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29 November 2024
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Featured FRI Magazine article: Structural collapse: voids and void exploration by Colin Deiner (FRI Vol 2 no 11)
Working in collapse voids is quite possibly one of the dangerous and most taxing activities that any rescuer can perform
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Dogs are able to cover a large area quickly
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Additional space may have to be created to safely move the patient out of the void space
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Any cutting of debris or collapsed structural elements must be done only when absolutely necessary, properly supported and only if a loose end is clearly visible
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https://www.frimedia.org/uploads/1/2/2/7/122743954/fri-vol-2-no-11_web.pdf
This week’s featured Fire and Rescue International magazine article is: Structural collapse: voids and void exploration written by Colin Deiner, Chief Director, Disaster Management and Fire Brigade Services, Western Cape Government (FRI Vol 2 no 11). We will be sharing more technical/research/tactical articles from Fire and Rescue International magazine on a weekly basis with our readers to assist in technology transfer. This will hopefully create an increased awareness, providing you with hands-on advice and guidance. All our magazines are available free of charge in PDF format on our website and online at ISSUU. We also provide all technical articles as a free download in our article archive on our website.
Structural collapse: voids and void explorationBy Colin Deiner, Chief Director, Disaster Management and Fire Brigade Services, Western Cape Government
As fire and rescue services, we don’t have to deal with building collapses often. When we do have to respond to such incidents, we must realise that we are entering a dangerous environment that will test our skills and training to its limits.
Why do buildings collapse?Buildings collapse for a variety of reasons, the cause of the collapse will generally dictate the shape that the structure assumes once it has settled. The prime reason structures collapse is due to a loss of stability. This happens when the shape and integrity of the structure is impacted upon by a specific force or a combination of forces. The structure is not able to withstand these forces and will change its shape and integrity until it finds a shape that is more stable.
Buildings generally collapse for more than one reason. A building with a structural deficiency might be involved in a fire, which will further weaken that deficiency and then cause a collapse. A solid building involved in an earthquake might suffer severe structural damage but still maintain its shape. Heavy machinery working close by, post-earthquake might compromise these weaknesses and cause a secondary collapse.
Let’s examine the causes of structural collapse in more detail.
FireA building fully involved in a fire is subjected to extremely high temperatures that cause expansion on certain elements as well as the failure of supporting structures. This will weaken floors and roof structures. Supporting walls could be forced out of shape by expanding steel beams thereby creating numerous collapse risks. The application of large volumes of water will increase the imposed load on an upper floor causing it to fail. It is important for fire fighting crews to anticipate the possible collapse zones and ensure that they are clearly indicated to all personnel on scene.
Geological effectsEarthquakes and landslides cause structural collapse due to the movement of the earth in which the foundations are laid. The movement can be either horizontal or vertical and exceeds the ability of the building to withstand the stresses imposed on it. A situation may also arise where the ground on which a building is constructed, becomes so saturated with subterranean water that it loses all integrity causing total collapse. This situation known as liquefaction is the most common cause of collapse of structures near a coast line during an earthquake. The 1999 Maramara earthquake in Turkey suffered a number of these collapses along the inland coastal areas around the cities of Cinarcik and Yalova. Due to the total failure of any supporting base, these structures tend to collapse completely.
Extreme weatherRegions that experience high wind speeds are susceptible to buildings being affected. Conditions such as high winds do not normally cause buildings to collapse completely but can cause roofs to be blown off, walls to collapse due to suction on the leeward side and excessive pressure created inside the structure. The failure of one building component may off course lead to a total failure.
Heavy rainfalls and flooding could cause a build-up of water within a building space, which could also place pressure on the structural elements and present a stability risk. Although South Africa has a mild temperature and does not experience heavy snowfalls as often as countries in the northern hemisphere, the possibility of an added load on a horizontal surface caused by excessive snow must be considered in such events.
Structural defectsUnfortunately, we have too often had to respond to structural collapse that has happened due to poor design, workmanship or the use of inferior materials. In some of these cases, contractors are in a hurry to finish a particular project and do not allow sufficient time for concrete slabs to set properly before removing stabilising struts. This is known as ‘green concrete’ but could also be called ‘greed concrete’ and is generally characterised by the slab punching through its supporting pillars and crashing to the floor below, then possibly causing multiple floors to collapse in a ‘pancake’ configuration.
