How much common sense do you know about flood control?

Various maintenance work to prevent flood disasters during flood control period. For example, the defense and emergency repair of dams, gates, dams, railways and bridges. Based on the principle of "prevention first, prevention is more important than robbery", we should do a good job in flood control, which mainly includes pre-flood inspection, flood reporting, organizing rescue teams, preparing flood control materials and technologies, studying flood laws and characteristics, and taking various countermeasures to minimize or prevent flood hazards. Flood control work mainly includes flood control planning and construction, management and application of flood control facilities, flood prevention and emergency rescue, flood forecasting and dispatching, post-disaster work, etc. It also includes anti-icing work.

Waterlogging disaster: due to excessive local precipitation, surface runoff can not be eliminated in time, and the accumulated water in farmland exceeds the flood resistance of crops, resulting in the disaster of agricultural production reduction. The reason of crop yield reduction is that the depth of accumulated water is too large and the time is too long, so that the air in the soil is discharged one after another, which leads to insufficient oxygen in the roots of crops, difficulty in breathing in the roots, and the production of toxic and harmful substances such as ethanol, which affects crop growth and even causes crop death.

Flood: Flood is a disaster caused by the surge of water levels in rivers, lakes and reservoirs, the overflow or breach of dams and the entry of guest water. Waterlogging not only caused great disasters to agriculture, but also caused losses to industry and even life and property.

The similarity between waterlogging disaster and flood disaster is that there is too much surface water (or runoff), but the difference is that waterlogging disaster is caused by too much local precipitation, while flood disaster is caused by the entry of guest water.

What is a flood?

Flood is a natural phenomenon with high peak and sudden rise of water level. Floods generally include river floods, urban storm floods, coastal estuary storm surge floods, mountain torrents and ice floods.

What is flood control planning?

Flood control planning is to determine flood control standards according to the natural geographical conditions, socio-economic conditions and the needs of national economic development on the basis of studying the characteristics and effects of flood in the basin, and to reasonably choose flood control schemes through analysis and comparison, so as to determine engineering measures and non-engineering measures.

What is flood control dispatching?

Flood control dispatching is to artificially change the temporal and spatial distribution law of natural floods through measures such as storage, discharge, flood detention and classification, so as to achieve the purpose of reducing flood disasters.

What is the standard of waterlogging control?

The standard of waterlogging elimination refers to how many years a rainstorm occurs, how much daily rainfall, and how many days it is eliminated. It is the main basis for designing drainage system.

What is El Nino?

Peru, located at 4 ~ 14 south latitude, is one of the largest fish producing countries in the world, and its fish meal output ranks first in the world. This is because there is a strong upwelling along the coast of Peru, that is to say, in that area, in addition to the horizontal current, there is an upwelling rising from the deep seabed to the sea surface. This upwelling can bring rich phosphate and other nutrients from the seabed to the upper ocean, nourishing the world-famous Peruvian fishing ground. If this upwelling weakens or disappears, the warm current near the equator will invade, causing the water temperature along the coast of Peru to rise. This phenomenon occurs around Christmas every few years. Local residents said that this warm current invaded southward seasonally, and the resulting rise in sea surface water temperature was called "El Nino".

In normal years, El Nino can only invade south latitude by a few degrees. By March next year, the sea surface temperature will return to normal, which will not have much impact on fish and birds living here for a long time. The El Nino phenomenon is not exactly the same every year. In some years, warm water invades farther, while in other years, it invades closer. When the warm current invades strongly, it can reach more than 10 degrees south latitude, and then the water temperature along the coast of Peru will rise rapidly. Plankton living in this sea area and all kinds of fish adapted to cold water environment will die in large numbers because of sudden changes in the environment. At the same time, all kinds of seabirds that feed on fish will also die in large numbers because of lack of food.

