Underground work – tunnels, wells, pipes

Work under ground can be tunnel work or other foundation-laying work with pipes, wells, earth reinforcement and so on.

The work often entails many different types of risks, for example:

  • risk of collapse
  • confinement
  • oxygen deficiency
  • air contaminants
  • machines
  • blasting
  • limited working space
  • working with health-endangering substances.

This therefore demands planning of ventilation, stabilising measures, evacuation and rescue of those in distress, emergency lighting, need for special personal safety equipment, firefighting, working hours and working rotation in limited working area, or risks around machines.

Reinforcement of tunnels and rock clearing

When tunnel and rockwork is carried out, there is a risk of collapse. To counteract collapse, regular checks and clearing of rock are carried out. The checks and clearing of rock should be carried out by staff with specific competence. In many cases, the rock needs to be reinforced.

During rockwork, one reinforces with, for example, special rock bolts or through spraying some type of shotcrete into the rock. It is important that the shotcrete has time to dry, and that special inspections are carried before staff is allowed into newly reinforced working areas. Those who carry out reinforcement work, or others who are in an area with risk of collapse, should use a machine with a specially reinforced safety roof that protects against a collapse. In the usage stage, the reinforcements need to be able to be regularly inspected.

Air contaminants underground

During blasting or the use of work vehicles, machines and chemical substances underground, one should specifically think about the risks of different types of air contaminants in a confined space.

Regular checks of air quality should be made, for instance with the help of direct-reading instruments and/or with stationary measuring instruments that warn about air contamination by, for example, quartz and carbon monoxide.

Only diesel-driven engines may be used underground. The vehicles’ emissions should be regularly checked. During stationary work, the first choice should be electric machines. If a truck has a crane that is regularly used, this should be able to be converted to operate on electricity when it is used in a stationary state. Special so-called cabin filters can also be required for certain vehicles, in order to minimise the risks from quartz.

Radon – risk during work underground

Radon is a further risk that exists during underground work. At underground workplaces, the radon level must be measured. Radon is counted as ionising radiation and should be described in the work environment plan.

Fire and evacuation during tunnel work

Fire is one of the most serious risks during tunnel work. A plan for evacuation is required. Existing equipment should be escape masks, fire-extinguishing equipment in vehicles and in different places in the tunnel, as well as access to a rescue chamber if the evacuation path is long.

Preventive work is especially important during the introduction of new employees, evacuation drills, inspection of the storage of flammable material, checks of vehicle fuel-lines and much more. During most underground work, special coordination is demanded with the local rescue services in order to ensure possible firefighting and evacuation of those in distress.

For safe evacuation and localising of those in distress, a system that notifies as to who is in the tunnel and where is required. Today there are electronic systems with specific positioning systems that can be a support for this, and which we at the Swedish Work Environment Authority often make demands about.

Laying pipes – partly or completely underground

There is other work that is carried out completely or partially underground. It can be work with water and drainage pipes, district heating pipes, installation pipes, or earth reinforcement, among others.

Pipe laying can mean that people completely or partly carry out the work in or around pipes, which can be very dangerous. It can be cramped, there can be a risk of collapse, there can be a risk of not having air in order to breathe, or that the air is contaminated. The work often means that one uses different machines that can entail risks during hoisting, drilling, with leakage of chemicals or compressed air, and with other technical equipment.

The work requires very thorough planning with the types of risks that the working methods can entail, both individually and together, for the employees.

Today, material and technical aids have developed within this working area. Eventually it could minimise manual work in and around pipes. It is therefore important to very early investigate and work from that which the Work Environment Act says ’to take into consideration the nature of the work and the technical and social development in society.’

The designer’s choice of method and technique is a clear example of which prerequisites are given for the work. In recent years, unacceptable working conditions have been declared in connection with the replacement of old water pipes and death has occurred in connection with work in district heating pipes. In both these areas, different development work is ongoing in order to improve the work environment.

Laying of foundations

The laying of foundations entails many different types of work. It can be piling, earth reinforcement, sheet piling and other types of support structures.

Piling

Means that a pile of concrete, steel or other material is driven into the earth as a reinforcement for a house or other construction.

Soil reinforcement

Entails that one drills a hole where one creates a type of pillar by adding reinforcing material in the earth. Lime is a common material used for reinforcing.

Sheet piling and other support structures

Entails that one creates a temporary structure in connection with excavation, so that one can begin to build, for example a foundation.

Sheet piling means that one sets down a type of support, often an iron structure, so that mud, earth and water does not seep down. The sheet piling becomes a type of wall around where one needs to carry out construction.

Secant pile walls are another method where one drills holes and casts a type of concrete reinforcing wall in an excavation in order to reinforce it before construction.

Piling, sheet piling, and earth reinforcement entail work with large machines that must lift the large structures of, for example, iron and concrete beams that will be set down into the ground, or machines that will spray chemicals into the ground under pressure. The work demands planning of the working area with regard to stability for heavy machines to move forward, safety during lifting, and risks with chemicals such as lime that can leak out under great pressure. The cutting of piling is also risk-filled work where accidents can occur.

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Last updated 2016-11-18