裂隙岩体冻胀力演化解析模型与裂纹亚临界扩展分析

Analytical model of frost heave force evolution in fractured rock mass and analysis of subcritical crack propagation

为揭示寒区边坡岩体裂隙扩展后冻胀力的演化机制与规律,开展裂隙岩体冻胀力演化解析模型研究具有重要意义。结合弹性力学、复变函数、弹塑性断裂力学理论推导裂隙岩体冻胀力演化解析模型。分析裂隙尺寸、冻结速率、水分迁移率等因素对失稳断裂前冻胀力演化过程的影响,在对失稳断裂后冻胀力进行估算的基础上研究冻胀力演化机制与全过程特征,并将解析计算结果与试验测试结果进行对比分析。结果表明:(1)所提出的冻胀力解析模型可以计算裂隙扩展后的冻胀力演化过程,合理解释冻胀力波动性变化机制,在一定程度上可为裂隙抗冻性评价提供依据;(2)断裂失稳前,最大冻胀力随裂隙长度的增加而减小,达到最大冻胀力所需时间随裂隙宽度增加而增加;冻结速率增加时会出现最大冻胀力减小;水分迁移率增加时,断裂失稳前的最大冻胀力增加,达到最大冻胀力所需时间也增加;(3)裂纹亚临界扩展与断裂失稳会引起冻胀力变化,裂隙冻胀力演化过程具有波动性变化特征;当冻结过程不发生失稳断裂时,冻胀力呈现波动上升的特征;当冻结过程中存在断裂失稳时,冻胀力呈现先增加后减小的特征。

The frost heave force is an important cause of rock mass failure in the cold region.The traditional analytical model cannot calculate the frost heave force after crack propagation.Considering the influence of crack propagation,it is of great significance to establish an analytical model of frost heave force in fractured rock mass.In this paper,an analytical model of frost heave force evolution in fractured rock mass is derived based on the theory of elastic mechanics,complex variable function and elastic-plastic fracture mechanics.The effects of crack size,freezing rate,water mobility and other factors on the evolution of frost heave force before fracture instability were analyzed.Combined with the estimation of frost heave force after fracture instability,the evolution mechanism and the whole process characteristics of frost heave force were studied.The analytical calculation results were compared with the experimental results.The results show that:(1)The analytical model of frost heave force proposed in this paper can calculate the frost heave force after crack propagation,rationally explain the mechanism of frost heave force fluctuation,and provide a basis for the evaluation of frost resistance of cracks to a certain extent.(2)Before fracture instability,the maximum frost heave force decreases with the increase of fracture length,and the time required to reach the maximum frost heave force increases with the increase of crack width.The maximum frost heave force may decrease with the increase of freezing rate.With the increase of water mobility,the maximum frost heaving force before fracture instability increases,and the time required to reach the maximum frost heave force also increases.(3)The variation of frost heave force can be caused by subcritical crack propagation and instability fracture,and the evolution of frost heave force in cracks is characterized by fluctuation.When there is no instability fracture in the freezing process,the frost heave force fluctuates and increases.When there is instability fracture in the freezing process,the frost heave force first increases and then decreases.