Abstract:

Based on the high and steep slope project of an open-pit slope in cold region, 30 freeze-thaw cycle tests were conducted. The temperature range was set from -30 ℃ to 20 ℃.Subsequently uniaxial variable upper limit cyclic loading-unloading tests as well as synchronous acoustic emission monitoring tests were carried out. Slope rock masses with fracture angles of 0, 25, 50 and 75° were used in potential slip zone. The freezing-dynamic (freeze-thaw cycles and cyclic loading and unloading) combined damage and deterioration characteristics and mechanical properties of slope rock mass were explored in macro and mesoscopic scales. Furthermore, the crack initiation, propagation and failure modes of fractured rock mass were studied. The results show that as the fracture angle increases, the freeze-thaw damage effect on the fractured rock mass gradually decreases, while the compressive strength and elastic modulus exhibit a linear increasing trend with the maximum deformation of fatigue resistance of 0.558 3% at 75°. Compared to ordinary uniaxial loading, the compressive strength of fractured rock masses under cyclic loading and unloading condition decreases by 5.6 MPa. The Felicity ratios of different rock masses decrease with the increase of cyclic levels, and the Felicity ratios at the final failure stage were all below 0.7. As the cyclic loading level increases, the increment of cumulative dissipated energy decreases with the increase of fracture angle. The rock masses mainly exhibit tensile failure, but when the angles exceeded 25°, there is a trend of transformation from tensile and mixed failure to shear failure.

Key words: cold regional open pit, slope rock mass, fractured rock mass, freeze-thaw cycles, freezing-dynamic combined, damage and deterioration, acoustic emission