CaCl_2作用下PAC改良膨润土滤饼的渗透特性研究  

Hydraulic conductivity of filter cakes of polyanionic cellulose-amended bentonite slurries in calcium chloride solutions

作　　者：沈胜强[1,2] 杜延军[1,2] 魏明俐[3] 薛强[3] 杨玉玲[1,2] 

机构地区：[1]东南大学岩土工程研究所,江苏南京210096 [2]东南大学江苏省城市地下工程与环境安全重点实验室,江苏南京210096 [3]中国科学院武汉岩土力学研究所岩土力学与工程国家重点实验室,湖北武汉430071

出　　处：《岩石力学与工程学报》2017年第11期2810-2817,共8页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家自然科学基金重点项目(41330641);国家自然科学基金资助项目(51278100);江苏省重点研发计划(BE2017715)~~

摘　　要：膨润土在盐溶液作用下化学相容性降低,严重影响膨润土系隔离墙的防渗性能。PB为提高膨润土在盐溶液作用下的防渗性能,通过将2%的聚阴离子纤维素(PAC)与钠化膨润土(CB)直接拌合,制备一种聚合物改良膨润土(PB)。基于改进滤失试验测试不同压力下受CaCl_2溶液和蒸馏水作用的PB滤饼渗透系数(分别为kc和kw)。结果表明,随CaCl_2浓度增大,PB试样的滤失液体积和滤饼渗透系数增大,但PB试样滤失液体积始终小于规范限值(25m L)。在试验溶液浓度范围内,PB滤饼渗透系数小于未经改良的CB滤饼渗透系数。相同有效应力作用下,随CaCl_2浓度增大,PB滤饼含水率w降低,导致孔隙比虽减小,PB但渗透系数增大;而有效应力的增长可抵消一部分化学溶液对滤饼渗透系数的影响。当CaCl_2浓度≤60 m M时,PB的kc/kw<10,其渗透系数无明显增长,表明采用PAC对膨润土进行改良,可有效提高盐溶液作用下膨润土滤饼的防渗性能。The incompatibility between the bentonite and inorganic solutions has adverse impact on the impermeability of the filter cakes and backfills in soil-bentonite slurry walls. To improve the hydraulic performance of bentonite were backfills exposed to inorganic solutions, the Polyanionic Cellulose（PAC） and sodium activated bentonite were directly blended to produce a polymer-amended bentonite termed as PB. The Calcium Chloride（CaCl2） solutions were selected as the test solutions, and the hydraulic conductivities of the bentonite filter cakes to distilled water（kw） and to concentrated CaCl2 solutions（kc） were measured through modified filtrate loss tests under various applied pressures. The results indicate that the kc of PB filter cake increases with the increase in CaCl2 concentrations,whereas the filtrate loss volumes（V） of PB specimens remainsless than the standard limits（25 m L）. The hydraulic conductivity of PB is lower than that of CB in the range of CaCl2 concentration used in the study. The water contents（w） of both filter cakes decrease with the increasing of CaCl2 concentration for a given average effective pressure, which results in the decreasing in the void ratio of filter cakes and increasing in the kc of both filter cakes. The increasing of average effective pressure can partially counteract the adverse effect on kc caused by the increasing of CaCl2 concentration. The hydraulic conductivity ratio（kc/kw） of the PB filter cake is less than 10 when the CaCl2 concentration is no more than 60 m M,illustrating that the kc of PB filter cake has no significant increasing. Therefore,mixing PAC with bentonite can improve the hydraulic performance effectively.

关 键 词：土力学 聚阴离子纤维素 膨润土 竖向隔离墙 渗透系数 化学相容性 

分 类 号：TU43[建筑科学—岩土工程]