库水循环加卸载条件下岸坡饱和土体变形特性试验研究
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摘要
水库运行期水位每年周期性涨落,岸坡土体在库水循环加卸载作用下会发生不同程度的阶梯状变形。为探求循环加卸载对岸坡深部变形的诱发机理,本文以水库防洪限制水位以下岸坡土体为研究对象,在饱和土应力路径三轴试验过程中,控制非等向受压试样的孔隙水压力周期变化,模拟岸坡土体的水力-力学状态,实时测定土体的周期性变形特性及破坏特征。研究结果表明:等偏应力孔压循环加卸载过程中,试样剪应变为台阶式上升趋势,而体应变是循环的弹性变化;孔压持续增大造成试样破坏呈现脆变和剪胀的特征。最后,结合等偏应力孔压增大条件下粉质黏土的破坏特征与常规三轴剪切试验成果,对比两种应力路径下试样的有效应力比和剪应变的发展过程,分析了其强度差异的内在原因。
The reservoir water level periodicly fluctuates every year,and different degree of ladder shapede formation will occur on the soil of the bank slope under the cyclic loading and unloading action of reservoir water. To explore the induced mechanism of deep soil deformation,in this paper,the deep silty clay of bank slope is selected as the main research object,it's hydraulic and mechanical state are simulated in the stress-path triaxial test by controlling the cyclic loading and unloading of pore water pressure in the condition of anisotropic compression,and it's deformation and damage characteristics are realtime mea-sured and analyzed. The result shows that the sample shear strain tends to terraced rising and the volumetric strain presents elastic change during the cyclic loading and unloading of pore water pressure under a constant deviatoric stress,and the samples are destroyed by continuous increasing pore water pressure with the characteristics of embrittlement and dilatancy. Finalily,the evolution processes of effective stress ratio and shear strain are contrasted between two different stress paths in combination with the result of conventional triaxial test,and the internal mechanism of their shear strength differences is analyzed.
The reservoir water level periodicly fluctuates every year,and different degree of ladder shapede formation will occur on the soil of the bank slope under the cyclic loading and unloading action of reservoir water. To explore the induced mechanism of deep soil deformation,in this paper,the deep silty clay of bank slope is selected as the main research object,it's hydraulic and mechanical state are simulated in the stress-path triaxial test by controlling the cyclic loading and unloading of pore water pressure in the condition of anisotropic compression,and it's deformation and damage characteristics are realtime mea-sured and analyzed. The result shows that the sample shear strain tends to terraced rising and the volumetric strain presents elastic change during the cyclic loading and unloading of pore water pressure under a constant deviatoric stress,and the samples are destroyed by continuous increasing pore water pressure with the characteristics of embrittlement and dilatancy. Finalily,the evolution processes of effective stress ratio and shear strain are contrasted between two different stress paths in combination with the result of conventional triaxial test,and the internal mechanism of their shear strength differences is analyzed.
引文
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[2]Berilgen Mehmet M.Investigation of stability of slopes under drawdown conditions[J].Computers and Geotechnics.2007,34(2):81-91.
[3]刘新喜,夏元友,张显书,等.库水位下降对滑坡稳定性的影响[J].岩石力学与工程学报,2005,24(19):1439-1444.
[4]张文杰,詹良通,凌道盛,等.水位升降对库区非饱和土质岸坡稳定性的影响[J].浙江大学学报:工学版,2006,40(8):1365-1370.
[5]年廷凯,万少石,蒋景彩,等.库水位下降过程中土坡稳定强度折减有限元分析[J].岩土力学,2010,31(7):2264-2270.
[6]薛星桥,张俊义,金枭豪,等.三峡库区淌里滑坡变形特征及影响因素分析[J].中国水土保持,2010,(6):47-49.
[7]李德营.三峡库区具台阶状位移特征的滑坡预测预报研究[D].武汉:中国地质大学,2010.
[8]彭令,牛瑞卿.三峡库区白家包滑坡变形特征与影响因素分析[J].中国地质灾害与防治学报,2011,22(4):1-7.
[9]陈蜀俊,姚运生,蔡永建.三峡库首区重点断裂围限区蓄水的加卸载效应[J].大地测量与地球动力学,2006,26(4):97-101.
[10]周斌,薛世峰,邓志辉,等.水库诱发地震时空演化与库水加卸载及渗透过程的关系——以紫坪铺水库为例[J].地球物理学报,2010,53(11):2651-2670.
[11]Stephen J V Hoven,Kip Solomon D,Gerilynn R Moline.Modeling unsaturated flow and transport in the saprolite of fractured sedimentary rocks:Effects of periodic wetting and drying[J].Water Resources Research,2003,39(7):1-11.
[12]曹玲,罗先启.三峡库区千将坪滑坡滑带土干-湿循环条件下强度特性试验研究[J].岩土力学,2007,28(S1):93-97.
[13]刘文化,杨庆,唐小微,等.干湿循环条件下不同初始干密度土体的力学特性[J].水利学报,2014,45(3):261-268.
[14]Won Jeong-Yun,Cotton Blake,Porter Byron W.Deformation and shear strength behaviors of overconsolidated clay from stress-path testing for a deep open cut excavation[J].Geotechnical Special Publication,2014,233:388-399.
[15]Gu Chuan,Wang Jun,Cai Yuanqiang,et al.Undrained cyclic triaxial behavior of saturated clays under variable confining pressure soil[J].Dynamics and Earthquake Engineering,2012,40(8):118-128.
[16]陈林靖,戴自航,刘志伟.应力路径对软土应力-应变特性影响试验研究[J].岩土力学,2011,32(11):3249-3257.
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