Abstract
It is particularly important to study the strength of unsaturated loess, and its accurate determination is crucial to the stability analysis of soil slope and foundation and calculation of earth pressure. In order to reveal the control mechanism of physical parameters on the shear strength of unsaturated loess, the intact and remolded loess were used as the research object; sandy silt, quartz flour, and quartz sand were used as contrast; the systematic direct shear tests of unsaturated loess, sandy silt, and quartz sand under different conditions of water content, dry density, and clay content were carried out. The results show that the cohesion, internal friction angle, and shear strength of unsaturated loess piecewise functionally decrease with the increase of water content, its shear strength increases linearly with the increase of dry density, and its internal friction angle shows an upward quadratic function relation with the increase of clay content. The law results of comparing sandy silt, quartz flour, and quartz sand with loess considering water content and dry density are the same; therefore, the equation of shear strength of unsaturated loess is proposed for practical engineering reference, and by the first derivative analysis of the equation, it is feasible to determine the control proportion of the three parameters on the shear strength of unsaturated loess. A stage-like difference between the three control proportions is observed, depending on the combination variations of water content and clay content.
Highlights
Loess is the sediments formed in the quaternary period
In this paper, unsaturated loess including intact loess and remolded loess is taken as the research object, and sandy silt, quartz flour, and quartz sand are taken as a comparative test; that is, the control law of three parameters on the shear strength of unsaturated loess is analyzed through controlling variable method and the control proportion of each parameter is determined
With the increase of water content, the internal friction angle of two kinds of loess samples has a decreasing trend; when the water content grows more than 10%, its rate of reduction will slow down
Summary
Loess is the sediments formed in the quaternary period. China is the country with the most perfect loess topographic development, the most extensive distribution, and the largest area in the world. From the current research results, it is seldom to study comprehensively the influence of different physical parameters on the shear strength of unsaturated loess. The author intends to study this problem from a simple and fundamental perspective, that is, starting from the idea of “science advocates simplicity” [30], instead of considering how the internal forces share the total shear strength, only considering the control effect of the physical properties parameters of the soil on the shear strength; it is necessary to analyze the control factors and control mechanism of shear strength of unsaturated loess. In this paper, unsaturated loess including intact loess and remolded loess is taken as the research object, and sandy silt, quartz flour, and quartz sand are taken as a comparative test; that is, the control law of three parameters on the shear strength of unsaturated loess is analyzed through controlling variable method and the control proportion of each parameter is determined
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