U-shaped trough construction plan (1)
1. Production equipment
U-shaped trough concrete prefabricated parts are produced using water-saving and anti-seepage methods recommended by the Ministry of Water Resources. The LZYB-1 concrete component forming machine produced by a professional manufacturer of channel forming machinery. The main feature of this machine is that one main machine is stacked with two working heads, which can install two molds and presses of the same or different specifications at the same time. Heads can be produced of the same type at the same time or separately. With various molds provided by the manufacturer, it can produce U-shaped prefabricated parts, curb stones, hexagonal blocks and other shapes of concrete components. The main machine power of this machine is 5.5KW, the vibration power is 2.2KW × 2 units (adjustable speed), each machine is equipped with 4 workers during production, and can produce 30 to 40 pieces of U-shaped components per hour, curb stones, and 50 to 60 hexagonal blocks. pieces.
The concrete ready-mixing machinery adopts the JB300 forced concrete mixer, which can mix dry hard and plastic clinker, mechanically feed materials, and quantitatively inject water.
The mold adopts the fixed U-shaped channel steel mold matched by the manufacturer. The structural dimensions, surface flatness and smoothness of the steel mold must be checked before use. Deformed molds cannot be used anymore.
2.1 Production site
U-shaped troughs can be produced by centralized prefabrication or on-site prefabrication at a certain construction site. On-site prefabrication must choose a flat, open site with convenient transportation and local access to water and electricity. On-site prefabrication can reduce the transportation links of prefabrication, reduce losses during transportation, and reduce project costs.
2.2 Manufacturing process
The prefabrication procedure of U-shaped components is: preparing sand and gravel - mixing fine concrete - forming machine to press U-shaped groove - demoulding and placing to solidify - —Take the backing board and sprinkle it with water for maintenance.
The mix ratio of concrete is in accordance with the ratio recommended by the manufacturer. Each cubic meter of concrete such as C20 requires 404Kg of No. 325 cement, 1256Kg of fine stone, and 542Kg of medium sand. The quantity of materials is controlled by weighing, and water is added with a bucket of specified volume. , mix it into dry hard concrete with a forced mixer, pour it into the mold manually, control the input amount through experiments, and mechanically force vibration to form it. After the spit is removed, it is supported by the layering strips and removed from the machine, and pushed to the curing field with a special trolley. After the concrete has finally set, turn over the U-shaped trough to take out the backing plate, sprinkle water regularly, and maintain it at room temperature for 14 days before it can be put out.
2.3 Measures to improve the smoothness of U-shaped groove prefabricated surfaces
During the actual production process, it is found that the surface of the produced U-shaped prefabricated components is relatively rough, and some even appear pitted and Honeycomb phenomenon. The reason is that due to the one-time vibration of the component, forced pouring and forming, the component molding scale is fast, the concrete vibration time is short, and the cement mortar is not easy to vibrate evenly and flow to the surface of the component, causing the surface of the component to be rough. In order to solve this problem, it is recommended to use a soft brush to brush the inner surface of the U-shaped groove back and forth several times immediately after the component is demoulded. If there are honeycomb holes, you can use a brush with a small amount of cement oil to polish it. After using this measure , the problem of rough surface of U-shaped prefabricated parts can basically be solved.
3. Construction technology of U-shaped trough channels
The construction process of U-shaped trough channels is: determining the center line of the channel - clearing the foundation - measuring and setting out - excavation of the foundation trench - Sanding and tamping on both sides - pouring concrete cushion - installing U-shaped channel prefabricated parts - pouring concrete sheath - mortar jointing - curing - delivery for use.
3.1 Measurement and stakeout
Use a total station (theodolite) to release the channel bus according to the designed coordinates, set the center pile every 20m, excavate and fix the side piles, and use white ash to release the control edge line It is controlled during excavation, and the center line and canal top lines on both sides are released after excavation.
