While Millions of Americans go on vacation yearly to beaches to search out sun, sand and sea, many will not be aware of how dangerous digging holes within the sand will be. In February 2024, a 7-year-old girl dies after a 1.5-meter-deep hole she and her brother had dug within the sand fell on her and buried her alive.

As a Coastal researchers I, who has been exploring beaches for a few years, was called to assist investigate the girl's death. While many individuals nearby intervened to free the girl after the sand hole collapsed, local firefighters couldn’t arrive until just a few minutes after the incident – too late to resuscitate the victim.

Digging holes within the sand could seem harmless, but when the opening is deep enough and collapses on an individual, it is incredibly difficult to flee. In fact, research suggests more people die more prone to die from suffocation through sand burial than from shark attacks.

Sand Basics

Sand will not be actually a cloth type. It is a category of fabric size, from 0.0025 to 0.08 inches (0.06 to 2 millimeters) in diameter. The Type of sand is set by the materials it’s fabricated from. Quartz sandcomposed of silicon dioxide, is essentially the most common sand found on beaches, apart from tropical coasts where there are coral sand beaches composed of calcium carbonate.

Material that’s coarser than sand doesn’t feel soft – you can not construct stable sandcastles out of it. Silt and clay, that are finer than sand, cloud the water and are commonly known as mud.

The weight of the sand is dependent upon the materials it’s fabricated from. Reiner Quartz sand Beaches with very white sand weigh about 90 kilos per cubic foot when dry.

However, most beaches contain a mixture of minerals that give the sand a tan or brown appearance. The minerals that make the sand darker are much heavier – the sand on most beaches weighs as much as 130 kilos per cubic foot when dry.

Dry, loose grains of sand form a pile with an inclination angle of about 33 degrees, which Angle of reposeThe angle of repose is the steepest angle at which a pile of grains stays stable, and the Frictional force between the person grains determines this stability.

Sand is more stable when it’s wet since the Surface tension between water and sand grains can hold the pile of sand vertically in place. However, once it dries, the pile collapses because there is no such thing as a longer any surface tension.

So in the event you dig a hole on the beach, it can stay stable so long as the sand stays moist. Once it dries, the opening will collapse.

Sand is unstable

If the sand forming the opening dries out, or someone stands near the sting of the opening and adds extra weight, the sand hole collapses and the heavy grains of sand fill all of the open spaces in the opening, leaving the trapped person with no air to breathe.

While skiers are trapped in avalanches, they will use their hands form an air bubble Snow is light, but collapsing sand will not be.

Rescuing an individual from a collapsed sand hole could be very difficult because sand is each heavy and unstable. While rescuers shovel away sand to free the victim, the opening will proceed to collapse under the burden of the rescuers and refill with sand again. The rescuers have only about three to 5 minutes to rescue an individual trapped in a sand hole before he suffocates.

When professionals similar to firefighters rescue someone from a collapsed sand hole, they place boards across the opening. This allows them to succeed in down and take away the sand with tools without putting weight directly on the sting of the opening.

Experts recommend never digging a hole deeper than the knee height of the smallest person in your group—the utmost depth is 2 feet (0.6 meters).

To rescue someone from a collapsing sand hole, deal with exposing the mouth and removing the sand from the chest. Exposing the mouth will help you Mouth to mouth resuscitation while other rescuers proceed to dig out their chests.

Too many individuals crowding right into a sand hole rescue can do more harm than good. Only two or three rescuers should work within the immediate area of ​​the victim while others work to clear the sand from the broader digging area, making it easier for the people in the middle to remove the sand. The people on the periphery can clear the sand from the central area with whatever they’ve at their disposal, from buckets and shovels to beach chairs and boogie boards.

Case studies

Collapsing sand holes resulted in 31 deathspredominantly children and 87% male, from 1997 to 2007 within the USA. During this era 21 others were involved within the collapse of a sand hole but survived, although many required cardiopulmonary resuscitation.

Victims of the sand hole collapse have aged 3 to 21 years. The Holes were generally 0.6 to 4.6 meters in diameter and 0.6 to three.7 meters deep. Digging, tunneling, jumping and falling into the opening have inadvertently led to the collapse.

These collapses can occur suddenlyand in situations that don't seem dangerous to most individuals. Next time you go to the beach, look ahead to sand holes and fill them as soon as possible. Even a shallow hole can injure someone who stumbles into it.

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How do you construct things like tunnels and bridges underwater? – Helen, age 10, Somerville, Massachusetts

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As a toddler I discovered a Calvin and Hobbes comic strip This led me to one among my burning questions: How do they know what the load limit of bridges is? Calvin's father tells him (incorrectly): “They drive over it with bigger and bigger trucks until the bridge breaks. Then they weigh the last truck and rebuild the bridge.”

