The Mechanical Properties of Lean Clay Filler under Freeze-thaw and Thermostatic Curing Cycles in Loess Plateau

The subgrade filler weakens its mechanical property after suffering from freeze-thaw (F-T) cycles, which threatens the trains' operation safety. It is essential to study the filler's mechanical property's evolution with the F-T cycles and reveal the test factors' incidence on the mechanical parameters. This study conducted a series of unconsolidated and undrained (UU) triaxial shear tests in the F-T and thermostatic-curing (T-C) groups, considering the temperature, confining pressure, and cycle times. As the control group, the T-C group can more prominently reflect the F-T effects on the soil's mechanical parameters, including the stress-strain curve, shear strength, and strength index. A piecewise and linear function can fit internal friction angle or cohesion's change with cycle times, respectively. The fitting parameters reflect the T-C and F-T effects on soil's mechanical properties. The absolute degree of incidence reveals the correlation between mechanical parameters and test factors. The -15 degrees C has the most significant incidence than -5 degrees C and 20 degrees C in shear strength, while -5 degrees C has the most considerable incidence than -15 degrees C and 20 degrees C in friction angle or cohesion. The water distribution and volume expansion due to the F-T cycles are the main reasons determining mechanical properties' evolution with the cycle times in different negative temperatures.

Automated summary

This study investigates the mechanical properties of subgrade filler after freeze-thaw cycles and examines the influence of test factors. The results show that water distribution and volume expansion are the main factors affecting the mechanical properties during freeze-thaw cycles.