Occupational health and safety risks can increase the probability of occurrence of Accidents at Work (AW) and Occupational Diseases (OD). This article will consider the differences, in terms of characterisation of AW and OD, between the two main tunnelling methods: CEM – Conventional Excavation Method (in this case, as per ITA definition: any non-TBM, non-drill and blast technique), and TBM – Tunnel Boring Machine Excavation Method.
AW and OD can have a very negative impact on the companies involved:
¦ Deadlines: The occurrence of a serious or fatal AW causes an interruption of works and may even have an impact on the overall execution time. This interruption may be short, lasting a few hours, or long, pending the gathering of all the data necessary for the investigation. In some cases, it may compromise the project’s success.
¦ Related costs: The interruption of works involves high economic implications with direct or indirect costs, such as loss of productivity and yield, low morale, compensation for damages, and time spent in the analysis of the AW. Together with those of OD, they are estimated in 8.5% of the construction (European Agency for Safety and Health at Work, 2014a). Since they lead to a reduction of the company’s profit margins, they affect its competitiveness. In addition, it is less likely that the company will become a preferred supplier, namely for project owners concerned with prevention. The characterisation of the most typical events’ causes is of great importance for their prevention2. Accidents and diseases can be used to learn from mistakes and from the legacy of previous works.
Statistical data on AW and OD in tunnelling are scarce. Not even the International Tunnelling Association, with its Working Group “Safety and Health at Works”, has compiled any statistics on the frequency or nature of AW or OD. The regulatory authorities of each country have compiled adequate statistical data on the construction sector but they seldom distinguish different types of construction, such as tunnelling. This gap led the authors to try and ascertain the most typical and frequent types of AW and OD. The methodology chosen for the AW and OD analysis used the Eurostat variables analysed in the European Statistics on Accidents at Work (ESAW) and in the European Occupational Diseases Statistics (EODS). The variables were chosen because they enable a basic characterisation of the setting of the occurrence of AW and appearance of OD. Since some variables in the ESAW were not fully suitable for this study, answer choices better suited to the objectives pursued were created. Data was collected from these sources:
AW: The Governmental Office for Strategy and Planning (GEP) (year 2013- the most updated data GEP had at the time). Since GEP did not have data for 2014 and 2015, and in order to assess whether those years followed the trends of the GEP data for 2013, information of AW occurred in those years was gathered from project owners and contractors of this type of works. A total of 150 AW between 2012 and 2015 were analysed.
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By GlobalDataOD: The Social Security Institute (the body responsible for producing private sector occupational disease statistics) provided information on 42 OD certified between 2001 and 2015.
ACCIDENTS AT WORK
Occupation of the victim
The occupations most affected by AW are “Handlers/operators/ drivers” and “Miner”.
“Handlers/operators/drivers” – the specificity of the construction process makes massive use of operators and drivers, for drilling, removal of muck, or concreting, in the case of CEM, or for transport of materials and equipment (namely using rail vehicles), in the case of TBM.
“Miner” – highly exposed to risks associated with proximity of the excavation front, such as fall of blocks from the excavation face or run-overs (especially in the case of CEM).
Time
The time period in which most AW occur is from 5pm to 8am, traditionally considered as supplementary or nocturnal. This can be justified with the fact that working in shifts or in overtime hours, which are traditional ways of organising work in tunnelling, may have implications for the way the human body responds, since the workers’ biological clock is altered, causing them to be awake at a time when the body is at a lower capacity level.
Place where the AW occurred
The place in which most AW occur is in formwork and concreting areas. Inside formwork and concreting area many workers gathered to perform the final lining, both in CEM (heavy machinery for waterproofing, installing reinforcements and formwork/concreting), and in TBM (installing prefabricated segments), with tasks carried out simultaneously.
Specific physical activity
The specific activities during which most AW occur are work with hand-held tools, movement, and handling objects.
Work with hand-held tools – hand-held tools are used for the installation of prefabricated parts (in TBM) and stabilisation devices (in CEM), and formwork assembly/disassembly, as well as for the maintenance and repair of equipment. Movement – personnel colliding with mobile equipment (vehicles) or falls from height or on the same level are included here, and are a major cause of AW3, as was confirmed in the transalpine experience, in which a great part of the AW occurred during movement and transport4.
