Chongqing landslide rescue update - 23rd June

Xinhua has a video report about the ongoing rescue attempts at the Chongqing landslide site. The report suggests that remotely sensed imagery allowed a number of locations in which the crags in the head scar area were found to be unstable and threatening the rescue teams. To this end, two artillery pieces were brought in and shells were fired at the crags to try to dislodge the unstable sections. This failed unfortunately, so now dynamite will be used instead.

Unfortunately there is no news of the rescue attempt itself.

Chongqing landslide - NASA satellite image

NASA have provided the first decent overview of the Chongqing landslide via a high resolution satellite image. This can be found here.


The morphology of this is decidedly odd - I will spend some time trying understand it better. According to the NASA page the source is to the north and the landslide has moved southwards and then spread out to the southwest.

Meanwhile, the search for victims continues according to Xinhua.

The Chongqing landslide - update 16th June

The latest update on the Chongqing landslide rescue is provided by Xinhua. Key points:

• Rescue operations continue, with 3,000 people working on site;
  
• Ten small-scale landslides have occurred at the landslide site since Friday;
• southwest China's Chongqing Municipality from Friday, and rescuers continued to search for 64 missing for the 10th day on Tuesday.
• The water level in the barrier lake has dropped to 10 m below the top of the temporary embankment;
• The rescuers have not yet found the mine entrance.

The Chongqing landslide - the rescue is probably about to be abandoned

Xinhua is reporting that the rescue at the Chongqing landslide is likely to be abandoned shortly. Given the length of time that has elapsed since the failure the chances of rescuing the miners alive are now very small. More worryingly, there is an increasing risk of further failures at the site:

"According to a geologist with the rescue headquarters who declined to be identified, cracks with the span of eight to ten meters wide and up to 30 meters deep have appeared on the landslide-induced hills. "If the 1.75 million cubic meters of soil and rocks fell down from 80 to 100 meters high, another massive landslide shall occur," he said. Four remaining big stones that stood on the edge of the mountains are also likely to slip off when it rains, he said. Two landslides of smaller scale forced suspension of rescue work twice early Friday morning. The landslide site has entered the flood season, and landslide-induced lakes are likely to trigger mud-rock flows, said Zhu Xiansheng, head of the water conservancy bureau of Chongqing."

Such rescues are always a balance between the benefits of successfully rescuing the victims and the risks to the search teams. Given the time that has elapsed, the difficulties involved in the operation and the lack of indications that the miners are alive, the increasing risks to the rescue teams do suggest that stopping the operation is probably prudent, even though it is a very difficult decision to make. Thirty metre deep cracks that are widening are a strong indication that all is not well on the hillside, although failure is certainly not inevitable.

The latest update on the Chongqing landslide rescue

Xinhua and CCTV have published updates on the Chongqing landslide rescue. The picture is looking increasingly grim given that the estimated survival time of the miners was five to seven days, and it is now a week since the landslide. Highlights of the reports are as follows:

• Drilling continues but to date no signs of life have been detected. Drilling (or is this tunnel construction - see below) is only progressing at 5 m per day as they are creating an inclined hole to try to prevent secondary failures;
• Unfortunately the mine plans were buried in the landslide, so the exact location of the mine entrances is unknown. The chances of being able to build a tunnel that will intersect the mine entrance is considered to be less than 20%;
  
• A small landslide that a the drilling platform interrupted rescue operations today. No-one was injured. However, it is now believed that over a million cubic metres of the slope above the site is unstable, and the possibility of more landslides is considered to be "very high".
• The heavy lift helicopter is transporting heavy equipment onto the site (see image above). This is expected to increase the rate at which excavation can occur;
• The barrier lake now contains 40,000 cubic meters of water (this is a big increase in estimated volume compared with yesterday - but is still not a huge amount of water as these things go); The lake level rose by 0.5 m in the last 24 hours.
  
