秸秆纤维改良黏土作为填埋场衬垫防渗材料的可行性研究
发布时间：2018-07-28 20:18
【摘要】：针对垃圾填埋场运行过程中压实黏土衬垫开裂破坏失效中的关键科学问题，试图采用农作物秸秆纤维改良传统压实黏土衬垫，以提高衬垫系统的抗开裂特性以及承载能力。为评价秸秆纤维改良黏土作为填埋场衬垫材料的可行性，开展秸秆纤维改良黏土开裂试验研究，研究连续失水干燥与干湿循环作用下改良黏土的开裂规律，提出秸秆纤维黏土混合料的最佳配合比。通过室内土工试验，研究不同秸秆纤维掺量的压实黏土以及酸碱化学溶液腐蚀的改良黏土的强度与变形特性。开展酸碱化学溶液腐蚀下秸秆纤维改良黏土的微观结构试验研究，分析了化学溶液腐蚀条件下改良黏土的微观形貌、孔隙结构以及物质相比的演化规律。基于流体运动方程、溶质对流弥散方程、力平衡方程以及相关边界条件，建立反映渗流-应力-溶质耦合作用下填埋场衬垫变形的数学模型，并采用此模型仿真分析了衬垫的变形破坏规律以及污染物运移扩散趋势。基于以上研究，得出如下主要结论： （1）干湿循环作用对压实黏土开裂影响显著，随干湿循环次数的增多，开裂愈发明显；秸秆纤维改良黏土具有较好的抗开裂特性，随纤维掺量的增加，开裂因子(CIF)出现了先增大后减小的趋势，且当纤维掺量为0.3%时，CIF仅为0.00813； （2）纤维掺量为0.3%的改良黏土承载能力较高，无侧限抗压强度达到459.15kPa、抗剪强度指标c、φ为80.97kPa、21.06°、渗透系数为5.0×10-8cm/s、压缩系数α和压缩指数Cc达到最小值分别为0.18MPa-1和0.065MPa-1，压缩模量Es值为9.356MPa。酸碱化学溶液对秸秆纤维改良黏土强度特性影响显著，其无侧限抗压强度、抗剪强度明显下降，且酸性化学溶液腐蚀强度高于碱性化学溶液。 （3）酸碱化学溶液对黏土微观结构具有较大影响。腐蚀后压实黏土表面愈发粗糙、平整度下降，沟壑明显，，比表面积增大；孔径增大，二次孔、中孔增多，颗粒排列由片堆结构演化至点-点排列结构。黏土中的有机质成分在酸碱化学溶液作用下出现腐蚀分解现象，且酸性腐蚀程度远大于碱性条件。 （4）基于秸秆纤维改良黏土衬垫变形与污染物运移数值仿真计算结果可知，在填埋场运行50天后，改良黏土衬垫层变形基本达到稳定状态，其应变为2.84%。衬垫层内作用点的变形量是呈轴对称变化，在衬垫层左右边界处其变形量为最大值。改良黏土中各点的浓度随时间的增加而增大，且污染物浓度随衬垫层深度的增加而减小。在600天时，渗滤液污染物已穿透衬垫层。污染物浓度的变化是呈轴对称变化，在衬垫层轴线处污染点的浓度为峰值。
[Abstract]:In view of the key scientific problems in the failure of the compacted clay liner cracking and failure during the operation of the landfill, the traditional compacted clay liner was tried to improve the anti cracking characteristics and bearing capacity of the liner system by using the crop straw fiber to improve the feasibility of the straw fiber modified clay as the landfill liner material. Experimental study on clay cracking of modified straw fiber and Study on the cracking law of modified clay under the effect of continuous water loss drying and dry and wet cycle, and put forward the optimum mix ratio of straw fiber clay mixture. Through indoor soil test, the strength of compacted clay with different straw fiber content and the strength of modified clay with acid alkali chemical solution corrosion is studied. The microstructure test of the modified clay with straw fiber under the corrosion of acid and alkali solution was carried out. The microstructure, pore structure and the evolution law of the material were analyzed under the corrosion condition of chemical solution. Based on the fluid motion equation, the solute convection diffusion equation, the force equilibrium equation and the related boundary conditions, A mathematical model is established to reflect the deformation of the landfill liner under the interaction of seepage stress and solute, and this model is used to simulate the deformation and failure of the liner and the trend of pollutant migration and diffusion. Based on the above study, the main conclusions are drawn as follows:
(1) the effect of dry and wet cycle on the cracking of compacted clay is significant. With the increase of the number of dry and wet cycles, the cracking is more obvious, and the improved clay with straw fiber has better cracking resistance. With the increase of fiber content, the cracking factor (CIF) increases first and then decreases, and when the fiber content is 0.3%, it is only 0.00813.
