超大直径（直径≥14 m）泥水盾构刀具在软硬不均地层受交变载荷作用，掘进参数选取难，刀具更换频繁，常压换刀装置刀座螺栓易发生过载失效、松动等问题，严重影响隧道施工安全。为实现对换刀装置载荷实时监测、感知载荷数据来指导施工，以汕头苏埃通道工程为依托，提出一套基于光纤光栅技术的载荷实时监测系统。该监测系统利用智能螺栓在泥水环境中对螺栓载荷进行测量，通过无线通信技术传输信号，最后基于数据采集软件对载荷数据进行存储、分析。结果表明： 1）该系统能够在恶劣的泥水环境下克服复杂电磁环境，稳定可靠地对载荷进行监测； 2）盾构在软硬不均地层掘进时，螺栓轴力载荷呈周期性变化且因安装位置不同差异性较大，利用软硬不均地层螺栓轴力载荷差异可估算岩石侵入高度并指导刀具配置； 3）通过对螺栓轴力监测能够发现螺栓松动、预紧力衰减现象，有助于及时抽检刀具、加强螺栓防松措施，对降低施工风险很有必要。该系统可用于载荷实时监测、螺栓松动识别、岩石侵入高度估算等，对盾构施工具有一定指导作用。

The extralarge diameter (over 14 m) slurry shield would be subjected to alternating loads when tunneling in soft and hard strata, which would lead to difficult tunneling parameters selection, frequent tool replacement, overload failure, and the loosening of the tool holder bolt, as well as seriously affect the tunneling safety. To achieve realtime load monitoring of tool replacement devices and guide the construction through sensing the load data, a suite of realtime load monitoring systems based on fiber Bragg grating technology are proposed based on the Su′ai tunnel in Shantou, China. The monitoring system measures the bolt load in a muddywater environment with smart bolts, then transmits the signal via wireless communication technology, and finally stores and analyzes the load data based on data acquisition software. The results show the following: (1) The electromagnetic environment has no harm on the system in a muddywater environment and the system can monitor the load stably and reliably. (2) When shield tunneling in soft and hard strata, the axial load of bolts changes periodically and varies greatly due to the different installation positions. The rock intrusion height can be estimated to guide the tool configuration according to the difference of the axial load of bolts in soft and hard strata. (3) By monitoring the bolt axial force, the phenomena of bolt loosening and pretightening force attenuation can be identified, which is conducive to timely conduct countermeasures for reducing the construction risk. The system can be used for realtime load monitoring, boltloosening identification, and rock intrusion height estimation of shield tunneling, as well as for providing guidance.