直流电场抑制潮湿土遗址毛细水上升应用研究

发布时间：2018-01-05 10:03

本文关键词：直流电场抑制潮湿土遗址毛细水上升应用研究　出处：《兰州大学》2015年博士论文　论文类型：学位论文

【摘要】：土遗址作为一种非常重要的人类文明遗址,在我国境内数量众多,分布广泛,所处的自然环境也千差万别。现存的土遗址往往具有重大的历史价值和考古价值,其中杭州良渚古城遗址是众多历史文化实物遗存的典型代表,它对于研究中华文明的起源有着非凡的意义。良渚古城遗址所在地区气候温暖湿润,属于典型的潮湿环境中的土遗址,遗址本体长期遭受地下水毛细上升作用的侵蚀,稳定性较差,如何长久有效地保存遗址本体成为一项极其重要的研究课题。21世纪以来,随着国家对文物保护工作的扶持和重视,文物保护工作者在露天土遗址的抢险加固保护中取得了很多优秀的成果,并且仍在不断探索关于潮湿土遗址保护方面有效的方法和措施,如使用改性材料加固、表面补砌、回填以及原地展出等。但值得注意的是,如何对潮湿土遗址内部的微观水环境进行有效地控制是处在潮湿环境中的土遗址长久保存的关键所在,现有的研究成果很少。潮湿环境下的土遗址产生破坏的主要原因为土体内部的毛细水上升及盐分的迁移,改变了原有土体的水。盐平衡结构。对此,本研究提出了利用电化学的方法来控制土遗址的内部环境,即在土遗址本体中加入直流电场,让土体内部的水分在电场力的驱动下从阳极向阴极移动,从而抑制毛细水的上升及盐分的迁移和富集,使土体内部的水-盐平衡结构维持在最佳状态,保持土体内部赋存环境稳定,从根本上解决潮湿环境下土遗址的破坏问题。本研究首先以吸水性较好的滤纸为研究对象,进行了不计重力的二维平面模拟,研究了直流电场作用下水分的水平运移状态,分析了直流电场驱动水分运移的机理；其次,以杭州良渚古城遗址为原型,对重塑土样进行直流电场抑制毛细水上升的三维模拟试验,研究了直流电场对土样中毛细水的抑制作用；然后,进行了遗址区地下水携带盐分毛细上升的模拟试验,研究了在直流电场作用下土样中水-盐的运移和分布；最后,以同样处于潮湿环境中的南京大报恩寺遗址地宫为原型,分析了毛细水上升造成土遗址破坏的机理以及直流电场对潮湿土遗址的保护加固的机理,应用直流电场抑制毛细水上升的保护加固技术构想。本文的主要研究内容和取得的研究成果包括：1.直流电场抑制水分迁移的平面模拟研究利用纤维结构的润湿机理对浸水后的滤纸和有毛细水补给的滤纸中水分分布状态进行描述,结果如下：浸水后的滤纸整体水分分布均匀；有毛细水补给的滤纸,受粘附作用和毛细吸附作用影响,滤纸含水率在水平方向随距透水石距离的增加而逐渐递减。运用Helmholtz-Smoluchowski模型分析滤纸中水分运移的机理,滤纸两端添加了直流电场后,受电场作用在滤纸中将形成额外的渗透压,使水分在滤纸的一端积累,试验表明滤纸含水率在200%以上时直流电场对滤纸中毛细水的抑制效果较好。2.直流电场抑制毛细水上升三维模拟研究在无毛细水补给的条件下,对照组土样中的水分仅受蒸发作用影响,试样整体含水率随着时间的增加而降低；同一时间下,试样中的含水率随高度增加而降低。随着电渗时间的增加,上行电场组土样中含水率从初始的随试样高度增加而降低变成了随着试样高度的增加而增加,电渗促进水分向上运移效果明显：下行电场组土样顶端含水率下降速度大于土样底端含水率下降速度,且含水率曲线斜率随时间增加迅速降低,电渗对试样中水分的抑制效果从下至上逐渐增强。在有毛细水补给的条件下,上行电场组中干密度为1.50g/cm3的试样在电场作用144h后顶端含水率较未添加电场时高5%；干密度为1.60g/cm3的试样的这一差值可达7.4%,说明电场促进毛细水上升的效果较好。下行电场组中,干密度为1.50/cm3的试样与对照组中相同干密度的试样相比,不同高度处含水率随电渗时间增加而降低,说明电场作用抑制了毛细水的向上运移。3.直流电场控制水-盐迁移耦合试验研究天然土试样和含盐土试样在施加下行电场时,毛细水抑制量均随高度增加呈线性递减趋势；在施加上行电场时,毛细水促进量均随高度增加呈线性递增趋势。在无水分补给的条件下,施加下行电场时,天然土和含盐土毛细水抑制量最多可分别达1.56%和4.68%；施加上行电场时,天然土和含盐土毛细水促进量最多可分别达2.09%和1.93%。在蒸馏水补给条件下,施加下行电场时,天然土和含盐土毛细水抑制量最多可分别达5.38%和6.30%；施加上行电场时,天然土和含盐土毛细水促进量最多可分别达3.39%和8.81%。在盐溶液补给的条件下,施加下行电场后,含水率曲线斜率降低,土样上部含水率减少,下部增加；施加上行电场后,天然土试样整体含水率升高2%左右,含盐土试样整体含水率升高4%左右。试验首次利用直流电场控制Na+和S042-的运移方向,再联合物理除盐方法,将电渗汇集的盐分脱去,可有效解决盐类风化对古代土建筑的破坏问题。4.直流电场抑制毛细水上升机理研究以大报恩寺遗址地宫为原型,根据毛细力学中毛细作用物理模型和非饱和土力学中收缩膜(水-气分界面)的表面张力模型对潮湿土遗址墙体坍塌破坏机理进行了分析。从电渗机理出发,结合试验数据,对直流电场抑制潮湿土遗址毛细上升效果进行了理论分析。分析认为潮湿土遗址在施加直流电场后,土中的水分重新分布,土体整体含水率降低,单位高度上的含水率变化增加。蒸发作用、毛细作用、电场作用三者最终达到动态平衡,遗址内部始终存在较大的基质吸力。应用直流电场可以从本质上解决土遗址中墙体坍塌破坏问题。提出了现场应用直流电场对潮湿土遗址进行电动控制防潮的技术构想。
[Abstract]:Soil sites as an important site of human civilization, in our country a large number, wide distribution, the natural environment is also different. Existing soil sites often have major historical and archaeological value, of which Hangzhou Liangzhu ancient city site is typical of many historical and cultural relics, it is extraordinary the significance for the study of the origin of Chinese civilization. The Liangzhu ruins of the ancient city area of warm and humid climate, which belongs to the typical soil sites in damp environment, erosion, body site suffered long-term groundwater capillary rise of stability is poor, since how long to effectively preserve the body site has become an extremely important research topic in the.21 Century, with the country of cultural relics the protection of the support and attention, the protection of cultural relics in the open soil site rescue workers strengthened protection and achieved excellent results, and And continues to explore about the methods and measures for the effective protection of wet soil sites, such as the use of modified material surface strengthening, reinforcing masonry, backfill and displays in situ. But it is worth noting that, how micro water environment on