摘要
膨润土遇水产生的膨胀变形以及膨胀力是由于颗粒间的斥力引起的,而该斥力大小与土体的固定负电荷密度(采用阳离子交换量CEC来表征)以及孔隙溶液的浓度有关,已有的对膨润土膨胀变形研究多针对孔隙溶液而非土体的阳离子交换量。现以钠基膨润土为研究对象,采用Li+固定法来控制膨润土的固定负电荷密度,以达到降低膨润土阳离子交换量的目的,再采用Li Cl为盐溶液,获得了上述不同阳离子交换量的膨润土在不同浓度的盐溶液作用下的膨胀指数。结果表明:随着溶液浓度升高,土样的膨胀指数降低;当浓度小于1 mol/L时,下降较为显著,之后则缓慢降低;随着阳离子交换量的减少,土样的膨胀指数也呈降低趋势。这是因为土颗粒的阳离子交换量和溶液浓度是影响土样与孔隙溶液物理化学作用的决定性因素,阳离子交换量越小,浓度越高,土颗粒之间的斥力降低,土样的膨胀指数则会降低。采用考虑颗粒间物理化学作用的粒间应力来描述试验结果,表明对于该种膨润土来说,不同阳离子交换量以及不同盐溶液作用下的回弹变形和回弹应力几乎在一条曲线上,这也进一步验证了粒间应力在膨胀土模拟中的有效性和适用性。
The swelling deformation and swelling force of bentonite in contact with water are caused by the repulsive force between particles,and the magnitude of this repulsive force is related to the fixed negative charge density of the soil(represented by the cation exchange capacity,CEC)and the concentration of the pore solution.The previous research on the swelling deformation of bentonite is mainly focused on the pore solution rather than the cation exchange capacity of the soil.In this paper,sodium bentonite is taken as the research object,and Li+fixation method is used to control the fixed negative charge density of bentonite,so as to reduce the cation exchange capacity of bentonite.Finally,the free expansion rates of reduced charge bentonite were obtained under different concentrations of LiCl solution.The results showed that the free expansion rate of soil samples decreased with the increase of solution concentration.When the concentration is less than 1 mol/L,the decrease was more significant,and then slowly decreased.With the decrease of CEC,the free expansion rate of soil samples also decreased.The physicochemical interaction between the soil particles and pore solution is dependent on CEC carried by soil particles and salt solution concentration.Lower CEC and higher salt concentration mean lower repulsive force between soil particles and lower free expansion rate of soil sample.The intergranular stress with the consideration of the physicochemical interaction between particles and pore solution was introduced to describe the experimental results,showing that the swelling deformation and swelling stress under different CECs and different salt solutions were merged on the same curve,which further verified the effectiveness and applicability of the intergranular stress in simulating expansive soil.
作者
于海文
马田田
韦昌富
郝丰富
YU Hai-wen;MA Tian-tian;WEI Chang-fu;HAO Feng-fu(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;Guangxi Key Laboratory of Geomechanics and Geotechnical Engineering,Guilin University of Technology,Guilin,Guangxi 541004,China)
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2023年第9期2603-2610,共8页
Rock and Soil Mechanics
基金
国家自然科学基金项目(No.41972290,No.51939011,No.52109133)。
