Experimental study on the performance and mechanism of high-pressure abrasive water jet cutting GFRP bars reinforced concrete structures.

Abrasive water jet (AWJ) cutting technology is considered an effective method to assist tunnel boring machines in efficiently breaking glass fiber reinforced polymer (GFRP) bar reinforced concrete structures. However, systematic investigations on the coupled cutting behavior of GFRP bars and concrete remain limited. To address this gap, this study presents the first comprehensive experimental analysis of AWJ cutting of GFRP-reinforced concrete, clarifying the removal mechanisms of both GFRP bars and concrete and revealing the key process parameters governing cutting depth. An innovative and systematic evaluation of AWJ process parameters was conducted by integrating single-factor experiments with orthogonal tests to elucidate the relative significance of each parameter on cutting depth. The results show that cutting GFRP bars with high-pressure AWJ can produce deeper cracks than cutting concrete. The cutting depth of GFRP bars and concrete is negatively correlated with traverse speed and standoff distance, and positively correlated with nozzle diameter, pump pressure, and number of cutting passes. When high-pressure AWJ cuts concrete, brittle fracture erosion is the main mechanism, resulting in smooth and flat cutting surfaces. The damage caused by pure water jet to concrete exhibits a water-wedge failure mode, propagating mainly along transitional weak interfaces and forming irregularly shaped failure surfaces. The relative importance of AWJ cutting parameters on concrete cutting depth is ranked as follows: traverse speed, number of cutting passes, standoff distance, pump pressure, and nozzle diameter. Recommended parameters for engineering applications include a pump pressure of 240 MPa, a traverse speed of ≤ 15 m/min, a standoff distance of approximately 40 mm, and a nozzle diameter of about 0.44 mm. Under these conditions, concrete can be cut with 2-3 passes and GFRP bars with a single pass, ensuring cutting efficiency while maintaining a balance among water consumption, equipment capacity, and construction safety. These findings extend the understanding of AWJ-assisted cutting of GFRP-reinforced concrete and provide theoretical guidance and practical references for jet-assisted rock breaking in Shield tunneling operations.