超固结黏土不排水剪切的屈服与临界状态  

Yield and Critical State of Over-consolidated Saturated Clay under Undrained Shear

作　　者：刘莹[1,2] 朱圣焱 李艳 马少坤[1,2] LIU Ying;ZHU Sheng-yan;LI Yan;MA Shao-kun(College of Civil Engineering and Architecture,Guangxi University,Nanning 530004,China;Key Laboratory of Disaster Prevention and Structural Safety,Guangxi University,Nanning 530004,China;Shenzhen Metro Group Operation Co.,Ltd.,Shenzhen 518000,China;College of Civil Engineering and Surveying,Guilin University of Technology at Nanning,Chongzuo 532100,China)

机构地区：[1]广西大学土木建筑工程学院,南宁530004 [2]广西大学工程防灾与结构安全重点实验室,南宁530004 [3]深圳地铁集团运营有限公司,深圳518000 [4]桂林理工大学南宁分校土木与测绘工程学院,崇左532100

出　　处：《科学技术与工程》2024年第19期8193-8200,共8页Science Technology and Engineering

基　　金：国家自然科学基金(52278337,51968005);广西自然科学基金(2019GXNSFBA185038)。

摘　　要：以研究超固结黏土的屈服与临界状态为目的,通过GDS三轴剪切试验仪(GDS triaxial shear testing apparatus)开展了一系列不同超固结状态的黏土不排水剪切试验。为对黏土的应力路径进行分析,选取了能描述超固结状态不同时土的屈服特性的ALPHA(α)模型。分析了黏土的偏应力/孔压-应变曲线变化趋势,并确定了孔压达到峰值时土体为破坏状态。根据应力破坏点拟合出临界状态线,提出了针对不同超固结比的不排水抗剪强度的计算公式。试验结果表明:不排水剪切试验中,前期固结压力相同时,超固结比越小,抗剪强度越高,但是屈服强度并非随超固结比的降低而单调递增变化;超固结比相同时,前期固结压力越大,抗剪强度越高,屈服强度也越高;正常固结和轻超固结土的破坏应变皆在5%左右,而重超固结土则呈现明显的剪胀现象和脆性破坏,破坏应变小于2.5%;正常固结和轻超固结土的应力路径呈“S”形,重超固结土的应力路径呈不断增长的趋势。根据破坏标准,重超固结土和轻超固结土、正常固结土共用一条临界状态线,不排水抗剪强度计算公式参数较少,易获取,易嵌入本构模型中,应用方便。To study the yield and critical state of over-consolidated saturated clay,a series of undrained shear tests of saturated clay in different over-consolidated states were carried out by GDS triaxial tester.To analyze the stress path of saturated clay,and the ALPHA(α)model was selected to describe the yield characteristics of soils in different over-consolidation states.The variation trend of deviatoric stress/pore pressure-strain curves of saturated clay was analyzed,The failure state was identified when the pore pressure increased to the maximum value.The critical state line is fitted according to the stress failure points.The calculated formulas for the undrained shear strength with different over-consolidation ratios are presented.The results show that with the same preconsolidation pressure,the shear strength increases with the decrease of over-consolidation ratio.However,the yield stress do not monotonically increases with the decrease of over-consolidation ratio.With the same over-consolidation ratio,the shear strength increases with the increase of the preconsolidation pressure,and so dose the yield stress.The failure strain of normal consolidated soil and light overconsolidated soil is about 5%,while that of heavy over-consolidated soil is less than 2.5%with obvious dilatation and brittle failure.The stress paths of normal consolidated and light over-consolidated soils are“S”type,while the stress paths of heavy over-consolidated soils are in trend of increasing.According to the failure criterion,heavy over-consolidated soils share the same critical state line with light over-consolidated and normal consolidated soils.There are few formula parameters for calculating undrained shear strength,which is easy to be obtained and embedded in the constitutive models,and it is convenient for application.

关 键 词：黏土 超固结比 临界状态 α屈服面模型 不排水抗剪强度 

分 类 号：TU411.3[建筑科学—岩土工程]