• The team continues to build an embankment to keep the water away from the rescue site. The water level is now 1 m below the embankment
• However, the drainage pipe is now in place and will start pumping today. With a capacity of 15,000 cubic metres per day this should keep the level below the maximum under current conditions;
• In due course a proper drainage channel will be needed, but at the moment the focus is on the rescue.

Three observations:
1. The news that the authorities do not know the actual location of the mine entrances is new - and very candid. One should not be critical of them for this - a characteristic of the Guinsaugon (Leyte) landslide was the huge difficulties that the rescuers, including the US Marine Corps, had in determining the former location of buildings and infrastructure;
2. It seems to me that there are two operations occurring simultaneously here - one to drill bore holes to allow detection equipment to be located and, I suspect, to try to find the mine entrances. This explains why 40 rigs are being used.
3. There is a double race occurring here - one associated with the limited survival time of the miners and the other to beat the seasonal rains. Unfortunately the slope could collapse even without further rain (i.e. through a progressive failure), so the danger to the rescuers is real and very immediate.

Latest update on the Chongqing landslide

The desperate rescue attempts continue at the site of the Chongqing landslide, but time is now clearly running out for the miners. The heavy lift helicopter, the same one that assisted at Tangjiashan, is now in full operation, and the drilling continues using 20 machines according to this report. The drilling operations have now reached 100 m below the surface and thus have reached the position of the portal. Unfortunately this appears to have collapsed (unsurprisingly). Additionally, the rescue teams have had to abandon their use of explosives due to the instability of the landslide mass.

There can be little hope for the trapped miners now, although it is still worth trying to get to them.

Meanwhile, according to this report the barrier lake volume has now reached 10,000 cubic metres (this is not a huge volume). Operations to lay a drainage pipe are ongoing.

Chongqing landslide update - 9th June

Image source: http://uk.news.yahoo.com/19/20090609/img/pwl-china-landslide-death-9-6f14af6c0f4b.html

The latest news from the Chongqing landslide site is as follows:

1. Attempts to build a tunnel to the trapped miners continue. The heavy lift helicopter is now in operation. Electric cables and a generator have been installed to provide power to the ongoing operations;
2. Heavy rain has now reduced to drizzle, but the water depth in the barrier lake increased by a metre in 24 hours;
3. Operations to create a channel to drain the lake continue. The image above appears to show the barrier lake in the background;
4. The rescue teams are using sandbags to try to prevent water from the barrier lake entering the mine - this would of course be disastrous for the trapped miners.
5. Satellite imagery was expected to be available from today (I would like to see this!). Meanwhile, monitoring points have been established to provide warning of any further landslides.

Time must be running out for the miners, but it sounds as if the Chinese are undertaking a huge effort to rescue them.

Meanwhile, some additional pieces of background information have been published in China Daily:

• The iron ore mine, which was called Sanlian, produced only 100 tonnes per day. This is very low.
  
• A similar accident occurred 0n 30th April 1994, creating a landslide deposit that blocked the river;
  
• Two days before the accident rockfalls were observed from the slope;
• The local authorities warned the villagers about the potential for a landslide in 2003. They were offered 5,000 yuan (c.£450 or 520 Euros) to move. Most villagers refused to leave.

Background to the Chongqing landslide

According to this report, rescue operations for the 27 miners trapped in a mine beneath the Chongqing landslide have been suspended due to bad weather. As I mentioned in my earlier post, working on a fresh rockslide deposit is exceptionally dangerous, so this is a wise decision. However, the outlook for the trapped miners must be looking increasingly bleak, given that it now appears that they are trapped 200 m underground and heavy machinery is not being used.

The above article has some very interesting and pertinent information about the context of the landslide. It quotes local residents as saying that the mine in question, which opened in 1949, was closed in 2000 "after being labelled dangerous by an official geological survey team". However, work resumed in 2004 under private ownership, whereupon landslides started to occur from the slope. In 2004 "masses fell from the mountain into the valley... after which the Tiekuang government offices, local school and circa 70 residencies were moved. But 40 of those people buried by the landslide decided to stay in the area, after local officials assured them that there were no problems."

