含水砂层的剪切流变力学特性试验分析

Experimental Research on Shear Rheological Mechanical Properties of Water-bearing Sand Layer

通过十字板剪切流变仪试验,得到了剪切阻力、含水量、孔隙水压力与应变速率的变化曲线。试验表明,含水砂层的流变曲线呈现稳态流变阶段和加速流变阶段。稳态流变阶段又可分为弹性变形、初始流变和非加速流变过程。初始流变过程含水量和孔隙水压力上升,后保持稳定;经过较长时间的流变后,进入非加速流变阶段,剪切阻力呈现波动下降趋势;达到屈服抗剪强度时,进入加速流变阶段,应变速率迅速增大。通过对加速流变过程曲线进行拟合,得出加载剪应力、屈服抗剪强度和应变速率的关系。分析表明,干燥细砂的抗剪强度主要来自颗粒间的摩擦力,当含水量增加时,颗粒被水分子包围,削弱了颗粒间的作用力,其流变特性就发生了明显的变化;反映这一变化过程的主要参数是屈服抗剪强度,其与加载剪应力和含水量有关。

The vane shear rheometer was used to study the rheological properties of the water-bearing sand layer.The test curves including shear resistance,water content,pore water pressure and strain velocity were obtained. The results show that the rheological curves of the sand layer appear obvious different phases,stable rheological stage and accelerated rheological stage,with the water content increasing. The former stage experiences the elastic deformation,initial and non-accelerated rheological processes. When shear resistance achieves the yield resistance strength,the sand layer entered the accelerated rheological stage,and the strain velocity increases quickly. Based on the fitted curves of accelerated rheological stage,the relations between loading shear resistance,yield shear strength and stress velocity were obtained. The analysis indicate that the resistance strength of dry sand comes from the friction between particles,when the water content increases the particles are surrounded by the water which decreases the acting forces between the particles. Therefore,the rheological properties change obviously. The yield resistance strength is the critical parameter to reflect the change process which is connected with the loading shear stress and water content.