饱水细砂岩动态抗拉与抗压强度试验对比研究

Comparative Study on Dynamic Tensile and Compressive Strength of the Saturated Fine Sandstone

使用霍普金森压杆(SHPB)装置对天然状态和饱水状态下的细砂岩进行单轴动态压缩试验和动态劈裂试验,研究水和加载速率对细砂岩动态抗拉、抗压强度的影响及其差异性,并且结合数字图像相关(DIC)技术,分析细砂岩动态抗拉、抗压时的破坏机制。试验结果表明:两种状态下的细砂岩动态抗拉、抗压强度有明显的率效应,随着加载速率的增大而增大,且相同加载速率下,细砂岩在饱水状态下比天然状态下的动态抗压强度小,而抗拉强度比天然状态下的大;水的存在对细砂岩动态抗压强度和抗拉强度的应变率效应影响不大,但水能提高细砂岩动态抗压和抗拉强度增强因子,并且对细砂岩动态抗拉强度增强因子的提高更显著;在动态受压过程中饱水状态岩样表面的应变集中处较天然状态下明显更少,应变梯度更显著,在动态受拉过程中拉剪效果被削弱。

Using split Hopkinson compression bar(SHPB)device,uniaxial dynamic compression tests and dynamic split tests on fine sandstone in natural state and saturated state were carried out.The influence and difference of water and loading rate on dynamic tensile and compressive strength of fine sandstone were studied,and the failure mechanism of the fine sandstone in dynamic tension and compression was analyzed with digital image correlation(DIC)technology.The test results show that the dynamic compressive strength and tensile strength of the fine sandstone under the two states have obvious strain rate dependent effect,and they increase with the increase of loading rate.Under the same loading rate,the dynamic compressive strength of fine sandstone in saturated state is smaller than that in natural state,while the tensile strength in saturated state is larger.Water has little effect on the strain rate effect of dynamic compressive strength and tensile strength for the fine sandstone.However,water can improve the dynamic compressive strength and tensile strength enhancement factor of the fine sandstone,and has a more significant effect on the dynamic tensile strength enhancement factor.In the process of dynamic compression,the surface strain concentration of the rock specimen in saturated state is significantly less than that in natural state,the strain gradient is more significant,and the tensile-shear effect is weakened during the dynamic tensile process.