Oblique detonation waves (ODWs) have attracted increasing attention in recent years due to their potential application to air-breathing hypersonic propulsion. Most of the previous studies on them were based on a semi-infinite wedge, considering the ODW itself but ignoring its interaction with geometric confinement. In this study, the ODWs based on bended tunnel geometry had been studied with a detailed hydrogen–air chemical reaction model. An expansion wave was introduced by the bended upper-wall, and then interacted with the original ODW surface, resulting in a series of complicated wave configurations along different positions of the upper expansion wave. When the expansion wave was induced far upstream before the original ODW surface, the ODW surface would be partially decoupled. And if the expansion wave has located downstream enough, the reflection of the ODW surface on the wall would induce an unsteady ODW. However, a modest distance between the ODW and expansion wave created a structure that had never been reported before. This novel structure was found to be combined by two high-temperature regions, one was from the original ODW reaction zone while the other append near the upper wall after the turning point. The new high-temperature region was found to be overlapped by a recirculation region, suggesting a balance between flow and heat release.