Abstract: To prevent quality accidents of building foundation pits, it is necessary to monitor the strain ofkey parts during the foundation pit construction process. This paper analyzes the working principle ofFBC strain sensors and conducts experimental research on strain monitoring by embedding these sensorsin the reinforced concrete interior support structures of building foundation pits. The experimental methodinvolves measuring the strain values of the interior bracing at three different embedded positions: the up-per part, middle part, and lower part on the surface. Additionally, it combines traditional vibrating wirestrain sensor measurementmethod, and processes and compare the experimental data of the two testingmethods. The monitoring results indicate that the stress states of the upper part differ from those of theniddle and lower parts of the interior bracing: the upper part is in compression, while the middle andlower parts are in tension. The test results are in good consistency with those obtained by the traditionalvibrating wire strain sensors. The experimental results show that compared with traditional strain gauges,FBG strain sensors have better reliability and precision, and can realize real-time monitoring during con-struction. It is feasible to use FBG strain sensors to monitor the interal forces of interior bracing in build-ing foundation pits; however, their higher use cost and more demanding requirements for on-site installa-tion and maintenance should be considered.

Key words: FBG strain sensor, vibrating wire strain sensor, building foundation pit, interior bracing,
strain monitoring