To meet the ever-growing needs of economic and social activities, an increasing number of tunnels have been built to narrow physical distances and to improve transport efficiency. However, engineers are faced with various complicated geological and operational environments, such as high temperature, high geo-stress, heavy vehicle load from cargo trains, and dynamic load from high-speed trains, as well as corrosive liquids.

These complicated geological and operational environments often significantly slow down construction progress and can induce decay and failure of tunnel structures, threatening the safety of the tunnel environment. Therefore, creative construction technology, innovative design methods, and scientific maintaining techniques that are applicable for building and maintaining tunnels in unfavourable environments should be systematically investigated and studied.

The purpose of this Special Issue is to create a channel for sharing knowledge of technical treatments toward tunnels in harsh geological and operational environments during the design, construction, and operation stages. Research in this field can be interdisciplinary, involving hazardous geology, chemistry, nondestructive testing, remote sensing, computer vision, machine learning, and numerical calculation. For instance, automatic displacement monitoring systems based on computer vision technology could be an ideal solution to identify abnormal deformation of tunnels in a rapid and efficient manner during the operation period. Additionally, we especially welcome hybrid artificial intelligence research in this field. Both original research and review articles are welcome.

Potential topics include but are not limited to the following:

• Novel site investigation and data collection techniques
• Advanced constitutive models for surrounding rocks and concrete tunnel linings
• Research on design and construction methods of tunnel structures in harsh geological conditions such as high ground temperature, high geo-stress, etc.
• Mechanical property evolution laws and corresponding treatments for bottom structures of tunnels under heavy train loads
• Deterioration characteristics and property control methods of tunnel structures against corrosive geological environments
• Intelligent systems for whole lifetime monitoring of service performance of tunnels using digital imaging and artificial intelligence technology
• Aerodynamic response of tunnel structures under high-speed train load
• Mechanical responses of both tunnel structures and surrounding rock media subject to dynamic loading or earthquakes
• Stability and risk analysis of tunnels under construction or operation
• Tunnel facility operation maintenance and management