Study on strength and deformation characteristics of loess under nonlinear continuous unloading path
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Abstract:
The strength and deformation characteristics of loess under vertical unloading state have important theoretical significance for the study of slope instability in excavation area. From the perspective of engineering application, this paper improves the indoor direct shear apparatus based on Bernoulli equation, which uses water tank instead of weight to load and unload. The strength and deformation characteristics of remolded loess under nonlinear continuous unloading path are studied. The results show that the shear stress-displacement curve of the soil under the nonlinear continuous unloading path is different from that under the non-loading state, which is reflected in that the shear stress in the process of nonlinear continuous unloading is related not only to the shear displacement but also to the unloading ratio (R). In the shear stress (τ)-shear displacement (δ) space, under the same initial consolidation pressure, the shear stress-shear displacement curve of the sample is basically coincident with that without unloading when the unloading ratio (R) is small. When the unloading ratio (R) increases to a certain value, the shear stress-shear displacement curve appears softening, and the greater the unloading rate, the more obvious the softening is. At the same time, under nonlinear continuous unloading conditions, the shear strength is related to the initial consolidation pressure. With the increase of the initial consolidation pressure, the over-consolidation effect caused by unloading increases significantly. Based on Mohr-Coulumb strength criterion, the mathematical model of exponential decay can be used to describe the evolution of the strength parameters in the process of nonlinear continuous unloading.