internal wet soil sites effectively is the key soil sites in the humid environment the long-term preservation of the existing research results. The main reason is rarely soil sites under moist environment damage to the capillary rise of water and salt migration within the soil, changed the original soil water. The salt balance structure. In this regard, this research proposes the use of electrochemical methods to control soil sites internal environment. Adding a DC electric field on soil sites in the body, let the soil moisture under the driving force of the electric field move from the anode to the cathode, migration and accumulation of salt increased and inhibit capillary water, the soil The water salt balance structure is maintained in the best condition, keep the soil environment stability, solve the problem of soil damage sites in humid environment fundamentally. In this study, using filter paper with good water absorption as the research object, a two-dimensional plane without gravity simulation, the horizontal migration state under the effect of DC field water the analysis of the mechanism of DC electric field driven water transport; secondly, to Hangzhou Liangzhu ancient ruins as the prototype, simulation 3D DC electric field of capillary rise on inhibition of remolded soil samples of DC electric field on the capillary water in the soil samples were then inhibition; site of groundwater carrying salt capillary rise the simulation experiment on the migration and distribution in the DC electric field of soil water and salt; finally, with the same in a humid environment in Nanjing Dabao'en temple ruins of Palace of the Earth As the prototype, analysis of the capillary water rise caused by the mechanism of protection mechanism of soil site failure and DC electric field on the moist soil site reinforcement, application of DC electric field suppression protection of capillary rise reinforcement technology idea. The main research contents and achievements are as follows: 1. the inhibition of moisture migration of plane DC electric field simulated by wetting the mechanism of fiber structure after immersion of filter paper and capillary water filter in water distribution are described. The results are as follows: the whole paper moisture distribution after soaking uniformly; capillary water filter, affected by the adhesion and capillary effect, increase the moisture content of the filter in the horizontal direction with the distance from the permeable distance diminishing. Use Helmholtz-Smoluchowski model to analyze the mechanism of water movement in filter paper, filter paper ends add DC electric field, electric field The role of the formation of additional osmotic pressure in the filter will make water accumulated in the filter paper is paper moisture test shows that the above 200% inhibitory effect of electric field on the capillary water filter in good.2. DC electric field numerical simulation study of inhibition of capillary rise in non capillary water supply conditions, the control group in soil samples only by water evaporation, the whole sample water content decreased with the increase of time; at the same time, water content in the sample rate decreases with height. With the increase of electroosmosis time, water from the initial sample with height increased became increased with the increase of the height of the sample rate of uplink electric field soil like, the moisture migration effect is obvious: promote the electroosmosis of soil samples at the top down field moisture content decreased faster than