Tunnel construction involves creating underground passages for various purposes, such as transportation, utilities, or water management. The process typically begins with site surveys and planning, followed by excavation using specialized equipment like tunnel boring machines or drilling rigs. Once the tunnel is excavated, it is reinforced with materials such as concrete or steel to ensure stability. Proper ventilation and drainage systems are also installed to maintain safety and functionality. Tunnels can be built using different methods, including cut-and-cover and immersed tube techniques, depending on the project's requirements and location.