改良黏土作为填埋场衬里土料的可行性研究

Feasibility study using improved clay as landfill liner-soil materials

针对传统压实黏土衬里不能有效阻止渗滤液中重金属离子迁移的缺点，采用颗粒活性炭、酸活化膨润土两种吸附剂改良黏土衬里以达到提高其吸附能力的目的．通过室内平衡吸附试验，对黏土、3％或6％颗粒活性炭改良的黏土以及3％或6％酸活化膨润土改良的黏土吸附重金属Cr（Ⅵ）的性质进行了观察．为了评价改良黏土作为填埋场衬里土料的可靠性，通过室内土工试验对衬里土料的体膨胀率、体缩率、渗透系数以及无侧限抗压强度等土力学参数进行了检测．吸附试验结果表明，经颗粒活性炭或酸活化膨润土改良的土料对Cr（Ⅵ）的吸附能力与黏土相比有了很大的提高，这说明改良方法是有效的．土工试验结果表明，在重型击实的条件下，所有衬里土料在一定含水率范围内均满足工程要求指标，即体缩率≤4％、渗透系数〈1×10^-7cm／s、无侧限抗压强度〉200kPa．因此，改良黏土在重型击实的条件下可以作为衬里的建造材料使用．

To prevent effectively the transport of heavy metal ions in landfill leachate, adding materials, granular activated carbon （GAC） and acid-activated bentonite capable of strongly adsorbing pollutants to the conventional compacted clay liner is one method that has been tried. The adsorption of Cr（VI） to clay, clay containing 3% or 6% GAC and 3 or 6% acid-activated bentonite were investigated by laboratory batch tests. In order to evaluate the feasibility of liner-soil materials, geotechnical properties, including volumetric swelling, proved clay used as volumetric shrinkage, hydraulic conductivity and unconfined compressive strength, were measured in laboratory geotechnical tests. The results of hatch tests indicate that the Cr（VI） sorption to clay containing GAC and acidactivated bentonite is much greater than Cr （VI） sorption to natural clay. GAC and acid-activated bentonite are two potential materials for use as sorptive amendments for trapping heavy metals in clay landfill liners. The results of geotechnical tests show that the clay containing GAC or acid-activated bentonite exhibits ≤4% of volumetric shrinkage, 〈1 × 10^-7 cm/s of hydraulic conductivity and 〉200 kPa of unconfined compressive strength in some scope of water content at modified compaction. These findings suggest that the clay containing GAC or acid-activated bentonite can be potentially utilized as compacted liner-soil materials.