When lining each canal section, the canal bottom elevation of each pile number must be controlled according to the actual measured specific drop of each canal section. The required water level, canal top elevation, and installation of canal trench masonry should be The canal top elevation is strictly controlled to make it smooth and beautiful.
3.2 Trench excavation
The trench is excavated manually. When digging, the cross-sectional size and elevation must be strictly controlled. The surface of the foundation trench must be smooth and the cross-section of the foundation trench must be avoided as much as possible. dig.
3.3 Cross-section modification
Use the level instrument to measure the elevation of the trench bottom again, dig out and repair the remaining sand and debris at the bottom of the trench and on the slope according to the designed excavation section, and fill in the insufficient sides. The slope or bottom of the ditch will make the ditch smooth and meet the requirements for installing U-shaped trough prefabricated parts. The sand slope protection and rammed sand on both sides of the trench must be dense according to the designed channel line, and the content of organic matter in the sand must be within the allowable range of the specification. The outer slope of the sand slope protection must meet the design requirements. If the terrain is complex, it is recommended to build bricks or bricks on both sides. For unprotected walls, the masonry mortar grade shall not be lower than M7.5.
3.4 Construction site transportation of U-shaped trough components
The construction site transportation of U-shaped troughs mainly adopts manual loading and unloading methods, and is transported directly to the dug construction canal section with rubber wheel frame trucks, and is lightly loaded Press lightly. Since the U-shaped groove is composed of curved surfaces and the components are thin, the components are unevenly stressed during loading, unloading, and transportation, which can easily cause breakage and damage to the components. Therefore, special attention should be paid to the handling process to reduce losses as much as possible.
3.5 Installation of U-shaped trough prefabricated parts
During installation, accurately measure and place the "standard blocks" according to the design elevation interval of 10, and control the straightness of the channel line by hanging wires on one side. Press The design requires that a 10mm muddy gravel cushion be poured at the bottom of the canal, and the U-shaped channel prefabricated parts should be placed before the concrete is initially set, and adjusted to a suitable position before being fixed.
After the sand slope protection on both sides is compacted and filled, M7.5 cement mortar is used as shoulder protection.
Pointing and plastering: After the paved channel section has passed the inspection, clean the joints of the prefabricated blocks and use 1:2 cement mortar to joint them. The joints should be filled, flattened and flattened with mortar. Plaster to ensure the density and smoothness of the cement slurry. Use 1:2 cement mortar to plaster various joints and calender the surface.
4. Engineering maintenance
After the jointing and plastering is completed, the surface of the channel should be covered with wet sacks for maintenance. During the maintenance process, water should be sprinkled in time to keep the mortar surface moist.
U-shaped trough construction plan (2)
1. Preparation before construction of cast-in-place concrete U-shaped channel
Before construction of cast-in-place concrete U-shaped channel , a detailed construction organization design should be carried out and a construction plan should be formulated based on relevant design documents and implementation plans. Since the construction front of the water-saving renovation project in the irrigation area is long, the construction sites are scattered, and the layout of the channels varies according to the different terrain conditions of the irrigation area. Before construction, the location of the construction management agency, the material yard and the mixing site should be reasonably determined, and the construction site should be reasonably planned. Make the layout, do a good job of "three connections and one leveling", and inspect and test the equipment required for construction. If it does not meet the requirements, it should be replaced and adjusted. When the construction conditions are extremely difficult and there are no experimental instruments and equipment, the test can be entrusted to a qualified experimental institution. Permanent and necessary temporary traffic road construction should also be done to create good construction conditions for cast-in-place concrete U-shaped channel lining.
