Quicksand is the most ingenious mechanism designed by nature. It may be hidden by the river or even in the backyard next door, quietly waiting for people to approach, which makes people in a dilemma. In A.D. 1692, quicksand was caused by soil liquefaction caused by earthquake in royle Port, which eventually led to the disappearance of one third of the city and the death of 2,000 people. The seemingly calm North Sea in England and the beautiful and dangerous Alaska Fjord have also had stories of people trapped by quicksand. However, most people have never seen quicksand, let alone witnessed others fall into quicksand or experienced it personally. People's impressions of quicksand are mainly based on various movies. In the scene created by the film, quicksand is a big monster that can suck people into a bottomless pit. Once people are trapped, they are often unable to extricate themselves, and their companions can only watch the trapped people being swallowed up by sand instantly.
Once the surface of quicksand is disturbed, it will "liquefy".
Bourne of the University of Amsterdam in the Netherlands met a local shepherd while on vacation in Iran. Pointing to quicksand, he told Bowen that once a camel sank in the village and disappeared immediately. Bern was skeptical about this and immediately studied it after returning to China. He carefully watched and analyzed dozens of movies describing the scene of quicksand eating people, and found that the descriptions of quicksand in these movies were simply full of mistakes. Later, Bourne mixed fine sand, clay and salt water in the laboratory and reconstructed a miniature indoor quicksand model for research.
After repeated experiments, researchers led by Berne found that it takes several days to make sand as sticky as toffee, but it is easy to lose its viscosity as long as proper pressure is applied to its surface. Once the surface of quicksand is disturbed by movement, it will "liquefy" quickly, the sand on the surface will become loose and soft, and the shallow sand will flow down quickly. This migration sinks objects moving on quicksand. However, with the increase of sinking depth, the sand and clay falling from the upper layer to the bottom layer gradually gather, which will form a thick sediment layer, which will increase the viscosity of the sand rapidly and prevent the object from sinking further.
Objects whose density is less than quicksand will float on quicksand.
It is also found that when an object sinks into quicksand, the sinking speed depends on the density of the object itself. The density of quicksand is generally 2g/ml, while that of human is 1g/ml. At this density, the human body will not be destroyed when it sinks into quicksand, and it will often stop when it sinks to the waist. The researchers also found that even some objects whose density is much higher than quicksand can float on quicksand. In the experiment, the researchers put an aluminum basin with a density of 2.7 g/ml on top of quicksand. Although its density is higher than that of quicksand, it can still stay on the surface of quicksand calmly because of its buoyancy and surface tension. The situation changed when scientists began to gently shake the aluminum container. The container is a little heavy. When they shook hard, the container slowly sank to the bottom of the sand.
It takes the strength to lift a car to pull your feet out of quicksand.
It is believed that people trapped in quicksand can't move generally, and the sand with increased density sticks to the lower body of the human body falling into quicksand, which causes great pressure on the human body and makes it difficult for people to make efforts. Even Hercules can hardly drag the trapped people out of quicksand at once. According to the researchers' calculation, it takes about 654.38+ million newtons to pull out a trapped person's foot at a speed of one centimeter per second, which is about the same as the force to lift a medium-sized car. So unless there is a crane to help, it is difficult to pull people out of quicksand at once. The study also pointed out that according to the calculation of this force, if you pull hard, the human body will be torn off by powerful force before the quicksand "lets go". The danger caused by this move is much higher than letting him temporarily stop in quicksand.
How to save yourself in quicksand
In fact, most quicksand is not much different from ordinary sand, and it is not as terrible as described in the movie. In principle, only sand has penetrated into the water. Due to the reduction of friction between sand grains, a semi-liquid sand-water mixture is formed, which is unbearable. Quicksand is usually found near the coast, usually shallow and rarely more than a few feet deep. Bowen said that there is only one situation in which quicksand can drown people, that is, the head falls into the sand first, but the probability of falling into quicksand is very small. People trapped in quicksand only feel some pressure in their chest, have difficulty breathing and are not life-threatening. The high tide near quicksand is the biggest enemy of the trapped.
But the description of quicksand in the film is at least correct, that is, if you are caught in quicksand, struggling hard or kicking will only make people sink faster. People mistakenly think that shaking can loosen the sand around their bodies and help them pull their limbs out of quicksand. Scientists point out that this movement can only accelerate the deposition of clay and enhance the viscosity of quicksand, and people who struggle at random will only get deeper and deeper.
Bowen pointed out that there is another way to escape from quicksand, that is, let the trapped person move his feet gently and let water and sand penetrate into the squeezed vacuum area as much as possible to relieve the pressure on the trapped person's body and let the sand loosen slowly. Trapped people should also try to separate their limbs, because only the greater the surface area of the body in contact with sand will the greater the buoyancy. As long as the trapped people are patient enough and slow enough, they can slowly get out of trouble.