【作者】 李敏；

【导师】 张虎元；

【作者基本信息】 兰州大学 ， 地质工程， 2012， 博士

【摘要】 土遗址是指主要由土质材料(如夯土、土坯、垛泥等)构成的遗存本体。依据土遗址所处气候类型(或800mm等降水量线)将土遗址分为北方干燥土遗址和南方潮湿土遗址2种类型。目前,对于干燥土遗址的保护研究工作相对较多,而潮湿土遗址的保护研究还处于探索阶段。潮湿土遗址处于降雨量大、地下水位浅的环境中,环境因素复杂且不可控,土遗址的消亡速度很快,迫切需要进行科学保护。本文针对那些虽位于北方干燥气候,但由于地下水位浅或与水相邻等原因,土遗址的自身含水量较大的现象,提出了潮湿状态土遗址的概念,并从环境结构论角度,给出了潮湿状态土遗址的“环境”物理模型和定量化分类。本文将土壤学中的斥水土理念引入土遗址保护,从传统材料中选取桐油和石灰作为潮湿状态土遗址的保护材料,提出了斥水-碳化相结合的保护思路。本文选取湿润区潮湿环境潮湿状态土遗址(南京大报恩寺遗址)为研究对象,分析了模拟地宫2009年初挖掘到2011年的破坏形态,并建立其与周围水文气候变化的关系。本文针对研究对象的非饱和特性、收缩病害及水稳定性要求,开展了遗址土和处理土的相关室内试验研究,包括界限含水量、土水特征曲线、非饱和渗透性、吸湿放湿性、收缩性、斥水性、浸水稳定性等,对选取材料的保护效果进行评价。本文建立了一维毛细吸渗模型,模拟了遗址土和3种处理土的毛细水上升特性,从上升高度,含水量分布等方面分析了处理方法对毛细水上升的阻滞特性。本文对比分析遗址土和处理土的微观结构,将宏观特性与微观结构相结合,对保护材料的处理机理进行了探讨。本文的主要研究内容和取得的研究成果包括：1.潮湿状态土遗址概念厘定土遗址所处的环境结构包括气候环境、区域环境和遗址本体环境。因此,选取潮湿系数、相对湿度和含水状态为界定参数,首先将遗址本体含水量大于20%的土遗址定义为潮湿状态土遗址土,然后依据潮湿系数和相对湿度的变化,对潮湿状态土遗址进行进一步描述,细分为湿润区潮湿环境潮湿状态土遗址、湿润区干燥环境潮湿状态土遗址、十早区潮湿环境潮湿状态土遗址、干旱区干燥环境潮湿状态土遗址。2.斥水-碳化理念的提出及保护材料选优选针对土遗址的病害,借鉴土壤学中的斥水土理念,特别是油污染引发土的斥水性方面的相关研究,提出了土遗址的斥水保护理念,并优选桐油为保护介质。于此同时,考虑桐油的防腐问题及土遗址结构稳定性,选取石灰作为另一种保护材料。选取桐油和石灰这两种传统材料为处理介质共同作用以期达到潮湿状态土遗址的斥水-碳化保护目的。3.遗址区的病害演变以模拟地宫为研究对象,分析模拟地宫开挖后(从2009年到2011年)的破坏形态、土层含水量分布变化及其所处气候环境特征,指出大气降雨及地下毛细水的上升是导致地宫失稳的关键因素。4.桐油和石灰处理对土遗址的吸水-失水形状的影响潮湿状态土遗址处于一种动态的非饱和状态,依据现场地宫土层密度分布,测定遗址土(US)、桐油处理土(TS)、石灰处理土(LS)、桐油和石灰处理土(TLS)的界限含水量、土水特征曲线特性、渗透性、收缩特性及吸湿放湿性等特性。结果如下：桐油和石灰的掺入提高了土的液限和塑限,降低了土的塑性指数；桐油处理可降低土的持水性,石灰处理土、桐油和石灰混合处理土的含水量随基质吸力的变化平缓；桐油和石灰处理降低了土的饱和渗透系数,混合处理措施,其饱和渗透系数为遗址土的0.6倍。对于非饱和渗透而言,遗址土和桐油处理土的非饱和渗透系数与含水量的关系曲线密度的增大逐渐平缓,而石灰处理土、桐油和石灰混合处理土的曲线变化随密度的增大还存在右移的趋势；桐油和石灰的处理可有效提高遗址土的吸湿放湿稳定性和收缩稳定性。5.斥水性和浸水稳定性研究为研究桐油和石灰处理土的斥水性及浸水稳定性,开展了水滴入渗试验(WDPT),酒精溶液入渗法(MED)和浸水稳定性的试验研究。遗址土具有亲水性,水滴在遗址土表面铺展并迅速渗入土中,渗入时间随密度的增大而增大。桐油和石灰处理土具有较高的斥水性,水滴在土样表面具有自聚成团,很难渗入。遗址土浸泡于水后迅速发生崩解破坏,桐油和石灰处理土样在浸水状态保持较好的完整性。采用桐油和石灰处理土遗址可提高遗址土的浸水稳定性。6.毛细水上升模拟研究建立了一维毛细吸渗模型,对遗址土(US)、桐油处理士(TS)、石灰处理土(LS)、桐油和石灰处理土(TLS)的毛细上升高度、不同高度毛细水上升的过程及含水量分布进行模拟计算,并利用改进的Washburn方程拟合回归了毛细平衡高度。结果表明桐油和石灰处理可有效减低毛细水的上升,进而减缓毛细水引发土遗址的破坏。7.机理分析结合宏观性质与微观结构,分析桐油和石灰的处理机理。桐油能在土颗粒表面均匀分散并穿入粘土颗粒的多孔表面氧化成膜,对土颗粒进行包裹。桐油氧化膜具有多孔性,在有效地阻止外界水分渗入的同时,让土颗粒内部的湿气得以散发,可避免土体因失水不均匀而引发的变形破坏。石灰的碳化及火山灰反应生成的晶体“生长”于土颗粒孔隙中,呈不规则的片状结晶成长结构,在土粒子间形成架桥结构,发挥固化强度。桐油的存在对石灰结晶具有有机调控作用,从分子水平到介观水平对碳酸钙分子尺寸、取向、晶型以及排列进行控制,形成更稳定的结构。桐油和石灰混合处理措施不仅发挥了桐油斥水性,石灰的碳化填充作用,还有效的利用了桐油的有机调控作用,石灰的杀菌作用。桐油和石灰混合处理不改变土遗址的原貌,可增强土遗址的收缩稳定性、浸水稳定性和结构性,并抑制毛细水的上升,满足潮湿状态土遗址的保护要求。研究成果不仅为传统材料的科学化研究提供参考,而且为潮湿状态土遗址的保护提供了一个新的思路。更多还原

【Abstract】 Earthen monuments are composed mainly of soil (rammed earthen, adobe, mud et al.) and classified to immovable earthen heritage. Nowadays, earthen monuments are classificated into the ones in arid and in humid weather condition according to the located climate or the800mm isohyet. Studies on earthen monuments in arid weather condition have been matured, but it is still at exploring stage for earthen monuments in humid weather condition. Earthen monuments in humid weather condition are easily to extinct in that of high rainfall and shallow groundwater condition. Therefore, it is an urgent responsibility to protect scientifically these earthen monuments.The conception of earthen monument in moist states is firstly proposed aiming at the natural phenomena of the earthen monuments that