开裂混凝土衬砌的渗透模型

Permeability Model of Cracked Tunnel Lining Concrete

混凝土的渗透性在控制混凝土的质量及混凝土结构的行为上起着关键性作用,裂缝的存在为水体及其他有损于混凝土结构耐久性的物质提供了入侵通道,这样,开裂混凝土的渗透性就直接影响混凝土的长期耐久性。文章从开裂混凝土衬砌的水体渗透特性出发,分析混凝土在裂缝开展过程中的渗透动态特征,在裂缝开度恒定时的稳定渗流特性。给出拉伸应力作用下混凝土的渗透模型,包括两部分,第一部分为裂缝开度与拉应力的关系模型,认为两者间存在着固定的线性关系;第二部分为裂缝开度与渗透性关系模型,认为在裂缝开度小于80μm时,其渗透规律与其他阶段有着显著的差别;从而推求混凝土拉应力与渗透性的直接关系。最后,通过成熟的试验数据对提出的开裂混凝土的渗透模型进行了实际验证,结果较为吻合。

Permeability of concrete plays a critical role in controlling the properties of concrete and the performance of concrete structures. Existing cracks offer penetration paths for water and any other substances that will cause deterioration to concrete structures. Permeability of cracked concrete influences the durability of concrete directly. Water permeability of cracked concrete is mainly discussed in this paper, the steady water permeability at the stable COD stage and the dynamic permeability at the cracking stage are discussed also. A permeability model of cracked concrete under tension is presented and it includes the relationship between Crack Opening Displacement （COD） and tension stresses and the relationship between COD and permeability coefficients. It is revealed that the relationship between COD and tension stresses remains linear, and the permeability characteristics of the concrete which has a COD width under 80 μm are obviously different as compared with the other COD stages. Hence the relationship of permeability coefficients to tension stresses is derived. Finally, the published trail test data is used to verify the permeability model mentioned. The verification results give good agreement between the model and the test data. The permeability model of cracked concrete discussed in this paper may be used in concrete construction directly.