Shear Strength Behavior of Coarse-Grained Saline Soils after Freeze-Thaw

摘要

The bearing capacity of embankment filled by coarse-grained saline soils will be deteriorated after freeze-thaw, especially when shallow groundwater is included. Direct shear tests were carried out on coarse saline specimens that experienced freeze-thaw cycling. The shear strength of soil specimens at three densities strongly depends upon the normal stress when freeze-thaw is not involved, manifesting as a linear increase. Strength indexes such as cohesion and internal friction angle grow at higher dry densities while little change noted in the residual. The cohesion increases with salt content but lowers with freeze-thaw, especially in initial five cycles, beyond which it stabilizes. The internal friction angle is not associated with the above two factors. The stress-strain curves after freeze-thaw are all strain softening, especially at higher densities. The shear stress exhibits larger influence on particle crushing than freeze-thaw. The modified relative breakage index was calculated based on particle grading curves, and is negatively correlated with the cohesion. An empirical equation was proposed by fitting test data incorporating both salt content and freeze-thaw cycles. Comparisons prove that the calculated cohesion agrees well with the measured data.