基于不同卸荷速率与路径影响下吹填土力学特性研究  

Experimental study of mechanical properties of dredger fill under different unloading rates and stress paths

作　　者：杨爱武 杨少坤[1,2] 张振东 YANG Ai-wu;YANG Shao-kun;ZHANG Zhen-dong(College of Environmental Science and Engineering,Donghua University,Shanghai 201620,China;Tianjin Key Laboratory of Soft Soil Characteristics and Engineering Environment,Tianjin Chengjian University,Tianjin 300384,China)

机构地区：[1]东华大学环境科学与工程学院,上海201620 [2]天津城建大学天津市软土特性与工程环境重点实验室,天津300384

出　　处：《岩土力学》2020年第9期2891-2900,2912,共11页Rock and Soil Mechanics

基　　金：国家自然科学基金项目(No.51978440);天津市科技计划项目(No.19JCZDJC39700,No.2016CJ01)。

摘　　要：运用应力路径三轴试验仪,对天津滨海吹填土开展等向固结条件下的不排水卸荷试验,探讨不同卸荷路径及卸荷速率对应力−应变关系、孔压变化规律及破坏强度特性的影响。试验结果表明:各卸荷路径下应力−应变曲都近似呈双曲线型。UU0.0(径向卸荷、轴向不卸荷)卸荷路径下试样变形表现为轴向压缩,且孔压变化曲线存在明显的屈服点;UU2.0(轴向和径向均卸荷),UU∞(轴向卸荷、径向不卸荷)及UL1.0(轴向卸荷、径向加荷)路径下试样变形表现为轴向伸长,孔压随着应变的增加而增大,最终速度减缓并趋于稳定增长状态。同种路径下,卸荷速率越大,卸荷初期孔压发展越缓慢,峰值孔压越大。对0.1、0.2、0.3 kPa/min卸荷速率下的应力−应变曲线研究发现,卸荷压缩路径下初始切线模量受卸荷速率影响较大,拉伸路径下则不明显。UL1.0路径下卸荷破坏强度最大,UU2.0路径下该值最小,UU∞路径下则居中。同一卸荷路径下,土体破坏强度随卸荷速率的增大而增大。对各应力−应变曲线进行归一化处理,构建了考虑卸荷速率及卸荷路径影响的初始切线卸荷模量和卸荷破坏强度预测公式。The undrained unloading tests of isotropic consolidation on soft dredger fill of Tianjin Binhai are performed using the stress-path triaxial apparatus to determine the effects of different unloading stress paths and unloading rates on stress-strain relationship,pore pressure variation and failure strength characteristics.Some findings are as follows.The stress-strain curves under each unloading path are approximately hyperbolic curves.Under the unloading stress path of UU0.0(radial unloading,axial not unloading),the deformation of samples exhibits axial compression,and the curves of pore pressure have sharp yield points.On the contrary,the deformation of samples under the path of UU2.0(both axial and radial unloading),UU∞(axial unloading,radial not unloading)and UL1.0(axial unloading,radial loading)show axial tension.In this way,the pore pressure increases with the increase of strain,and finally the growth rate of the pore pressure slows down and tends to increase steadily.Under the same stress paths,the larger the unloading rate,the slower the development of the pore pressure in the initial stage of unloading and the greater the peak pore pressure.The stress-strain curves at unloading rate of 0.1,0.2 and 0.3 kPa/min are found that the initial tangent modulus is greatly affected by unloading rate under unloading compression paths,while it is not influenced under the tensile paths.The value of unloading failure strength is the maximum under the UL1.0 path,the minimum in the UU2.0 path,and centered in the UU∞path.Under the same unloading path,the failure strength increases with the increase of the unloading rate.According to the normalization of stress-strain curves,the formulas,which considers the influence of unloading rates and unloading stress paths,are developed to estimate the initial tangent modulus and the unloading failure intensity.

关 键 词：吹填土 卸荷路径 卸荷速率 应力−应变 初始卸荷模量 卸荷破坏强度 

分 类 号：TU411[建筑科学—岩土工程]