三轴加卸载下混凝土损伤特性及抗渗性能研究

Study on damage characteristics and impermeability of concrete under triaxialloading and unloading

地下跨江隧道混凝土衬砌在其服役期间会承受车辆等循环荷载的作用,导致混凝土衬砌产生不同程度的力学损伤,从而弱化了混凝土衬砌的抗渗性能。为此,针对高性能混凝土开展了三轴循环加卸载试验,研究了三轴循环加卸载全过程中高性能混凝土变形及力学特性、力学损伤特性及抗渗性能演化规律及机制。研究结果表明:①循环加卸载引起的混凝土力学损伤随循环次数的增加而逐渐增大,并与塑性应变呈现出良好的指数形式演化关系。②循环加卸载下混凝土渗透率演化规律可分为稳定期、迅速增长期、缓慢变化期3个阶段,其中,围压水平对渗透率演化的第一阶段和第三阶段有明显的影响。③Logistic经验模型可以很好地描述混凝土渗透率与力学损伤之间呈现出的3阶段演化规律。研究结果有助于了解三轴循环加卸载全过程中高性能混凝土抗渗性能及力学损伤演化机制,同时可为确定不同应力水平下混凝土结构物力学损伤及抗渗性能提供参考。

The concrete linings of underground river-crossing tunnels bear the cyclic load of vehicles during its service,which leads to different degrees of mechanical damage in concrete linings,thus weakens the impermeability of concrete lining.Therefore,the triaxial cyclic loading and unloading test was carried out for high performance concrete.The evolution of the deformation and mechanical properties,mechanical damage characteristics and impermeability of high performance concrete in the whole process of triaxial cyclic loading and unloading were studied.The results show that:①The mechanical damages of concrete caused by cyclic loading and unloading increase with the increase of cycles,and it shows a good exponential evolution relationship with the plastic strain.②The evolution of concrete permeability under cyclic loading and unloading can be divided into three stages:stable period,rapid growth period and slow change period.Among them,the confining pressure level has an obvious influence on the first stage and the third stage.③The three-stage evolution law between permeability and mechanical damage of concrete can be well described by Logistic empirical model,and both of them decrease with the augmenting of confining pressure.The research results are helpful to understanding the evolution mechanism of impermeability and mechanical damage of high performance concrete in the whole process of triaxial cyclic loading and unloading,and provide a reference for determining the mechanical damage and impermeability of concrete structures under different stress levels.