【作者】 赵燕茹；

【导师】 张永兴； 谢强；

【作者基本信息】 重庆大学 ， 土木工程， 2014， 博士

【摘要】 近二十年来，随着城镇化建设的加快以及城镇人口的增加，越来越多的工业垃圾和生活垃圾出现在日常生活中，引起了严重的生态环境污染问题。目前国内外对垃圾主要采用填埋作业的方式进行处理，但是随着各种超大型垃圾填埋体的建设，填埋场的不规范填埋作业以及封场后因内部有机物质降解引起的滑坡灾害和不均匀沉降问题，给人居环境带来了巨大的威胁。本文从垃圾土抗剪强度影响机理出发，以重庆市长卫生桥垃圾填埋场的垃圾土样作为测试对象，从以下几个方面对垃圾土的力学及降解沉降特性进行了相关试验研究。1）为了研究有机物降解对垃圾土抗剪强度影响机理，并总结影响抗剪强度参数的相关因素（降解、含水率、有机物含量以及剪应变标准等），选取重庆市长生桥垃圾填埋场的垃圾土样作为研究对象，基于室内直剪试验和三轴固结排水试验，对新鲜重塑垃圾土和陈垃圾土的抗剪强度参数进行了测试；通过240d的降解-剪切试验，得出重塑新鲜垃圾土在0d～30d，其抗剪强度与垃圾土初始组成结构和预压应力有关，而受有机物含量以及降解程度的影响较小；抗剪强度随降解的进行在30d～240d，其粘聚力c在3.54kPa～22.24kPa之间变化，呈递增趋势；内摩擦角φ在27.86°～20.35°之间变化，呈先增后减的趋势；陈垃圾土的直剪试验表明，随着垃圾土中含水率的增加，其抗剪强度的整体趋势是减小的；陈垃圾土的三轴固结排水试验（CD）结果表明，随剪切应变标准的增大（5%～20%），抗剪强度呈递增趋势，其中粘聚力c从0kPa增大为66.42kPa，而内摩擦角φ从29°增大为38°。2）为了研究垃圾土蠕变-降解沉降特性，基于室内蠕变观测试验得到蠕变～降解沉降过程曲线（0d～360d），最后对沉降影响因素进行了详细分析。试验结果表明，因外部荷载和内部蠕变沉降引起的垃圾土总沉降量可达试样总高度的33.2%；填埋体中渗滤液在前期的溢出量受外部荷载和有机物中初始含水量控制；通过对不同有机物含量的垃圾土试样的降解沉降试验，得出垃圾土的累计沉降量和累计渗滤液产量之间符合指数函数关系；垃圾土中既有利于初期压缩变形，又有利于后期厌氧降解沉降的垃圾土中最优有机物含量区间为29.1%～36.47%；垃圾土内部温度监测结果显示，22℃～45℃是一个能够加速其内部有机物降解速率的温度区间，且在41℃时作用最大。本次研究结果可用于降解-沉降和温度场的分析，也可为进一步了解垃圾土的沉降特性提供理论支持。3）为了研究垃圾土的降解-蠕变沉降特性，通过对试样在室内分别进行加载压缩试验，测试了垃圾土在360d内其降解沉降变化特性，试验结果显示：垃圾土在好氧和厌氧降解阶段的变形特性符合弹塑性变形特征；根据蠕变理论和垃圾土的实测变形特点，推导了符合其变形特性的Burgers蠕变沉降模型，并对该模型的正确性进行了验证，发现该模型能够较好的模拟垃圾土在不同降解阶段的变形特性，并且能够为准确预测垃圾土的沉降以及计算后期填埋场的容量提供帮助。4）基于Mitchell三元导电模型和室内实测资料，在确定原状垃圾土试样的结构和土性参数基础上，推导了适合重庆长卫生桥填埋场垃圾土电阻率的计算模型。通过分析电阻率影响因素（孔隙率，渗滤液浓度，温度，湿密度等）得出当其它参数不变，而只改变其中一个变量时：电阻率随孔隙率的增加而呈幂函数减小；相比添加NaCl和ZnCl2溶液的垃圾土，孔隙率的增加对添加柴油时垃圾土电阻率的影响要大于前两者；在孔隙率一定时，渗滤液对垃圾土电阻率的影响受稀释作用控制，并且影响程度随含水率的增加而减小；随着随温度的升高，垃圾土电阻率呈线性递减趋势；在含水率一定时，孔隙率的变化是导致垃圾土中三种导电模式发生互相转化的主要原因,并对电阻率造成影响；最后采用高密度电阻率层析技术，对垃圾填埋体进行了尝试性测试，通过对比电阻率实测值和计算值，证明了电阻率模型的正确性，研究结果能够为分析垃圾填埋体渗滤液的含量和富集状态，以及评价垃圾土的力学特性供理论支持。更多还原