(2) the bearing capacity of the modified clay with 0.3% fiber content is higher, the unconfined compressive strength reaches 459.15kPa, the shear strength index is C, 80.97kPa, 21.06 degree, and the permeability coefficient is 5 x 10-8cm/s, the compression coefficient a and the compression index Cc reach the minimum value 0.18MPa-1 and 0.065MPa-1 respectively, and the Es value of the compression modulus is a 9.356MPa. acid base chemical solution to the straw. The strength of fiber improved clay has significant influence, and its unconfined compressive strength and shear strength decrease obviously, and the corrosion strength of acid chemical solution is higher than that of alkaline solution.
(3) the acid base chemical solution has a great influence on the microstructure of clay. After corrosion, the surface of the compacted clay becomes more rough, the smoothness is reduced, the ravine is obvious, the specific surface area is increased, the pore size increases, the two holes, the mesopore increase, the particle arrangement evolves to the point arrangement structure from the pile structure. The organic matter in the clay is affected by the acid base chemical solution. The phenomenon of corrosion decomposition appears, and the degree of acid corrosion is much greater than that of alkaline condition.
(4) based on the numerical simulation results of the modified clay liner deformation and pollutant transport by straw fiber, it is found that the deformation of the modified clay lining layer is basically stable after 50 days in the landfill, and the strain of the 2.84%. liner is axisymmetric and its deformation amount is the maximum at the left and right boundary of the liner. The concentration of each point in the modified clay increases with the increase of time, and the concentration of pollutants decreases with the increase of the depth of the lining layer. In the 600 day, the pollutants of the leachate have penetrated the lining layer. The concentration of pollutants is changed axisymmetric, and the concentration of the pollution point at the axis of the liner is the peak.
【学位授予单位】：武汉轻工大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU993
本文编号：2151459
[Abstract]:In view of the key scientific problems in the failure of the compacted clay liner cracking and failure during the operation of the landfill, the traditional compacted clay liner was tried to improve the anti cracking characteristics and bearing capacity of the liner system by using the crop straw fiber to improve the feasibility of the straw fiber modified clay as the landfill liner material. Experimental study on clay cracking of modified straw fiber and Study on the cracking law of modified clay under the effect of continuous water loss drying and dry and wet cycle, and put forward the optimum mix ratio of straw fiber clay mixture. Through indoor soil test, the strength of compacted clay with different straw fiber content and the strength of modified clay with acid alkali chemical solution corrosion is studied. The microstructure test of the modified clay with straw fiber under the corrosion of acid and alkali solution was carried out. The microstructure, pore structure and the evolution law of the material were analyzed under the corrosion condition of chemical solution. Based on the fluid motion equation, the solute convection diffusion equation, the force equilibrium equation and the related boundary conditions, A mathematical model is established to reflect the deformation of the landfill liner under the interaction of seepage stress and solute, and this model is used to simulate the deformation and failure of the liner and the trend of pollutant migration and diffusion. Based on the above study, the main conclusions are drawn as follows:
(1) the effect of dry and wet cycle on the cracking of compacted clay is significant. With the increase of the number of dry and wet cycles, the cracking is more obvious, and the improved clay with straw fiber has better cracking resistance. With the increase of fiber content, the cracking factor (CIF) increases first and then decreases, and when the fiber content is 0.3%, it is only 0.00813.
(2) the bearing capacity of the modified clay with 0.3% fiber content is higher, the unconfined compressive strength reaches 459.15kPa, the shear strength index is C, 80.97kPa, 21.06 degree, and the permeability coefficient is 5 x 10-8cm/s, the compression coefficient a and the compression index Cc reach the minimum value 0.18MPa-1 and 0.065MPa-1 respectively, and the Es value of the compression modulus is a 9.356MPa. acid base chemical solution to the straw. The strength of fiber improved clay has significant influence, and its unconfined compressive strength and shear strength decrease obviously, and the corrosion strength of acid chemical solution is higher than that of alkaline solution.
(3) the acid base chemical solution has a great influence on the microstructure of clay. After corrosion, the surface of the compacted clay becomes more rough, the smoothness is reduced, the ravine is obvious, the specific surface area is increased, the pore size increases, the two holes, the mesopore increase, the particle arrangement evolves to the point arrangement structure from the pile structure. The organic matter in the clay is affected by the acid base chemical solution. The phenomenon of corrosion decomposition appears, and the degree of acid corrosion is much greater than that of alkaline condition.
(4) based on the numerical simulation results of the modified clay liner deformation and pollutant transport by straw fiber, it is found that the deformation of the modified clay lining layer is basically stable after 50 days in the landfill, and the strain of the 2.84%. liner is axisymmetric and its deformation amount is the maximum at the left and right boundary of the liner. The concentration of each point in the modified clay increases with the increase of time, and the concentration of pollutants decreases with the increase of the depth of the lining layer. In the 600 day, the pollutants of the leachate have penetrated the lining layer. The concentration of pollutants is changed axisymmetric, and the concentration of the pollution point at the axis of the liner is the peak.
【学位授予单位】：武汉轻工大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU993
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