赤泥渗滤液对改性GCL防渗性能的影响

旨在评价商用土工合成材料黏土衬垫(GCL)用于阻隔赤泥渗滤液的有效性。赤泥渗滤液作用下GCL的防渗特性是评价其防污性能的关键因素。以商用改性GCL中膨润土为研究对象,通过自由膨胀试验,研究了4种赤泥渗滤液中膨润土的自由膨胀指数。以商用改性GCL为研究对象,通过改进滤失试验,研究了4种赤泥渗滤液作为渗透液作用下GCL渗透系数的变化规律,评价了预水化作用对渗透系数的影响。研究还采用清洁自来水作为GCL的渗透液作为对照。结果表明,随着离子强度的增加,改性GCL中的膨润土自由膨胀指数随之减小。预水化处理改性GCL的渗透系数相较于未预水化处理试样降低了5倍左右。在实际工程应用中,建议采用自来水预水化处理GCL,以此充分发挥其防渗性能。随着改进滤失试验中施加气压的增大,不同赤泥渗滤液作用下的改性GCL渗透系数均下降。随着离子强度和一价二价离子摩尔数比的增加,改性GCL的渗透系数随之增大。随着膨润土自由膨胀指数的增加,改性GCL的渗透系数随之减小。与自来水渗透情况相比,赤泥渗滤液渗透作用下,改性GCL渗透系数增大4.35~12.0倍。

Influences of red mud leachates on hydraulic performance of a modified geosynthetic clay liner

The effectiveness of a commercial modified geosynthetic clay liner(GCL) for the containment of the red mud leachates is investigated. The hydraulic conductivity(k) of GCL permeated with red mud leachate is an important index reflecting its containment performance. A series of free swell tests are conducted to evaluate the free swell index(FSI) of bentonite of the GCL in four types of red mud leachates. A series of modified fluid loss tests are conducted to evaluate k of the GCL using four types of red mud leachates as permeating liquids. The clean tap water is tested as a benchmark for comparison purpose. The influence of prehydration methods on k of the GCL sample are assessed. The results indicate that the FSI decreases with the increasing ionic strength(I). The k of non-prehydrated GCL is about 5 times that of the prehydrated GCL. The prehydration of GCL with tap water is suggested to achieve superior hydraulic performance exposed to the red mud leachate. The results show that k decreases slightly with the increasing air pressure and FSI, while it increases with the increasing I and relative abundance of monovalent and divalent cations(RMD). In the tested red much leachates, the hydraulic conductivity ratio(k in red mud leachate to that in tap water) of the GCL is found to vary within 4.35 to 12.0.