TBM adaptability analysis in small-radius curved tunnels in Kurkar strata in Israel

In shield tunnelling, both alignment and geological conditions not only influence the performance of the tunnel boring machine (TBM) but also affect disturbance of the strata. Based on an analysis of the challenges posed by alignment and geological conditions, a targeted design was implemented for a TBM for small-radius curved tunnels in the Kurkar strata in Israel. The adaptability of the TBM was verified through a comprehensive analysis of strata disturbance, variations in boring parameters, tunnel alignment and cutter wear. The results indicated that, to accommodate small-radius curves, the TBM could be adapted by shortening the shield length, setting articulation cylinders and configuring overcutting tools. To adapt to the Kurkar strata, 2.5‰ of foaming agent (CLB F5/M) can be added, along with appropriately increasing the soil chamber pressure. The TBM parameters can be set as follows: total thrust 20 000–24 000 kN, cutterhead rotation speed 1.3–1.4 rpm, TBM advance rate reaching 30–45 mm/min and cutterhead torque ranging from 2500–3500 kN.m. Double-disc cutters should be avoided in the Kurkar strata, especially in central regions of the cutterhead.