With the rapid development of high-speed railroads and subways, there has been an increasing number of bridge–tunnel overlapping structures. To study the dynamic response characteristics of bridge–tunnel structures under the synergistic effects of the vibration generated by high-speed railway and subway trains, the dynamic response characteristics of a bridge–tunnel structure under single-point vibration loading was analyzed by conducting numerical simulations and model tests, with the frequency response function and peak acceleration as the evaluation indices. The dynamic response characteristics of the overlapping structure under moving vibration loads of the high-speed railway and subway trains were further analyzed. The results showed that the dynamic response of the bridge–tunnel overlapping structure increased with the increase in the frequency under the full frequency domain single-point sweep vibration load. The dynamic response of the tunnel hance near the pile foundation side was significantly greater than the vault and invert. Compared with the effect of high-speed train loads alone, the dynamic response of the bridge–tunnel overlapping structure under the synergistic effects of high-speed railways and subways increased significantly and varied at different locations. This investigation provides theoretical support for the design and construction of bridge–tunnel overlapping structures under the synergistic effects of high-speed railways and subways, contributing to improving engineering quality and safety.

When the tunnel passes through the slope area, once the slope stability changes or landslide disasters occur, large additional stress, deformation, or cracking are easily caused in the tunnel, which results in high risk to the tunnel operation. The deformation and failure mode of the tunnel induced by different types of tunnel-related landslides are different. However, there is no systematic classification of tunnel structure deformation and the failure mode in the tunnel-related landslides systems. By investigating the typical cases of tunnel diseases caused by landslide in China, this study analyzes the relationship between the tunnel-related landslide types and tunnel disease characteristics. It also summarizes five typical tunnel deformation failure modes and corresponding deformation characteristics and determines the relationship between tunnel-related landslide types and deformation failure modes. This study can provide a technical support for the identification of landslide types through the tunnel deformation characteristics in practical engineering applications. Finally, it provides a reference for tunnel location selection, the design of tunnel structure, and the treatment of landslide in landslide areas.

In order to study the dynamic response characteristics of a pile-soil foundation when an adjacent tunnel exists, both model tests and numerical simulations were performed in this study. Taking the peak vibration acceleration, peak vibration velocity, and peak vibration displacement as the evaluation indexes of the dynamic response, the dynamic response of the pile-soil foundation with an adjacent tunnel under high-speed train loads is studied. A method of dividing the affected zones of the dynamic response based on the safety threshold is provided in this paper, which can evaluate the safety of the adjacent tunnel under the action of train load. Additionally, the effect of train speed on dynamic response is further analyzed. The results show that the dynamic response index inside the foundation decays significantly with increasing distance from the surface when the train load is applied, regardless of the presence or absence of the adjacent tunnel. Compared with an ordinary pile-soil foundation, the dynamic response indexes inside the foundation increase significantly when there is an adjacent tunnel. With the increase in the horizontal distance from the pile foundation, the distribution characteristics of the horizontal transverse direction of each dynamic response index inside the foundation change from a “wavy” distribution to a monotonically decreasing distribution. According to the safety threshold of vibration velocity, the foundation is divided into the hazardous affected zone, strongly affected zone, and weakly affected zone, and then the corresponding vibration reduction measures are adopted. With the increase in train speed, the effect of tunnel structure on the attenuation of dynamic response in a pile-soil foundation becomes more obvious.

Mudstone is highly sensitive to water. When it comes into contact with water, the softening phenomena such as the decrease of strength and the increase of deformation are prominent. It is of great significance to clarify its related mechanical properties. For the tertiary mudstone, a triaxial compression test and a Brazilian splitting test are carried out under the conditions of four kinds of water content (0, 10.1%, 12.5%, and 14.1%) and four kinds of confining pressures (0 MPa, 2 MPa, 5 Mpa, and 10 MPa). The test results show that (1) with the increase of confining pressure and water content, the mudstone changes from brittle failure to ductile failure. The higher the confining pressure, the greater the strength and elastic modulus. The higher the water content, the significantly lower the strength and elastic modulus, and the higher the strain. (2) With the increase of water content, the influence of confining pressure on strength is more prominent. High confining pressure can effectively inhibit the trend of strength attenuation. (3) When the water content is low (0–10.1%), the strength of the mudstone is mainly related to its own water content. When the water content increases to 10.1%–14.1%, both the confining pressure and the water content are important factors affecting the strength of the mudstone. Then, the applicability of five commonly used strength criteria to the strength prediction of softened mudstone is compared and analyzed. The results show that the Rocker strength criterion can more accurately and conveniently predict the strength of mudstone under different water content. Finally, based on this strength criterion, a nonlinear strength prediction model of softened mudstone considering water content and confining pressure effect is proposed and its good applicability is verified.

In this study, a tunnel temperature field model test bed is built according to the similarity principle to study the variation law of temperature in the tunnel in the cold season. According to the variation law of temperature in the tunnel, a new active thermal insulation measure, namely, an air curtain system, is developed. According to the principle of flow function superposition and heat balance, the governing equation of air curtain system is obtained. Taking the Zhengpantai tunnel as an example, the feasibility of the air curtain system is verified, and the jet angle of air curtain is optimized. The research results show that outside temperature and surrounding rock temperature are the main factors affecting the temperature field of tunnels in cold regions. The calculation results show that the air curtain system can effectively prevent tunnel freezing damage. The optimal jet angle of air curtain system should be 30°–40°. When the outside temperature is extremely low, multiple air curtains can be used in series to heat the temperature in the tunnel, and it is recommended that the distance between the two air curtains is not less than 20 m.