土石坝心墙掺砾土的渗透特性冻融演化规律试验研究  

Experimental study on permeability characteristicsof clay-gravel mixtures under freezing-thawing actions in core wall of earth-rock dams

作　　者：鲁洋[1,2] 刘斯宏 张勇敢[1] 杨蒙 王柳江 李卓[3] LU Yang;LIU Sihong;ZHANG Yonggan;YANG Meng;WANG Liujiang;LI Zhuo(College of Water Conservancy and Hydropower,Hohai Univ.,Nanjing 210098,China;International Joint Laboratory of Long-term Behaviour&Environmentally Friendly Rehabilitation Technologies on Dams,Nanjing 210098,China;Dame Safety Management Department,Nanjing Hydraulic Research Institute,Nanjing 210029,China)

机构地区：[1]河海大学水利水电学院,江苏南京210098 [2]大坝长效特性及环保修复技术中西联合实验室,江苏南京210098 [3]南京水利科学研究院大坝安全与管理研究所,江苏南京210029

出　　处：《水利学报》2021年第5期603-611,共9页Journal of Hydraulic Engineering

基　　金：国家自然科学基金雅砻江联合基金重点项目(U1765205);国家自然科学基金面上项目(51979091,51979173);中国水利水电科学研究院水利部水工程建设与安全重点实验室开放研究基金(202006)。

摘　　要：高土石坝普遍采用掺砾黏土作为心墙区的压实填筑材料,而高寒区土石坝心墙在施工过程中面临严峻的冻融问题。对经历冻融作用后的压实掺砾黏土料开展一系列三轴渗透试验,研究冻融条件下其渗透特性的演化规律。试验结果表明:冻融作用后,掺砾黏土的渗透系数较未冻融时增大,且增加程度受冻融次数、围压、掺砾量和初始含水率等因素影响。随着冻融次数的增加,渗透系数逐渐增大,且在第1~2次冻融过程中增幅最大;低围压和高初始含水率情况下冻融导致的劣化作用更为突出,渗透系数增大更显著;掺砾量对渗透特性冻融演化规律的影响与掺砾黏土内部的土-石细观结构分布密切相关;随着初始含水率的增加,冻融后的渗透系数逐渐增大,但增幅在压实试样处于最优含水率的干侧时较大,而在湿侧时则较小一些。研究结果可为高寒季冻区高土石坝的防渗设计和冬季施工过程的冻融防控提供一定的指导依据。Clay-gravel mixture is generally used as the compacted impermeable material in the core wall of high earth-rock dams.In high cold regions,it will endure severe freeze-thaw actions during the construc⁃tion process.In this study,a series of triaxial permeability tests were performed to investigate the evolution law of permeability characteristics after freeze-thaw cycles.The results show that:(1)the permeability coef⁃ficient increased significantly after freeze-thaw cycles,and the degree of increase was controlled by various factors such as confining pressure,number of freeze-thaw,gravel content and the initial molding water con⁃tent;(2)the 1st-2nd cycle of freezing-thawing has the most prominent influence on the increase of permea⁃bility;(3)a lower confining stress and a higher molding water content will dominate the increase of perme⁃ability induced by freeze-thaw actions;(4)the effect of gravel content on the permeability is closely relat⁃ed to the inner meso-structural distribution of clay-gravel particles;(5)the freeze-thaw triggered variation of permeability will significantly increase with increasing the initial molding water contents,and a greater increasing amplitude will be found on the dry side of optimum water content,while a smaller amplitude on the wet side.The results can provide useful guidance for the design of impervious structures in high earth-rock dam as well as the prevention of freeze-thaw damages during its construction in winter.

关 键 词：高寒区 心墙坝 掺砾黏土 冻融循环 渗透 土石细观结构 

分 类 号：TU43[建筑科学—岩土工程]