soil body has high water content but locates in arid weather condition. Furthermore, it puts forward the "environment" physical model and quantitative classification of earthen monument in moist states in view of environment structure theory.Water repellency soil theroy is introduced into earthen monument protection, and materials of tung oil and lime are selected theoretically to achieve the goal of hydrophobicity and carbonation protection.The archeological site of Da Bao’en Temple in Nanjing, Jiangsu province, China, is chosen as the research object. The failure patterns of the simulation underground palace from unearthing are compared and the relevant around hydrology-climate change are analyzed.Tests of atterberg limits, soil-water characteristic curve (SWCC), unsaturated permeability, shrinkage, water absorption and dcsorption, water repellency and stability in water are carried out for unsaturated characteristic, shrinkage disease and water stability protected requirement. Furthermore, the capillary water rise characteristics of untreated and treated soil are simulated and microstructures are obtained with the help of scanning electron microscope (SEM).The main research contents and results are as follows:(1) Definition of earthen monument in moist statesEnvironment structure of earthen monument includes climate environment, regional environment and underground environment, which can be characterized by damp coefficient, relative humidity (RH) and water content, respectively. Thus, earthen monument in moist states can be defined as the one has high water content. and can be further subdivided into four classfications:earthen monuments kept wet at huimd environment in humid areas, earthen monuments kept wet at humid environment but in arid areas, earthen monuments kept wet at arid environment but in humid areas, earthen monuments kept wet at arid environment in arid areas.(2) Selection of protected materialsTung oil is selected as one protected material draw lessons from water repellence of soil contaminated by oil. Meanwhile, lime is selected as the other protected material in view of antiseptic and structure stability. Hydrophobicity and carbonation protection is achieved by combining traditional material of tung oil and lime.(3) Diseases of earthen monument in humid statesDiseases of the simulation underground palace from unearthing (2009～2011) are studied. Rainfall and capillary water rise are the key factors for the unstability based on the changes of water content at different soil layers and its climatic environment.(4) Water absorption and desorption characters of untreated and treated soilChange in soil water content due to rainfall, groundwater lever elevation and air humidity variation is responsible for the soil structure deterioration. Specimens of earthen soil (US), tung oil treated soil (TS), lime treated soil (LS), tung oil and lime treated soil (TLS) are prepared at five levels of dry densities to cover the density variation measured from site investigation.Tung oil and lime treatment, alone or compound, increase the liquid limit and plastic limit of soil and decrease the plasticity