水压作用下硫酸盐在混凝土桩中的侵蚀分布规律

Distribution Behavior of Sulfate Erosion in Concrete Piles Under Water Pressure

摘要:

为模拟地下桩身混凝土硫酸盐侵蚀机理，考虑水压力对硫酸盐在混凝土桩中的侵蚀分布影响，基于达西定律，探讨渗流速度与水压力和时间的关系，建立了水压作用下的渗透深度计算模型.依据Fick第二定律，建立水压力作用下的硫酸盐在混凝土桩中的扩散侵蚀方程.采用分离变量、变量代换和积分变换得到对流侵蚀方程的解析解，以及水压影响范围外的扩散侵蚀方程解析解.同时，分析了水压力对渗透深度影响的敏感性，以及水压力、水灰比、渗透深度，裂缝宽度对桩中硫酸盐质量分数分布的影响.结果表明，随着水压力的增大，渗透深度显著增大；水压力作用下，混凝土桩中的硫酸盐质量分数分布明显高于无水压作用时的硫酸盐质量分数分布；水灰比、渗透深度、裂缝宽度对硫酸盐在混凝土桩中的质量分数分布影响显著.

Abstract:

To simulate the degradation mechanism of concrete piles underground exposed to sulfate attack, the effect of water pressure on sulfate erosion distribution in concrete piles was considered. Based on Darcy law, the relationship between flow velocity and water pressure and time was established. Furthermore, the penetration depth calculation model of water pressure was established. Considering the existing water pressure, a diffusion erosion equation of sulfate in concrete piles was established based on Fick’s second law. Via the method of separation of variables, variable substitution and integral transformation, the analytical solution of the convection erosion equation and diffusion erosion equation without the influence of water pressure were obtained. At the same time, the sensitivity of water pressure to penetration depth was analyzed. The effect of water pressure, water cement ratio, seepage depth, and crack width on the sulfate concentration distribution was analyzed. The results show that with the water pressure increasing the penetration depth increases significantly. Under water pressure, the concentration of sulfate in concrete is significantly higher than that of sulfate when there is no water pressure. The watercement ratio, penetration depth and the crack width have significant effects on the concentration distribution of sulfates in concrete.