非饱和土在直流电场作用下水分分布研究

发布时间：2018-10-25 12:28

【摘要】：非饱和土中水分的迁移主要是在基质势和重力势的共同驱动下产生的。受毛细上升作用的影响,潮湿土遗址中发生水分运移及含水率波动,导致一系列干缩开裂、盐害等问题,促进土遗址的劣化。本论文研究直流电场控制毛细水上升的学术机理,探讨向土体施加直流电场抑制潮湿土遗址中毛细水上升的可行性。本论文从非饱和土中能量状态分析出发,基于非饱和达西定律、欧姆定律、电荷守恒定律以及质量守恒定律,建立了描述非饱和土在直流电场作用下的水分分布的理论模型,并具体讨论了模型中涉所及的参数(如土体电导率、基质吸力以及非饱和渗透系数)与含水率的关系。利用室内的直流电场抑制毛细水上升试验数据,检验了直流电场作用下的水分分布理论模型的可靠性。测定土水特征曲线、土体的非饱和渗透系数,获得理论模型所包含的参数;以具体试验情况为基础,设定初始条件和边界条件,实现理论计算结果与试验结果的对比。本论文阐述了毛细水与土遗址劣化的关系,分析了施加直流电场抑制毛细水上升进而保护土遗址的原理。研究认为,土遗址的劣化,不是水分本身造成的,而是在毛细水作用下含水率的变化及盐分的运移造成的。施加直流电场,能够通过电势来削弱基质势引起的毛细水迁移问题。研究发现,直流电场作用下的水分分布的理论模型,理论计算结果与试验结果吻合良好,能够定量地描述直流电场对毛细水运移的影响。研究结果表明,直流电场通过抑制非饱和土中毛细水运移,能够有效减少遗址土中水分波动,进而减少遗址土湿胀-干缩和盐分反复溶解-结晶,达到保护土遗址的目的。
[Abstract]:The migration of water in unsaturated soil is mainly driven by the matrix potential and gravity potential. Under the influence of capillary rising, moisture migration and water content fluctuation occur in moist soil sites, which lead to a series of problems such as dry shrinkage, cracking, salt damage, and promote the deterioration of soil sites. In this paper, the academic mechanism of direct current field controlling capillary water rise is studied, and the feasibility of restraining capillary water rising in moist soil site by applying direct current field to soil is discussed. Based on the analysis of the energy state in unsaturated soil, based on the unsaturated Darcy law, Ohm law, charge conservation law and mass conservation law, a theoretical model is established to describe the water distribution of unsaturated soil under the action of DC electric field. The relationship between soil conductivity, matrix suction and unsaturated permeability coefficient is discussed in detail. The reliability of the theoretical model of water distribution under the action of DC electric field is tested by using the experimental data of the indoor DC field to suppress the rise of capillary water. The characteristic curves of soil and water, the unsaturated permeability coefficient of soil are measured, and the parameters contained in the theoretical model are obtained, and the initial and boundary conditions are set on the basis of specific test cases, and the comparison between the theoretical calculation results and the experimental results is realized. In this paper, the relationship between capillary water and soil site deterioration is discussed, and the principle of applying direct current field to restrain capillary water rising and protect earth site is analyzed. It is concluded that the deterioration of earth sites is not caused by water itself, but by the change of water content and the movement of salt under the action of capillary water. The application of DC electric field can weaken the capillary water migration caused by matrix potential. It is found that the theoretical model of water distribution under the action of DC electric field is in good agreement with the experimental results, and the effect of DC field on capillary water transport can be quantitatively described. The results show that the direct current electric field can effectively reduce the fluctuation of water in the soil by restraining the capillary water migration in unsaturated soil, and then reduce the swelling and drying shrinkage of the soil and the repeated dissolution and crystallization of salt to protect the soil site.
【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU43

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