库水循环加卸载条件下岸坡饱和土体变形特性试验研究

Experiment study on deformation characteristics of slope deep soil under the cyclic loading and unloading action of reservoir water

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 shape deformation will occur on the soil of the bank slope under the cyclic loading and unloading action of reser- voir 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 real-time mea- sured and analyzed. The result shows that the sample shear strain tends to terraced rising and the volumet- ric 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 conven- tional triaxial test, and the internal mechanism of their shear strength differences is analyzed.