What are the construction points of farmland irrigation project?

It is very important to understand the key points of water conservancy project construction. The formulation of key points can better solve practical problems, and the treatment of every detail is crucial. Zhong Da Consulting will explain the key points of farmland irrigation project construction for you.

I. Irrigation Project of Farmland Water Conservancy

Drainage and irrigation, regulation of small and medium-sized rivers, construction of key counties for local agricultural water use, improvement of water conservancy soil in low-yield fields, farmland water and soil conservation, land improvement and water supply for agriculture and animal husbandry, etc. Irrigation system is the infrastructure to realize irrigation, which can be divided into channel irrigation system and pipeline irrigation system. Generally, it consists of irrigation canal head works, canals or water pipelines, canal system buildings and irrigation pumping stations. The most common canal structures are water distribution structure and aqueduct, culvert, inverted siphon, falling water, steep slope, water measuring structure and grit chamber. When groundwater is used for irrigation, or when self-flow irrigation cannot be realized and water is needed for irrigation, or when self-flow drainage cannot be realized in low-lying areas, irrigation and drainage pumping station should be built for electromechanical irrigation and drainage. Irrigation areas should implement effective irrigation management, pay attention to canal seepage prevention, strengthen water management, and improve the effective utilization coefficient of canal system. Drainage system is the infrastructure to realize drainage, generally including drainage ditches (pipes) at all levels and their buildings, drainage accommodation areas, drainage pumping stations (see irrigation and drainage pumping station), etc. The type, structure and function of drainage canal buildings are the same as those of irrigation canal system buildings.

Second, the main points of farmland irrigation project construction

(A) underground pipe network construction technology

The width and depth of pipe trench should be determined according to the characteristics of water conservancy pipeline construction site. Then clean up the stones or other sundries in the pipeline to ensure that the levelness of the bottom of the pipeline is not inclined, so as to avoid the problems of water running and leakage. It should be noted that the main elbow or tee with the same diameter are two main details when turning in the pipeline construction process, and the control of its construction quality should be strengthened. The underground pipe network engineering of water conservancy irrigation project generally adopts welded pipes for installation. In the installation process, according to the design requirements, PVC pipes are installed in the order of main branch pipe first and branch pipe later. In the installation process, it is necessary not only to roughen the joint before bonding, but also to wipe and decontaminate the joint. The length of napping treatment should be within 5 cm ~ 10 cm, and PVC plastic commensurate with it should be selected as adhesive to avoid safety problems during installation. In the process of bonding, the bonding of the first pipe joint should be daubed evenly, then padded with wooden mats and rammed hard until the socket is 2 cm ~ 3 cm thick.

(2) Construction of seepage control channels

1, masonry seepage control

Masonry seepage control is suitable for channels with rich stone sources and requirements of frost resistance and erosion resistance. In China, mortar masonry seepage control channels are mostly built directly on the channel foundation without cushion. Because the slate is thin, in order to make it closely combined with the canal bed, a layer of sand or low-grade mortar with a thickness of 2 ~ 3 cm is often laid as a cushion. In order to improve the anti-seepage effect of masonry, clay, concrete, plastic film and other cushion layers are also laid under the masonry.

2, concrete lining seepage control

Plate structure is widely used in concrete lining, and its cross-sectional forms are rectangular, wedge-shaped, ribbed and trough-shaped. Rectangular plate is suitable for channels in areas without frozen accounts; Wedge plates and ribs are suitable for canals in frost heaving areas; Slotted plates are used for prefabrication and installation of small channels. Most large-scale channels are cast-in-place, and the integral cast-in-place U-shaped groove has good hydraulic performance, small section and less land occupation. Good overall stability and other advantages, suitable for small and medium-sized channels in areas without frost heaving or weak frost heaving. In areas with strong frost heaving, under the action of uneven frost heaving force, U-shaped groove is easy to move up and produce cracks, so it is not suitable for use.

3, asphalt material seepage control

Asphalt concrete lining is a flexible structure with good deformation adaptability, stability, durability and anti-seepage effect. Before the formal construction of asphalt concrete lining, trial paving must be carried out to determine the technological parameters such as asphalt mixture ratio, paving thickness, construction temperature and rolling times. The construction procedure of asphalt concrete lining is paving and leveling cemented layer, paving impervious layer and brushing seal layer. Rolling is a key link in asphalt concrete lining construction. After paving, it shall be carried out uniformly according to the selected paving thickness, with static pressure for 0 ~ 2 times first, and then vibrated and compacted.

4, plastic film seepage control

The canal lined with plastic film is impervious, with strong impervious performance, light weight, convenient transportation, high frost resistance and heat resistance, good flexibility and extensibility, and simple construction technology. Plastic film is used for laying seepage prevention, and there are two laying methods: open laying and buried laying. Surface paving is to lay a plastic film on the surface of the canal bed, and underground paving is to add a protective layer on the paved plastic film, which is now adopted in China.

