Analysis on the key points of strengthening small reservoirs?

what is the specific content of the analysis of the key points of small reservoirs? here, Zhongda Consulting will answer your questions.

the reinforcement of small reservoirs is a top priority in the current water conservancy project construction. How to use limited funds to solve the potential safety hazards in small reservoirs to the maximum extent and determine the project quality is a problem that the majority of front-line water conservancy workers must care about.

I. Status of Small Reservoirs

At present, more than 9, reservoirs have been built in China, which have brought remarkable social and economic benefits in flood control, irrigation, power generation and power supply. Due to historical reasons, there are many dangerous reservoirs in China, which are widely distributed and in serious danger. In order to complete the task of danger removal and reinforcement of dangerous reservoirs, the Ministry of Water Resources has carried out the compilation of the national special plan for danger removal and reinforcement of dangerous reservoirs. The scope of planning is large, medium and small dangerous reservoirs under the jurisdiction of the water conservancy department; Focus on the planning of large-scale and small-scale dangerous reservoirs that affect towns above the county level and important railway trunk lines, and the planning level will be in 215 in the near future. According to the national western development strategy, a number of small and medium-sized dangerous reservoirs in the western region have been identified as the key points of the reinforcement project. By the end of 21, there were 143 large-scale dangerous reservoirs in China; 1,92 small and dangerous reservoirs, including 543 key small and dangerous reservoirs; There are 29,147 small and dangerous reservoirs, with a total investment of 54.4 billion yuan. The short-term planning goal is to complete the reinforcement of 119 dangerous reservoirs in 215, including 143 large-scale reservoirs and 543 key small-scale reservoirs; There are generally 119 small seats in the western region; There are 385 key small-scale buildings in the western region, with a planned total investment of 27.2 billion yuan. The long-term planning goal is to complete the reinforcement of other dangerous reservoirs by 215, with a total investment of 27.2 billion yuan. The second-class reservoirs are required to meet the national flood control standards.

2. Common problems in reinforcement of small reservoirs

1. Earth dam cracks

2. Top foundation leakage

3. Dam body leakage

4. Dam head seepage

5. Earth dam landslide

6. Termite breeding

3. Solutions to the above problems

1. For the treatment of non-sliding cracks, excavation and backfilling are often used.

(1) If the crack width is small, the depth is within 1m, and it is stable, it can generally be used for fine sandy loam, which is poured through the crack, and then compacted with bamboo sticks. Important and relatively important small reservoirs should be excavated to .3m below the crack depth, and then backfilled and compacted, and the treatment can be carried out in sections, while paying attention to the combination of new and old soil.

(2) If the crack is wide and the crack depth is within 5m, and the crack has stopped developing, it should generally be backfilled after excavation. When excavating, a trapezoidal section is adopted, or a stepped pit is excavated. When backfilling, the steps are cut off, and the trapezoidal section is maintained, so that the backfilled soil can be closely combined with the original dam.

2. Treatment of dam foundation leakage

The root cause of dam foundation leakage is that effective anti-seepage measures were not taken during design and construction, or the dam foundation treatment was not thorough. The basic principle of dealing with dam foundation leakage is "upper cut and lower drainage, with drainage as the main principle". The specific measures for intercepting water should be adopted according to the actual situation of different dam types, leakage parts and harm degree.

(1) Clay cutoff wall is a simple method to deal with seepage in homogeneous earth dam or inclined wall dam, and its seepage control effect is also good. It is shallow in the impervious layer of dam foundation, which is convenient to be combined with the impervious body in the dam, and is generally widely used when the construction conditions permit.

(2) If the impervious layer of the dam foundation is deep and it is difficult to deal with the seepage of the dam foundation, clay impervious blanket can be made on the water surface. The function of clay impervious blanket is mainly to prolong the seepage diameter and reduce the seepage quantity of dam foundation, but it can't cut off the seepage. It is required to control the seepage velocity within the safe allowable range in design. Therefore, a certain depth, length and thickness are necessary.

(3) Curtain grouting is to press cement clay slurry into the sand egg layer of dam foundation by drilling holes with grouting machine, and glue sand pebbles into a cutoff wall with a certain thickness, which is applied to various types of dams with deep permeable layers. Various measures can be taken for the drainage downstream of the dam according to local conditions, such as filter drainage ditch, filter cover weight, combination of drainage culvert and cover weight, and drainage well.

3. Treatment of dam leakage

Due to different designs, poor construction quality or improper management and application, dam leakage will occur. The performance of leakage is that some dams have wet water droplets, which are called loose leaching, and some form concentrated leakage, resulting in a stream of water leakage. Leakage has a very negative impact on dam safety. The treatment of dam leakage is all around "plugging" and "drainage". In addition to plugging in the upstream, filtration and drainage facilities should be done in the downstream. The common treatment methods of earth dam leakage are pumping slot to fill the soil, clay inclined wall to intercept leakage, grouting to stop leakage, trenching to conduct seepage, conducting seepage and thickening.