After years of observation and research, it is found that when the El Ni? o phenomenon appears, it will not only bring disaster to the coast of Peru, but also affect the global climate anomaly. Whenever the El Ni? o phenomenon is serious, it is often found that some parts of the world are either flooded by heavy rain, while others are chronically dry and crops fail. Scientists have closely linked this global climate change with the El Ni? o phenomenon and found that there is a close relationship between them. Precursors of global climate anomalies can often be found in the occurrence of El Ni? o phenomenon last year or early this year. With the deepening of scientific research, there is a new understanding of the mechanism of El Ni? o phenomenon, and the original meaning of El Ni? o phenomenon has also changed. At present, only the large-scale sea water temperature rise in the central and eastern equatorial Pacific Ocean, which usually lasts for more than one year, is called El Ni? o phenomenon.

How to grab and protect piping

The principle of grasping and protecting pipeline

The practical experience of protecting piping danger in the middle and lower reaches of the Yangtze River proves that the principle of dealing with piping should be to stop sand gushing and leave a way out for seepage. In this way, silt and fine sand can no longer be destroyed, and the seepage pressure nearby can be reduced, thus stabilizing the dangerous situation. It is worthy of vigilance that piping is an extremely obvious and common cause of dike burst, but its danger is still not fully understood, or the measures are improper, or careless, which delays the opportunity. If the wells are surrounded by large wells, they can't be built rashly, or the high wells collapse, which will cause dike failure and bring serious losses to the country and people. The painful lessons of history must be remembered.

Grasping and protecting methods of pipelines

Piping is a serious danger. As long as we are vigilant, careful and equal, and deal with it in time, we can get rid of it. The following are the effective methods to protect pipelines since 1954:

1. Surround the low weir with soil bags around the water tunnel. To fill the hole with filter material, it is best to fill coarse sand first, then melon, rice and stones, and finally stones. It can effectively prevent sand from being taken out, but coarse sand can't be filled in because of water inrush, so it can be filled with gravel and stones to kill water inrush first, and then filled in according to gradation, which is slightly higher than the original ground. If there is no suitable stone nearby, brick slag can be used instead. If the sand can stop at the end of one time. You can remove a part of the upper coarse filler, and then fill it according to the above gradation until the water seepage is smooth and no sand particles are brought out. After the filter material is filled, you still need to pay attention to defense. If the filler is found to be sinking, you can continue to fill a stone until it is stable.

2. The method is the same as above, except that the cofferdam is not built, and the filter material can be directly filled.

3. If the embankment foundation soil loses too much due to piping, the cracks in the embankment body will collapse, which is a breach danger and should be rebuilt and reinforced in time.

4. After the emergency, we should still strengthen the defense, observe the relationship between surrounding changes and seepage and river fluctuation, and provide reference for post-disaster treatment.

How to carry out loose soaking rescue

Grasping and protection principle in bulk leaching

Based on the principle of "intercepting seepage near the river and guiding seepage at the back of the river", the infiltration line will be reduced and the dike will be stabilized. Using clay with low permeability as the outer wall of waterfront slope can reduce water infiltration into the embankment; The backwater slope is filtered by sand or firewood with high permeability, which can make the water that has penetrated into the dike flow out without taking away soil particles, thus reducing the infiltration line and stabilizing the dike body.

Grasping and protecting methods of loose heap leaching

When the danger of loose leaching is found, the reason and the degree of danger should be found out. If there is loose immersion on the inner slope of the dike, but there is only slight tide or a small amount of clear water oozing out on the slope, the dike body is stable and the danger has not developed, it can be closely monitored and will not be treated for the time being. If the dike slope is seriously seeped or washed by immersion, it shows that the danger is developing gradually and needs protection. The main method of robbing and protecting is seepage guidance. If the embankment is wide and there is clay nearby, and the danger is very serious, it is necessary to adopt the methods of external wall seepage prevention and internal slope seepage prevention at the same time, and it is forbidden to use cohesive soil as a pressure immersion platform on the internal slope of the embankment. Eliminating hidden dangers before the flood season is also an extremely important work to prevent the danger of loose soaking, nesting and leakage during the flood season. For example, the repair and prevention department specially set up an ant control team to chase, pump and turn over the termite damage of Jingjiang levee, which greatly reduced the risk of loose immersion, nest loss and loopholes in flood season.

How to carry out nesting protection

Principles of grasping and protecting falling nests

The sinkhole is partially collapsed, so it should be backfilled in time to prevent water erosion from expanding. Moreover, because loopholes often occur, there must be loopholes and dangers in handling them.

