River sand is very expensive, why not dig sand from the Yellow River as building materials? Can you dred the Yellow River?
In our daily life, sand is the most common type of material, and in the construction industry, river sand is a very important building material , and almost all human buildings are inseparable from river sand. Unlike the sand grains that exist in nature, industrial sand has many different process standards and requirements .
What you may not know is that although river sand can be seen everywhere in life, with the continuous construction and development of human beings, a large number of roads and houses have been built so that river sand is consumed in large quantities, and the price of river sand is also rising . Nowadays, the price of river sand per cubic meter is generally more than 200 yuan. Compared with the past, the price of river sand is very expensive . Some people may think, since there is a lot of sand in the Yellow River, why not make use of the sand in the Yellow River? At the same time, it can also control the sediment accumulation problem in the Yellow River and carry out dredging , which kills two birds with one stone.
Yellow River Sediment
Speaking of which, let's take a look at the Yellow River. As the second longest river in China , the Yellow River originates from Qinghai, flows through many places, and passes through 9 provinces. From the perspective of the development of Chinese civilization, the culture of the Yellow River Basin derived the later Chinese civilization . And the name of the mother river of the Yellow River also comes from this, it can be seen that the Yellow River has a very important influence on China .
The Yellow River has been aggressive from the very beginning. From the days of Dayu to today, the Yellow River has been managed by continuous man-made regulation. The Yellow River will pass through the Loess Plateau in the middle reaches of the river . It is also here that the Yellow River begins to become turbid and carries a lot of sediment .
The sediment carrying capacity of the Yellow River can be said to be the largest in the world, with the largest annual sediment transport reaching 3.91 billion tons. Due to the accumulation of a large amount of sediment, the downstream riverbed continues to rise, and the Yellow River is also known as the "river in the sky" . It is precisely because of the turbulent changes of the Yellow River that the problem of the Yellow River has been difficult to cure for a long time.
sand
Generally, we refer to the finely divided rock mineral particles as sand, and the formation and composition of sand particles depend to a large extent on the local geographical environment . In inland areas, such as desert areas, the sand in these places is mainly composed of silica, usually in the form of quartz. The sand in these areas has been weathered for a long time , and the sand grains are very fine and smooth .
Another kind of sand is also more common, the main component of this kind of sand is calcium carbonate. Most of them are small sand grains formed by various life forms such as corals and shellfish after hundreds of millions of years of changes .
Sand for construction is essentially the same as general sand, except that sand is more artificially manufactured or obtained by grinding stones . In addition, in nature, river sand is mainly produced by the force of water, through repeated collision and friction for a long time, and is a non - metallic ore with complex composition and high content of impurities .
From the perspective of human time scale , sand has become a non-renewable resource because it takes hundreds of millions of years to form and can only be formed after natural long-term grinding .
sand for construction
After a brief understanding of the formation process of sand, let's talk about why the Yellow River sand is not used. In the construction industry, there will be an engineering standard requirement for the use of all building materials, and river sand is no exception.
Sand for construction is generally divided into fine sand, medium sand, medium-coarse dissolved sand, and coarse sand. There is a standard value for the distinction of each sand grain fineness, and the standard grain size of fine sand is between 0.25mm-0.35mm. During the long-term scouring of the Yellow River sand, most of the particle sizes are less than 0.15mm, which is completely inconsistent with the engineering use regulations.
The use of river sand is mainly used as concrete, because the irregular particle surface of river sand can be well combined with cement, and after mixing, it can achieve the required viscosity and strength of concrete. The sand of the Yellow River is fine and smooth, and cannot guarantee the overall quality of the building after mixing, and naturally the sand of the Yellow River cannot be used as a building material .
And the sea sand is even worse , not only the particles of sea sand are small , but also calcium carbonate and salt in the structural components . If sea sand is used as concrete raw material, the chloride ions in the sand will corrode the steel bars in the concrete , damage the building structure and seriously shorten the safe service life of the building . However, in some special cases, these fine sands can be mixed into concrete for anti-seepage treatment , but generally no one uses extremely fine sands such as the Yellow River sand.
In fact, the particle sand below the construction sand specification can be used to burn some hollow bricks , or these fine sand particles can be mixed with a certain soil ratio to form sand for some plant cultivation . In addition, sea sand is a relatively common industrial material in the field of machinery manufacturing. The characteristics of sea sand can be used to make molds. By grinding the material, it can also be used for rust removal, descaling treatment, and the manufacture of some refractory materials .
In addition, the sand in the Yellow River is actually just an incidental. The reason why the Yellow River is so yellow is due to the soil brought by the scour in the middle of the river. In other words, the Yellow River carries more soil-like substances, and sand is only a part of it .
