摘要
为探究应力路径对含裂隙膨胀土力学特性的影响,采用引江济淮渠段膨胀土进行常规三轴压缩(CTC)试验和减压的三轴压缩(RTC)试验,系统分析膨胀土在不同应力路径和裂隙贯通率条件下的破坏机理和变形特征。研究表明:试样的破坏模式受裂隙贯通率影响。随着裂隙贯通率增大,应力-应变曲线由应变硬化型向应变软化型转变,土体抵抗剪切破坏的能力也逐渐减弱。当裂隙贯通率一定时,RTC路径下土体的侧向约束减小,偏应力对应变更为敏感。在卸荷初期,应力-应变曲线的增长趋势比较陡峭,轴向应变不到3%就接近峰值偏应力;而在CTC路径下,在轴向应变达到3%后才接近峰值偏应力。不同应力路径下试样的体变特征也存在差异,CTC路径下,体变表现为剪缩,而RTC路径下表现出剪胀特征。RTC路径下试样的极限破坏偏应力与抗剪强度指标均低于CTC路径下的试验值。当固结围压相同时,RTC路径的极限破坏偏应力值约为CTC试验值的54.7%~65.8%;裂隙贯通率相同时,RTC路径的极限破坏偏应力值约为CTC试验值的60.2%~77.6%;RTC试验中的黏聚力和内摩擦角分别为CTC试验值的69.1%和82.1%。改进的D-C模型能够很好地描述含裂隙膨胀土的应力-应变曲线软化特征。CTC路径下,膨胀土的初始切线模量随着固结围压的增大而增大;而RTC路径下,初始切线模量随固结围压的增大而减小。研究成果可为防止土体开挖卸荷引起的工程灾害问题提供参考。
In order to explore the influence of stress paths on the mechanical properties of expansive soil with cracks,the conventional triaxial compression(CTC)test and the reduced triaxial compression(RTC)test were conducted using the expansive soil in the channel section of the Yangtze-to-Huaihe Water Diversion Project.The destruction mechanisms and deformation characteristics of the expansive soil under different stress paths and crack penetration rates were systematically analyzed.The findings reveal that the failure mode of the sample is affected by the crack penetration.As the crack penetration increases,the stress-strain curve shifts from strain hardening to strain softening,and the soil’s ability to resist shear failure gradually weakens.When the crack penetration rate remains constant,the lateral restraint of the soil under the RTC path decreases,and the deviatoric stress becomes more sensitive to the change in strain.At the initial stage of unloading,the growth trend of the stress-strain curve is relatively steep,and the peak deviatoric stress is reached when the axial strain is less than 3%.However,under the CTC path,the peak deviatoric stress is attained only after the axial strain reaches 3%.There are also differences in the volumetric strain characteristics of the specimens under different stress paths.The volumetric strain under the CTC path exhibits shear contraction,while under the RTC path,it shows shear dilation characteristics.The ultimate failure deviatoric stress and shear strength index of the specimens under the RTC path are lower than those under the CTC path.When the consolidated confining pressure is the same,the ultimate failure deviatoric stress of the RTC path is approximately 54.7%to 65.8%of the CTC test value.When the crack penetration rate is the same,the ultimate failure deviatoric stress of the RTC path is approximately 60.2%to 77.6%of the CTC test value.The cohesion and internal friction angle in the RTC test are 69.1%and 82.1%of the CTC test value,respectively.The improved D-C model can effectively describe the softening characteristics of the stress-strain curve of expansive soil with cracks.Under the CTC path,the initial tangential modulus rises with the increase of consolidated confining pressure,while under the RTC path,the initial tangential modulus decreases with the increase of consolidated confining pressure.The research results can offer a reference for preventing engineering disasters caused by soil excavation and unloading.
作者
王帅
胡波
鲁松
孙慧
WANG Shuai;HU Bo;LU Song;SUN Hui(Key Laboratory of Geotechnical Mechanics and Engineering of Ministry of Water Resources,Yangtze River Scientific Research Institute,Wuhan 430010,China)
出处
《铁道科学与工程学报》
北大核心
2025年第5期2168-2179,共12页
Journal of Railway Science and Engineering
基金
中央级公益性科研院所基本科研业务费项目(CKSF2023327/YT)
安徽省引江济淮工程科技创新项目(YJJH-ZT-ZX-20230118528)。
关键词
膨胀土
裂隙贯通率
应力路径
剪切破坏
抗剪强度
expansive soil
crack penetration rate
stress path
shear failure
shear strength
