饱和城市固废一维降解固结理论研究

发布时间：2018-06-10 15:27

本文选题：固结 + 降解　；参考：《浙江大学》2016年硕士论文

【摘要】：我国城市固废以快速易降解的厨余组分为主,渗滤液产量大,容易引起填埋体水位雍高达到饱和状态。填埋后的城市固废因降解产生固相质量损失,从而造成在外力作用下的固结是一个相当复杂的过程。主要体现在以下三个方面：(1)可降解固相水解和胞内水释放引起固相和孔隙体积的变化；(2)胞内水释放引起孔隙水质量变化；(3)可降解固相水解和胞内水释放导致压缩性衰变。本文重点研究饱和城市固废一维降解固结特性。主要内容和成果如下：(1)建立了饱和城市固废一维降解固结普遍模型。不同于传统土体,可降解固相水解产生的孔隙需要额外孔隙水填充,使得超静孔压减小；胞内水释放产生的孔隙由释放形成的等体积孔隙水填充,不产生额外的超静孔压变化；固相质量损失导致骨架疏松,压缩性增大,使得超静孔压增加。因此实际过程中超静孔压的响应是上述三方面超静孔压响应的综合结果。(2)基于已有城市固废降解、压缩和渗透特性研究,获得了考虑可降解固相水解、胞内水释放为孔隙水及降解导致压缩性衰变的一维降解固结简化模型；基于简化模型,针对饱和城市固废填埋层底部淤堵不透水和顶部自由排水工况,获得了一维降解固结解析解。针对我国填埋场新鲜固废的计算结果表明：在瞬时常荷载作用下,固结初期,填埋层底部的超静孔压值会超过初始值,这主要是因为降解引起固相质量损失导致骨架疏松、压缩性增大；固结后期,整个填埋层出现负的超静孔压,这主要是因为后期填埋层孔隙比因固相质量损失而增大,而压缩性衰变相对较小。参数敏感性分析表明：次压缩速率越大,固结初期超静孔压越大；增加填埋层的先期固结压力会延缓超静孔压的消散。(3)基于饱和城市固废一维降解固结简化模型,去除常数固结系数假定,获得了考虑固结系数变化的饱和城市固废一维降解固结简化模型。验证了COMSOL Multiphysics求解的可靠性,并数值求解该简化模型,以研究固结系数变化对降解固结性状的影响。结果如下：固结初期,固结系数随着深度的增加而增大,填埋层上部的固结系数小于初始值,填埋层底部出现固结系数超过初始值。但整个填埋层超静孔压值大于对应的常数固结系数工况中的相应值,这主要是因为填埋层上部固结系数减小,固结系数越小超静孔压的消散越慢。由于固结后期固结系数相对较小,负的超静孔压的消散也较慢。相比常数固结系数工况,考虑固结系数变化时,主压缩的发展相对较慢,次压缩几乎不受影响。(4)基于实测不同龄期试样的可降解固相质量、胞内水质量和沉降值,结合一阶动力学模型拟合得到可降解固相水解速率、胞内水释放速率和次压缩速率；并研究不同降解环境对胞内水释放速率和可降解固相水解速率的影响；分析胞内水释放完成程度与可降解固相水解完成程度的关系；假定用可降解组分质量损失程度表征次压缩的完成程度,并基于实测结果对该假定进行验证。基于第四章中考虑固结系数变化的饱和城市固废一维降解固结简化模型,结合三个速率的相关性,本章获得了变固结系数条件下,同时考虑可降解固相和胞内水对次压缩影响的饱和城市固废一维降解固结简化模型；通过算例分析得到如下结果：次压缩速率由胞内水速率控制这一假定导致固结初期超静孔压偏大,后期则偏小；胞内水释放速率相同时,可降解固相水解速率越大,固结初期超静孔压越小。
[Abstract]:The municipal solid waste is the main component of rapid and easy - to - degrade kitchen waste components , the leachate production is large , the water level of the landfill can be easily caused to reach the saturation state . The solid waste caused by the landfill is a rather complicated process due to the degradation of solid phase quality . The main expression is that : ( 1 ) the degradable solid phase hydrolysis and the release of intracellular water cause the change of solid phase and pore volume ;
( 2 ) the release of intracellular water causes the change of pore water quality ;
( 3 ) degradable solid phase hydrolysis and intracellular water release result in compressibility decay . The main contents and results are as follows : ( 1 ) A generalized model of solid waste one - dimensional degradation consolidation in saturated cities is studied .
the pores generated by the release of the intracellular water are filled with the equal volume pore water formed by the release , and no extra superstatic pore pressure change is generated ;
( 2 ) Based on the existing research on solid waste degradation , compression and permeation characteristics , a simplified model of one - dimensional degradation consolidation considering degradable solid phase hydrolysis and intracellular water release as pore water and degradation leads to compression decay is obtained .
Based on the simplified model , the analytical solution of one - dimensional degradation consolidation is obtained for the bottom slurry of saturated municipal solid waste landfill . The results show that under the action of instantaneous constant load , the overpressure value at the bottom of the landfill layer will exceed the initial value , which is mainly because of the loss of solid phase caused by degradation , which causes the skeleton to be loose and the compressibility is increased ;
In the late consolidation period , the negative superstatic pore pressure appears in the whole landfill layer , which is mainly because the pore ratio of the later landfill layer increases due to the loss of solid phase quality , and the compressibility decay is relatively small . The parameter sensitivity analysis shows that the higher the secondary compression rate , the greater the static pore pressure at the initial stage of consolidation ;
( 3 ) In the early consolidation period , the consolidation coefficient increases with the increasing of depth , the consolidation coefficient of the upper part of the landfill layer is smaller than the initial value , and the consolidation coefficient is less than the initial value .
The effects of different degradation environment on the release rate of intracellular water and the rate of degradable solid phase hydrolysis were studied .
analyzing the relationship between the degree of completion of intracellular water release and the degree of completion of degradable solid phase hydrolysis ;
It is assumed that the degree of completion of the secondary compression is characterized by the degree of loss of the degradable component , and the assumption is verified based on the measured results . Based on the correlation of three rates , a simplified model of one - dimensional degradation consolidation of saturated cities affected by secondary compression of degradable solid phase and intracellular water is considered .
The results are as follows : the sub - compression rate is controlled by the rate of internal water velocity , which leads to a large initial static pore pressure and a small later period ;
The higher the release rate of the intracellular water , the higher the degradation rate of the degradable solid phase , the smaller the superstatic pore pressure at the initial stage of consolidation .
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TU411

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