Abstract: To address the challenging nature and slow tunneling of hard rock tunnel boring machines in the hard rock stratum, a tunnel boring machine equipped with a water jet cutterassisted rock breaking system is developed. This system enables rock breaking through the integrated action of a water jet and a disc cutter. Certain aspects of water jet cutterassisted rock breaking technology have been already studied: (1) The carrying and design concept of water jet cutterassisted rock braking system is introduced, and the working principles and parameters of the jet system pump station, transport system, and jet system are presented. (2) An experimental test is conducted to obtain the relationship between the index parameters of rock breaking and highpressure jet parameters. (3) The water jet cutterassisted rock breaking technology is equipped and applied in the field. Further, the test measures and data, tunneling effect, environmental temperature, system power, and existing problems are obtained using realtime data collection, and corresponding measures are proposed. (4) The approaches for optimizing and improving the water jet cutterassisted rock breaking technology are proposed based on the field tests. The results show that the water jet cutterassisted rock breaking technology is feasible. The field and torque penetration indices under 270 MPa water pressurecoupled tunneling are reduced by 38.1% and 16.9%, respectively, demonstrating good rock breaking effect. Moreover, temperature increase in the tunnel and abnormal wear of highpressure water pipelines should be addressed in the future as they affect the normal tunneling of equipment.

Key words: hard rock tunnel boring machine, water jet cutterassisted rock breaking, highpressure water jet, coupled rock breaking, experimental research