赤泥渗滤液对压实黏土衬垫的侵蚀机理研究

Study on erosion mechanism of red mudleachate on compacted clay liner

针对赤泥渗滤液生态环境污染严重这一热点问题,研究赤泥渗滤液对压实黏土衬垫的侵蚀机理。通过地球化学平衡软件(Visual MINTEQ)模拟赤泥渗滤液中各个元素的赋存形态,同时开展渗透试验、污染物离子浸出测试、剪切试验以及微观结构观测,分析化学腐蚀作用对压实黏土渗透性、抗剪强度和微观结构的影响规律及作用机理。结果表明:赤泥渗滤液中铝主要以Al(OH)_(4)^(-)的形态赋存;赤泥渗滤液作为渗透溶液,压实黏土的渗透系数为4.07×10^(-11)m/s;赤泥渗滤液降低了压实黏土的抗剪强度,且主要体现在黏聚力上,对内摩擦角影响甚微;黏土与渗滤液之间的水化反应产生了一些水化产物和胶结结构,同时水的渗透压力附带土粒填充了土体原有的结构空隙,土体结构得到优化。赤泥渗滤液使压实黏土化学相容性有所提高。

To solve the serious pollution problem of the red mud leachate to the ecological environment,the erosion mechanism of the red mud leachate on the compacted clay liner was studied.The geochemical balance software(Visual MINTEQ)is used to simulate the occurrence of various elements in the red mud leachate.Besides,the penetration test of compacted clay under the influence of red mud leachate was conducted and the leaching chemical features of red mud leachate were analyzed.Finally,by analyzing the influence of red mud leachate on the cohesion and internal friction angle of the compacted clay and combining with the scanning electron microscope(SEM),the influence of red mud leachate on the shear strength and microstructure of the compacted clay was expounded.The results of our investigation indicate that:the aluminum ions in the red mud leachate mainly exist in the form of Al(OH)4.Moreover,Al(OH)_(4)^(-)in red mud leachate reacts with Al^(3+)and Fe^(3+)on clay particles,forming precipitation.The viscosity and sedimentation of the newly formed cemented salt in illite lead to the decrease of pore connectivity.And the newly formed cemented salt blocks the pore throat,which are formed many dead-end pores.Thus,the permeability coefficient of the soil decreases when the seepage path is blocked.Using red mud leachate as the infiltration solution,the hydraulic conductivity of compacted illite is 4.07×10^(-11)m/s.The hydraulic conductivity of compacted illite is 7.00×10^(-11) m/s when pure water is used as a seepage solution.Also,the cohesive force of compacted clay is 24.963 kPa and the internal friction angle is 4.97°before infiltration.However,the cohesive force of compacted clay is 17.945 kPa and the internal friction angle is 5.92°after infiltration.The red mud leachate reduces the shear strength of the compacted clay,which is mainly reflected in the cohesion but has little effect on the Angle of internal friction.Finally,the hydration products and cementation structure are produced by the hydration reaction between clay and red mud leachate.Besides,the infiltration pressure of water with soil particles filled the original structural voids of soil,and the soil structure is optimized.The red mud leachate improves the chemical compatibility of compacted clay.