Extending 3D Concrete Printing to Hard Rock Tunnel Linings (2023-02)¶

As an emerging automated construction technology, 3D concrete printing opens the opportunity for the construction of hard rock tunnel linings. However, very limited studies were carried out in this regard, especially the adhesion between freshly printed cementitious materials and the excavated rock wall deserves further attention. In this study, the adhesive performance of the fresh cementitious material at two representative surface inclinations, including the overhead position (inclination of 180◦) and the side position (inclination of 90◦), was explored by a tack test and a shear test. This was further studied by two series of 3D concrete printing tests including horizontal printing at the underside of a supported slab and vertical printing against an upright slab. Results demonstrated the adhesion at the overhead position was limited by both the shear resistance of the fresh cementitious material and the property of the material-to-substrate interface, while the adhesion at the side position was mainly constrained by the shear resistance of the fresh cementitious material. Moreover, the stress state analysis of the printed layers at the overhead position and the side position indicated that the tack test and shear test gave a good prediction about the printing capacity of the fresh cementitious material for hard rock tunnel linings.