养护龄期和铅含量对磷酸镁水泥固化/稳定化铅污染土的固稳性能影响规律及微观机制  

Effect of curing time and lead concentration on mechanical properties of lead-contaminated soils stabilized by magnesium phosphate cement

作　　者：张亭亭[1,2] 王平 李江山[1,3] 万勇 薛强[1,3] 王士权[1,2] ZHANG Ting-ting;WANG Ping;LI Jiang-shan;WAN Yong;XUE Qiang;WANG Shi-quan(State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, Hubei 430071, China;University of Chinese Academy of Sciences, Beijing 100049, China;Hubei Key Laboratory of Contaminated Clay Science ＆ Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences,Wuhan, Hubei 430071, China)

机构地区：[1]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 [2]中国科学院大学,北京100049 [3]中国科学院武汉岩土力学研究所污染泥土科学与工程湖北省重点实验室,湖北武汉430071

出　　处：《岩土力学》2018年第6期2115-2123,共9页Rock and Soil Mechanics

基　　金：国家自然科学基金(No.51625903;No.41602315;No.51479194);中国科学院学科交叉与合作创新团队项目(No.Y426011C01);岩土力学与工程国家重点实验室资助课题(No.Z015003;No.Z017019)~~

摘　　要：采用磷酸镁水泥(MPC)对铅污染土进行固化/稳定化处理。基于无侧限抗压强度试验、渗透试验和浸出试验,研究了养护龄期和铅含量对污染土固稳性能的影响规律。试验结果表明:固化土的强度随养护龄期增加而增大,渗透系数和浸出浓度减小,7 d龄期的固化土强度和浸出浓度分别为0.36 MPa、1.75 mg/L,均满足环境安全标准;铅含量对固化土的强度及渗透特性的影响均存在临界值,为500 mg/kg。铅含量低于临界值时,固化土的强度随着铅含量的增加而增加,渗透系数随着铅含量的增加而减小。浸出浓度随铅含量的增加而增加,但浸出浓度均低于浸出安全标准。压汞试验结果表明,随养护龄期的增大,固化土孔隙体积减小,铅含量不超过临界值时,固化土孔隙体积随着铅含量的增大而减小。扫描电镜试验结果表明:随着养护龄期的增加,土颗粒团聚化越明显,胶结程度加强;铅含量不超过临界值时,土颗粒团聚体增多。镁钾磷酸盐晶体(MKP)主要通过减少孔径大于0.1?m的孔隙体积来影响固化土的渗透特性。Magnesium phosphate cement（MPC） was used to stabilize or solidify lead-contaminated soils. Unconfined compressive strength test, permeability test and leaching test were conducted to investigate the variation of mechanical properties of lead-contaminated soils treated by MPC under different conditions of curing time and lead concentration. Results show that the unconfined compressive strength increases significantly with curing time, while the hydraulic conductivity and leaching concentration change oppositely. The unconfined compressive strength and leaching concentration under 7-day curing time are satisfied by the regulations. There is a threshold value 500 mg/kg for lead concentration in terms of its influence on unconfined compressive strength and hydraulic conductivity. The unconfined compressive strength and leaching concentration increase with the lead concentration before they reach the threshold value, while the hydraulic conductivity changed oppositely. MIP test results show that the total void volume reduces as the curing time, the total void volume of soil reduces as the lead concentration before they reach the threshold value. SEM test results show that a larger aggregation formation, with a smaller void space in soils as the curing time increases. More obvious aggregation and cementation occurs in soils space as the lead concentration less than the threshold value. MgKPO4·6 H2O（MKP） decreases the pore volume of soil pores with the diameter larger than 0.1 mm, so as to affect the permeability of soil.

关 键 词：固化/稳定化 铅污染土 无侧限抗压强度 渗透系数 浸出浓度 微观结构 

分 类 号：TU449[建筑科学—岩土工程]