为解决完整硬岩小半径转弯螺旋隧道TBM施工难题，依托北山地下实验室螺旋斜坡道工程，采用数值模拟、室内试验、工厂试验、工地现场试验等方法，针对高效破岩与出渣、小半径转弯、螺旋转弯高精度控制开展研究、创新与实践，取得的成果有： 1）重载508 mm（20英寸）滚刀承载力、最大允许磨损量分别提升19%、23%；采用锥面刀盘实现了最优临空距破岩；前置式滚刀刀间距为60 mm，较常规刀盘减小13 mm；采用微爆破人造裂隙辅助破岩技术使完整硬岩破岩效率显著提高。2）创新TBM主机结构、优化后配套设计，定制化移动测站导向系统，实现小半径转弯螺旋隧道TBM精准导向与调向。3）采用多点驱动、定制胶带、减小带强、加大带宽、减小带速、双储带仓、2段搭接、适应性调整等近20项措施，保证小半径转弯螺旋连续皮带机顺利高效出渣。依托上述关键技术，“北山1号”TBM完成全部施工任务，历经7处下坡叠加水平转弯，工程成洞质量优良，轴线控制精度可靠，施工对围岩扰动程度低。
To address the construction challenges of tunnel boring machine (TBM) for intact hard rock small-radius curved spiral tunnels, a case study is conducted on the spiral ramp project of the Beishan Underground Laboratory. Numerical simulations, laboratory tests, factory tests, and on-site tests are employed to conduct research, innovation, and practice focusing on efficient rock breaking and mucking, small-radius turning, and high-precision control of spiral turning. The following results are achieved: (1) For heavy-duty 20-inch disc cutters, the load-bearing capacity and maximum allowable wear are increased by 19% and 23% respectively. The conical cutterhead realizes optimal rock breaking with proper free surface distance. The front-mounted disc cutters with a spacing of 60 mm is 13 mm smaller than that of conventional cutterheads. Combined with the micro-blasting artificial fracture-assisted rock breaking technology, these multiple measures significantly improve the rock breaking efficiency in intact hard rock. (2) By innovating the main structure of the TBM and optimizing the design of its rear auxiliary system, a customized mobile survey station guidance system is developed to achieve precise guidance and direction adjustment of the TBM in small-radius curved spiral tunnels. (3) Nearly 20 measures are implemented, including multi-point drive, customized conveyor belt, reduced belt strength, increased belt width, reduced belt speed, double belt storage bins, two-section lap joint, and adaptive adjustment. These measures ensure the smooth and efficient mucking of the spiral continuous belt conveyor in small-radius turns. Relying on the aforementioned key technologies, the Beishan No. 1 TBM successfully completed all construction, and traversed seven compound curves with negative gradients. The project demonstrates excellent borehole quality and alignment control accuracy, while maintaining minimal disturbance to the surrounding rock.