Moreover, as an important construction raw material, river sand has always been an important material controlled by the state . For the Yellow River, the sediment in it also plays a very important role in the governance of the Yellow River. Any river sand mining without the consent of the government is Illegal and criminal behavior .
River Sand and Yellow River Management
The governance of the Yellow River has been a thorny issue since ancient times. Almost every dynasty has diverted the Yellow River or built dams. During the Han Dynasty, the Sui Dynasty and the Ming and Qing dynasties, it was repaired to varying degrees. However, the Yellow River will continue to silt up, and building dams can only ensure temporary stability .
Judging from the relevant data of the Yellow River, the Yellow River has an average of 1.6 billion tons of sediment per year , of which 75% will flow into the sea, and the rest will accumulate in the river. If the river channels are diverted and the river sand is introduced separately , it only needs to reach 5% of the total sediment transport each year to ensure the long-term safety of the Yellow River .
In fact, it is not without sand dredging in the Yellow River. Another means of controlling the Yellow River is to rely on sand suction boats to pump sand to fill the pits . The high-pressure water pump of the sand suction ship will pump the water of the Yellow River to the sediment layer of the river channel, and then transport the extracted mud and sand to the shore through the pipeline . The extracted sediment is used to fill the pits to build embankments or to build fields for greening .
But in general, these are temporary protection measures. Whether it is dredging and transporting or diverting the river, the sedimentation of the Yellow River will always exist . The fundamental problem of the Yellow River is still at the source. The special geographical structure of the Loess Plateau makes it continuously scour the Yellow River, which will take away a large amount of sediment on the banks of the river . Greening on the Loess Plateau will be an important plan for the governance of the Yellow River in the future.
In addition, for the Yellow River sand, although the fine sand cannot be directly used for construction, it can be fired into porous bricks as building materials. After nearly 20 years of hard work, the Zibo government in Shandong has finally made effective use of the Yellow River sand and solved the problems of difficulty in sintering river sand and making bricks . These fired porous bricks will make an important contribution to the governance of the Yellow River in the future, and also bring economic benefits .
Nowadays, various methods have also achieved initial results on the governance of the Yellow River. It can be seen that the governance of the Yellow River is a long-term process and cannot be solved by simple sand dredging.
Sand digging is risky
Returning to the issue of sand dredging, one of the very important reasons why the state does not allow private sand dredging operations is that uncontrolled sand dredging will damage the river environment .
For rivers, bed sediments have always been in a dynamic equilibrium. Unreasonable dredging activities will change the river bed and affect the flow of water . The tunnels after the excavation of the riverbed occupied the original channel, which changed the original flow direction of the river. Under the scouring action of water flow, new river channels will gradually form, but this process will change the appearance of the original river and cause irreversible situation to the surrounding ecology and geographical environment .
If there are bridges, ports or some hydropower stations on the river bank, the river channel that has lost its original bank foundation will be washed by the current and will directly act on the building foundation. This will make the original support of the building fail, and the ability to resist lateral loads will be greatly reduced , which is very likely to cause the building to collapse .
The formation of new river channels changes the flow direction of the original rivers, and some important waterways may be affected or even impassable. The pits left by dredging will form eddies and undercurrents under the action of water flow . Illegal sand dredging without reasonable management and control will make the river completely out of control.
For the ecology around the river, both the bottom organisms of the river channel and the organisms living on the river bank may suffer devastating damage . The once frenzied gold rush activities in Europe and the United States have been verified in Canada. Canadian rivers have been illegally dug gravel due to the gold rush , causing the river to change its flow direction and ecological damage . And these rivers have barely recovered a little bit of life after half a century.
Sand crisis
Since 2019, the United Nations has regarded sand and gravel as a future shortage resource, and the world is facing a sand crisis . Global sand use has doubled over the past few decades. Humans need 10 tons of sand to produce one ton of cement, and the world consumes 50 billion tons of sand every year .
As a populous country and also a developing country, China consumes 20 billion tons of sand and gravel every year. Not only China, but the world will continue to increase the demand for sand and gravel in the process of industrialization and urbanization in the future. The emergence of the sand supply crisis is also due to the rapid development of global urbanization , and nature cannot produce more sand in time .
The massive use of sand and gravel requires us to have an effective and sustainable sand mining strategy , while also protecting the river. The unreasonable mining of river sand has begun to slowly disappear the Mekong Delta in Vietnam , coupled with the factors of climate change. The Mekong Delta is now losing the equivalent of one and a half football fields of land every day.
The current alternative to river sand is manufactured sand, which is a type of sand made by mechanical force . The sand making machine uses pebbles, granite, marble, and even some waste construction waste to crush the raw materials into sand and gravel aggregates by mechanical force . This kind of machine-made sand is low in cost and can also replace natural sand in construction use. Machine- made sand will be an important development trend in the future.