The mine owner has been arrested, but the local people are critical that the local media is reporting the landslide as having been natural: “it wasn’t a natural disaster; human error is the only thing to blame for the tragedy”.

Guatemala landslide update: 33 killed and up to 70 people reported missing

A short update on the Guatemala landslide, which is looking like a dreadful tragedy.

Diaro de Centro America has published this dramatic image of the site:


Meanwhile Prensa Libre is reporting that the number of people killed is now known to be 33, with more people still missing. Telediaro suggests that the number missing may be as high as 70 people! Landslides are continuing to hamper the rescue operations.

Saving landslide victims

In the last few days there have been two landslides that have led to searches in the hope of finding buried victims. The higher profile slide was this one that occurred in the Bukit Antarabangsa suburb of Kuala Lumpur (Malaysia) on Saturday (pictures from The Star):


This landslide, which has dominated the news in Malaysia over the last few days, killed four people and injured a further 15. One person is reported to still be missing - searches are continuing for her.

The other slide happened in Papua New Guinea when a slope above a camp at a goldmine collapsed, burying ten people. The Australian Government dispatched a search and rescue team, but no victims were recovered alive.

These two events set me thinking about how we go about recovering people who have been affected by landslides. As far as I know there has yet to be a proper scientific study of how and why people survive landslides and of where we should look for victims. This is a crucial shortcoming that urgently needs to be corrected. The key must be the type of landslide that has occurred. So lets start with our basic landslide classification (this diagram, from the Geonet web site, is pretty much the best that is available - click on the image for a better view):

So let's look at these one by one:
1. Falls
All falls basically involve free movement through the air, meaning that objects at the toe of the slope are likely to be buried. Therefore, if the likely victims were located at the toe of the slope then the victims are likely to be under the rubble. This is what we usually see with rockfalls on roads for example:

Image from www.cbc.ca

However, away from the toe of the slope movement is often parallel to the ground surface, meaning that objects in the way get pushed outwards. Hence, vehicles away from the toe of the slope often get pushed off the road rather than buried:

In many cases, on roads this results in vehicles ending up in the river. For buildings this means that structures close to the toe of the slope will be buried, whereas those further away will be pushed outwards and usually collapsed.

2. Topples
Topples on the other hand rarely have any substantial horizontal component to their movement. Therefore, in a toppling failure the victims are likely to be buried under the rubble. This was illustrated by the recent Manshiet Nasser failure in Cairo:

Here, almost all of the buildings were buried beneath huge boulders. Unsurprisingly, few people were recovered alive. However, in the case of topples buildings may at least partially survive and there are often gaps between the boulders, which means that there is a real possibility of recovering victims if search operations are undertaken quickly and efficiently.

3. Slides
In the case of slides the key issues are:

1. The location of the victims at the start of movement;
2. The rate of movement;
3. The distance moved; and
   
4. The degree to which the slide breaks up.

There is a fundamental difference between the impact of the event if the victim is on the slide body rather than in its path. If the victim is on the top of the slide then the survival rate is probably quite high, even for long and reasonably fast events. In fact the Malaysia slide shows this quite well - structures on the surface are recognisable at the end of the event:


Of course there is usually a huge amount of internal movement of the landslide body, so buildings will often collapse. Thus, there is a real danger that people will be killed or injured in buildings, as above. Even in very fast and turbulent slides people sometimes survive on the surface. Below is the Hattian Bala landslide that was triggered by the 2005 earthquake in Kashmir. Two women who were cutting grass near to the crown (top) of the slide walked off unhurt at the bottom:


At the toe of the slide, objects in the way are hit and may be buried. Interestingly, in general it seems that in most cases structures are pushed outwards by the slide rather than being incorporated within it. Therefore, victims are likely to be found in the arc at or near to the toe rather than where the building originally was located:


Inevitably the level of damage to structures, and the survivability in general, is dependent upon the rate of movement and the distance that the landslide (and the victim) travels. Faster landslides moving longer distances have a far higher chance of killing the victim.

