Research on crack development and strength attenuation of expansive soil under wet-dry freeze-thaw effect

Abstract

[Objective] Shallow instability of expansive soil water conveyance channel is easy to occur under the action of dry and wet freeze-thaw cycles in cold and arid regions, which is the key problem for the safe operation of expansive soil water conveyance channel. [Methods] Taking the expansive soil of the North bank of the Ili River in northern Xinjiang as the research object, the simulation of wet-dry freeze-thaw cycle effect and low stress direct shear test were carried out on the sample. The crack parameters of the expansive soil during the test were analyzed, and the changing rules of the crack parameters and the strength characteristics of the expansive soil were discussed. The influence of crack parameters on the strength characteristics of the expansive soil was studied. [Results] The result show that the fracture parameters and cohesion decay rate of the expanded soil sample will increase with the decrease of wet-dry freeze-thaw effect and the density degree, and the mechanical properties will further deteriorate. Under the wet-dry freeze-thaw cycle effect, the crack structure of expansive soil experienced rapid cracking, steady expansion and steady development, corresponding to the rapid decay, slow decay and steady decay stages of cohesion, indicating that the shear strength has a certain correlation with the fracture parameters, and the change trend of the connectivity coefficient is most closely related to the decay of cohesion. [Conclusion] The correlation degree ranges from 0.730 to 0.878 and the weight ranges from 0.260 to 0.300, which can quantitatively characterize the fracture development characteristics and strength attenuation rule of expansive soil under the effect of wet-dry freeze-thaw cycle.

Keywords

expansive soil / wet-dry freeze-thaw cycle / fracture parameter / the intensity attenuation / degree of association / deformation