The suspension pipe bridge has become the main span type due to its large span, light structure, and other characteristics, playing an important role in the construction of the oil and gas backbone network and energy layout. Tunnel-type anchorage (TTA) is a special underground structure that provides anchorage tension for the suspension bridge. Since its form and bearing mechanism are complex, there is no general design method for tunnel-type anchorage so far, and the theoretical and normative research is not mature. In this paper, a field-scale experiment was carried out to study the north side tunnel of Wujiagang Bridge in Yichang, China. According to the similarity principle, the 1:12 tunnel anchor scale model was established. The tunnel anchor scale model is selected in the area adjacent to the actual project site to ensure the similarity of stratigraphic conditions. Through the use of a displacement meter, inclinometer hole, strain gauge, micrometers, and other comprehensive monitoring methods, the design load test, overload test, overload rheological test, and ultimate bearing capacity failure test were carried out. Through the structural deformation observation and stress observation of the anchorage body and surrounding rock, the stress deformation characteristics and rheological characteristics of the anchorage body and surrounding rock in the field-scale experiment were analyzed. The deformation failure mechanism, deformation failure process, potential failure mode, and overload capacity of solid tunnel anchor were studied. The control indexes such as deformation and stress values of key parts of the solid tunnel anchor at different stages are predicted. Based on the limit equilibrium analysis results of the model, the safety and rationality of the tunnel anchorage structure design of the actual suspension bridge were evaluated.

Tunnel anchors are critical for suspension bridge stability, yet their theoretical framework remains underdeveloped, limiting engineering applications. This study addresses this gap through a pioneering 1:12 in situ scaled model test, combining geological surveys, rock mechanics testing, and large-scale experimentation on a Yangtze River bridge case. Key findings include (1) quantified rock mechanics parameters for anchorage conglomerates, (2) load–displacement relationships revealing surrounding rock-dominated failure, and (3) deformation thresholds for anchor integrity. The 1:12 in situ model overcomes lab-scale limitations, providing the first high-fidelity validation of tunnel anchor behavior. The results offer essential design benchmarks, advancing both theory and practice for large-span bridges.

This study aims to investigate the mechanical behavior and failure mechanisms of tunnel-type anchorages for suspension bridges under complex geological conditions, using the Wujiagang Yangtze River Bridge as a case study. A scaled physical model (1:40) was employed to systematically examine deformation patterns, stress transfer, and ultimate bearing capacity under incremental loading. Key results demonstrate a quasi-symmetrical “double-hump” deformation response under service load, with axial stress concentrated at the rear anchorage face. The critical safety threshold was identified at 9 times the design load (9P), beyond which plastic damage initiates. Uplift resistance was found to rely primarily on rear rock mass confinement, while sandstone interlayers and mortar joints showed negligible impacts on stability. These findings provide practical criteria for the design and safety assessment of tunnel anchorages in rock-dominated environments.

Tunnel anchorages are critical components in long-span suspension bridges, transferring immense cable forces into the surrounding rock mass. Although previous studies have advanced the understanding of their pullout behavior through field tests, laboratory models, numerical simulations, and theoretical analyses, significant challenges remain in predicting their performance in complex geological conditions. This study investigates the pullout failure mechanism and bearing behavior of tunnel anchorages situated in heterogeneous conglomerate rock, with application to the Wujiagang Yangtze River Bridge in China to employ a tunnel anchorage in such strata. An integrated research methodology is adopted, combining in situ and laboratory geotechnical testing, a highly instrumented 1:12 scaled field model test, and detailed three-dimensional numerical modeling. The experimental program characterizes the strength and deformation properties of the rock, while the field test captures the mechanical response under design, overload, and ultimate failure conditions. Numerical models, calibrated against experimental results, are employed to analyze the influence of key parameters such as burial depth, inclination, and overburden strength. Furthermore, the long-term stability and creep behavior of the anchorage are evaluated. The results reveal the deformation characteristics, failure mode, and ultimate pullout capacity specific to weakly cemented and stratified rock. The study provides novel insights into the rock–anchorage interaction mechanism under these challenging conditions and validates the feasibility of tunnel anchorages in complex geology. The findings offer practical guidance for the design and construction of future tunnel anchorages in similar settings, ensuring both safety and economic efficiency.