As Coastal Science Researcher Having studied the beach for many years, I was called in to assist in the investigation of the girl’s death. I tried to help herHowever, as they continued digging, the sand hole continued to collapse, causing more sand to pour in. Firefighters arrived minutes after the incident, too late to revive the victims.
Digging a hole in the sand may seem harmless, but if the hole is deep, it can be extremely difficult to escape if someone falls in. In fact, some research suggests that more people die from suffocating under sand than from being attacked by sharks.
Collapsing sand hole Between 1997 and 2007, 31 people died in sand pit collapses in the United States, most of them children and 87% were men. During the same period, 21 people survived reported sand pit collapses, many of whom required CPR.
Sand pit collapse victims ranged in age from 3 to 21 years old. The holes typically ranged in diameter from 2 to 15 feet and depths from 2 to 12 feet. Digging, tunneling, diving, or falling into the holes have all unintentionally caused the collapses.
Sand isn’t actually a type of material; it’s a size category of material. from The diameter ranges from 0.0025 to 0.08 in. The type of sand is determined by the materials that make up the sand. Quartz SandCoral sand, made of silicon dioxide, is the most common type of sand found on beaches, except on tropical coasts where you will find coral sand beaches made of calcium carbonate.
Materials coarser than sand are not soft to the touch;You can’t build a sturdy sand castleSilt and clay, which are finer than sand, make the water cloudy and are commonly called mud.
The weight of sand depends on the materials that make up the sand. Quartz SandThis very white plant weighs about 90 pounds per cubic foot when dry.
However, most beaches contain a mixture of minerals that cause the sand to appear tan or brown. The minerals that make the sand black are much heavier, with most beach sand weighing up to 130 pounds per cubic foot when dry.
Dry, loose sand grains form a pile with an inclination angle of about 33 degrees. This inclination angle is called the angle of repose. The angle of repose is the steepest angle at which a pile of sand can remain stable, and its stability is determined by the forces of friction between the grains.
When sand is wet, it is more stable because the surface tension between the water and the sand grains keeps the pile vertical, but when it dries, the surface tension disappears and the pile collapses.
So if you dig a hole on the beach, it will remain stable as long as the sand is moist. If the sand dries, the hole will collapse.
If the sand that makes up the hole dries out or if someone stands near the edge of the hole and adds extra weight, the sand hole will collapse and the heavy sand grains will fill all of the open space in the hole, leaving the trapped person with no air to breathe.
A skier caught in an avalanche holds up his hands Forming air pockets The snow is light and the sand doesn’t crumble.
Sand is heavy and unstable, making it very difficult to rescue someone from a collapsed pit. As rescuers scoop out the sand to free the victim, the pit continues to collapse under the rescuer’s weight and refills with sand. One study found that rescuers Approximately 3 to 5 minutes Rescue someone trapped in a hole in the sand before they suffocate.
When firefighters or other professionals rescue people from sand pit collapses, they place a board across the pit so they can reach in and use tools to remove the sand without putting their weight directly on the edge of the pit.
Experts recommend digging a hole no deeper than knee height of the shortest person in the group, with a maximum depth of 2 feet.
To rescue someone in a collapsing sand pit, focus on exposing the mouth and removing the sand above the chest. If you can expose the mouth, Artificial respiration Other rescuers continue to dig up bodies.
Overcrowding a sand pit rescue can do more harm than good. Having two or three rescuers work in the area immediately surrounding the victim while others work to remove sand from a larger excavation area makes it easier for the person in the middle to remove the sand. People on the periphery can use whatever is available, from buckets and shovels to beach chairs and bodyboards, to remove sand from the central area.
Sand hole collapses can happen suddenly and in circumstances that seem unlikely to most people. Even shallow holes can injure someone who trips and falls. So the next time you go to the beach, be sure to watch out for sand holes and fill them in as quickly as possible.
Stephen P. Leatherman is professor of coastal science at Florida International University.
This article is translation:.