Nest-falling and protecting method

Taking the experience of Jingjiang levee rushing to protect the nest as a reference to deal with the nest falling;

1. The sinkhole occurs on the inner slope near the top of the dike, and there is no loophole in the sinkhole. Remove the loose soil in the sinkhole and fill it with good soil to restore it (Figure 1).

2. The collapse occurred on the inner slope of the dike, and there was a hole outside the dike, so water directly leaked into the collapse. We should cooperate to plug the hole on the outer slope of the dam to prevent water leakage. If it is necessary to rescue at the same time with the external plugging source, the loose soil at the landslide can be removed, and coarse sand, melon and rice stones, brick slag and pebbles can be backfilled to make an inverted filter well to prevent water leakage from bringing out soil and stabilize the danger. (After the flood season, the sinkhole should be rebuilt immediately, and the holes in the sinkhole should be built later, and then the loose soil in the sinkhole should be removed, backfilled and compacted. )

3. The collapse occurred on the high beach or high slope outside the dike, and there were loopholes in the dike. First, build a bag-soil cofferdam on the bank above the water surface, drain the accumulated water in the cofferdam, dig up the landslide part, find out the leakage source, and backfill it after the hidden dangers are eliminated.

4. If the landslide occurs at the top of the dike with thin dike body and narrow dike surface, external help should be added before excavation and filling to ensure the safety during excavation. When digging, you should first eliminate hidden dangers. If there is any loophole, it should be plugged first, and then backfilled and compacted.

5. If the sinkhole occurs in the underwater part of the outer slope, it can be filled with bagged soil and cotton wool. , and then added as external help.

How to grasp and protect the inner slope

Principle of grabbing and protecting inner slope

The main reason of inner slope peeling is that seepage reduces the shear strength of embankment slope soil. Therefore, the principle of grab protection is to first eliminate the water seepage in the sliding embankment slope, partially restore the shear strength of the sliding soil, and make the embankment slope stable. Then carry out slope repair and reinforcement.

The method of grabbing and protecting the inner slope.

The basic methods of grasping slope protection include ditching to guide seepage, filling pond to tamp foundation, adding soil to slope, and intercepting seepage with foreign aid. At the same time, combined with the specific situation, according to local conditions, different treatment. It should be pointed out here that piling is not suitable for slope rescue in some places. Not only can it not resist the huge thrust produced by landslide soil, but it is easy to promote the development of landslide. Therefore, we don't advocate piling to rescue the slope. Now several commonly used and effective rescue methods are listed as follows:

1. Permeable soil and water support

Scope of application:

If the scope of the reverse slope embankment is large, some water and soil permeable supports can be made along the reverse slope embankment. The specific size can be determined according to the specific situation. This method is effective in Jingjiang flood diversion area levee, Jingjiang levee and 1954 Wuhan levee.

Construction method:

(1) At the supporting position, cut the loose soil after slope cutting into slopes and dig ditches, and place the filtering materials, such as sand and gravel, brick slag, reeds, etc. , in the trenches. (2) If the embankment foundation is not good, the toe of the slope supported by soil should be fixed with stones or bagged soil, but care should be taken not to block the water seepage in the ditch. (3) The width of soil support depends on the water situation, danger and the difficulty of borrowing soil. Generally, the width is 5-8m, the slope ratio 1: 5, and the supporting height is generally 0.5- 1.0m below the flood level. (4) The filler shall be broken and compacted.

2. Permeable pressure immersion platform

Scope of application:

The dike section is insufficient, the slope falls off seriously, there is soil nearby, and there is a lack of sand and gravel.

Construction method:

(1) The practice is the same as that of permeable soil and water support. However, in terms of layout, the permeable pressure immersion platform is built in an all-round way, while the permeable soil support is built in sections. (2) See the construction method of permeable pressure sinking platform for loose sinking joint.

3. Foreign aid

The peeling of the inner slope is serious and the scope is wide. It takes time to build a permeable pressure immersion platform, ditch and conduct seepage in the dike. If there is a bank, clay external wall can be added to the outer slope while protecting the inner slope, so as to reduce water seepage, alleviate the danger and gain time to complete the protection of the inner slope.