that of the bottom soil moisture decline rate, water content and slope of the curve with time Increase rapidly decreased, the inhibitory effect of electroosmosis on moisture from the bottom gradually. In the capillary water, the density of 1.50g/cm3 samples in the electric field after 144H at the top of the water content is not added when the high electric field of 5% dry field uplink group; dry density for sample 1.60g/ cm3 the difference up to 7.4%, indicating good electric field promotes the capillary rise of water. The effect of electric field down group, compared with the dry density of 1.50/cm3 samples and the control group in the same dry density samples, water content at different height rate with the working time increased, the electric field induced by the capillary water upward migration of.3. DC electric field control of water salt migration test study on the coupling of natural soil samples and saline soil samples in the field put downward, capillary water suppression were decreased linearly with increasing altitude in exert upward trend; the electric field, promote the quantity of capillary water With the height increased linearly with increasing trend. In the absence of water supply conditions, put downward electric field, natural soil and saline soil capillary water suppression up to 1.56% and 4.68% respectively; the uplink applied electric field, the natural soil and saline soil capillary water promote maximum amount can respectively reach 2.09% and 1.93%. in distilled water. Under the condition of applying downward electric field, natural soil and saline soil capillary water suppression up to 5.38% and 6.30% respectively; the uplink applied electric field, the natural soil and saline soil capillary water promote most can respectively reach 3.39% and 8.81%. in salt solution. Under the condition of applying downward electric field, the moisture content of the slope of the curve decreases the soil water content is reduced, the upper and lower increase; exert upward electric field, 2% increase in natural soil moisture around the whole sample, 4% increase in saline soil sample water content. The first use of DC electric field control test Na The migration direction of + and S042-, and then combined with physical salt removal method, the electroosmotic collection salt off, can effectively solve the problem of soil salt weathering and damage of ancient buildings.4. DC field inhibition of capillary rise mechanism with the Palace of the Earth temple ruins as the prototype, according to the physical model of capillary capillary membrane shrinkage and unsaturated soil mechanics mechanics (water gas interface) the surface tension model is analyzed on wet soil wall sites collapse mechanism. Starting from the electroosmosis mechanism, combined with the test data, inhibition of wet soil sites on capillary DC electric field was analyzed. The effect of rising damp soil sites in the analysis that the applied DC electric field, the soil moisture in the re the distribution of soil water content decreased, the overall height of the unit, the water rate increase. Evaporation, capillary effect, electric field three reach the dynamic balance in the ruins There is always a large matrix suction. The application of direct current electric field can fundamentally solve the problem of wall collapse in earthen sites. A technical conception of on-site application of DC electric field to control damp soil sites by electric control is put forward.

【学位授予单位】：兰州大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU46;TU-87

【引证文献】