裂隙岩体冻融损伤研究进展与思考

ADVANCE AND REVIEW ON FREEZING-THAWING DAMAGE OF FRACTURED ROCK

裂隙岩体具有不同于土体的结构和强度特征,现有冻土理论不能解决低温岩体裂隙冻胀开裂、扩展演化问题,冻融过程中水分迁移机制、冻胀力的量值与萌生消散机制以及裂隙冻融扩展演化机制等是研究裂隙岩体冻融损伤的关键问题。对裂隙岩体中的水分迁移机制研究应立足于微观尺度,从分凝冰理论入手,关注于未冻水膜的迁移机制。低温裂隙岩体冻融损伤程度受到裂隙中冻胀力大小控制,而冻胀力大小和裂隙冻融扩展机制与裂隙的空间位置形态、未冻水含量、冻结温度以及岩石的物理力学性质等因素有关。几十年来,对岩体冻融裂隙扩展的研究主要集中在理论模型探究、室内裂隙岩体冻融试验和现场监测分析3个方面,取得了丰硕的成果,但目前关于冻岩的研究还远未成熟,要深入揭示裂隙岩体冻融损伤演化机制,还应借助于室内试验从裂隙岩体冻融水分迁移机制入手,以探究冻胀力量值的求解方法为初步目标,进而结合岩体裂隙扩展准则研究冻胀力对岩体裂隙网络发展的影响。

The structure and strength of fractured rock mass are different from those of soil,so the existing theory for frozen soil is not applicable to the problems of crack initiation,propagation and network development in rock mass under low temperature. The moisture migration and the pressure due to frost heaving in freezing-thawing process and the crack propagation after freezing-thawing process have been the key issues. The research on the mechanism of moisture migration should be based on the micro-scale and more attentions should be focused on the flow characteristics of unfrozen water film considering ice segregation. The damage degree of fractured rock under freezing-thawing is directly affected by the frost heaving pressure. However,the frost heaving pressure and crack extension are affected by many factors,such as the crack shape and the spatial position,the unfrozen-water content,the freezing temperature and the rock properties. During the last several decades,the efforts have been focused on the investigation of the extension of frost cracks with theoretical analysis,laboratory tests and field monitoring. Although remarkable achievements have been obtained,research on freezing fractured rock at present is far from mature. In order to reveal the mechanism of damage development of fractured rock mass under freezing-thawing,future studies should be based on the investigation of water migration in fractured rock mass with laboratory tests and the establishment of calculation method of frost heaving pressure. Then,the influence of frost heaving pressure on the development of fracture network can be studied combined with the criterion of crack extension.