摘要
针对湖南省某高速公路的路基粉土填料,开展了控制基质吸力的三轴试验,获取了基质吸力在0.05~300MPa范围内粉土的抗剪强度,探讨了基质吸力与抗剪强度参数、应变软化幅度、脆性指数以及破坏模式的关系,并采用了两种预测模型对毛细黏聚力测试值进行拟合分析。结果表明,随着基质吸力上升,内摩擦角φ’保持恒定,基本不受基质吸力和围压的影响,(σ-ua)-τ平面上的破坏包络线逐渐向上偏移,导致了毛细黏聚力增大;当粉土含水率由最优含水率(13.1%)向饱和含水率(16.3%)变化时,基质吸力将快速减小,从而引起粉土抗剪强度的大幅衰减。同时,基质吸力越大,应变软化幅度和脆性指数越高,随着脆性指数由0向1变化,试样的破坏模式由鼓胀、多组剪切面向单一贯穿破坏面发展;对于本研究中的粉土,采用Vilar改进模型可以对毛细黏聚力进行较好的预测(R^2=0.94)。
A series of Suction-controlled Triaxial Tests were carried out on subgrade silt filling from a certain expressway in Hunan province. The shear strength behavior was acquired from tests conducted between 0.05~300 MPa suction range. The relationship between matrix suction and shear strength parameter,strain softening amplitude,brittleness index,failure mode was discussed. And two prediction models were adopted for fitting analysis on testing data. The results show that with the increase in matrix suction,internal friction angle ?′ almost keeps constant and is little influenced by matrix suction and confining pressure. The failure envelope on (σ-u a )-τ plane gradually shifts upward,leading to capillary cohesion rise. When the moisture content of silt changes from the optimal moisture content (13.1%) to saturated moisture content(16.3%),the matrix suction will decrease rapidly with a significant attenuation in shear strength. Meanwhile,strain softening amplitude and brittleness index will increase when matric suction is enhanced. With brittleness index varies from 0 to 1,the failure mode of the specimen develops from expansion and multi-group shear plane towards single throughout failure plane. It is proved that Vilar improved model shows good prediction effect on capillary cohesion of silt in this study ( R^ 2=0.94).
作者
贺海涛
HE Haitao(Hunan Road and Bridge Construction Group Co.,Ltd.,Changsha,Hunan 410004,China)
出处
《公路工程》
北大核心
2019年第5期252-257,共6页
Highway Engineering
关键词
路基粉土
抗剪强度
三轴试验
基质吸力
应变软化
脆性指数
subgrade silt
shear strength
tri-axial test
matrix suction
strain softening
brittleness index
