尾矿砂非均质性堆积结构严重威胁尾矿库的安全稳定运行，但现有冻融循环作用导致尾矿砂非均质堆积体力学性能退化分析较少。基于三轴压缩试验、核磁试验对冻融循环作用下尾矿砂非均质堆积结构宏观力学性能、细观孔隙演化进行分析。结果表明：随着冻融循环次数增加，不同界面倾角试件抗剪强度均明显降低，降幅与倾角大小呈正相关；低围压下，倾角较大的试件应力-应变曲线表现为应变软化；冻融循环作用下，粗砂、细砂及各倾角试件变形模式可归纳为剪胀、剪胀-收缩并存，破坏模式为横向断裂；冻融循环导致尾矿砂试件孔隙水发生“迁移积累”作用，而不同粒径尾矿砂堆积界面结构可大幅缩短“迁移积累”周期，表现为更剧烈的小孔隙连通与大孔隙塌陷现象；围压对尾矿砂起到强化作用，可放大冻融循环对尾矿砂强度劣化的影响；小颗粒对下层孔隙空间的填充作用，导致界面处尾矿砂强度增加，界面上方小颗粒处为弱结构面，更易出现结构劣化特征。该研究结果可为冻融作用下砂、土体力学性能退化提供宏-细观角度参考。The heterogeneous accumulation structure oftailings sand poses a serious threat to the safe and stable operation oftailings ponds. However

analyses of how freeze-thaw cycles affect themechanical properties of heterogeneous tailings-sand accumulations are limited.In this paper

based on triaxial compression tests and nuclear magneticresonance tests

we analyze the macroscopic mechanical properties andmesoscopic pore evolution of the heterogeneous accumulation structure oftailings sand under the action of freeze-thaw cycles. Results show that as thenumber of freeze-thaw cycles rises

the shear strength of specimens withdifferent interface inclination angles decreases significantly

and the magnitude ofdecrease correlates positively with the inclination angle. Under low confiningpressure

the stress-strain curves of specimens with larger inclination anglesexhibit strain softening. Under the action of freeze-thaw cycles

thedeformation modes of coarse sand

fine sand

and specimens at variousinclination angles can be categorized as shear dilation or a combination ofshear dilation and contraction

with the failure mode being transversefracture. Freeze-thaw cycles cause the “migration and accumulation” of porewater in tailings sand specimens. Interface structures of tailings sandaccumulations with different particle sizes can significantly shorten the “migrationand accumulation” period

presenting more intense phenomena of small poreconnectivity and large pore collapse. Confining pressure strengthens tailingssand and can amplify freeze-thaw–induced strength deterioration. The filling ofthe lower-layer pore spaces by fine particles increases the interfacialstrength of the tailings-sand at the interface. The small particles locatedabove the interface act as weak structural planes and are more prone todeterioration. These findings provide both macroscopic and microscopicperspectives on how freeze-thaw cycles degrade the mechanical properties ofsand and soil.