ExplosionsThese collapses are all ‘man-induced’ but can be categorised as either accidental or intentional. Accidental explosions are caused by factors like leaking gas that ignite and cause an over pressurisation in a building or the effects of a fire. A rapid introduction of air into a severely compromised, heavily involved building could cause a backdraught causing a collapse. Similarly, a dust explosion or detonation of highly volatile products stored within a building space could lead to a catastrophic failure.
Recent intentional collapse incidents have been the result of terrorism. We are all familiar with the bombing of the Murrah Building in Oklahoma City, the 911 incidents and the very recent shopping mall incident in Kenya. Although the 911 incidents were caused by large passenger aircraft flying into buildings, other incidents are generally caused by explosives being detonated inside or alongside a (normally occupied) structure. An explosive detonated inside a structure creates a shockwave of air that usually displaces the doors, windows, roofs and floor and can cause additional damage to other structural elements.
An exterior detonated explosion will have an amplified shockwave (due to its unconfined nature) that will penetrate the building through its natural openings. Walls and roofs will be subjected to great pressure. The shockwave could also propel debris at a high velocity, which can impact against the structural components causing a collapse.
Some of the main risks here are the possibility of secondary collapse due to the compromised nature of the building that also has to deal with a shifted, imposed load and the location of victims, which could be some distance away from the initial impact.
Transportation emergenciesMany incidents have occurred where an aircraft, road vehicle or train, has collided with a building or structure resulting in a partial or total collapse. The severity of the collapse will be dependent on the size and purpose of the vehicle as well as its purpose.
I have only dealt with collapses of occupied structures but we must also plan and prepare for the collapse risk of other structures such as bridges, tunnels, leisure facilities and piers. Temporary structures such as scaffolding, cranes and temporary stands at sporting and cultural events could also cause the entrapment of people and require the same kind of response as required for an occupied building collapse.
How do buildings collapse?When a building collapses the altered shape which it ultimately assumes, will be in a number of generic patterns. These patterns can be internal, external or total collapse.
Internal collapse patterns can be any of the following four:
Pancake collapse: These happen when the load bearing walls fail causing floors to impact suddenly on the floors below. This will assume a stack up configuration in the shape of a heap of pancakes. This is a particularly catastrophic type of collapse and generally very few voids remain after the collapsed floors have settled. These voids can be shaped by machinery, appliances or furniture that interrupts the stacking effect. A pancake collapse is the most complex type and will require extensive searching procedures and prolonged debris removal operations.
Lean-to collapse: This occurs after a failure of a supporting wall, beam or column at one end fails and causes the floor to tilt down causing a triangular shaped collapse void. In these types of collapses, large voids are formed that allow for increased possibilities of survival of any victims. Lean-to collapses can either be supported or unsupported. A supported lean-to collapse is formed when the collapsed end of the floor comes to rest on top of debris, furniture, machinery or the next floor. Thus, both ends of the floor are supported. An unsupported lean-to collapse happens the same way as the supported lean-to however in this case the failed end hangs suspended with no support and is held together by reinforcing and other binding elements keeping it in one piece. This is an extremely hazardous environment for people to work around and plans must be put in place to stabilise these precariously hanging structures before any search and rescue work can be done.
‘V’ collapse: This is caused when a heavy load at any given point, normally towards the middle of an upper floor, causes the floor to collapse creating two triangular voids. These voids will form on both sides of the load failure that will mean that victims could be found over a larger area. Victims on the top of the collapsed floor will be propelled down in the direction of the load which caused the collapse. They may be trapped by huge amounts of debris that will require the use of a wide range of cutting and breaching tools to extricate them.
A-frame collapse: This is the opposite of a ‘V’ collapse and is caused by the separation of exterior walls while still being supported on the inside by one or more interior load bearing walls or non-load bearing structures. This can be caused by explosions, earthquakes (liquefaction), the excavation of adjoining areas or extreme water damage. The best chance of finding survivors will be close to the partition wall near the centre of the collapse. The further away from the interior wall the less chance you will have of finding survivors.
Exterior collapses can occur in five different ways
90º angle collapse: This is when a wall falls outwards to a distance that is equal to its height, causing debris to spread as it hits the ground. This is a particular risk at a structural fire in a large commercial or industrial facility when it is difficult to judge the collapse zone. As with the ‘pancake’ collapse, above voids will only be formed by elements that will be in the collapse zone.
