秸稈纖維改良黏土作為填埋場(chǎng)襯墊防滲材料的可行性研究
發(fā)布時(shí)間：2018-07-28 20:18
【摘要】：針對(duì)垃圾填埋場(chǎng)運(yùn)行過(guò)程中壓實(shí)黏土襯墊開(kāi)裂破壞失效中的關(guān)鍵科學(xué)問(wèn)題，試圖采用農(nóng)作物秸稈纖維改良傳統(tǒng)壓實(shí)黏土襯墊，以提高襯墊系統(tǒng)的抗開(kāi)裂特性以及承載能力。為評(píng)價(jià)秸稈纖維改良黏土作為填埋場(chǎng)襯墊材料的可行性，開(kāi)展秸稈纖維改良黏土開(kāi)裂試驗(yàn)研究，研究連續(xù)失水干燥與干濕循環(huán)作用下改良黏土的開(kāi)裂規(guī)律，提出秸稈纖維黏土混合料的最佳配合比。通過(guò)室內(nèi)土工試驗(yàn)，研究不同秸稈纖維摻量的壓實(shí)黏土以及酸堿化學(xué)溶液腐蝕的改良黏土的強(qiáng)度與變形特性。開(kāi)展酸堿化學(xué)溶液腐蝕下秸稈纖維改良黏土的微觀結(jié)構(gòu)試驗(yàn)研究，分析了化學(xué)溶液腐蝕條件下改良黏土的微觀形貌、孔隙結(jié)構(gòu)以及物質(zhì)相比的演化規(guī)律�；诹黧w運(yùn)動(dòng)方程、溶質(zhì)對(duì)流彌散方程、力平衡方程以及相關(guān)邊界條件，建立反映滲流-應(yīng)力-溶質(zhì)耦合作用下填埋場(chǎng)襯墊變形的數(shù)學(xué)模型，并采用此模型仿真分析了襯墊的變形破壞規(guī)律以及污染物運(yùn)移擴(kuò)散趨勢(shì)�；谝陨涎芯�，得出如下主要結(jié)論： （1）干濕循環(huán)作用對(duì)壓實(shí)黏土開(kāi)裂影響顯著，隨干濕循環(huán)次數(shù)的增多，開(kāi)裂愈發(fā)明顯；秸稈纖維改良黏土具有較好的抗開(kāi)裂特性，隨纖維摻量的增加，開(kāi)裂因子(CIF)出現(xiàn)了先增大后減小的趨勢(shì)，且當(dāng)纖維摻量為0.3%時(shí)，CIF僅為0.00813； （2）纖維摻量為0.3%的改良黏土承載能力較高，無(wú)側(cè)限抗壓強(qiáng)度達(dá)到459.15kPa、抗剪強(qiáng)度指標(biāo)c、φ為80.97kPa、21.06°、滲透系數(shù)為5.0×10-8cm/s、壓縮系數(shù)α和壓縮指數(shù)Cc達(dá)到最小值分別為0.18MPa-1和0.065MPa-1，壓縮模量Es值為9.356MPa。酸堿化學(xué)溶液對(duì)秸稈纖維改良黏土強(qiáng)度特性影響顯著，其無(wú)側(cè)限抗壓強(qiáng)度、抗剪強(qiáng)度明顯下降，且酸性化學(xué)溶液腐蝕強(qiáng)度高于堿性化學(xué)溶液。 （3）酸堿化學(xué)溶液對(duì)黏土微觀結(jié)構(gòu)具有較大影響。腐蝕后壓實(shí)黏土表面愈發(fā)粗糙、平整度下降，溝壑明顯，，比表面積增大；孔徑增大，二次孔、中孔增多，顆粒排列由片堆結(jié)構(gòu)演化至點(diǎn)-點(diǎn)排列結(jié)構(gòu)。黏土中的有機(jī)質(zhì)成分在酸堿化學(xué)溶液作用下出現(xiàn)腐蝕分解現(xiàn)象，且酸性腐蝕程度遠(yuǎn)大于堿性條件。 （4）基于秸稈纖維改良黏土襯墊變形與污染物運(yùn)移數(shù)值仿真計(jì)算結(jié)果可知，在填埋場(chǎng)運(yùn)行50天后，改良黏土襯墊層變形基本達(dá)到穩(wěn)定狀態(tài)，其應(yīng)變?yōu)?.84%。襯墊層內(nèi)作用點(diǎn)的變形量是呈軸對(duì)稱(chēng)變化，在襯墊層左右邊界處其變形量為最大值。改良黏土中各點(diǎn)的濃度隨時(shí)間的增加而增大，且污染物濃度隨襯墊層深度的增加而減小。在600天時(shí)，滲濾液污染物已穿透襯墊層。污染物濃度的變化是呈軸對(duì)稱(chēng)變化，在襯墊層軸線(xiàn)處污染點(diǎn)的濃度為峰值。
[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.
【學(xué)位授予單位】：武漢輕工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2013
【分類(lèi)號(hào)】：TU993
本文編號(hào)：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.
【學(xué)位授予單位】：武漢輕工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2013
【分類(lèi)號(hào)】：TU993
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