Buildings (structures) with various structural forms are becoming increasingly prevalent and are encountering more challenging engineering issues. Field investigations, laboratory tests, and numerical simulations were used to study the disaster-causing mechanism and the control technology for a variable cross-section tunnel passing through layered, expansive mudstone stratum. The deformation and stress characteristics of the surrounding rock and supporting structure were examined by both numerical simulation and field monitoring. The results indicated that the stress was more complex at different section positions; the rock and supporting structure underwent substantially more deformation and stress in the broadened sections. The mean values of the surrounding rock’s horizontal convergence and vault settlement in the broadened section were 15.71% and 16.36% higher than those in the general section, respectively, and the value of lining stress was 35.51% higher. Additionally, the simulation results under the improved construction measures matched the measured results. The maximum deformation and stress of the surrounding rock were reduced by 16.95% and 40.04%, respectively, under the improved scheme, while the lining stress was reduced by 45.38%. The stress state of the secondary lining was significantly improved; in particular, the tensile stress in the lining structure under the original construction scheme was converted into a compressive state under the new measures, fully utilizing the bearing effect. Finally, the rationality and effectiveness of the adopted reinforcement measures were evaluated, and the experiences and lessons learned were summarized to provide insights for preventing similar incidents from reoccurring.

Underground engineering construction is facing increasingly complex geological conditions and engineering challenges, such as surrounding rock deformation and lining cracking, that seriously threaten the safety of tunnel construction and operation. Aiming at these problems, a pipeline tunnel crossing jointed expansive mudstone strata was taken as an example, and the disaster characteristics of surrounding rock and lining were analyzed through field investigation. The disaster-causing mechanism and corresponding control measures were studied through laboratory tests and numerical simulations, which were then applied to actual construction. Meanwhile, the deformation and stress response of the surrounding rock and tunnel structure were analyzed and investigated through monitoring and numerical data. The results showed that the vault settlement and horizontal convergence deformation of surrounding rock were reduced by 64.69 mm and 54.74 mm, respectively, under the improved construction scheme. The maximum surrounding rock stress was 430.26 kPa under the improved construction scheme, which was 18.15% lower than the original stress. The maximum axial force of the steel arch frame was 33.02 kN, ensuring the stability of the supporting structure and tunnel construction safety. Finally, the rationality and effectiveness of the reinforcement measures adopted were assessed.