(2) Culvert construction

Before construction, position the culvert with total station, and set out the axis, four corners and foundation sideline of the middle pile culvert. According to the scope of foundation pit, mechanical excavation shall be carried out to 30cm above the designed basement elevation, then artificial leveling shall be carried out, and finishing shall be carried out as required. Test the bearing capacity of foundation. If the bearing capacity can not meet the design requirements, the change should be reported for foundation reinforcement. If it meets the requirements, the construction can be continued. Gravel cushion layer compaction, each layer thickness is not more than 30cm. According to the size of culvert foundation, both sides of foundation pit are formed or poured with formwork. The pipeline foundation is poured twice. The first casting is 2-3 cm below the outer wall of the pipe bottom. After the strength reaches 50% of the design strength, install the pipe joint. After the installation is completed, the second pouring is carried out. The concrete is mixed by the mixing station according to the design requirements and transported to the construction site. The first pouring should make the top surface of concrete conform to the design slope, and the surface should be smooth. Before the second pouring, the top surface should be roughened and poured symmetrically on both sides of the pipe joint. After the pipe joint is prefabricated and the strength reaches 70%, it can be installed. During installation, it should be carried out from the middle settlement joint to both sides to ensure that the pipe end and settlement joint are on the same vertical section. At the same time, 2-3 cm cement mortar is placed at the bottom of the pipe to ensure that the pipe joint is straight and stable. After the installation is completed, the gaps between pipe joints shall be bound with hemp rope, four layers of asphalt impregnated linen and thick lead wire according to the design requirements. Within the range of not less than 2 times the pore diameter on both sides of culvert, both sides should be compacted symmetrically in layers. The thickness of layered cushion is not more than 20cm, and the degree of compaction is not less than 95%. During the construction, when the thickness of covering soil is less than 0.5m, it is forbidden for any heavy machinery and vehicles to pass through. ..

(3) Main concrete works of water conservancy pumping station

The pump station has large structural size, uneven structural thickness, complicated inlet and outlet water channels and many structural layers. It is important and difficult to ensure concrete appearance quality, concrete crack prevention and quality assurance of construction joints. Set a reasonable construction level, use rubber formwork and high-quality release agent for exposed concrete surface, and use fixed processing formwork for on-site assembly of special-shaped parts. Some measures should be taken, such as optimizing concrete mix ratio, mixing concrete with cold water, strengthening the structure of weak parts of the structure, setting keyways and temporary water stops in construction joints, and strengthening concrete thermal insulation and curing, to ensure the appearance quality of concrete, improve the crack resistance of concrete and improve the quality of concrete. The main concrete construction is as follows:

1, concrete cushion

After the construction of pile foundation and cutoff wall, the leakage test should be carried out on the section of cutoff wall according to the design requirements, and the bottom plate construction of pumping station can only be carried out after the seepage control effect meets the design requirements. The concrete pump truck will directly drive the cushion to the pouring bin surface and level it manually. When pouring, flat vibrator shall be used for vibration compaction.

2. Concrete structure at the bottom of the station

During the construction of the base plate of the station, the combined large steel formwork is used to erect the formwork, and double rows of small steel pipes are used for the outline drawing. When reinforcing the splayed formwork with steel pipes, attention should be paid to protecting the horizontal water stop, vertical water stop and expansion joints. The pumping station occupies a large area, and the floor height difference at the entrance side, the exit empty box side and the manhole empty box position is large. Using subsection and horizontal layering method, from low to high construction, the corridor layer is completed first, and then the entrance and exit side layers are constructed. The retarder used in the construction of bottom silicon is determined by experiments to prevent cold joint. After the bottom plate pouring is completed, the settlement observation nails shall be laid on the top surface according to the design drawings to observe the settlement value. For each additional level of load, the building should be observed once until the building moves to the top surface.

3. Pump station main runner concrete

The inlet and outlet flow channels are connected with the pump chamber. When arranging the process, retaining walls, piers and other retaining structures in contact with the water phase should be cast integrally with the runner at one time. Structures that are not in contact with water, such as internal partitions, machine piers, beams and slabs, can be poured in stages or in advance. The formwork, support and scaffold for casting runner should be well designed, and the fabrication and installation of runner formwork and reinforcement should be arranged in a unified way and coordinated with each other. There are many curved surfaces in the installation of runner formwork, which should be pre-assembled in the factory and transported to the construction site for installation after inspection. Ensure that the formwork support system is firm, safe and humanized, and ensure safe production.

The operation surface of runner concrete pouring is narrow, so it is necessary to start from a lower place and step by step, and the concrete in the silo should rise roughly in balance. A sufficient number of chutes should be set in the warehouse to ensure that the concrete can be delivered in place, and a vibrator should not be used to collect materials from a distance. The construction team should not neglect the quality of concrete pouring and vibrating because of the small working face of runner construction. At the same time, strengthen sprinkler maintenance, and the concrete surface should always be moist. And make maintenance records, regularly observe indoor and outdoor temperature changes to prevent cracks in concrete due to excessive temperature difference.

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