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以干燥试样为对照,对自然、吸水和饱水3类含水试样进行单轴冲击试验,分析水-动力耦合作用下红砂岩试样的动态强度与变形特征以及损伤破坏前后的能量演化机制。试验结果表明:试样的动态抗压强度和峰值应变受含水率和冲击荷载影响较大,而峰值模量主要受含水率影响较为明显,这是由于红砂岩在水弱化作用下颗粒结构疏松膨胀、胶结强度减弱,加之在中高应变率下孔隙水所具有的细观力学效应,致使试样表现出低强度和高应变,而冲击荷载带来的应变率效应则使试样强度增强,塑性变形受到抑制;试样峰值点前吸收的总应变能U多以可释放弹性能Ue存储起来,耗散能Ud占比较小,各部分应变能随着脉冲强度的升高而增加,但随着含水率的变化趋势则不尽相同;不同脉冲强度下的脆性指标修正值BIM(Ud与Ue的比值)显示红砂岩试样的含水率以及冲击荷载的脉冲强度均存在一个阀值,使其塑性变形在水-动力耦合作用下的响应截然不同,而引入的有效冲击能指标K_(eff)显示应变率效应对干燥试样和自然试样的冲击倾向性具有显著影响,对于含水率较高的吸水试样,水弱化作用降低了应变率效应,达到饱水状态时,因为饱和液体对应变率效应的促进作用,饱水试样的应变率效应得到强化。
The dry specimens were used as a control to test the natural, water-saturated and water-saturated three types of water samples for uniaxial impact tests. The dynamic strength and deformation characteristics of the red sandstone samples under water-power coupling and the energy evolution mechanisms before and after the damage were analyzed . The experimental results show that the dynamic compressive strength and peak strain of the sample are greatly affected by the water content and impact load, while the peak modulus is mainly affected by the water content, which is due to the loose expansion of the red sandstone under water weakening , The cementation strength weakened, and the microscopic mechanical effect of pore water at medium and high strain rates resulted in low strength and high strain of specimen, while strain rate effect caused by impact load increased the strength of specimen and plastic deformation The total strain energy U absorbed before the peak of the sample is more than that of Ue which can be released by elastic energy Ue. The energy dissipation Ud accounts for a small proportion and the strain energy of each part increases with the increase of pulse intensity. However, The change trend of the rate is different; the BIM (Ud / Ue ratio) of the brittleness index at different pulse intensities shows that there is a threshold value for the water content of the red sandstone sample and the pulse intensity of the impact load, so that the plastic deformation The response under water-power coupling is quite different, and the effective impact energy index K eff (eq) introduced has shown that the strain rate effect has a significant effect on the impact propensity of dry and natural samples. In water-absorbent samples with higher water content, water weakening reduces the strain rate effect. When the saturated water is saturated, the strain-rate effect of the saturated water sample is enhanced due to the promoting effect of the saturated liquid on the strain rate effect.