index. US specimen has higher water retention in that the composition of hydrophilic minerals, but it is reduced by tung oil treatment. SWCCs of TLS specimen are a little stepper than that of LS specimen, but the whole change is gentle, especially at higher density.Saturated permeability coefficient of four soil specimens decrease with increasing of density. Tung oil and lime treatment can decrease permeability, especially the combine treatment, where the saturated permeability coefficient of treated soil is0.6time as that of earthen soil. The unsaturated permeability coefficients of US and TS specimen present gradient descending shape with the increasing of density, but it present right moving tendency to LS and TLS specimens. Generally, tung oil and lime treatment improve the stability of shrinkage and water absorption and liberation, equally important, the secondary shrinkage.(5) Water repellencyWater drop penetration time (WDPT), molarity of ethanol droplet (MED) and stability in water test are carried out to evaluate the water repellency in the long run. Water drop on tung oil and lime treated soil surface is different from earthen soil, where the formers tend to "balls up" into individual droplets and hardly infiltrate the interior and the latter spreads out and infiltrates quickly in10s. Earthen soil specimen disintegrate completely as soon as being immersed into water, Whereas, other three soil specimens can keep the original shapes, especially the TLS specimens, which are kept well the original shapes even after being immersed in water seven-days. Reduction in water absorption makes water menisci ineffective, and then prevents the destruction of soil. Therefore, decrease of wettability plays an important role on the water stability of soil.(6) Capillary water rise simulationOne-dimension mathematical modeling of capillary rise is built to studies the capillary height, rise process and water distribution at different soil lays for four soil specimens. Modified washburn equation is used to fit to obtain the balance height. tung oil and lime treatment has obvious retardation on capillary rise. Lime treatment is superior to water repellency in lower density, but it will be vanish gradually in higher density. Unite treatment with tung oil and lime can control well soil seepage.(7) Mechanism AnalysisTung oil film can well adapt to the contour and coated closely on soil particles. Calcium carbonate (CaCO3) formed by the carbonation reaction of lime can fill effectively the pores of soil and then improve the compactnes. As treated with both of tung oil and quicklime, there is a regulatory action on the carbonated reaction of calcium hydroxide (Ca(OH)2). Tung oil restricts the crystallization process of calcium carbonate (CaCO3), generates fine crystals, and then forms a firmer and closer structure. The interaction between tung oil and lime can be illustrated from the perspective of biomineralization, liposome changes the microenvironment of carbonated reaction by the way of enriching locally the ion of Ca2+, CO2-3and the hydrophobic chain of liposome restricts the growing of calcium carbonate(CaCO3).更多还原