冻融循环次数和含水率对尾细砂力学性质的影响研究

为研究冻融循环次数和含水率对尾细砂力学性质的影响,利用GDH-2005B型高低温试验箱对尾矿砂试样进行冻融循环,并通过FST-200型应变控制式三轴剪力仪开展五种冻融循环次数(1次、3次、5次、7次、9次)和五种含水率(11%、13%、15%、17%、19%)尾矿砂试样常规三轴试验。研究表明:(1)相同含水率时,随着冻融循环次数的增大,变形模量逐渐减小,内聚力和内摩擦角均呈现降低的趋势;经历9次冻融循环后,内聚力降低至17.4kPa,内摩擦角降为14.82°。(2)相同冻融循环次数条件下,随着含水率的增大,尾矿砂的峰值应力降低,对应峰值应变增大;围压100kPa时,含水率19%的尾矿砂在经历9次冻融循环后应变为18.21%,应力为139.37kPa;各冻融循环次数下的尾矿砂抗压强度均呈现下降的趋势,内聚力和内摩擦角均随着含水率的增大而减小。研究成果可为尾矿砂物理力学性质理论的丰富以及尾矿砂相关工程的安全运营提供参考。

On the Influence of Freeze-Thaw Cycles and Moisture Content on the Mechanical Properties of Tailings Fine Sand

In order to study the influence of freeze-thaw cycles and moisture content on mechanical properties of tailings fine sand,tailings samples were subjected to cyclic freezing and thawing by using GDH-2005B high-low temperature test-box,conventional tri-axis experiment was carried out for tailings sand samples with five kinds of moisture content (11％,13％,15％,17％,19％) and subjected to five kinds of freeze-thaw cycles (1 time,3 times,5 times,7 times,9 times),respectively,based on FST-200 strain control type tri-axial shear apparatus.Results show that (1) Under the condition of same moisture content,along with the increase of freeze-thaw cycle number,the deformation modulus decreases gradually,and cohesive force and internal friction angle present decreasing trend.After 9 freeze-thaw cycles,the cohesive force is reduced to 17.4kPa,and the internal friction angle is reduced to 14.82 degrees.(2) Under the condition of same freezing and thawing cycles,along with the increase of moisture content,the peak stress of tailings sand decreases,and corresponding peak strain increases.When confining pressure is 100kPa,the strain of tailings with 19％ moisture content is 18.21％ after 9 times of freeze-thaw cycles,its stress is 139.37kPa.The compressive strengths of tailings under various freeze-thaw cycles show a decreasing trend.Both cohesive force c and internal friction angle ψ decrease with the increase of moisture content.Above results have certain significance for safety management and stability evaluation of tailings dam.