Several a long time later I’m a geotechnical engineer. This implies that I work on all construction projects that involve earth. Now I do know the actual answers to the questions people ask about infrastructure. Often, like Calvin's father, they think from the incorrect direction. Engineers don’t often determine the load limit of a bridge, but somewhat construct the bridge to support the expected load.

The same goes for one more query I hear once in a while: How do engineers construct things underwater? They don't often actually construct things underwater – as a substitute they construct things that find yourself underwater. That's what I mean by that.

Building underground, under water

Sometimes you construct underwater, actually underground. It's not concerning the water you see on the surface, but what surrounds the actual structure you're constructing.

If your construction project is surrounded by rock or earth on all sides, it is mostly known as an underground construction – even when there may be a layer of water above it and you possibly can't see the rest from above.

In underground mining, powerful Tunnel boring machines to excavate soil directly. This machine is commonly called a mole for good reason. Like the animal, it digs a tunnel that resembles a burrow by digging horizontally through the soil and removing the excavated material behind it. This method could be used successfully to construct a tunnel through the soil beneath a body of water, which might then be lined and reinforced.

Using this method, the engineers were able Construction of the tunnelfor instance, a railway tunnel under the English Channel connecting England and France.

Although modern machines are quite advanced, this construction method began about 200 years ago with the Tunnel shield. Originally these were temporary support structures that provided a protected space for the employees to dig. As the tunnel grew, latest temporary structures were built deeper. As experience increased, the designs became higher and higher, the shields were built to be mobile and eventually developed into the fashionable tunnel boring machine.

Building on dry land before moving in

Some structures will ultimately be surrounded by water and rest on a river or sea floor. Fortunately, engineers have a couple of tricks up their sleeves to construct bridges and tunnels whose components are in direct contact with the water.

Underground structures are dangerous and difficult to access. Dealing with water brings additional challenges. While soil and rock could be disregarded to create a stable opening, water will all the time seep in to fill any gap and should be continually pumped out.

People, materials and machinery don't really work well underwater either. People need a continuing supply of air. Concrete pouring is difficult underwater and a few materials only work on land. And because gas engines depend on air to operate, underwater equipment may be very limited.

Some minor tasks – aligning and connecting prefabricated tunnel sections or checking that nothing has been damaged by immersion – might be carried out underwater, but the majority of the development work is unlikely to be. Once the structure is in place, constant monitoring and assessment will happen underwater.

Since it’s fundamentally unimaginable to construct underwater, there are two options: either you construct outdoors after which move the constructing underwater, otherwise you temporarily convert the underwater site right into a dry site.

In the primary option, staff often construct parts of the structure on dry land after which sink them in place. For example, the Ted Williams Tunnel in Boston was inbuilt sections in a shipyard. Workers dredged the long run tunnel path in Boston Harbor, clearing mud and other debris out of the best way. They then placed the sealed segments along the prepared trench. After the segments were connected, they opened the ends of the segments to create an extended, continuous tube. Finally, the tunnel was covered with earth and rock. Very little of the development actually took place underwater.

In other cases, comparable to in shallow water, construction staff may have the ability to construct directly from the surface. For example, staff can drive sheet metal shore retaining partitions directly into the bottom from a barge without having to divert water.

Temporary removal of water

The second option is to eliminate the underwater problem completely.

Although it’s difficult to create a dry spot on the underside of a body of water, it has an extended history. After leading the sack of Rome in 410 AD, the Visigothic King Alaric died on his way home. To protect his magnificent tomb from grave robbers, Alaric's men had temporarily diverted an area river to bury him and his prey within the riverbed before the river overflows its banks again.

Nowadays, for such a project, one would Cofferdam: a brief, watertight enclosure that could be pumped dry to create an open and protected construction site. Once the world is enclosed and the water pumped out, you’re in the world of ​​regular construction work.

Using a caisson is one other technique to create a dry area on a construction site that will normally be underwater. A caisson is often a prefabricated and waterproof structure in the form of an upside-down cup that’s sunk into the water by a crew. They keep it pressurized to make sure that no water gets in. Once the caisson is on the underside of the body of water, the air pressure and pumps keep the location dry and permit construction staff to construct inside. The caisson becomes a part of the finished structure.

construction employee constructed the pillars of the Brooklyn Bridge with caissons. Although the caissons were structurally protected, the pressure difference affected many staff, including chief engineer Washington Roebling. He contracted caisson disease – higher often known as decompression sickness – and needed to resign.

Building underwater is a posh and difficult task, but engineers have developed several ways to construct underwater…often by not constructing underwater in any respect.

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