The living environment and maintenance theory of tunnel

Tongji University

Xu P. Yao

Some Features about Tunnel

The total amount of tunnel under mountains, rivers and straits is leaping and the total length and width of the tunnels is enlarged. The environment of tunnel becomes more complex because people hope that the tunnels should be more secure and practicable. The tunnel construction needs large expenditures including man powers, materials and financial ability.

First, in tunnel construction the features are:

Tunnel maintenance must be given MORE attention for ensuring that they can complete their service mission in planning.

There is NO a systematic guidance for the tunnel maintenance today under the complex life environment.

Second, in tunnel maintenance the features are:

The Complexity of the Living environment of Tunnel

The living environment of the over-ground structure can not be compared with the one of the underground structure.

The underground structure, such as tunnel, is always limited and influenced by the environment in both the construction period and the operation span.

The mountain tunnel

The earth stress in the rock mass will be disturbed and then redistributed when the behavior of excavation is done in them. The high earth stress would create rockburst which could break the equipments and lead to the loss of personnel during construction, and even make the tunnel out of service earlier. Gas and terrestrial heat in rock mass as all above are not avoided in mountain tunnel.

The undersea tunnel

The undersea tunnel engineering is complex and arduous because it always lasts long time and lies in intricate environment. The huge hydraulic pressure, the geological features of the seabed and the earthquake and so on will bring some adverse impact to the construction of the tunnel. The crack and the water leakage are liable to take place during the construction of the undersea tunnel so that some effective measures of the waterproof must be implemented.

The subway in city

The construction of the subway has to be done in rock and soil and disturb them so as to lead to settlement and deformation in soil of the earth’s surface which may endanger the buildings and the pipelines. The subway should be kept away from the natural disaster like earthquake which is regarded as a important task by practitioners. The subway takes on a lot of public transport and conveys many people every day.

The influence to tunnel construction and operation from hydraulic geology

Whether during construction or in service, water always threatens tunnel. And because of the water, tunnel construction becomes difficult and the life span of tunnel set in plan and design will be disserved. In 1998, on the conference of ITA, the harm induced by water and the measures to prevent and cure are all regarded as key issues.

The major ways which water influence the tunnel lining:

The water eroded the tunnel lining by reacting with them and destroyed the intrinsic mechanic performance of the materials and the tunnel lining so as to decease the life-span of the tunnel.

The earthquake makes the tunnel lining crack easily and water flowed into the crack erodes the reinforcing steel bars. The carrying capacity of the tunnel lining will decrease

The mass defect of construction is profound hazard to the reliability and maintenance of the tunnel. In all questions meeting in tunnel construction, to control and prevent water is most important.

The research and implementation condition of the tunnel maintenance

The necessity of tunnel maintenance

General speaking, there are four reasons about tunnel maintenance:

To repair the existing tunnels and to build the substitutes of them will expend substantive funds.

The tunnel is in service long time.

The planned capacity of the tunnel is low.

New technology’s requirement.

The common measures in tunnel maintenance

The followings are the international monitoring measures:

To establish the files about monitoring and diagnoses, including the design criterions, the construction means, the service environment and the materials in use.

To establish the system about the monitoring and inspection.

To establish expert system.

The theory research and development of tunnel maintenance

Classification of tunnel maintenance

1 、 Reactive Maintenance (RM)

2 、 Preventive Maintenance (PM)

3 、 Predictive Testing & Inspection (PT&I)

4 、 Proactive Maintenance

Life-cycle maintenance policy of tunnel

In tunnel maintenance, the followings should be accomplished:

To insure the inner reliability of tunnel

To maintain the tunnel to its intrinsic level when the degradation happens

To collect indispensable information for improving the tunnel design without enough reliability

To implement the tunnel maintenance in the lowest maintenance cost and the minimum failure loss.

In some literatures thought, the reliability of production is buried in it, while the maintenance can hold the inner reliability of the production and ensure its service span by designed. So, the maintenance should happen in the following four phases:

Tunnel Planning Phase

Tunnel Design Phase

Tunnel Construction Phase

Tunnel Operation Phase

Conclusion

Tunnel is very important in modern traffic. Whether the mountain tunnel or the trans-strait tunnel and the subway, they are seriously affecting the order of society and economy. Tunnel characterizes the high investment and the complex living environment. Because of the limited social resource, to protect the existing tunnel is sensible. So, it is indispensable to study the tunnel maintenance theory.

Thank you.