Experimental study on shield machine cutting steel-reinforced concrete diaphragm wall

•This study performs a full-scale field test using shield machine to cut a diaphragm wall.•The cutterhead design and machine operation parameters are recommended.•The test shows that shield machine can effectively break steel reinforced concrete wall.•Cutter wear and wall vibration are relatively small when machine is properly operated. Shield tunneling during metro construction frequently hits steel reinforced concrete diaphragm walls. A high risk is involved in using a shield machine to cut through a diaphragm wall owing to limited theoretical research and engineering experience. To evaluate the performance of the shield machine and obtain feasible operation parameters, this study conducts a full-scale field test using a shield machine to cut through a diaphragm wall in Suzhou, China. The machine has a diameter of 6.84 m, equipped with 38 disc cutters and 48 scrapers. The wall has a width of 8.8 m, height of 9.7 m, and thickness of 0.6 m, reinforced with 25 mm and 28 mm diameter main steel rebars. The study finds: 1) the shield machine has adequate capacity to cut the diaphragm wall with small wear (maximum amplitude of 0.7 mm) to disc cutters and light damage to scrapers; 2) the concrete is mainly damaged under compression shear and peel-off with 95 % of particle size smaller than 10 cm, whereas the steel rebars are broken under the combined effects of compression shear and pull-apart with five damage modes identified based on different damage mechanism; and 3) a low advance rate (1–2 mm/min) and medium rotational speed (0.6 rpm) are recommended such that the machine can cut the wall smoothly with wall acceleration below 0.15 g and maintains its thrust and toque close to 10 % and 15 % of rated thrust and torque, respectively. The findings prove the feasibility of using a shield machine to cut through a diaphragm wall, and provide guidance for project implementation.