Experimental study on the freezing-thawing behavior of compacted earth

Most of compacted earthen constructions are located at temporary and seasonal frozen areas, consequently exposed to repeated freezing-thawing (F-T) environment induced by significant temperature fluctuations. The F -T cycles can cause severe damage to the compacted earthen materials and reduce the structure's durability. In this paper, a series F-T tests were performed in order to study the damage mechanism of the compacted earthen materials subjected to F-T cycles. The experiments were carried out under two confining pressures (sigma c = 0 kPa and 50 kPa) and three freezing temperatures (TF =-5 degrees C,-8 degrees C and-13 degrees C), with a thawing temperature of TT = 9 degrees C. Evolution of elastic moduli and accumulation of irreversible strain at the end of each F-T processes were analyzed through cyclic loading-unloading tests under undrained condition. Results indicate that each F-T cycle could be characterized by main six stages, whose physical meaning has been explained through a thermodynamic approach. With increasing number of F-T cycles, a growth of the Young's modulus was observed when the material was in a frozen state, and the opposite was found for the thawed state. This may be explained by an increase in macro-porosity as F-T cycles progress, which would be in line with the accumulation of residual deformation and the increase of freezing and thawing temperatures. The applied confining pressure was eventually found to provide a positive resistance against permanent deformation. This discovery can provide experimental support to the safety design of earthen wall situated in cold regions.

Automated summary

This paper investigates the damage mechanism of compacted earthen materials subjected to freezing-thawing cycles. The study finds that with an increase in freezing-thawing cycles, the Young's modulus of the material increases in the frozen state and decreases in the thawed state. This can be attributed to the increase in macro-porosity, accumulation of residual deformation, and higher freezing and thawing temperatures. The applied confining pressure provides resistance against permanent deformation.