Shale gas is becoming a new energy development focus worldwide with advances in horizontal wells and hydraulic fracturing, and spontaneous water-based working fluid imbibition is one of the strongest phenomena that can impact borehole stability and the gas extraction rate. Our present experimental work was carried out on shale Brazilian discs with 5 different bedding orientations (0°, 30°, 45°, 60° and 90°) after air-drying and spontaneous water imbibition using a split Hopkinson pressure bar. The results illustrate that under the same loading rate (100–900 GPa/s), spontaneous water imbibition obviously weakens the dynamic tensile strength of shale discs, except for shale discs with a bedding orientation of 90° when the loading rate exceeds 400 GPa/s, and does not change the anisotropic dynamic tensile strength variation trend versus bedding orientations. Models that can well fit test data and reveal the coupling effects of bedding orientation and loading rate on the dynamic tensile strength of shale after air-drying and spontaneous water imbibition are proposed. The rate-dependent failure mode only appears among shale discs with bedding orientations of 30°, 45° and 60°, and this phenomenon is exacerbated and more complex after spontaneous water imbibition. Bedding planes of shale discs after air-drying and spontaneous water imbibition both play three different roles in affecting the failure crack propagation, i.e., intersecting propagation, promoting propagation and promoting turning. Finally, the dynamic tensile strength responses of shale after spontaneous water imbibition are analyzed and discussed, and potential field applications in borehole stability, perforation design and hydraulic fracturing are suggested.

随着水平井和水力压裂技术的进步，页岩气正成为全球新能源开发重点，而自发的水基工作液自吸是影响井眼稳定性和采气率的最强现象之一。我们目前的实验工作是在使用分离式霍普金森压力棒风干和自发吸水后，在具有 5 种不同层理方向（0°、30°、45°、60° 和 90°）的页岩巴西圆盘上进行的。结果表明，在相同加载速率（100~900 GPa/s）下，自吸水明显削弱页岩盘的动态抗拉强度，但当加载速率超过400 GPa/s时，层理取向为90°的页岩盘除外。年代，并且不改变各向异性动态抗拉强度随层理方向的变化趋势。提出了能够很好地拟合试验数据并揭示层理方位和加载速率对页岩风干和自吸水后动态抗拉强度耦合影响的模型。速率相关失效模式仅出现在层理方位为 30°、45°和 60°的页岩盘中，自吸水后该现象加剧且更为复杂。页岩盘风干和自吸后的层理面在影响破坏裂纹扩展方面均发挥了三种不同的作用，即相交扩展、促进扩展和促进转向。最后，