Frost heaving and frost cracking of elliptical cavities (fractures) in low-permeability rock

A 9% expansion of freezing water in the elliptical cavities (fractures) of rock leads to frost heaving pressure and thermal stress, which are the main cause of the freeze-thaw damage of a fractured rock mass. Considering the influence of thermal stress and water flow in elliptical cavities (fractures), a mathematical model for predicting frost heaving pressure in the elliptical cavities (fractures) of rock is presented, assuming that the rock matrix is impermeable. The maximum tensile stress and frost cracking angle on the elliptical cavity are deduced and the critical condition for simplifying the elliptical cavity to planar fracture is suggested based on the method of complex variable function and elastic mechanics theory. Moreover, the effects of the main parameters on frost heaving pressure and frost-cracking conditions are determined to investigate the frost cracking of water-filled elliptical cavities (fractures). The flow flux of water, the aspect ratios of cavities (fractures) and the elastic moduli of rock have a great direct influence on the frost heaving pressure and cracking angle, whereas the dip angle of the cavity (fracture) and the thermal expansion coefficient of rock indirectly affect them by changing the thermal stress. It is suggested that the stress intensity factor is adopted to predict the frost propagation of planar elliptical cavities only if the aspect ratio exceeds fifteen.