干湿循环后膨胀土力学特性的真三轴试验研究  

True triaxial experimental study on mechanical properties of expansive soils after drying and wetting cycles

作　　者：方瑾瑾[1] 杨小林 冯以鑫 龚健[1] 牛海成[1] FANG Jinjin;YANG Xiaolin;FENG Yixin;GONG Jian;NIU Haicheng(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5期1043-1055,共13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);河南省自然科学基金(182300410247)。

摘　　要：为了研究原状膨胀土经过反复干湿循环稳定后的力学性状,利用非饱和土真三轴仪对经历不同干湿循环后的膨胀土进行了一系列脱湿-吸湿试验、常吸力等向固结试验和常吸力真三轴剪切试验,研究干湿循环对膨胀土土-水曲线、胀缩特性、压缩特性和强度特性的影响。研究结果表明:随着干湿循环次数的增加,脱湿曲线和吸湿曲线形成的滞回圈越来越小,甚至发生了逆向回滞;脱湿速率和吸湿速率随着循环次数的增加而增大。脱湿—吸湿过程中体变性状皆呈明显的屈服特性,验证了膨胀土本构模型中SI和SD屈服包线的存在,脱湿屈服吸力均大于吸湿屈服吸力,且二者皆随着循环次数的增加而减小。在低围压和低吸力条件下,干湿循环对膨胀土的压缩特性影响较大,而在高围压和高吸力条件下影响较小。干湿循环使膨胀土的黏聚力和内摩擦角降低,干湿循环后膨胀土的黏聚力随着吸力和中主应力的增大而增大,内摩擦角随着中主应力的增大而减小。在低吸力范围内(s≤200 kPa),干湿循环后的膨胀土的吸力摩擦角φb是一个变量。经历3次干湿循环后膨胀土的强度逐渐趋于稳定,其吸力摩擦角可看作是一个常量,其值随着b值的增大非线性增大。A series of drying-wetting tests,constant suction isotropic consolidation tests and constant suction true triaxial shear tests were carried out on intact expansive soils subjected to different drying and wetting cycles to investigate the mechanical properties of intact expansive by using unsaturated true triaxial apparatus.The effects of drying and wetting cycles on the soil-water curves,expansion and contraction characteristics,compression characteristics and strength characteristics were studied.The results show that as the number of drying and wetting cycles increases,the hysteresis loop of the drying curve and the wetting curve is smaller and smaller,even reverse hysteresis,but the drying rate and the wetting rate increase.The volumetric strains in the process of drying and wetting show obvious yield characteristics,which verifies the existence of the SI and SD yield envelopes in the expansive soil constitutive model.The drying yield suction is larger than the wetting yield suction,and both of them decrease with increasing the number of cycles.Drying and wetting cycles have a great influence on the compression characteristics under low confining pressure and low suction while have little effect on the compression characteristics under high confining pressure and high suction.The cohesion and the internal friction angle of expansive soils will be reduced by drying and wetting cycles.After drying and wetting cycles,the cohesion of expansive soils increases with increasing the suction and the intermediate principal stress,but the internal friction angle decreases with increasing the intermediate principal stress.In the range of low suction(s≤200 kPa),the suction friction angle φb of expansive soils after drying and wetting cycles is a variable.After three drying and wetting cycles,the strength of expansive soils tends to be stable,and the suction friction angle increasing nonlinearly with b value can be regarded as a constant.

关 键 词：土力学 膨胀土 非饱和土真三轴仪 胀缩 干湿循环 

分 类 号：TU43[建筑科学—岩土工程]