毛细黏聚与冰胶结作用对非饱和粉质黏土冻结强度及变形特性的影响  

Effect of capillary cohesion and ice cementation on strength and deformation of unsaturated frozen silty clay

作　　者：刘振亚[1] 刘建坤[1] 李旭[1,2] 房建宏 LIU Zhenya;LIU Jiankun;LI Xu;FANG Jianhong(Key Laboratory for Urban Underground Engineering of Ministry of Education, Beijing Jiaotong University, Beijing 100044, China;Qinghai Researeh and Observation Base, Transportation Industry Laboratory of Highway Construction and Maintenance Technology in Permafrost Regions, Qinghai Research Institute of Transportation, Xining, Qinghai 810001, China)

机构地区：[1]北京交通大学城市地下工程教育部重点实验室,北京100044 [2]青海省交通科学研究院多年冻土地区公路建设与养护技术交通行业重点实验室青海研究观测基地,青海西宁810001

出　　处：《岩石力学与工程学报》2018年第6期1551-1559,共9页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家自然科学基金资助项目(41731281;41471052;51479001)~~

摘　　要：为探究毛细黏聚和冰胶结作用对冻土强度及变形特性的影响,通过室内试验测定不同饱和度、初始孔隙比情况下,压实、冻结和风干土样的强度及三维等温冻结变形和压缩特性。试验结果及数据分析表明:非饱和粉质黏土冻结强度的提高是基质吸力增加导致的毛细黏聚与冰胶结黏聚共同作用的结果。饱和度较低时,毛细黏聚作用占较大比重;随着饱和度的提高,冰胶结逐渐占主导作用。假定相同吸力条件下,冻土和非饱和土毛细黏聚力相当,发现冰胶结黏聚力和冻土体积含冰量之间存在线性关系。对于粉质黏土体变,当饱和度高(>0.75)时,土体表现为冻胀,当饱和度低(<0.75)时,土体表现为冻缩,说明冻土体变由黏聚力增加导致的体缩作用与冰水相变导致的体胀作用共同决定。当土样初始饱和度和孔隙比相同时,由黏聚力增加导致的体缩量和受到压力时产生的压缩量相当,可由压缩曲线预估土体的体缩量,体积含冰量与冰水相变导致的体胀量存在线性关系。The strength increase and volume shrinkage during freezing of unsaturated soil may relate to the capillary cohesion and ice cementation. In this paper,shear strength,three dimensional deformation and compaction characteristics of compacted,frozen and air-dried samples were experimental studied using silty clay. The saturation degree and void ratio were considered as variable parameters. The contributions of ice cementation and capillary cohesion to strength were investigated experimentally. The experimental results demonstrate that the strength increase of unsaturated frozen silty clay is due to the capillary cohesion enhanced by suction increase and ice cementation. The capillary cohesion is remarkable in frozen soil with low initial degree of saturation,and the ice cementation is major source of cohesion in frozen soil with increasing of the initial degree of saturation. The volumetric ice content has a linear relationship with ice cementation on the assumption that capillary cohesion of frozen soil equals to that of unsaturated soil at the same matric suction. For the silty clay used,the samples with degree of saturation lower than 0.75 shrink upon frozen while the samples with degree of saturation higher than 0.75 swell. So,the sum of shrinkage induced by cohesion and expansion induced by icing are the total deformation of unsaturated frozen soil. Such shrinkage strain can be inferred from the curve of soil compression. The expansion induced by transformation from water to ice has a linear relationship with volumetric ice content on the assumption that compression caused by load equals to shrinkage caused by increasing of capillary cohesion.

关 键 词：土力学 非饱和土 粉质黏土 冻胀 体缩 黏聚力 

分 类 号：TU411[建筑科学—岩土工程]