地震多发区尾矿抗液化强度与动力变形特性试验

Experimental study on the liquefaction resistance and dynamic deformation characteristics of tailings in earthquake-prone areas

为了研究地震多发区尾矿的抗液化强度和动力变形特性,以某上游法尾矿库中尾矿为研究对象,首先探究沉积固结方式与尾矿细粒含量(FC)的关系;此外,通过开展动三轴试验研究FC对尾矿抗液化性能和动力变形特性的影响,并从尾矿的微观结构特征出发,分析FC对尾矿动力变形特性的作用机制.结果表明:上层尾矿主要经历淋滤固结和化学固结,下层尾矿主要经历自重固结,而FC随取样深度非线性增加.对数坐标下的动剪应力随动循环次数增加近似线性减小,而有效固结围压(σ′_(3c))增大使尾矿颗粒接触更加紧密,导致尾矿结构破坏需要更强的动载荷.尾矿的抗液化强度随FC增加先降低后升高,FC越小,尾矿的抗液化强度越高、循环应力比衰减越快,而FC变化对动孔隙水压比的影响较小.尾矿的动孔隙水压比–振次比曲线呈现“减速增长—稳定增长—加速增长”的3阶段发展趋势,而较大的固结压力能够在一定程度上抑制动孔隙水压增长,此外,基于三参数动孔隙水压模型,得到了适用于本文尾矿的两参数动孔隙水压简化模型.随着FC增大,尾矿的动剪切模量先减小后增大、阻尼比先增大后减小,尾矿的动力变形特性逐渐由粗颗粒控制向细颗粒控制转变,该过程细粒含量存在临界值.研究结果可为地震多发区尾矿库稳定性评价及尾矿动力分析提供理论依据.

To investigate the liquefaction resistance and dynamic deformation characteristics of tailings in earthquake-prone areas,this study focused on samples from an upstream tailing pond.Initially,it examined how sedimentation and consolidation behaviors are affected by the fine content(FC)of the tailings.Subsequently,dynamic triaxial tests were conducted to assess the impact of FC on the liquefaction resistance and dynamic deformation characteristics.Furthermore,this study analyzed the impact of FC on the dynamic deformation characteristics of tailings considering their microstructural features.The results revealed distinct consolidation processes at different depths in the tailing pond;leaching and chemical consolidation predominate in the upper layers,while self-weight consolidation is more common in the lower layers,with the FC increasing nonlinearly with depth.The dynamic shear stress,when plotted on a logarithmic scale,decreased approximately linearly as the number of dynamic cycles increased.An increase in effective consolidation confining pressure enhances particle contact,requiring stronger dynamic loads to destroy the tailing structure.The liquefaction resistance of the tailings first decreases and then increases with rising FC levels.A lower FC resulted in a higher liquefaction resistance and a quicker attenuation of the cyclic stress ratio in the tailings,whereas the FC variations weakly affected the dynamic pore water pressure ratios.The relationship between the dynamic pore water pressure ratio and vibration ratio follows a three-stage pattern:decelerating,stable,and accelerating growth.A larger consolidation pressure can partially suppress the dynamic pore water pressure growth to a certain extent.In addition,a two-parameter simplified model for dynamic pore water pressure,tailored to the tailing characteristics,was derived from a more complex three-parameter model.Moreover,the dynamic shear modulus of the tailings initially decreased and then increased with FC,whereas the damping ratio initially increased and then decreased.The dynamic deformation characteristics of the tailings gradually shift from being controlled by coarse particles to fine control,with a critical FC value observed during this process.Before and after reaching this critical FC,the dynamic shear modulus and damping ratio of the tailings exhibit opposite trends in relation to FC.However,further detailed dynamic triaxial testing across different FC ratios is necessary to determine the precise value of the critical FC value for the tailings.These results provide a theoretical foundation for assessing the stability of tailing ponds and analyzing tailing dynamics in earthquake-prone areas.