Curtain fall collapse: This happens when a wall collapses straight down and creates a rubble pile near its base. Virtually no voids will exist following a curtain wall collapse.
Inward/outward collapse: Occurs when walls crack on a horizontal line around its centre line. The top half falls in one direction usually inwards) and the lower half in another (outwards).
Total collapse: This is the most severe form of structural failure and occurs when all the floors have collapsed to the ground or basement level and all walls have collapsed onto the floors.
Basement collapse: This is rare and happens when a ground floor collapses into a basement while the other floors remain intact. If the ground floor is a shop front, it could cause the floors above to tilt in a forward direction leaving it very unstable. Searching for victims in the basement is extremely difficult. During the 2003 Algerian earthquake, the South African urban search and rescue (USAR) team were faced with such a challenge. One of the biggest of these being the establishment of an access point from the basement into the upper floors of the unstable structure. Another important consideration was to ensure the monitoring of the building stability and progressive stabilisation that accompanied this process.
Managing the incidentIn previous articles, I have dealt with the broad response to structural collapse incidents. Here, I will narrow it down to the identification, exploration and stabilisation of collapse voids.
The rescue operation will start with the reconnaissance and initial scene survey. It is here where all possible hazards are identified and isolated, information gathered and determination of resources required is done. The first arriving units will be the fire department, emergency medical services and other public safety authorities.
The need for a specialist urban search and rescue capability (rescue squad or USAR task force), must quickly be identified and they should be activated.
Any utilities that may pose a risk to victims and rescuers must also be isolated and locked out at this stage. This includes electricity, water and gas supplies.
At most structural collapse incidents there will be a percentage of victims who are injured but not trapped or lightly trapped and immediately visible and accessible. These victims can be accessed and extricated by the first arriving units. Personnel directed to perform this activity must move with care to ensure that they do not injure themselves by tripping over unstable debris and also take care that they are not stepping over areas where persons may be trapped and be further compromised.
If any doubt to the stability of the structure exists, incident commanders must not commit personnel into the incident but rather await specialist urban search and rescue intervention.
First responders can also conduct a ‘line-and-hail’ search that entails a team of rescuers forming a straight line and moving in unison across the collapse sight. When they encounter an opening or potential collapse void, they will then examine the opening and shout down the hole to try and ascertain if someone is trapped there.
Upon completion of this phase, you can move on to deploying search and rescue dogs onto the site. Dogs are able to cover a large area quickly and will allow you to narrow the search down and only concentrate on certain areas. It is critical, however, to realise that the dogs might pick up a scent that is being channelled through a long void. When a scent is picked up and a dog does indicate the location of a victim, you will need to examine the terrain and evaluate it for its viability. Is there a void? Could a person survive in the void? Is the opening linked to further voids?
After the canine search you can move on to a seismic and acoustic search that will provide a more precise location.
Once the surface search is complete and voids have been identified, the difficult task of entering, stabilising and identifying the collapsed voids will begin.
Void explorationWhile the safety concerns are being addressed and the necessary shoring to ensure sustained access is being erected, a void search team should prepare themselves for their task. Depending on the extent of the incident, it may be necessary for multiple teams. Void search teams should be involved in the entry and searching of collapse voids rather than tunnelling into and through debris. Voids are the most viable locations for live victims.
The void search team should be a six-member unit consisting of an officer and five rescuers. This team will be split into an entry team and a support team. The entry team will be responsible for entry into the void space and shoring it. The support team will be responsible for expanding the void and managing the required rescue tools.
Within the void, the team will encounter a large amount of debris in various shapes and positions. Some of this debris is providing natural stabilisation to the void. Before removing any debris, it should be carefully assessed to ensure that it is not holding up any part of the structure. If it must be removed to provide for further access, a supplemental shore should be constructed in its place before removal.
Shoring and stabilising is a very involved job and will require highly trained and experienced rescuers. It might be necessary to cut a large amount of timber and move it into the void. Communication here is of the essence. Measurements taken by the entry team must be clearly and accurately communicated to the cutting team. A variance of as little as two centimetres could result in the shore having to be sent back and cause a delay that could cost someone’s life.
The entry team officer is responsible for safe void exploration operations. He/she must evaluate each phase of the operations and make adjustments as necessary. This person is also in communication with both the entry and the support team and will be crucial in relaying information between them. He/she must also be familiar with the team members and direct their activities according to the incident needs and their abilities. The entry team officer will select the entry routes and determine the procedures and tools that will be used to achieve the decided objectives.