2. Earthworks
2.1 Before the construction of earthworks for channel staking, the center line, length and horizontal elevation of the channel should be re-measured based on the relevant information provided by the design technology, using a theodolite. Review the center control line of the channel and check the direction of the channel line. The error of the two angle measurements shall not exceed 30″. Use a steel ruler to review the length of the channel, and add a center stake every 50m at the center line of the channel. Set up a central pile 3 to 5m away from the bend. Use a steel ruler to measure the distance, and the error shall not exceed 1/1,000. Secondly, the height is controlled according to the requirements of the fourth grade level, and the closing accuracy is required to be controlled at 20mm. A temporary elevation point is set up every 200m as the elevation control point of the excavation channel. Finally, according to the center line and elevation control points, the channel earth excavation or backfill edge lines and temporary soil piles and soil borrowing boundaries are staked out.
2.2 Canal earthwork ramming and filling. The filling of the channel should meet the following technical requirements: ① Clear the base, remove weeds, bricks, frozen soil, surface virtual soil, humus and hidden masonry in the channel bed. ② The backfill soil should be taken from the nearest location to reduce transportation costs, and the moisture content of the backfill soil should be controlled between 16 and 20%. If the backfill soil is relatively dry, watering should be used to adjust the moisture content of the backfill soil. If the moisture content is large, drainage, drying, soil replacement, etc. should be used to control the moisture content within the allowable range. ③ When compacting and filling, the construction method should be determined according to the actual situation and the construction machinery should be selected. ④ The backfilling and compaction adopts the method of layered compaction. The thickness of each layer of soil is controlled within 20 to 30cm. The layered compaction should be no less than 4 times. The occurrence of leakage, empty soil layer, rubber soil and other phenomena should be eliminated. The dry soil after compaction should be avoided. The bulk density is not less than 1.55t/m3. The working surface of one backfill and compaction shall not be less than 100m, and a slope of 20-50cm should be reserved inside the channel.
2.3 Channel earthwork excavation
2.3.1 Main channel excavation. During channel excavation, the main channel is excavated and leveled first, and then the U-shaped channel is excavated. The main channel should be excavated along the channel measurement line and excavation depth. The bottom elevation of the excavation shall be based on the top height of the U-shaped channel. During mechanical excavation, it should be preliminarily 10cm, and then manual cooperation shall be performed to trim the channel to the actual elevation to avoid mechanical excavation. Over dig when digging.
2.3.2 U-shaped channel earth excavation. Whether the excavation quality is qualified or not directly affects the smooth progress of channel lining. If the lower arc diameter of the U-shaped channel section is greater than 50cm, construction machinery will be used to excavate it, while for smaller ones, manual excavation will be used. Construction machinery generally uses trenching machines, which are suitable for conditions with flat terrain and long channels. When the trenching machine is operating, it must drive at an even speed along the excavation line placed in the U-shaped channel, and a designated person must randomly inspect it. If any Debris such as rocks or thick roots must be dealt with immediately, otherwise the impeller of the trenching machine will be easily damaged and the size of the excavation section will be affected. When manually excavating, you should first excavate according to the edge line and excavation depth of the channel, leaving about 10cm, and then use the stereotyped U-shaped channel excavation mold to shovel and repair a certain cross-section of the channel until it matches the U-shaped channel. Until the channel mold is completely matched, then renovate a standard U-shaped channel cross section 4 to 5m away from the section, hang a line along the channel wall at the same height from the two sections to the top of the channel, and conduct the channel between the two sections. After many renovations, the channel excavation section formed is relatively standardized. If the slope is excessively cut and cannot be backfilled with floating soil, it should be filled with concrete of the same grade as the cast-in-place or new soil should be backfilled and compacted.
3. Concrete engineering
U-shaped channels are generally lined with formed lining machines, and different types of lining machines are selected according to the size of the channel section.
3.1 Concrete material
3.1.1 Water quality requirements. Water that meets drinking standards can be used for mixing and curing concrete. If under difficult conditions of extreme water shortage, other water such as surface water, groundwater or other types of water can also be used, but the water quality must be tested and it can only be used if it meets the "Water Standard for Concrete Mixing".
