低温冻结岩体单裂隙冻胀力与数值计算研究

寒区岩体工程中含水裂隙随温度降低会发生水冰相变产生冻胀力,内部冻胀力会驱动裂隙发生Ⅰ型扩展,从单裂隙入手,基于弹性力学、渗流力学和相变理论,建立了考虑水分迁移下的冻胀力求解模型,冻胀力不仅随着水分迁移通量的增加而迅速降低,还与岩石基质以及冰体的力学强度参数有关。采用等效热膨胀系数法对低温裂隙中水冰相变下热力耦合应力场进行了模拟分析,并与理论模型计算结果进行对比,结果表明冻胀力解析解与数值解吻合较好;结合断裂力学,利用应力外推法得出了裂隙尖端应力强度因子的数值解,与理论解析解及半解析解也具有较好的一致性,最后通过实例验证了等效热膨胀系数法的可靠性,可为研究低温裂隙岩体冻融损伤与裂隙扩展研究提供参考。

Numerical and theoretical studies on frost heaving pressure in a single fracture of frozen rock mass under low temperature

The frost heaving pressure is induced by water-ice phase transition in water-bearing crack for rock mass at low temperature, which may cause modeⅠcrack propagation. Based on the elastic mechanics, seepage mechanics and phase transition theory, an analytical model for frost heaving pressure in a single fracture is established considering moisture migration. This pressure not only reduces rapidly with the increase of moisture migration flux, but also changes with the mechanical parameters of rock and ice. The crack-tip stress fields under coupled thermal-mechanical condition are simulated by the method of equivalent coefficient of thermal expansion considering water-ice phase transition in crack under low temperature. The numerical solutions of frost heaving pressure and crack-tip stresses are compared with the calculated values from theoretical model. The results show that the analytical solutions are in good agreement with the numerical ones. Then the based on with the fracture mechanics, by using the stress extrapolation method, the numerical solutions of stress intensity factor are obtained, which also coincide well with the analytical and semi-analytical ones. Finally, the numerical simulation method of using the equivalent coefficient of thermal expansion is validated by an example. This study can be a reference for further studies on the damage mechanism and frost propagation of fractured rock mass under freeze-thaw.