The rate-dependent mechanism is analyzed for frictional contact between a blunt tool and a fluid-infiltrated porous rock under pressurized condition. The dimensional analysis is adopted to derive a dimensionless number $$\lambda$$ λ that predominantly governs the rate-dependent mechanism from pore pressure diffusion. The governing nature of $$\lambda$$ λ is analyzed by finite element modeling using the software ABAQUS for an idealized plane strain frictional contact problem. After validating the finite element model against analytical solutions for special cases, the rate-dependent frictional contact is analyzed for poroelastic, poroelastoplastic, rigid-poroplastic, and elasto-visco-plastic rocks, respectively. Three pore pressure regimes exist depending on $$\lambda$$ λ : low speed (0 < $$\lambda$$ λ ≲ 10 –1 ), transient (10 –1 ≲ $$\lambda$$ λ ≲ 10 3 ), and high speed ( $$\lambda$$ λ ≳ 10 3 ). The pore pressure generally increases, and the average effective contact stress decreases with increasing $$\lambda$$ λ for a poroelastic rock and a typical poroelastoplastic rock. The average effective contact stress generally decreases with increasing $$\lambda$$ λ for a rigid-poroplastic rock at a small dilatancy angle due to compactive weakening, but increases with $$\lambda$$ λ at a large dilatancy angle due to dilatant strengthening. A transition occurs from compactive weakening to dilatant strengthening with increasing the dilatancy angle. The average effective contact stress increases with decreasing the interface friction angle for a rigid-poroplastic rock. It is inferred from numerical results that the high-speed regime dominates with cavitation for frictional contact on shales in deep drilling, and that the strain rate effect is negligible in typical experiments on dry rocks at ambient pressure.

中文翻译：

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多孔岩石摩擦接触的速率效应

分析了钝头工具与加压条件下流体渗透多孔岩石之间的摩擦接触的速率相关机制。采用量纲分析推导出无量纲数 $$\lambda$$ λ，该数主要控制孔隙压力扩散的速率相关机制。对于理想化的平面应变摩擦接触问题，使用 ABAQUS 软件通过有限元建模分析了 $$\lambda$$ λ 的控制性质。在针对特殊情况的解析解验证有限元模型后，分别针对多孔弹性、多孔弹塑性、刚性-多孔塑性和弹-粘-塑性岩石分析了与速率相关的摩擦接触。根据 $$\lambda$$ λ 存在三种孔隙压力状态：低速 (0 < $$\lambda$$ λ ≲ 10 –1 )，瞬态（10 –1 ≲ $$\lambda$$ λ ≲ 10 3 ）和高速（ $$\lambda$$ λ ≳ 10 3 ）。对于多孔弹性岩石和典型的多孔弹塑性岩石，孔隙压力普遍增大，平均有效接触应力随着λλ的增大而减小。硬质孔隙塑性岩石在小剪胀角由于压实弱化，平均有效接触应力通常随着 $$\lambda$$ λ 的增加而减小，但在大剪胀角由于剪胀作用，平均有效接触应力随着 $$\lambda$$ λ 增加强化。随着剪胀角的增加，发生从压实弱化到剪胀强化的转变。刚性-孔塑性岩石的平均有效接触应力随着界面摩擦角的减小而增加。