| 李业学*,张启明,周炜,王学斌,范建辉.干燥和饱水砂岩孔隙度对应力波能耗的影响[J].实验力学,2020,35(1):174~182 |
| 干燥和饱水砂岩孔隙度对应力波能耗的影响 |
| On the influence of dry and saturated sandstone porosity on stress wave energy consumption |
| 投稿时间：2018-05-27 修订日期：2018-08-30 |
| DOI：10.7520/1001-4888-18-128 |
| 中文关键词: 孔隙度 能耗 饱水 砂岩 应力波 |
| 英文关键词:degree of porosity energy consumption saturated water sandstone stress wave |
| 基金项目:湖北省教育厅科学技术研究计划重点项目(D20172601) |
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| 中文摘要: |
| 为探讨应力波穿越干燥、饱水砂岩时孔隙度对能耗的影响规律，开展了孔隙砂岩的SHPB试验，并采用核磁共振分析了SHPB试验前后孔隙的变化特征。结果表明：(1)砂岩冲击试验前后T2谱波峰数没变，但对应小孔径孔隙的波峰峰值有所增加。这说明，砂岩结构内部仍停留在微裂纹形成阶段，应力波能量仅能够促使新的微裂纹形成，而不足以撕裂扩展孔隙使其孔径更大。(2)相同孔隙度时，饱水砂岩比干燥砂岩能耗小；随着孔隙度增加，前者能耗相应减小，后者能耗反而增加。这一现象可分别解释如下：(a)由断裂力学理论可知，水的表面张力和Stefan效应使裂纹扩展受到很大阻力，因而，相对干燥砂岩，相同孔隙度的饱水砂岩更难产生新表面耗散应力波能量。(b)冲击加载时饱水砂岩处于不排水状态，饱水砂岩变形可近似等于砂岩和水的压缩变形之和。由于水比砂岩压缩变形小，随着孔隙度增大，即含水量增加，饱水砂岩变形量减小，出现塑性变形和新裂纹的概率减小，能耗值也随之减小。(c)随着孔隙度增大，干燥砂岩的动态强度相应降低，加载时更易出现新裂纹以表面能形式耗散应力波能量，因而孔隙度越大则能耗越大。 |
| 英文摘要: |
| In order to investigate the influence of porosity degree on energy consumption during stress wave traversing dry and saturated sandstone, split Hopkinson pressure bar (SHPB) experiment for porous sandstone was carried out in this paper, and the characteristics variation of pore before and after SHPB experiment were analyzed by nuclear magnetic resonance (NMR). Results indicate that before and after sandstone impact experiment, the peak number of T2 spectrum remained unchanged, but the peak value of wave peak corresponding to small size pore increases. This means that the sandstone structure is still in the micro-crack formation stage, the stress wave energy can only promote the formation of new micro-cracks, and the energy is not enough to tear the expanded pores to make its pore size larger. Under the condition of same degree of porosity, the energy consumption of saturated sandstone is lower than that of dry sandstone, and with the increase of porosity degree, the energy consumption of the former decreases and that of the latter increases. This phenomenon can be explained as follows：(a) According to theory of fracture mechanics, the surface tension of water and the Stefan effect make the crack growth suffer great resistance. Therefore, it is more difficult for saturated sandstone with the same porosity degree to produce new surface consumption stress wave energy than dry sandstone. (b) Under impact loading, the saturated sandstone is in an undrained state, and the deformation of the saturated sandstone can be approximate to the sum of the compressive deformation of the sandstone and the water. Water is less deformed than sandstone compression. With the increase of porosity degree, that is, the increase of water content, the deformation of saturated sandstone decreases. The probability of plastic deformation and new cracks decreases, so does the energy consumption. (c) With the increase of porosity degree, the dynamic strength of dry sandstone decreases accordingly, and new cracks are more likely to appear in the form of surface energy to dissipate stress wave energy. Therefore, the larger the porosity degree is, the greater the energy consumption. |
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