Mechanical cutting assisted by high-pressure jet is a common and efficient drilling method in the exploration of hot dry rock (HDR). The drilling efficiency can be further improved with an in-depth understanding in the rock-breaking mechanism, which is a complex process involving the coupling of thermal stress, jet impact pressure and cutting force. To address such a multi-physics coupling issue, a loosely coupling method was adopted in this work to accomplish the exchange of data, including temperature, heat flux, nodes deformation and impinging pressure of jet in every time increment. In the fluid subdomain, the liquid nitrogen (LN2) jet and water jet were modeled and compared to demonstrate the potential of the novel jet in improving the drilling rate. In the solid subdomain, cutting force monitored in the experiment was loaded, and the concrete damage plastic model was employed to evaluate damage behaviors of the rock. Relative experiments were conducted to validate the reliability of simulation results. Results indicate that a great temperature difference develops on the coupling surface under the impingement of LN2 jet due to its cryogenic feature and lower heat transfer efficiency. Thereby, irreversible damage of the rock can be induced even at room temperature (298 K). As for the water jet, tensile damage is not observed until the rock temperature increases to 473 K. The assistance of jet impact on rock breaking is mainly reflected in two aspects: (1) the occurrence of tensile damage on the coupling surface facilitates the subsequent rock cutting; (2) the enhancement of tensile damage around the cutter promotes the initiation of cracks. Higher rock temperatures significantly improve the heat transfer rate and enhance the advantage of jet assistance. The present study can provide a new sight for the exploration of HDR.

在高压干岩（HDR）勘探中，高压射流辅助机械切割是一种常见且有效的钻探方法。深入了解破岩机理可以进一步提高钻井效率，这是一个复杂的过程，涉及热应力，射流冲击压力和切削力的耦合。为了解决这种多物理场耦合问题，在这项工作中采用了一种松散耦合的方法来完成数据的交换，包括温度，热通量，节点变形以及每一次增量的射流冲击压力。在流体子域中，对液氮（LN2）射流和水射流进行了建模和比较，以证明新型射流在提高钻井速率方面的潜力。在实心子域中，加载了在实验中监控的切削力，并采用混凝土破坏塑性模型评估岩石的破坏行为。进行了相关实验以验证仿真结果的可靠性。结果表明，由于LN2射流的低温特性和较低的传热效率，在LN2射流的撞击下，耦合表面上会出现很大的温差。由此，即使在室温（298K）下也可以引起岩石的不可逆破坏。对于水射流，直到岩石温度升至473 K才观察到拉力破坏。射流对岩石破碎的帮助主要体现在两个方面：（1）在耦合表面上发生拉力破坏有利于后续工作。凿岩；（2）刀具周围的拉伸损伤的增强促进了裂纹的产生。较高的岩石温度显着提高了传热速率，并增强了射流辅助的优势。本研究可以为探索HDR提供新的视野。