原状膨胀土强度和变形特性的真三轴试验研究  

True triaxial experimental study on strength and deformation characteristics of intact expansive soil

作　　者：方瑾瑾[1] 杨小林 冯以鑫 王立平[1] FANG Jinjin;YANG Xiaolin;FENG Yixin;WANG Liping(School of Civil Engineering,Henan Polytechnic University,Jiaozuo,Henan 454000,China;Infrastructure Department,Henan Polytechnic University,Jiaozhuo,Henan 454000,China)

机构地区：[1]河南理工大学土木工程学院,河南焦作454000 [2]河南理工大学基建处,河南焦作454000

出　　处：《岩石力学与工程学报》2021年第S02期3379-3388,共10页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家自然科学基金资助项目(51808197);河南省科技攻关项目(212102310293);河南理工大学博士基金项目(B2018-64)。

摘　　要：为了研究中主应力和基质吸力对原状膨胀土的强度和变形特性的影响,利用非饱和土真三轴仪,对原状膨胀土进行吸力平衡、等吸力排水固结和等吸力等b值剪切试验,研究原状膨胀土的胀缩特性、屈服特性及强度变,化特性。研究结果表明:原状膨胀土在吸湿和脱湿过程中呈弹塑性体变性状,屈服吸力s_(p)=71 kPa,当目标吸力值s有0kPa≤S≤37 kPa时,膨胀土呈弹性膨胀:当37 kPa<s≤71 kPa时,膨胀土呈弹性收缩:当s>71kPa时,膨胀土呈塑性收缩,验证了膨胀土弹塑性模型脱湿路径中SI屈服线的存在。等向压缩屈服应力随吸力的增大而增大,验证了膨胀土弹塑性模型中LC屈服线的存在。随着吸力的增大,原状膨胀土的剪胀性增强,剪胀性不仅与净围压和吸力密切相关,而且还受到中主应力的影响,中主应力越大,剪胀性越弱。不同b值条件下,黏聚力皆随着吸力的增大呈非线性增大,且吸力一定时,黏聚力随着中主应力的增大而增大;b值一定时,不同吸力膨胀土的内摩擦角相差不大,且内摩擦角随着中主应力的增大而减小:吸力摩擦角随着中主应力的增大呈非线性增大。A series of suction balance,equal suction drainage consolidation and equal suction and equal b-value shear tests were carried out on intact expansive soil by using unsaturated soil true triaxial apparatus to investigate the effect of intermediate principal stress and matric suction on the strength and deformation characteristics of intact expansive soil.The swelling and shrinking characteristics,yield characteristics and strength change characteristics of intact expansive soil were studied.The results show that the intact expansive soil shows an elasto-plastic volumetric strain in the process of wetting and drying,and yield suction s,is equal to 71 kPa.When O kPaSs≤37 kPa,the expansive soil exhibits elastic swelling,when 37 kPa<s≤71 kPa,the expansive soil exhibits elastic shrinkage,when s>71 kPa,the expansive soil exhibits plastic shrinkage,indicating the existence of the Suction-Increase(SI)yield locus in the drying path of the expansive soil elastoplastic model.The isotropic compressive yield stress increases with an increase in suction,which verifies the existence of Loading Collapse(LC)yield locus in the elastoplastic model of expansive soil.As the suction increases,the dilatancy of the intact expansive soil increases.The dilatancy is not only closely related to the net confining pressure and suction,but also affected by the intermediate principal stress,and the dilatancy is weaker as the intermediate principal stress is larger.The cohesion increases nonlinearly with an increase in suction at different b values,and when the suction is constant,the cohesion increases with an increase in intermediate principal stress.For a given b value,the internal friction angles of expansive soils with different suctions have little difference,and the internal friction angle decreases with an increase in the intermediate principal stress.While,the suction friction angle increases nonlinearly with an increase in intermediate principal stress.

关 键 词：土力学 原状膨胀土 胀缩特性 屈服特性 吸力 中主应力 

分 类 号：TU43[建筑科学—岩土工程]