4. Spreads
Spreads are generally low velocity and therefore unlikely to kill, although buildings can and do collapse. The exception is in earthquakes, when spreads can be quite rapid and very large. Collapse of structures is the greatest hazard.

5. Flows
As with slides, flows depend on the location of the victim and the rate of movement. In this case, people on the surface when movement starts are far less likely to survive as the turbulence of the movement means that they can easily be drawn into the slide. Structures are likely to collapse completely. A mistake that is sometimes made is to look for buildings in their original location, whereas in fact they are likely to have been displaced a considerable distance. The best advice to rescuers is to look for debris as an indicator of the location of survivors

Image from Monsters and Critics

The survival of structures in the way of a debris flow depends on the speed and size of the flow, and on the properties of the material that forms it. Unprotected people stand very little chance is the flow is anything other than small, but well-built structures are surprisingly resilient:

Image from USGS

However, larger flows and those with a high proportion of soil and rock, are very destructive:

Here the key is took for the location of debris from structures that might contain survivors. For weaker buildings this is unlikely to be in the location of the original structure. There is some evidence that the flow pushes debris ahead of it, at least for a short distance, so looking around the toe of the slide might be a good option, as was the case for the second La Conchita landslide:

Image from the New York Times

The danger to rescuers
Landslides often occur in stages. Therefore, there is a very real danger to rescue staff that they might be affected by another event. This story, from Taiwan last week, is a graphic illustration of this issue:

"The body of a worker who was buried in dirt from landslides at a landfill construction site in the central city of Taichung for more than 10 hours was recovered late Sunday after many twists and turns, city officials said. Wu Cheng-wei showed no vital signs when his body was pulled out of dirt at 11 p.m., and he was pronounced death on arrival (DOA) after being rushed to nearby Taichung Veterans General Hospital. Wu was the first to be buried in a series of landslides at the suburban site where a landfill retaining wall reinforcement project was underway, but he was the last to be recovered from the dirt because subsequent landslides claimed another victim and injured two municipal Fire Department staff members. Wu was buried when the first landslide hit at around 9 a.m. Sunday. The city government's Fire Department dispatched a rescue team immediately after it received a distress call. While Fire Department staff and volunteers were busy searching for Wu, there was a second landslide which buried Fu Chia-sen, a volunteer firefighter. Fu's colleagues then rushed to mount a new search mission. At around 1 p.m., two Fire Department staff members, identified as Lin Hung-yi and Chen Chieh-chi, spotted part of Fu's clothing and tried to pull him out. However, another landslide hit, causing the pair to sink into the soft dirt. Lin Hung-yi was rescued first and was sent to the nearby Taichung Veterans General Hospital, where it was found that he had sustained only slight injuries. Chen Chieh-chi, who was buried in dirt from his chest down, was not rescued until around 5 p.m. He complained of acute pain in his legs and was sent to hospital for examination and treatment of his injuries. Fu Chia-sen was also pulled out of the dirt at 5: 35 p.m., but he showed no vital signs. He was pronounced DOA after being sent to the hospital."

Summary
I guess my take-home messages are:

1. We really need to look at this issue properly!
2. The type of landslide determines how, where and why people might survive. Therefore, getting someone who knows about landslides, and about landslide rescues, involved at an early stage is critical;
3. There is also a need to protect the rescuers against further landslides. A landslide specialist can help in this;
4. If in doubt, look for the location of debris from buildings. This is most likely to tell you where the victims are.

I would welcome any comments or thoughts on this. Has anyone any experience to share?