## 1 Introduction
Since the anchoring structure of ground anchored suspension bridges and the surrounding rock mass bear the main bridge load, there are more application cases of ground anchored suspension bridges than self-anchored suspension bridges, which improves the crossing ability of suspension bridges on the basis of ensuring the deformation of bridges [13]. Among the bridges built and put into use at different times, the proportion of tunnel anchor suspension bridges is gradually increasing, but the application of tunnel anchors is affected by factors such as topography, formation lithology, and surrounding rock properties, etc. The early design is relatively conservative, and the application is mostly concentrated on short-span bridges. With the development of tunnel anchor technology, tunnel anchors are gradually applied to long-span suspension bridges. At present, the construction and application of suspension bridges using tunnel anchors are gradually increasing, and the anchoring strata continue to expand to the soft rock mass with poor rock quality and low mechanical properties, shallow surface rock mass, and areas with complex geological conditions. However, the bearing mode of the tunnel anchor structure and the creep deformation of the surrounding rock mass bearing the uplift load affect the stability of the joint bearing system formed by \"tunnel anchor and surrounding rock\" [14; 15]. Therefore, with the increasing application range of tunnel anchors and the trend of complex and diversified anchoring strata, it is of great significance to understand the load-bearing mode of tunnel anchors, the stress and deformation trend of anchoring structure and surrounding rock, and the failure mode and stability of the \"tunnel anchor-surrounding rock\" co-bearing system [16; 17]. Tunnel anchor is a key component for the main cable tension transfers to rock mass, and the stability of rock mass in the anchoring area is also a key factor affecting the use of tunnel anchor. The mechanical properties of rock mass in the anchoring area and the bearing state of the anchoring structure jointly affect the safety performance of the suspension bridge and the overall stability of the bridge structure [18]. Although the parameters of the surrounding rock mass determined by the laboratory model test can reflect the mechanical properties of the anchorage rock mass in the engineering area, the synergistic effect between the \"tunnel anchor and surrounding rock\" is difficult to be fully revealed due to the length contraction effect. Therefore, before the actual construction of the tunnel anchor suspension bridge, in order to fully guarantee the optimal design and safe construction of the tunnel anchor, the influence of geological conditions and rock mass characteristics similar to the actual anchoring area on the tunnel anchor system can be determined through in situ model experiments, and the structural and mechanical properties of the rock mass can be further obtained. Currently, some scholars have investigated tunnel anchor system performance through in situ scaled model tests. However, bridge construction applications based on such test results remain limited in China, particularly regarding tunnel anchors in deep overburden conglomerate strata--an area that still lacks systematic in situ scale research. Some scholars have analyzed the deformation characteristics and failure modes of tunnel anchor-surrounding rock systems by in situ scaling model tests. [PERSON] et al. revealed the mechanical rock mass characteristics of tunnel anchors under different load conditions through large-scale field model tests and evaluated the potential load-bearing performance of tunnel anchors in the proposed super-large railway suspension bridge based on practical application cases [19]. Based on field model tests, [PERSON] et al.