Handling objects- both methods imply handling a large amount of objects, such as stabilisation devices, blocks, rolls of waterproofing systems, rails for reinforcement and formwork panels (CEM), and prefabricated segments (TBM), and pieces of equipment or components of electrical, compressed air, water or ventilation infrastructures.
Deviation leading to AW
The deviations most seen are body movements under or with physical stress (internal injury) / body movements without physical stress (external injury) and slips/falls.
For body movements under physical stress (internal injury) – the authors consider works near the excavation face (in the case of CEM), where blocks falling from the crown are one of the major causes of AW, adding to the vast amount of heavy machinery required, which leads to the risk of run-overs. Also relevant is the road or rail transport of material and workers to the work place (TBM). There is also the important risk of sprayed concrete fragments falling down.
Body movements without physical stress (external injury) covers people coming into contact with objects, equipment, tools, ground, etc., leading to external injuries, such as cuts, lacerations, enucleations, haematomas, burns, etc. Relevant for this is the assembly of formwork panels (CEM) and the application of prefabricated segments (TBM).
‘Slips and falls’ can be explained with people falling down while using temporary working platforms for waterproofing, reinforcement and concreting (CEM) and during the assembly, disassembly and positioning of the tunnel boring machine (TBM). It can happen due to uneven ground (CEM) or during walking along the TBM. The manual handling of loads can obstruct visibility and worsen this situation5.
Type of injury
The most common types of injury are classed as ‘wounds and superficial injuries’, ‘dislocations, sprains and strains’. Wounds and superficial injuries are common when using the hand-held objects and materials required by this type of work. Dislocations, sprains and strains are a common result of a person falling over (not from height).
Part of body injured
The parts of body most injured are the upper and lower extremities Upper extremities are typically injured by the use of hand-held tools (usually heavy in nature, such as bars for scaling and crowbars, or contact with rolling material or prefabricated segments. Also, the high amount of loads handled, and the manual handling of loads, both in CEM (e.g. stabilisation devices), and in TBM (e.g. handling parts of the TBM for assembly and disassembly, or prefabricated segments for positioning and assembly) means there is a high tendency to have contact with hands, arms, legs and feet, whether due to falls or to other types of contact.
The lower extremities, meanwhile, are more prone to be injured during slipping or falling, can also be connected to objects falling, e.g. bocks, or to strains due to uneven ground, namely in CEM.
Number of lost days
The average number of lost days is 60.8, which is very high. One possible explanation is the greater severity of ‘wounds and superficial injuries’, resulting in a high number of days lost.
OCCUPATIONAL DISEASES
Occupation of the victim
The occupational groups with a higher number of OD is “Miners”. Miners, working close to the excavation face, are exposed to breathable dust, sometimes with a high level of silica.
They are also exposed to fumes from explosives, dust from sprayed concrete, oil mists and exhaust gases in the confined space of the excavation face.
Diagnosis
The most common diagnoses are respiratory/pulmonary disorders and Hearing disorders.
For respiratory/pulmonary disorders it is important to distinguish the disorders affecting the airways from the ones affecting the lungs. As for the inflammation of the airways, exposure to particles and gases from diesel combustion products (heavy machinery, in CEM, and locomotives, in TBM) and from blasting of explosives (CEM), namely ANFO-based explosives, has been associated to the on-set or worsening of asthma and chronic bronchitis conditions6. Dust from the cement used in sprayed concrete can contribute to worsening asthma conditions, reducing the lung function of con-crete spray robots operators7. Due to their composition, the oils used to protect machinery against concrete splatters and build-up or to clean the formwork moulds can also lead to airways problems, namely asthma. As for pneumoconiosis, it is important to distinguish the ones caused by deposition of silica dust from the rock mass, more typical in this type of work from the ones caused by the dep-osition of asbestos particles, less typical. The occupations most affected by dust and gases are borers and boring machine workers, but these risks affect those working nearby as well as those working far away, in places crossed by fumes, vapours or particles.
As for hearing disorders, underground this problem is aggravated by the reverberation of the noise made, e.g. by drilling equipment, fans and compressors.
CONCLUSIONS
The statistical data obtained are now a source of information available to anyone who wants to use information on AW or OD to improve risk analysis.
