values for k: When k> 0, the principal stress difference increases with decreased values for k, and k≤0 vice versa. Through the triaxial tests under different stress paths, it is known that pore pressure-strain curves of saturated reshaped soil are different separately with the different dry density, confining pressure and values for k. The pore pressure increases with the increased initial confining pressure under the same stress path. For the loess with different dry density, the effects of pore pressure are different separately when the sign of k is not in the same time. When k> 0, the larger the dry density is, the smaller k value is, and the greater the pore pressure of soil is. When k≤0, the effect of dry density on the pore pressure is relatively larger. The greater the dry density is, the smaller the value for k is, but soil pore pressure decreases; Comparison, the opposite occurred. The stress path and the effective stress path of soil based on experimental data presents that saturated loess with different dry density represents different separately under different consolidation pressure and the value for k. Moreover this paper also proposes pore water pressure curves normalized byσc. Its normalization is good, and is approximately fitted with a line. The parameters of line are different with the different stress path. The pore water pressure of saturated soil is basically caused by increment of the average principal stress and shear stress. And a equation of pore water pressure of the saturated reshaped loess is also drawn in this paper.