## 1 Introduction
Over the years, both theoretical systems and equipment technology have made significant progress. For instance, [PERSON] et al. [15] developed an automatic tunnel monitoring and early warning system based on geostationary technology satellites, enabling information management and the early warning and forecasting of tunnel monitoring and measurement data. [PERSON] et al. [16] conducted tunnel monitoring at the Qiyueshan tunnel site, analyzed the deformation characteristics and development trends of the tunnel surrounding rock by processing and evaluating the measurement data of tunnel section arch settlement and surrounding displacement, and revised and optimized tunnel design and construction accordingly. [PERSON] et al. [17] described the construction process of the tunnel opening excavation monitoring and measurement system in a mountainous area based on the actual situation of the tunnel opening excavation monitoring and measurement in a mountainous area of Chongqing. The portal stability analysis method and monitoring information feedback process based on multisource data were analyzed. [PERSON] et al. [18] analyzed the deformation and mechanical characteristics of the surrounding rock and initial support of the plateau wetland tunnel in the construction process of the Bodhisattva Hill wetland tunnel and introduced monitoring and measurement projects and methods in the construction process of the new Austrian method. Furthermore, [PERSON] et al. [19] presented a tunnel monitoring method based on distributed fiber sensing, which provides hundreds of strain and temperature sensing points within the structure, offering new information about the tunnel lining behavior. [PERSON] et al. [20] evaluated the applicability of two noncontact measurement methods for monitoring a series of small model tunnels, while [PERSON] et al. [21] introduced BOTDR, a newly developed strain measurement and monitoring technology, and analyzed its feasibility in TST strain monitoring through the BOTDR monitoring results of a tunnel in Nanjing. [PERSON] et al. [22] conducted a comparative test of three-dimensional coordinate measurement, RDM, and traditional measurement at the tunnel construction site, while [PERSON] et al. [23] proposed a prediction method based on monitoring the roadway crown dip angle along the roadway axis and applied it in field tests. Additionally, [PERSON] et al. [24] developed and proposed the CNU-TS-1 mobile tunnel monitoring system based on an in-depth study of tunnel monitoring methods. This method can effectively obtain the cross-section of the tunnel and eliminate the control measurement that depends on design data. [PERSON] et al. [25] conducted finite element calculation and analysis on the stability of surrounding rock at the overpass of the upper and lower reaches of the Fengze Street tunnel and emphasized the importance of mastering the mechanical dynamics of surrounding rock and support, timely feedback adjustment of construction methods and supporting parameters, and on-site monitoring projects. [PERSON] et al. [26] introduced the field measurement results of deformation at the fork of the Y-shaped fork of the mainline tunnel and branch tunnel of Guangzhou Rail transit line 3 during construction. [PERSON] et al. [27] provided a detailed description of the on-site monitoring and measurement method of deformation in the bifurcation section of the Shanghai Metro Line 2 tunnel and Metro Line 1 tunnel during the construction process of shield tunneling. Finally, [PERSON] et al. [28] carried out on-site monitoring and measurement during the construction of the Nanjing Xuanwuhu tunnel and subway bifurcation section. In recent years, research on the monitoring and measurement of bifurcated tunnels has mainly focused on subway and shallow buried bifurcated tunnel engineering.