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为研究主动围压状态人工冻结砂土的动态力学性能,利用直径50 mm变截面分离式Hopkinson压杆试验装置,以取自山东济宁某矿-94.52 m处冻结砂土为研究对象,对长径比为0.5的冻结砂土试件进行主动围压状态下的冲击压缩试验,分析了主动围压和应变率对冻结砂土动态力学性能的影响。研究结果表明,无围压状态下,冻结砂土动态应力-应变曲线可分为弹性阶段、塑性阶段、黏性阶段和破坏阶段,冻结砂土呈脆性破坏;主动围压状态下,应力-应变曲线塑性阶段明显增长,无黏性阶段,冻结砂土呈微裂破坏。相同条件下,主动围压状态下冻结砂土的动态抗压强度均高于无围压状态,且随着围压的增大,动态抗压强度逐渐增大;当应变率为220 s-1,温度为-15℃时,主动围压为0.5、1.0、1.5、2.0 MPa的动态抗压强度为无围压状态下的119%、140%、158%和181%。不同主动围压下的应力-应变曲线表现出汇聚现象,汇聚点趋向于无围压状态。冻结砂土的动态抗压强度随应变率的提高而增加。
In order to study the dynamic mechanical properties of artificially frozen sand under active confining pressure, a split Hopkinson pressure bar test rig with a diameter of 50 mm was used to study the frozen sand at a depth of 94.52 m from a mine in Jining, Shandong Province. The impact compression test under the condition of active confining pressure was carried out on frozen sand specimens with a ratio of 0.5, and the influence of active confining pressure and strain rate on the dynamic mechanical properties of frozen sand was analyzed. The results show that under the condition of no confining pressure, the dynamic stress-strain curves of frozen sand can be divided into elastic stage, plastic stage, viscous stage and destructive stage, and the frozen sandy soil presents brittle failure. Under active confining pressure, the stress- The stage of curve plasticity obviously increases, and in the stage of no stickiness, the frozen sand and soil is micro-cracked. Under the same conditions, the dynamic compressive strength of frozen sand under active confining pressure is higher than that without confining pressure, and the dynamic compressive strength increases with the confining pressure increasing. When the strain rate is 220 s-1 , The dynamic confining pressure is 0.5, 1.0, 1.5 at the temperature of -15 ℃, and the dynamic compressive strength at 210 MPa is 119%, 140%, 158% and 181% under no confining pressure. The stress-strain curves under different confining pressures showed convergence phenomenon, and the convergence point tended to have no confining pressure. The dynamic compressive strength of frozen sandy soil increases with the increase of strain rate.