Once a victim is reached he/she needs to be assessed, stabilised and packaged for removal. It may be necessary for additional medical staff to enter the void for these activities. If it is suspected that the patient is suffering from possible crush syndrome injury, it could be an extended period of time before he/she may be removed.
Additional space may have to be created to safely move the patient out of the void space. This should be done using the same approach as the initial entry phase.
Due to the heavy workload and pressure on this team, the void entry team officer must monitor the health and fatigue of the team and rotate when necessary. Rescuers generally become more determined when they are close to the victim and tend to neglect their own physical condition. It is very difficult to replace a rescuer who has got this far but it is a decision that will have to be made…..and obeyed.
The void entry officer will rely on the entry team for his/her information as they are the first people to enter the void and will be the only ones with ‘eyes on’ the inside. These rescuers must be comfortable working in confined spaces, able to evaluate associated risks and respond to them.
When debris is identified for removal, it must be moved as far away from the entry route as possible. Ideally, all debris should be removed from the void and placed somewhere outside. In a small void space it might be necessary for loose debris to be passed backwards until it reaches the outside. This might require more people as the distance increases. Each rescuer handling this debris must do so carefully ensuring they do not dislodge any shoring or injure other rescuers.
Any cutting of debris or collapsed structural elements must be done only when absolutely necessary, properly supported and only if a loose end is clearly visible.
The entry team members must always be in verbal contact with each other and stay in close physical proximity. They must also stay in verbal contact with the entry team officer.
The support team will be responsible for expanding the void if prolonged operations are envisaged. One member should be placed at the mouth of the void and should assist with the removal of the debris and relaying information to incident command. If the void entrance is too narrow and confined they will be responsible for widening this area and establish a better and more sustained space.
The support team must also be able to rapidly enter the void to assist the entry team with victim or debris removal or an emergency rescue of an entry team member. In addition, they will be called on to move any tools into the void and provide personnel relief to the entry team.
As with any rescue operation, a tool staging area needs to be established close to the entrance and easily accessible. Due to the limited space in the void, all tools must be removed from the void once they have been used.
In conclusionWorking in collapse voids is quite possibly one of the dangerous and most taxing activities that any rescuer can perform. No amount of preparation will be totally sufficient but it is important that rescuers identified for this task are prepared mentally and physically for a prolonged and extremely taxing activity. We are the last line of defence.
This week’s featured Fire and Rescue International magazine article is: Structural collapse: voids and void exploration written by Colin Deiner, Chief Director, Disaster Management and Fire Brigade Services, Western Cape Government (FRI Vol 2 no 11). We will be sharing more technical/research/tactical articles from Fire and Rescue International magazine on a weekly basis with our readers to assist in technology transfer. This will hopefully create an increased awareness, providing you with hands-on advice and guidance. All our magazines are available free of charge in PDF format on our website and online at ISSUU. We also provide all technical articles as a free download in our article archive on our website.
Structural collapse: voids and void explorationBy Colin Deiner, Chief Director, Disaster Management and Fire Brigade Services, Western Cape Government
As fire and rescue services, we don’t have to deal with building collapses often. When we do have to respond to such incidents, we must realise that we are entering a dangerous environment that will test our skills and training to its limits.
Why do buildings collapse?Buildings collapse for a variety of reasons, the cause of the collapse will generally dictate the shape that the structure assumes once it has settled. The prime reason structures collapse is due to a loss of stability. This happens when the shape and integrity of the structure is impacted upon by a specific force or a combination of forces. The structure is not able to withstand these forces and will change its shape and integrity until it finds a shape that is more stable.
Buildings generally collapse for more than one reason. A building with a structural deficiency might be involved in a fire, which will further weaken that deficiency and then cause a collapse. A solid building involved in an earthquake might suffer severe structural damage but still maintain its shape. Heavy machinery working close by, post-earthquake might compromise these weaknesses and cause a secondary collapse.
Let’s examine the causes of structural collapse in more detail.
FireA building fully involved in a fire is subjected to extremely high temperatures that cause expansion on certain elements as well as the failure of supporting structures. This will weaken floors and roof structures. Supporting walls could be forced out of shape by expanding steel beams thereby creating numerous collapse risks. The application of large volumes of water will increase the imposed load on an upper floor causing it to fail. It is important for fire fighting crews to anticipate the possible collapse zones and ensure that they are clearly indicated to all personnel on scene.
