城市生活垃圾的压缩性

城市生活垃圾是人们在日常生活中或为城市日常生活提供服务的活动中产生的固体废物。近几年来,城市生活垃圾的处理一直是环境岩土工程的热门课题。国外自60年代就已开始研究城市生活垃圾的填埋课题,我国自90年代中期开始用岩土工程的方法研究生活垃圾的填埋问题。 本文首先采用国内传统的土工仪器,研究了城市生活垃圾填埋场中生活垃圾的基本土工参数如天然密度、比重、含水量、孔隙比、有机物含量、内聚力、内摩擦角及其分布规律。研究表明:天然密度大多分布在0.9-1.2t/m3之间;含水量的变化范围较大,一般分布在40%-100%之间;比重的大小与生活垃圾中有机物的含量有关,大多分布在2.0-2.4之间:有机物含量大多分布在20%-40%之间;孔隙比与深度的关系为一条直线,根据天然密度与深度的相关关系,得到了现场生活垃圾的孔隙比与自重应力的关系曲线,从而得到了现场生活垃圾的压缩系数及压缩模量的变化范围;生活垃圾的小试样三轴不固结不排水及固结不排水试验结果表明,生活垃圾的应力-应变曲线可以近似为双曲线。 然后本文研制了城市生活垃圾专用压缩仪器（BHMSW-2035型）,该仪器最大行程30cm,最大承受1600kPa的压力,压缩筒高度为35cm,内直径19cm,筒的周围加二道钢箍,筒的底部设有4个排水孔,可以排出垃圾的渗滤水。采用该仪器,研究了垃圾的压缩性及其压缩规律性。单级恒定荷载的长期试验结果表明:24h前,压缩速率变化较大,24h后,压缩曲线趋于平缓;24h的压缩量约占90天总压缩量的90%。试验研究还表明:压缩时间和压缩应变的比值与压缩时间的关系为一条直线,因此,生活垃圾的压缩应变与压缩时间的关系符合双曲线函数。当压缩时间趋于无穷大时,压缩应变趋于极限压缩应变。垃圾的24h压缩应变与极限压缩应变相差不大,可以近似用24h压缩应变代替极限压缩应变。当压力超过50kPa时,垃圾的极限压缩应变与压力的对数具有直线关系。根据垃圾的压缩试验结果,进一步解释了垃圾的力学压缩机理,制定了垃圾压缩试验的24h稳定标准,建议了垃圾室内压缩试验的方法。
电加热器
Municipal Solid Waste （MSW） is rubbish that generated by people in the activity of daily life or service for the everyday life. Recent years, the management for MSW is the hot topic of geo-environmental engineering. It had been studied about the subject in the half of sixty years of twenty centuries, but in ninety years of twenty centuries in China by the geo-technical engineering method.In this paper, the basic geo-parameters such as natural density、 specific gravity、 moisture content、 porosity ratio、 the content of organic substance、 cohesive force、 internal friction angle and its regularity of distribution has been studied by domestic traditional geo-apparatus. The results can be draw as （1） The natural density is range 0.9-1.2t/m3. （2） The moisture content is range 40%-100%. （3） The specific gravity is range 2.0-2.4, and its value is dependence of the content of organic substance.（4） The content of organic substance is range 20%-40%. （5）The relationship between porosity ratio and the depth is linear. The relationship between self-weight stress and porosity ratio is been studied based on the relationship between natural density and the depth. The range of compression modulus and compression ratio is been obtained. The between stress and strain is belong to the hyperbolic model by the results of unconsolidated-undrained and consolidated-undrained triaxial test.The big-high pressure MSW compression apparatus （BHMSW-2035） has been developed. The apparatus has the structure of worm and gear. The maximum stroke is 30cm. The maximum bear pressure is 1600kPa. The height of the compression barrel is 35cm. The inner diameter is 19cm. It has two steel bands around the surface of the barrel. It has four drain holes in the bottom of the barrel, then the water（generated by MSW） can be drain out.The compressibility and its regularity had been studied for MSW by the compression apparatus. The results can be draw as: （1） The cumulative decrement of MSW grows by the time elapsed, but The primary compression and secondcompression of the MSW can be not separated. ? The decrement of first 24h is about 90% of the total decrement of three months. ?The steady standard of 24hours is developed. @The relationship between t and tie is linear, and the relationship between t and e is belong to hyperbolic model. ?If the compression time is to be infinitely large quantity, then the compression strain is to be ultimate compression strain. ?The ultimate compression strain can be instead of the compression strain of 24hours. ?If the pressure is over 50kPa, then the relationship between ultimate compression strain and logarithm pressure is linear. ?The mechanical compression mechanism of MSW has been further explanted based on the results of the compression test. The steady-state standard of 24h has been developed. The method of the compression test is been suggested for MSW.The parameters of Duncan-Chang model has been studied based on the results of the large-scale triaxial test. The simplified calculating method of Duncan-Chang model has been put out by the results of the axial direction compression test and shearing test. The relationship between the model parameter K and initial void ratio e0 is linear. The model parameter n is about 1.05. The model parameter G is range 0.3-0.4. The model parameter F is range 0-0.1, and can be draw as linear.The law of the organic matter degradation of MSW has been studied by soil mechanics theory and laboratory and in-situ testing consequence. The results can be draw as: ? The relationship between the content of organic matter and time is e exponent reduced. The degradation parameter is 0.095/yr. ? Based on the dry density is not changed in the process of organic matter degradation of MS W, the new settlement model of organic matter degradation is developed by applied the primary theory of soil mechanics. The model is only relevant of content of organic matter. ? The design method of storage capacity of MSW landfill is developed by considering the organic matter degradation.The calculating method of one-dimension mechanics compression has been presented according to the reclaiming features of MSW. The law of two-dimension mechanical compression has been studied for MSW by the finite element program worked out by professor Lin dao-sheng about Duncan-Chang model. The predict method of capacity of MSW landfill has been presented by compare and analysis the results of the one-dimension and two-dimension.