饱和开裂混凝土氯离子二维扩散的数值模拟

Numerical Simulation of Two-Dimensional Chloride Diffusion in Saturated and Cracked Concrete

对饱和状态下开裂混凝土裂缝附近区域氯离子的二维扩散进行了数值模拟.以Fick第二扩散定律(FSDL)修正模型及二维氯离子扩散理论模型为基础,建立了开裂混凝土氯离子扩散有限差分数值模型,并编制了计算程序.通过与试验结果的对比,证明了模型的有效性.利用建立的模型分析了裂缝、水胶比、衰减系数和时间因素对氯离子扩散的影响,提出了裂缝影响区的概念.在裂缝影响区内,氯离子呈二维扩散,在其外,氯离子呈一维扩散;在时间上,氯离子扩散存在快速期、过渡期与缓慢期;从长期来看,裂缝深度对氯离子的扩散影响显著,而裂缝宽度几乎对其无影响.

Numerical simulation of two-dimensional chloride diffusion is carried out in the crack area of saturated and cracked concrete. Based on correction model of Fick＇s second law and two-dimensional model of chloride diffusion,a finite differential model for chloride diffusion in cracked concrete is established. A calculation program is coded and turns out to be effective through the comparison with experimental results. The effect of crack,water-binder ratio,attenuation coefficient and time on chloride diffusion is analyzed through the established numerical model. The concept of crack-affected zone is put forward,within which,chloride diffuses in two-dimensional way,and beyond which,chloride diffuses in one-dimensional way. There are three stages in chloride diffusion,including rapid diffusion period,transitional period and slow diffusion period. The simulation results show that crack depth has significant effect on chloride diffusion in the long-term situation,while crack width nearly makes no difference.