Geological effectsEarthquakes and landslides cause structural collapse due to the movement of the earth in which the foundations are laid. The movement can be either horizontal or vertical and exceeds the ability of the building to withstand the stresses imposed on it. A situation may also arise where the ground on which a building is constructed, becomes so saturated with subterranean water that it loses all integrity causing total collapse. This situation known as liquefaction is the most common cause of collapse of structures near a coast line during an earthquake. The 1999 Maramara earthquake in Turkey suffered a number of these collapses along the inland coastal areas around the cities of Cinarcik and Yalova. Due to the total failure of any supporting base, these structures tend to collapse completely.
Extreme weatherRegions that experience high wind speeds are susceptible to buildings being affected. Conditions such as high winds do not normally cause buildings to collapse completely but can cause roofs to be blown off, walls to collapse due to suction on the leeward side and excessive pressure created inside the structure. The failure of one building component may off course lead to a total failure.
Heavy rainfalls and flooding could cause a build-up of water within a building space, which could also place pressure on the structural elements and present a stability risk. Although South Africa has a mild temperature and does not experience heavy snowfalls as often as countries in the northern hemisphere, the possibility of an added load on a horizontal surface caused by excessive snow must be considered in such events.
Structural defectsUnfortunately, we have too often had to respond to structural collapse that has happened due to poor design, workmanship or the use of inferior materials. In some of these cases, contractors are in a hurry to finish a particular project and do not allow sufficient time for concrete slabs to set properly before removing stabilising struts. This is known as ‘green concrete’ but could also be called ‘greed concrete’ and is generally characterised by the slab punching through its supporting pillars and crashing to the floor below, then possibly causing multiple floors to collapse in a ‘pancake’ configuration.
ExplosionsThese collapses are all ‘man-induced’ but can be categorised as either accidental or intentional. Accidental explosions are caused by factors like leaking gas that ignite and cause an over pressurisation in a building or the effects of a fire. A rapid introduction of air into a severely compromised, heavily involved building could cause a backdraught causing a collapse. Similarly, a dust explosion or detonation of highly volatile products stored within a building space could lead to a catastrophic failure.
Recent intentional collapse incidents have been the result of terrorism. We are all familiar with the bombing of the Murrah Building in Oklahoma City, the 911 incidents and the very recent shopping mall incident in Kenya. Although the 911 incidents were caused by large passenger aircraft flying into buildings, other incidents are generally caused by explosives being detonated inside or alongside a (normally occupied) structure. An explosive detonated inside a structure creates a shockwave of air that usually displaces the doors, windows, roofs and floor and can cause additional damage to other structural elements.
An exterior detonated explosion will have an amplified shockwave (due to its unconfined nature) that will penetrate the building through its natural openings. Walls and roofs will be subjected to great pressure. The shockwave could also propel debris at a high velocity, which can impact against the structural components causing a collapse.
Some of the main risks here are the possibility of secondary collapse due to the compromised nature of the building that also has to deal with a shifted, imposed load and the location of victims, which could be some distance away from the initial impact.
Transportation emergenciesMany incidents have occurred where an aircraft, road vehicle or train, has collided with a building or structure resulting in a partial or total collapse. The severity of the collapse will be dependent on the size and purpose of the vehicle as well as its purpose.
I have only dealt with collapses of occupied structures but we must also plan and prepare for the collapse risk of other structures such as bridges, tunnels, leisure facilities and piers. Temporary structures such as scaffolding, cranes and temporary stands at sporting and cultural events could also cause the entrapment of people and require the same kind of response as required for an occupied building collapse.
How do buildings collapse?When a building collapses the altered shape which it ultimately assumes, will be in a number of generic patterns. These patterns can be internal, external or total collapse.
Internal collapse patterns can be any of the following four:
Pancake collapse: These happen when the load bearing walls fail causing floors to impact suddenly on the floors below. This will assume a stack up configuration in the shape of a heap of pancakes. This is a particularly catastrophic type of collapse and generally very few voids remain after the collapsed floors have settled. These voids can be shaped by machinery, appliances or furniture that interrupts the stacking effect. A pancake collapse is the most complex type and will require extensive searching procedures and prolonged debris removal operations.
