摘要
非饱和土的抗剪强度指标随饱和度变化的规律错综复杂,为了用数学模型描述这些规律,对现有文献中非饱和土的黏聚力、内摩擦角、剪胀角随饱和度变化的规律进行分析。分析结果表明:(1)当土体饱和度降低,土体从毛细作用主导逐步过渡到吸附作用主导时,土体内摩擦角会增大,其变化规律存在一个转折点,可以定义为临界饱和度Src。当饱和度Sr大于临界饱和度Src时,内摩擦角可视为常数;当饱和度Sr小于临界饱和度Src时,内摩擦角随着饱和度的减小线性增加,传统扩展摩尔-库仑准则等模型不再适用。(2)黏聚力随饱和度的变化过程存在山峰效应,即黏聚力先随饱和度Sr的降低呈指数函数关系增加,当饱和度Sr达到非饱和土强度极值对应的饱和度Srv时达到最大,随后有所降低,这也是导致非饱和土强度存在山峰效应的主要原因。(3)剪胀角随饱和度的降低和垂直压力的降低而增大,可采用线性模型描述。基于以上规律,提出了一个宽饱和度范围内的非饱和抗剪强度演化模型。通过与文献中的试验数据及现有强度模型拟合结果进行对比发现,新模型在描述宽饱和度范围内的土体强度时具有更好的适用性。
The variation of shear strength indices of unsaturated soil with the degree of saturation Sr is complicated.In order to describe the experimental phenomena,the existing literature on the variations of cohesion,internal friction angle and dilation angle with Sr is analyzed.The results show that:(1)When Sr decreases and the pore water gradually transits from capillary water to adsorbed water,the friction angle increases.The turning point can be defined as critical degree of saturation Src.When Sr is greater than Src,the value of the friction angle is constant;when Sr is less than Src,the friction angle increases linearly with the decreasing Sr,and the extended Mohr-Coulomb criterion is no longer applicable.(2)The“peak effect”exists in the process of cohesion changing with Sr,i.e.the cohesion first increases exponentially with the decrease of Sr and reaches its maximum when Sr reaches Srv corresponding to the peak unsaturated strength,and then decreases,which is the main reason for the“peak effect”.(3)A linear model can describe how the dilation angle increases with the decrease of Sr and vertical load.In addition,an unsaturated shear strength model over a wide Sr range is proposed.The proposed model is verified by the comparisons between the published experimental data and the predicted results of the proposed and existing equations,which illustrate the superiority of the proposed model.
作者
赵煜鑫
李旭
赵红芬
刘艳
ZHAO Yu-xin;LI Xu;ZHAO Hong-fen;LIU Yan(Key Laboratory of Urban Underground Engineering of Ministry of Education,Beijing Jiaotong University,Beijing 100044,China;School of Civil Engineering,Sun Yat-sen University,Zhuhai,Guangdong 519082,China;Southern Marine Science and Engineering Guangdong Laboratory,Sun Yat-sen University,Zhuhai,Guangdong 519082,China)
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2023年第10期2809-2820,共12页
Rock and Soil Mechanics
基金
国家自然科学基金(No.51979002,No.52279121,No.52278325)。
关键词
非饱和土
饱和度
抗剪强度指标
非饱和强度模型
unsaturated soil
degree of saturation
shear strength indices
unsaturated shear strength model
