非饱和开裂混凝土中水分运移研究

Water Transport in Cracked Unsaturated Concrete

关键词:  非饱和混凝土  裂缝  水分运移  渗水深度

Key words:  unsaturated concrete  crack  water transport  penetration depth

摘要:

根据双重孔隙介质模型将开裂混凝土视为由完好混凝土和裂缝组成的复合孔隙材料，基于非饱和混凝土的水分运动方程和裂隙渗流的立方定律提出非饱和开裂混凝土中的水分运动方程，同时采用渗水装置对预制裂缝混凝土试块进行渗水试验，研究混凝土初始饱和度、水胶比和裂缝宽度对渗水深度的影响；采用TOUGH 2软件数值分析开裂混凝土中饱和度和水分流速的变化，根据平均流速计算渗水深度并与试验结果比较.研究发现：混凝土初始饱和度越小、裂缝宽度越大，则渗水深度越大，且渗水深度增长先快后慢，反映了混凝土基质势是开裂混凝土中水分运移的驱动因素；裂缝宽度与混凝土渗透性正相关；水分入渗开裂混凝土后流速差和平均流速随时间延长逐渐降低；采用平均流速计算的渗水深度能更好地反映渗水试验中渗水深度的变化趋势.

Abstract:

According to double porosity medium model, cracked concrete is regarded as a composite porous material composed of intact concrete and crack. Based on the equation of water transport in unsaturated concrete and cubic law for fracture flow, the equation of water transport in cracked unsaturated concrete was proposed. Penetration tests on prefabricated cracked concrete blocks were conducted with infiltration device. The influence of initial saturation degree of concrete, water binder ratio and crack width on penetration depth was studied. TOUGH 2software was applied to numerically analyze the change of water saturation and flow velocity in cracked concrete, after that, penetration depth was calculated according to the average flow velocity and compared with the test results. The results show that the less the initial saturation degree of concrete and the greater the crack width, the greater the penetration depth. Moreover the penetration depth inereases fast at first and then slows down. It reflects that matric potential is driven force of water transport in cracked concrete, and crack width is positively correlated with concrete permeability. Both the difference of flow velocity and the average flow velocity go down with increasing time after water infiltrating in cracked concrete. The penetration depth calculated by average flow velocity can better reflect the trend of penetration tests.