4. Treatment of seepage around the dam head

The seepage path of reservoir water can be along the joint surface between the dam and the bank slope, or it may seep downstream through the mountain body of the dam head. The seepage around the dam will lose water, affect the stability of the slope at the dam head, and cause collapse and landslide, so the seepage around the dam head can not be ignored. Before treatment, we must investigate the construction situation in detail, check the leakage position, analyze the leakage reasons, and then make an appropriate treatment plan. The principle of treatment is similar to that of dam foundation leakage.

(1) Clay lime-soil blanket seepage control method.

general seepage can be excavated and cleaned at the boundary between the upstream slope of the dam and the dam impervious body, and covered with yellow mud or lime yellow mud according to a stable slope and compacted to prolong the seepage diameter and reduce the seepage.

(2) plug the loopholes and cracks.

pour cement mortar or cement clay mortar at the entrance and then block the hole with concrete.

(3) cutoff wall method.

erect a shaft on the hillside at the dam end, check the depth and position of water leakage, and then take anti-seepage measures such as slotting as clay cutoff wall, concrete cutoff wall or curtain grouting to block it. For the core dam and cutoff wall, it must be connected with the dam body and mind wall; For inclined wall dam or homogeneous soil increase, it is necessary to add clay inclined wall blanket at the junction of upstream dam slope and bank slope and extend it upstream appropriately to expand the coverage.

(4) laying drainage filter layer.

at the outlet section of seepage around the dam on the downstream bank slope, a seepage-guiding drainage filter layer is laid to prevent soil particles from being taken away by seepage, or a dry masonry open ditch can be made at the junction of the dam end and the hillside in combination with drainage, and a filter layer is made under the masonry to eliminate rainwater and seepage.

5. Treatment of landslide of earth dam

Landslides may be caused by weak interlayer in dam foundation, soft clay layer, improper selection of soil materials when filling dam body, poor compaction, steep dam slope or the overflow point of saturation line of backwater slope increased due to drainage failure, and sudden drop of water level in operation, earthquake, rainstorm and other influences. For the dam surface where landslide has occurred, the treatment principle is mainly to reduce the load on the upper part and reduce the load on the lower part.

(1) The dam foundation is good, and the landslide appears on the downstream surface above the foundation surface, and the slope locally collapses. Therefore, the water level of the reservoir can be appropriately reduced, and seepage drainage measures can be taken. After the soil in the sliding part is dehydrated and consolidated, the loose soil can be removed, and then the soil with strong permeability can be repaired from bottom to top. If necessary, the dam slope can be appropriately slowed down or the abutment can be made of permeable materials.

(2) In case of landslide caused by silt interlayer or collapsible loess layer in the dam foundation, an anti-skid toothed wall with a fixed foot by riprap can be built at a certain distance outside the dam foot, and it should be properly higher than the foundation surface, and then permeable material or rockfill should be backfilled between the dam foot and the toothed wall to make a heavy platform, and a filter layer should be made between the platform and the toothed wall.

6. termite control and treatment of ant nests in earth dams

The earth dams of most reservoirs in southern provinces of China are harmed by soil-dwelling termites to varying degrees. Once termites are found on the dam, the dam is often destroyed. Therefore, in areas with serious termite damage, the policy of "prevention is more important than treatment, combining prevention with control and comprehensive treatment" should be implemented to prevent termites.

(1) Smoke suppression method.

For large nests of soil-dwelling termites, smoke suppression is often used to kill them. This method is simple and effective. The principle is that the smoke is automatically pressed into the ant nest to poison the ant colony by using the expansion pressure generated by the explosion when the smoke is burned. After termites are poisoned, there are gaps and passages in the dam body, and it is necessary to cut the nest and fill it with soil to block the gaps in the ant nest. Therefore, attention should be paid to observing the smoke on the surface when pressing the smoke. There are often small passages and pores at the top of the termite nest in the active period, and the smoke enters the ant nest and ejects the surface through various holes, and the dense place is the nest top. During termite activities, smoke should be suppressed at the crossing near the ant nest as far as possible, which is convenient for breaking the nest and backfilling.

(2) grouting method to kill ants.

Combining termite control with blocking the ant passage, the slurry with medicine is pressed into the ant nest and ant passage from the borehole by grouting machine, which kills termites and blocks the cave at the same time. The advantages of this method are that it can replace manual excavation to fill the ant path and nest, avoid destroying the original structure of the dam, and can be constructed all year round without being affected by seasons, and can be combined with compaction of dam pores; The disadvantage is that it is not easy to wipe out termites, and at the same time, it is necessary to prevent water pollution to avoid adverse effects on underground drinking water.

(3) Artificial excavation to kill ants.

After observing and checking, the ant path and nest position are found, and then the ant nest is hunted by manual excavation, and then the ant nest is compacted by layers. The disadvantages of this method are: a large amount of excavation, a lot of labor, and a considerable part of the ant tunnel can not be dug, which may leave hidden dangers due to incomplete treatment; at the same time, it will destroy the original structure of the dam, and if the backfill is not well compacted, it will also increase the unsafe factors of the dam; it is also not suitable for construction in flood season.

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