【Abstract】 In recent decades, industrial and Municipal Solid Waste (MSW) production hasrapidly increased as a result of significant population growth in the global. As aeconomical disposal way of MSW, most of urban waste production were land filled intoregulated centers both in china and aborad. However, with the continuing increase ofMSW in the city, which can pose important environmental disasters. Based on themechanism evolution of landslides for the landfills, Chongqing landfill was selected forthe research and the the mechanical behavior of MSW was elaborately studied in thispaper as follows:1) In order to study the effect of biodegradation on the shearstrength as well asother related factors such as moisture content, organic content, shear strain standard onthe shear strength of MSW. Laboratory tests were applied during the process of organicmatter degradation in the specimens, which was collected from landfills located inChongqing area. The shear tests results during the240days shows that the shear strengthof shredded fresh samples in the initial phase (0d～30d) depends on initial structure andpre-compressive pressure, the effects of organic content and moisture content on shearstrength are not obvious; In the second phase(30d～240d), the shear strength ofcohesion c increases steadily from3.54kPa to22.24kPa while internal friction angle φincreased from14.41°to27.84°during the0~30days and then decreased gradually from27.86°to20.35°. Direct Shear tests results for landfills sample shows that the increaseof moisture content in the waste may caused the decreased of shear strength.Consolidated drained tri-axial tests result shows that the shear strength increasesprogressively as defined axial strain increases from5%to20%, corresponding cohesionc varies from0kPa to66.42kPa and internal friction angle φ ranges from29°to38°.2) In order to study the creep–degradation settlement properties of municipal solidwaste, the change of static-creep-settlement for fresh municipal solid wastes whichcollected from the Chongqing landfill were observed elaborately during the360daysLaboratory test. By analyzing leachate-degradation-strain-time relational curves, thenumber of total creep settlement caused by external load and inner degradation in thewaste can reach33.2%of the sample height, and the leachate production can becontrolled by the external load and organic content; the tests results indicated that thedegradation rule of MSW can be expressed as the Richards model，the relation of cumulative settlenment with cumulative leachate fitting the exponential function model;The corresponding section for organic content that suit for the initial compressiondeformation and the creep-degradation settlement could be ranged from29.1%to36.47%. During the monitoring for settlement and internal temperature field in theanaerobic reaction stage, a optimum temperature zones that varied from22℃to45℃were found and which could accelerate degradation speed of organic matters in thewaste, and it becoming more fasterwhen the temperature reached to41℃.With thepreliminary study for degradation-settlement and temperature field, the tests result willprovide some theoretical help for further settlement analysis in the waste and landfilldesign.3) The creep-settlement properties of municipal solid waste are investigated usingthe compressive experiments indoor. According to the experiment results, deformationof waste sample under respective loading condition is recorded and it can be expressedas elastic-plastic biodegradation induced model in both aerobic and anaerobic phases.Based on creep theory and monitored dates, a creep models called Burgers model isproposed which could better describe the deformation properties of landfills. Based onone dimension compression experiments and data available from published literature,the model parameters are obtained. In order to illustrate the applicability of proposedmodel, settlements due to respective loading of waste with time are predicted for typicallandfill conditions. The proposed Burgers models is capable of reproducing quite wellthe results obtained from tests performed in the laboratory as well as the settlementrecorded in sanitary landfills, both of creep model are valuable for predicting thecapacity calculation and settlement research of landfills.4) Based on the Mitchell’s three-Element conductive model and tests dates, A newlandfill resitivity model was estabilished after the structure and properties parameters oflandfill sample were determined and which was better suitable for ChongQing areas. Byanalysis the effect factors (temperature, moisture density, leachate concentration,porosity), Tests results shows (only one parameter is variable but the other parametersare unchanged): The resistivity of landfill decreased as the increase of porosity in thelandfill and their relationships could be represented by power equations. With morepollutants adding to the specimen, great change has been happened to oil pollutant thanadding NaCl、ZnCl2leachate with increasing porosity of landfill. Suppose the porosityof landfill is fixed, The effect of leachate on the resisitivity can mainly controlled by thedilution process of landfill, and which decreased with the rising of moisture content. The resistivity is liner against the temperature andwhich increased as the increase oftemperature during the aerobic and anaerobic phase in landfills. When assume themoisture content is constants, three kinds of conductive model may be changed due tothe change of porosity in the waste, and it could even cause a change for the electricalresistivity of MSW. Finally, a high-density resistivity chromatography is applied in thefield tests, and the comparison of electrical resistivity between tested value andcalculated was conducted the the results prove that the proposed electrical resistivitymodel is reasonable. These study results could better predict the leachate content in thewaste and evaluate the mechanic behavior in the landfill.更多还原