Ultrasonic time-frequency method to evaluate the deterioration properties of rock suffered from freeze-thaw weathering

Cyclic freeze-thaw (F-T) is a serious natural weathering mechanism for rock engineering and stone constrictions in cold regions. Considering the universality and destructiveness of rock F-T weathering, evaluation of rock deterioration is of vital importance. In this work, ultrasonic detections and mechanical experiments including uniaxial compression, splitting tension and angle-changed shear tests were carried out on red-sandstone specimens without and after different F-T cycles. Attenuation occurred to almost all of the indexes of red-sandstone after F-T weathering, including mechanical properties such as uniaxial compressive strength (UCS), deformation modulus (Ed), splitting tensile strength (STS), cohesion (C) and friction angle (ϕ), and ultrasonic properties such as the P-wave velocity (Vp), head-wave amplitude (Ah), centroid frequency (fc) and kurtosis of frequency spectrum (KFS). After 25 F-T cycles, the UCS, Ed, STS, C, ϕ, Vp, Ah, fc and KFS decreased by 42.5, 63.0, 87.3, 33.7, 22.6, 50.6, 24.6, 38.3 and 0.56%, respectively. With increasing number of F-T cycles, similar convergent decrease tendencies between the UCS, Ed, STS, C and the Vp, Ah, fc, KFS were found, confirming the effectiveness of the ultrasonic time-frequency method to estimate the deterioration of rock suffered from F-T weathering. Similar degradation behavior in ultrasonic time-frequency properties and in mechanical properties resulted from the microscopic damages of red-sandstone suffered from F-T weathering. An ultrasonic evaluation auxiliary graph is suggested as a convenient practical evaluation method in rock engineering.