Frost heaving pressure and characteristics of frost cracking in elliptical cavity (crack) of rock mass under coupled thermal-mechanical condition at low temperature

The frost heaving pressure is induced by water-ice phase transition in water-bearing cracks in addition to thermal stress at low temperature in rock engineering in cold regions. The freeze-thaw damage and cracking are caused by the combined action of frost heaving pressure with thermal stress. Considering the influence of thermal stress on elliptical cavity (crack), an analytical equation for the frost heaving pressure is deducted. Based on the maximum tensile-stress criterion, the maximum tensile stress and frost cracking angle on the elliptical cavity (crack) are derived. Besides, the critical condition for simplifying elliptical cavity to crack is also established under coupled thermo-mechanical condition at low temperature. Finally, the developed method for the equivalent thermal expansion coefficient is adopted to simulate the frost heaving pressure in crack and stress field at crack tip. The research results show that: (1) The maximum frost heaving pressure in the elliptical cavity is affected by the thermal expansion of rock, dip angle of crack, ratio of crack length to width χ and so on; (2) When χ≥10, the flat elliptical cavity can be simplified as the crack, and the frost cracking appears at the crack tip with obvious stress concentration; (3) The frost heaving pressure and stress field at crack tip can be well simulated by the developed method for the equivalent thermal expansion coefficient.