3.1.2 Quality control of cement. At the construction site, a warehouse with good drainage and ventilation conditions should be selected to store cement. Note that the cement transported to the construction site should be marked with the variety, strength level, manufacturer and factory batch number, and should be stored separately or in piles, and should not be mixed. A moisture-proof layer should be installed at the stacking location, at least 30cm away from the ground and side walls. The stacking height should not exceed 15 bags, leaving a transportation channel. Cement should be waterproof and moisture-proof during transportation and storage. Cement that has become damp and agglomerated can only be used after it has been processed and inspected to pass the inspection. The storage time of cement is calculated based on the date of production and should generally not exceed 3 months.
3.1.3 Sand quality control. The sand used for cast-in-place concrete is medium sand. It is better to use natural river sand with good gradation, hard texture and clean particles. Artificial sand crushed by hard rock can also be used. It requires hard texture, clean particles and good durability. And it must not contain clumps, salt, loam, organic matter and other harmful impurities. The fineness modulus of artificial sand should be within the range of 2.40 to 2.80, and the fineness modulus of natural sand should be controlled within the range of 2.20 to 3. The mud content should be less than 3%, and the water content should be less than 4%. The moisture content of fine sand should remain stable, and the saturated moisture content of artificial sand should not exceed 6%. If necessary, measures should be taken to accelerate dehydration.
3.1.4 Stone quality requirements. According to current national standards, the maximum particle size of stones should not exceed 2/3 of the minimum clear spacing of steel bars, 1/4 of the minimum size of component sections, and 1/2 of the thickness of plain concrete slabs. For concrete structures with few or no reinforcements, larger stone particle sizes should be used. During construction, since the lining thickness of the U-shaped channel section is generally 80 to 40 mm, the stones should be divided into two levels: D20 and D40 according to particle size, and the oversize and undersize content of aggregates at all levels should be controlled. The surface of the stones should be clean. If there is powder, mud or pollution, it should be removed. When using pisolite, general attention should be paid to controlling the mud content. When using crushed stones, the particle size of the gravel should be controlled.
3.1.5 Additives. Concrete cast-in-place U-shaped channels all have anti-freeze and anti-seepage requirements. Some additives should be added to improve their anti-freeze and anti-seepage properties. PC-2 type air-entraining agent, whose main components are rosin soap and its thermal polymer, has the functions of entraining air, reducing water, and improving the anti-permeability and anti-freezing properties of concrete. It is prepared according to weight ratio, and the general amount added is the weight of cement. 0.50-1/0,000; M-type water-reducing agent, whose main ingredients are lignin and calcium carbonate, has the properties of reducing water, increasing aeration, improving strength, and preventing seepage and freezing. It is added at 0.20-0.70% of the cement weight during preparation.
3.2 Concrete mix ratio
The mix ratio of cast-in-place concrete should meet the requirements of strength, frost resistance, anti-seepage and workability. The concrete construction mix ratio must pass the test and be approved before use. Concrete construction ingredients must be issued after review, and the ingredients must be made strictly in accordance with the issued concrete construction ingredients list. Unauthorized changes are strictly prohibited. In the construction of U-shaped channels, the concrete strength grade is C15, the frost resistance is F50, the seepage resistance is W4, the maximum allowable value of the water-cement ratio in the ingredients is 0.6, and the slump of the concrete is controlled at 1-3cm. In low-temperature seasons or when the canal bed surface is relatively humid, the slump should be appropriately reduced; in high-temperature seasons or when the canal bed surface is relatively dry, the slump should be appropriately increased.
3.3 Mixing and transportation of concrete
3.3.1 Mixing of concrete. During the construction of U-shaped channels, according to the distribution of the channels and the surrounding environment of the irrigation area, a mixing station should be set up in a location with a short distance from the lined channel, flat terrain, and open space. Concrete mixing generally uses a mixer. When mixing, the concrete ingredients must be proportioned according to the determined mix ratio. In the construction of small channels, in order to facilitate mixing and improve mixing efficiency, the amount of sand and stone can be converted into volume ingredients, and the corresponding volume of sand and stone required for a bag of cement can be calculated, but it cannot exceed the error range. The concrete mixture should have workability suitable for the construction conditions.