4. All kinds of robbing and protecting methods are combined.

If there is serious water seepage in a large area of the inner slope, and there are dangers such as water leakage and slope detachment, the situation is complex and urgent, which cannot be solved by simple emergency measures. It is necessary to study and choose several rescue methods suitable for dangerous situations and embankment conditions, and at the same time be aware of them and determined. 1954 the experience of emergency rescue in flood season proves that these methods are effective and successful when used together. For example, Dongjiaguai in Jintuo section of Jingjiang levee is particularly dangerous, that is, measures such as digging ditches to prevent seepage, building external walls with soil bags and loose soil to prevent seepage, filling ponds to tamp the foundation and adding soil supports, connecting soil supports on the basis of silting and tamping the foundation and adding soil to the slope to prevent slippage, filling filter materials around wells where muddy water leaks, and lengthening the external walls on the external slopes were taken to successfully escape from danger. The major slope break of Wuqing levee in Wuhan is to grab the outer wall with bagged soil, throw stones in the pond at the foot of the levee to stabilize the foot, or squeeze silt with dry soil, and use Chai Lu and sandstone as the seepage guide ditch of the inner slope to filter the water back to the slope. The result was a total victory.

How to snatch and protect loopholes

The principle of catching and protecting loopholes

Because there is a hole in the water slope, the grab and protection should be mainly blocked from the outside, supplemented by a filter well at the exit of the embankment as appropriate, or both. Dealing with loopholes must not adopt piling at the outlet of loopholes or filling soil to seal pressure. Doing so will only aggravate the danger. It is theoretically feasible to store water around the outlet of the hole in the dike to balance the water pressure, but if the outlet occurs at the lower part of the dike slope or near the toe of the dike, if the water is stored around the well to balance the water pressure, it will be high and difficult to build for a while, and the well body will be thin and collapse after water storage, which will suddenly further aggravate the danger. These situations deserve our attention.

Methods of robbing and protecting loopholes

1. External plugging source is a direct and effective measure to prevent leakage caused by external plugging. But to block the hole, we must first find out the location, size and quantity of the hole. The way to find the hole can be to sprinkle some light objects on the water outside the dike, so that you can find the vortex on the water to find the hole. Or diving. But for the sake of safety, divers must be tied with ropes to avoid being sucked into the hole by the current. Once a loophole is found, it should be blocked immediately. If the hole is small, it can be fastened with an iron pan first, or blocked with cotton-padded clothes and cotton wool. If the hole is large or there are several holes around it, you can lift the quilt and drag it down along the embankment slope to cover the hole; If it is a leak or sewer, you can put the soil in a cloth bag and let it suck in, then plug the hole with a wooden wedge and cover it with cotton wool. After plugging the hole according to the above method, press the soil bag again, and pour the soil as an external aid, which is higher than the water surface.

If there are no obvious holes outside the dike, clay with high water content can also be used to fill along the slope, which can reduce the infiltration of water seepage.

It is forbidden to throw stones and soil bags at will when plugging holes, so as to avoid overhead and increase the difficulty of plugging holes.

2. Do a good job of inverted filter

At the same time, the leakage inside the dike should also be done well. Especially when leakage occurs at the bottom of the dike, muddy water with silt and fine sand appears, and it is difficult to tell whether it is leakage or piping at the moment, so we must take measures to protect piping and pour the filter well. As long as the inverted filter layer keeps the fill of the dam from losing, the danger will stabilize.

3. Road cutting (pumping and reconstruction)

This is a thorough but also the most dangerous way to cut off the roadway. This method can only be used as a last resort when there are sufficient and necessary conditions (such as wide dike body, large dike body and sufficient human resources and equipment). ). It is best to make a surprise attack when the water level recedes slightly during the flood season, but it is not suitable when the water level is too high. In the process of construction, we must concentrate and pay more attention to the filling quality.

The opening of the roadway is to dig a ditch at the top of the dike, and the position of the ditch is below the water leakage. The width of the trench is limited to the minimum width suitable for excavation, especially for deep trench openings.