Lean-to collapse: This occurs after a failure of a supporting wall, beam or column at one end fails and causes the floor to tilt down causing a triangular shaped collapse void. In these types of collapses, large voids are formed that allow for increased possibilities of survival of any victims. Lean-to collapses can either be supported or unsupported. A supported lean-to collapse is formed when the collapsed end of the floor comes to rest on top of debris, furniture, machinery or the next floor. Thus, both ends of the floor are supported. An unsupported lean-to collapse happens the same way as the supported lean-to however in this case the failed end hangs suspended with no support and is held together by reinforcing and other binding elements keeping it in one piece. This is an extremely hazardous environment for people to work around and plans must be put in place to stabilise these precariously hanging structures before any search and rescue work can be done.
‘V’ collapse: This is caused when a heavy load at any given point, normally towards the middle of an upper floor, causes the floor to collapse creating two triangular voids. These voids will form on both sides of the load failure that will mean that victims could be found over a larger area. Victims on the top of the collapsed floor will be propelled down in the direction of the load which caused the collapse. They may be trapped by huge amounts of debris that will require the use of a wide range of cutting and breaching tools to extricate them.
A-frame collapse: This is the opposite of a ‘V’ collapse and is caused by the separation of exterior walls while still being supported on the inside by one or more interior load bearing walls or non-load bearing structures. This can be caused by explosions, earthquakes (liquefaction), the excavation of adjoining areas or extreme water damage. The best chance of finding survivors will be close to the partition wall near the centre of the collapse. The further away from the interior wall the less chance you will have of finding survivors.
Exterior collapses can occur in five different ways
90º angle collapse: This is when a wall falls outwards to a distance that is equal to its height, causing debris to spread as it hits the ground. This is a particular risk at a structural fire in a large commercial or industrial facility when it is difficult to judge the collapse zone. As with the ‘pancake’ collapse, above voids will only be formed by elements that will be in the collapse zone.
Curtain fall collapse: This happens when a wall collapses straight down and creates a rubble pile near its base. Virtually no voids will exist following a curtain wall collapse.
Inward/outward collapse: Occurs when walls crack on a horizontal line around its centre line. The top half falls in one direction usually inwards) and the lower half in another (outwards).
Total collapse: This is the most severe form of structural failure and occurs when all the floors have collapsed to the ground or basement level and all walls have collapsed onto the floors.
Basement collapse: This is rare and happens when a ground floor collapses into a basement while the other floors remain intact. If the ground floor is a shop front, it could cause the floors above to tilt in a forward direction leaving it very unstable. Searching for victims in the basement is extremely difficult. During the 2003 Algerian earthquake, the South African urban search and rescue (USAR) team were faced with such a challenge. One of the biggest of these being the establishment of an access point from the basement into the upper floors of the unstable structure. Another important consideration was to ensure the monitoring of the building stability and progressive stabilisation that accompanied this process.
Managing the incidentIn previous articles, I have dealt with the broad response to structural collapse incidents. Here, I will narrow it down to the identification, exploration and stabilisation of collapse voids.
The rescue operation will start with the reconnaissance and initial scene survey. It is here where all possible hazards are identified and isolated, information gathered and determination of resources required is done. The first arriving units will be the fire department, emergency medical services and other public safety authorities.
The need for a specialist urban search and rescue capability (rescue squad or USAR task force), must quickly be identified and they should be activated.
Any utilities that may pose a risk to victims and rescuers must also be isolated and locked out at this stage. This includes electricity, water and gas supplies.
At most structural collapse incidents there will be a percentage of victims who are injured but not trapped or lightly trapped and immediately visible and accessible. These victims can be accessed and extricated by the first arriving units. Personnel directed to perform this activity must move with care to ensure that they do not injure themselves by tripping over unstable debris and also take care that they are not stepping over areas where persons may be trapped and be further compromised.
If any doubt to the stability of the structure exists, incident commanders must not commit personnel into the incident but rather await specialist urban search and rescue intervention.
First responders can also conduct a ‘line-and-hail’ search that entails a team of rescuers forming a straight line and moving in unison across the collapse sight. When they encounter an opening or potential collapse void, they will then examine the opening and shout down the hole to try and ascertain if someone is trapped there.
