Timber lagging is not a common type of tunnel lining due to its limited load-bearing capacity and susceptibility to decay in moist environments.

A tunnel ventilation system serves multiple purposes, including removing harmful gases and pollutants, controlling temperature and humidity, and providing fresh air for workers.

Drill and blast is the most common method used for excavating tunnels in hard rock due to its versatility and effectiveness in breaking through tough geological formations.

Budget and cost constraints are not a key factor to consider when designing a tunnel, as the primary focus is on ensuring safety, functionality, and compliance with regulations.

The tunnel invert serves multiple purposes, including providing a smooth surface for vehicles to travel on, collecting and draining water away from the tunnel, and supporting the tunnel lining to prevent settlement.

Heavy machinery accidents are not a common safety hazard associated with tunnel construction, as strict safety protocols and regulations are in place to minimize the risk of such incidents.

The primary function of a tunnel crown is to support the tunnel lining and prevent collapse, ensuring the structural integrity of the tunnel.

Drill and blast is not a common method used for constructing tunnels in soft ground due to the risk of ground collapse and instability.

The purpose of a tunnel drainage system is to collect and drain water away from the tunnel, prevent flooding and water damage, and maintain a dry and safe environment for workers and users.

Open-face TBM is not a common type of tunnel boring machine, as it is primarily used for excavating tunnels in stable and non-cohesive soils.

The primary purpose of a tunnel lining is to support the tunnel structure and prevent collapse, provide a smooth surface for vehicles to travel on, and protect the tunnel from water infiltration and damage.

Trapezoidal is not a common type of tunnel cross-section, as it is less efficient in terms of space utilization and structural stability compared to other shapes.

The purpose of a tunnel portal is to provide a transition zone between the tunnel and the outside environment, control the flow of traffic and vehicles entering and exiting the tunnel, and house ventilation and electrical equipment.

Drill and blast is not a common method used for constructing tunnels in urban areas due to the potential for ground disturbance, noise, and vibration, which can cause disruption and inconvenience to nearby residents and businesses.

The purpose of a tunnel fire safety system is to detect and suppress fires within the tunnel, provide safe evacuation routes for occupants in case of a fire, and minimize the spread of smoke and toxic gases.