Papers by Keyword: Unsaturated Soil

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Authors: Jing Yu Chen, Ying Hai
Abstract: Generally the shear strength of saturated soils has been predicted by the Mohr-Coulomb theory. However, field data accumulated in the past have evidently shown that saturated conditions are actually never reached in arid and semi-arid regions. An analytical model is developed to predict shear strength of an unsaturated soil with respect with matric suction. The formulation takes into account the influence of the mean stress on soil water retention curves. The results of the model developed for predicting the shear strength are compared with available experimental results. The good agreement between the estimates and the experimental data indicates that the proposed equation is promising and reliable for estimating preliminary unsaturated shear strength parameters.
425
Authors: Yan Liu
Abstract: A constitutive model for unsaturated soils is developed. Based on the SFG approach, the deduced LC curve has a smooth transition from saturated state to unsaturated state. The yield stress does not increase with increasing suction monotonically, and thus could reproduce plastic volume change of a slurry soil caused by drying. The model takes account of the effect of saturation, lead to different yield surface for wetting and drying. Soils with same suction but different saturation can have different yield stress. The model is used to simulate exited test data and the predicted curves agree well with the data points.
11
Authors: Jian Jun Dong
Abstract: The strength and deformation behaviors of unsaturated soil can be approximately described by elasto-plastic constitutive model that was proved by abundance academic and test researches. The Barcelona elastic-plastic model is an excellent model that can simulate the strength and deformation of unsaturated soil. But their calculated result of shear strength is low. So an improved Barcelona model is settled by using drop-shaped shear yield surface and hardening theory of dual stress. The results show that the improved model can more accurately predict the strength and deformation behaviors of unsaturated soil under suction-controlled triaxial compression stress states.
2748
Authors: Li Wang, Cui Ran Liu
Abstract: There is suction in unsaturated soil. This is the most obvious difference between unsaturated soil and saturated soil. It is very difficult to measure it, so research has always been done without account of the influences of matric suction of unsaturated soil. In this paper, based on the test result of engineering characteristics of unsaturated soil from Yellow River Embankments, the stability of slope of Yellow River Embankments is analyzed using ultimate equilibrium method and the influencing rule of matric suction on slope is advanced.
3186
Authors: Fu Li Ma, Mei Wang, Jing Yang, Xiao Hong Bai
Abstract: This paper studies the microstructure of 16 group samples from three different sites of North-west region in P. R. China. Pictures of microstructure were processed with imaging processing program to acquire the geometer parameter and fractal dimension of pores. The range of pores’ fractal dimension is between 1.816~1.936. The pore distribution function of unsaturated soil is established based on fractal geometry theory. The pore water distribution of loess under natural moisture is analyzed. The relationships of collapsibility coefficient with fractal dimension and porosity of unsaturated pores are analyzed with the method of regression analysis. A larger fractal dimension represents a more complex pore-structure. The collapsibility coefficient of loess increases with the increase of fractal dimension and porosity of unsaturated pores.
435
Authors: Hu An Li, Qin Xiang Wang, Yong Xiang Yang, Ge He Zhu, Long Xin Wang, Zhan Yin Zhang
Abstract: Soil-water characteristic curve describes the relationship between suction and volumetric water content of unsaturated soils. Air-enter have great influence on the drying scanning curves while the starting points of the scanning curve were at the highly saturated range. Based on capillary hysteresis internal variable model and conventional soil-water characteristics theory of unsaturated soils, a modified model which can simulate soil-water characteristic relationship that could consider the influence of air-enter is proposed. The influence of the air-enter on the drying scanning curves while the starting points were at the highly saturated range could be considered while this model is used. Numerical calculations are carried out on several kinds of soils. The simulating results show that the modified model is able to simulate the drying scanning curves while the starting points of the scanning curve were at the highly saturated range better than the capillary hysteresis internal variable model does.
215
Authors: Jun Su Choi, Ki Il Song, Gye Chun Cho, Seok Won Lee
1653
Authors: Hao Feng Xu, Wen Jun Wang, Zhi Xiang Zha
Abstract: One-dimensional consolidation equation of unsaturated soils was derived in order to solve this special case of consolidation. The presented equation, not similar to Terzaghi’s equation, is a type of absolute nonlinear partial differential equation, and it was solved by finite difference method. An example was analyzed and the case of incompressible fluid consolidation was compared. Finally the experimental results from laboratory tests reported in the literature, was fitted by the presented equation, and the agreement was good. The results show that (1) the process of pore-air pressure dissipation is similar to that of pore-water pressure of saturated soils; (2) the compressibility of pore fluid is not an advantageous factor to quicken the consolidation; (3) the presented equation is effective to analyze the process of consolidation of unsaturated soils which consolidate mainly due to the dissipation of pore-air pressure.
160
Authors: Panich Voottipruex, Anuchit Uchaipichat, Ekachai Man Koksung
Abstract: This paper presents a variation of effective stress parameter with matric suction for unsaturated soils using a comprehensive data set of suctioned-controlled shear tests under drying and wetting processes. The effective stress parameter is determined by assuming that the slope of the critical state line in the plane of deviator stress against mean effective stress is independent of matric suction. This study shows a different in relationship between the effective stress parameter and matric suction for drying and wetting processes. The values of effective stress parameter obtained from the experiments were compared with those obtained from the expressions proposed in literature.
1093
Authors: Song Xu, Fu You Zhang, Jun Pin Yuan, Hong Wei Chen, Ming Gu
Abstract: Permeability of pore air is one of the main basic characters of unsaturated soil. Measuring it accurately is important in anti-seepage design. In this paper, a new kind of device was invented that could test permeability of pore air of unsaturated soil in situ quickly and accurately. With this apparatus, the relationship of air permeability coefficient with various dry densities and saturation of ground soils were obtained in a reservoir. Compared with routine indoor test, field test can decrease the disturbance to the soil and the result is more accurately.
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