Upon completion of this phase, you can move on to deploying search and rescue dogs onto the site. Dogs are able to cover a large area quickly and will allow you to narrow the search down and only concentrate on certain areas. It is critical, however, to realise that the dogs might pick up a scent that is being channelled through a long void. When a scent is picked up and a dog does indicate the location of a victim, you will need to examine the terrain and evaluate it for its viability. Is there a void? Could a person survive in the void? Is the opening linked to further voids?
After the canine search you can move on to a seismic and acoustic search that will provide a more precise location.
Once the surface search is complete and voids have been identified, the difficult task of entering, stabilising and identifying the collapsed voids will begin.
Void explorationWhile the safety concerns are being addressed and the necessary shoring to ensure sustained access is being erected, a void search team should prepare themselves for their task. Depending on the extent of the incident, it may be necessary for multiple teams. Void search teams should be involved in the entry and searching of collapse voids rather than tunnelling into and through debris. Voids are the most viable locations for live victims.
The void search team should be a six-member unit consisting of an officer and five rescuers. This team will be split into an entry team and a support team. The entry team will be responsible for entry into the void space and shoring it. The support team will be responsible for expanding the void and managing the required rescue tools.
Within the void, the team will encounter a large amount of debris in various shapes and positions. Some of this debris is providing natural stabilisation to the void. Before removing any debris, it should be carefully assessed to ensure that it is not holding up any part of the structure. If it must be removed to provide for further access, a supplemental shore should be constructed in its place before removal.
Shoring and stabilising is a very involved job and will require highly trained and experienced rescuers. It might be necessary to cut a large amount of timber and move it into the void. Communication here is of the essence. Measurements taken by the entry team must be clearly and accurately communicated to the cutting team. A variance of as little as two centimetres could result in the shore having to be sent back and cause a delay that could cost someone’s life.
The entry team officer is responsible for safe void exploration operations. He/she must evaluate each phase of the operations and make adjustments as necessary. This person is also in communication with both the entry and the support team and will be crucial in relaying information between them. He/she must also be familiar with the team members and direct their activities according to the incident needs and their abilities. The entry team officer will select the entry routes and determine the procedures and tools that will be used to achieve the decided objectives.
Once a victim is reached he/she needs to be assessed, stabilised and packaged for removal. It may be necessary for additional medical staff to enter the void for these activities. If it is suspected that the patient is suffering from possible crush syndrome injury, it could be an extended period of time before he/she may be removed.
Additional space may have to be created to safely move the patient out of the void space. This should be done using the same approach as the initial entry phase.
Due to the heavy workload and pressure on this team, the void entry team officer must monitor the health and fatigue of the team and rotate when necessary. Rescuers generally become more determined when they are close to the victim and tend to neglect their own physical condition. It is very difficult to replace a rescuer who has got this far but it is a decision that will have to be made…..and obeyed.
The void entry officer will rely on the entry team for his/her information as they are the first people to enter the void and will be the only ones with ‘eyes on’ the inside. These rescuers must be comfortable working in confined spaces, able to evaluate associated risks and respond to them.
When debris is identified for removal, it must be moved as far away from the entry route as possible. Ideally, all debris should be removed from the void and placed somewhere outside. In a small void space it might be necessary for loose debris to be passed backwards until it reaches the outside. This might require more people as the distance increases. Each rescuer handling this debris must do so carefully ensuring they do not dislodge any shoring or injure other rescuers.
Any cutting of debris or collapsed structural elements must be done only when absolutely necessary, properly supported and only if a loose end is clearly visible.
The entry team members must always be in verbal contact with each other and stay in close physical proximity. They must also stay in verbal contact with the entry team officer.
The support team will be responsible for expanding the void if prolonged operations are envisaged. One member should be placed at the mouth of the void and should assist with the removal of the debris and relaying information to incident command. If the void entrance is too narrow and confined they will be responsible for widening this area and establish a better and more sustained space.
The support team must also be able to rapidly enter the void to assist the entry team with victim or debris removal or an emergency rescue of an entry team member. In addition, they will be called on to move any tools into the void and provide personnel relief to the entry team.
As with any rescue operation, a tool staging area needs to be established close to the entrance and easily accessible. Due to the limited space in the void, all tools must be removed from the void once they have been used.
In conclusionWorking in collapse voids is quite possibly one of the dangerous and most taxing activities that any rescuer can perform. No amount of preparation will be totally sufficient but it is important that rescuers identified for this task are prepared mentally and physically for a prolonged and extremely taxing activity. We are the last line of defence.