Abstract: By using the method of loading and unloading at the relative lossless low-stress level without causing a large additional damage, freeze-thaw cycle tests were conducted by considering the time effect. In the case of limited experimental cost, the number of rock samples required can be drastically reduced. Compared with the conventional test method, this novel procedure can obtain more efficient data from the limited data of certain rock samples without subjectively screening testing data due to the discreteness of samples. With the increase of the number of freeze-thaw cycles, the pore and micro-cracks on the surface of rock specimen are expanded and a softening layer is formed. The crack is deepened and the degree of particle shedding is aggravated. The occurrence of erosion makes moisture moving to the inside of rock specimen, and the degree of freezing and thawing damage gradually deepens from inside to outside. The development of titration technology calibrates the gradual damage. We further analyzed the dynamic response of rock samples under different upper limit stress cycles with different freezing and thawing cycles. The results show that the damping ratio, the damping coefficient and the dynamic Poisson’s ratio are linearly increasing with the number of the freeze-thaw cycles. The dynamic elastic modulus decreases linearly with the number of the freeze-thaw cycle, but increases linearly with the amplitude stress. However, the damping ratio and dynamic Poisson’s ratio decrease linearly with the amplitude stress. The quantitative relationships are established between the damping ratio, the dynamic Poisson’s ratio, the damping coefficient and the dynamic elastic modulus. One known parameter can be used to predict the changing pattern of other parameters. Under the limited testing conditions and times, the numbers of parameters to be tested can be effectively reduced. If the amplitude stress is greater, the response of elastic deformation is more rapid, the irreversible deformation is smaller, and the energy absorbed is less. With the increase of the number of freeze-thaw cycles, the slope loading section of rock specimen gradually becomes longer, and the slope of the stress-strain curve becomes smaller before loading and unloading. The axial strain of rock specimen is linearly related to the number of freezing and thawing cycles after loading and unloading when the stress limit is reached for the first time in each cycle. It indicates that the porosity of rock specimen under the freeze-thaw cycle is gradually increased while the degree of density reduces. Rock specimens tend to soften gradually. When the amplitude stress is high, the plastic accumulation of rock specimen expands in the exponential relationship with the number of freeze-thaw cycles. However, when the amplitude stress is low, the plastic accumulation increases in a linear relationship with the number of freezing and thawing cycles. It is shown that the amplitude stress is significant to accelerate deterioration.

Key words: freezing-thawing cycle, damping ratio, damping coefficient, dynamic elastic modulus, dynamic Poisson’s ratio, linear relationship