3.3.2 Transportation of concrete. Concrete transportation is the intermediate link between concrete mixing and pouring, and must meet the requirements of ready mixing, transportation and use. According to the requirements of different conditions for U-shaped channel construction, trolleys, rack trucks, dump trucks, automatic unloading trucks, etc. can be used. However, special vehicles must be used, and the transportation equipment must be tight, smooth, and free of slurry. Each time the material is unloaded, the Unload the concrete and clean the carriage at any time. If slight concrete separation occurs during transportation, mix it manually again at the pouring site. The entire process from loading to warehousing and unloading is controlled within 30 to 60 minutes. If the transportation time is stopped for any reason, and the concrete has initially set or lost its plasticity, it should be treated as waste.
3.4 U-shaped channel concrete pouring
The channel is lined with a matching U-shaped lining machine. The machine is equipped with a U-shaped guide sliding membrane, a powder feeding system, and is installed in the middle. Vibration equipment, equipped with a diesel engine as the driving power, is fixedly installed in front of the channel, connected to the lining machine with a wire rope, and pulls the lining machine forward at a uniform speed. At present, the new CU4 type channel concrete lining machine has become an updated product of the U-shaped lining machine. It integrates traction and vibration lining, and has automatic seam cutting and edge pressing functions, and is easy to control mechanically. Before lining, if the canal bed is dry and the soil is removed, it should be moistened first with water to avoid fine cracks on the surface of the poured concrete slab due to excessive water loss. When the lining machine is working, the mixed concrete is continuously loaded into the feed port manually, and the vibration equipment works at the same time, so that the channel lining is formed in one go. In order to ensure the quality of the lining, the forward speed of the lining machine is generally controlled at 0.50-0.80m/min. At the same time, 3-4 iron sheets of 2m×3m are prepared beside the canal as concrete placement objects. Prevent other substances on the side of the ditch from being mixed into the concrete. Since the lining machine is in motion, the position of the transported concrete on the canal side must also be moved forward at any time. According to the speed of the lining machine, the iron sheet behind it must be switched forward at any time to ensure the position where the transported concrete is dumped. Synchronized with lining machine.
3.5 U-shaped channel calendering and finishing
After the lining machine, the lined channel surface must be calendered and finished manually. The finishing work is an important part of U-shaped channel lining. The process of finishing the U-shaped channel lining can reduce the roughness, improve the water delivery capacity, enhance the anti-seepage effect, and extend the service life. The finishing work requires the surface to be smooth and smooth, with no stones leaking out and no honeycomb pitting. The finishing surface should be finished with original slurry immediately after the concrete is poured. No additional mortar should be applied to finish the surface, and no water should be sprinkled to finish the surface. The process is to use a long wooden trowel to apply it roughly once to make the surface smooth, pause for a moment, and then apply it finely with iron mud. Finally, after a large amount of water evaporates, use iron mud to apply it again until it is dense and smooth. smooth.
3.6 Maintenance
Concrete maintenance is an important link to ensure and improve the quality of concrete. Especially the U-shaped channel concrete lining structure has the characteristics of thin wall and large exposed area, so maintenance is not timely. , dry cracks and gaps will appear on the surface, affecting the quality of the project, so maintenance work is particularly important. Someone must be responsible. The most commonly used maintenance method is to cover the concrete surface with wet straw mats, wet reed mats, etc. Generally, under normal temperatures, concrete can be cured 6 to 18 hours after pouring. The curing time is also different depending on the practical cement and the temperature. During curing, water should be sprinkled frequently to keep the concrete surface moist at all times. So that the concrete can be fully maintained.
4. Channel expansion joint engineering
Expansion joints are longitudinal joints in the channel that are installed to avoid channel collapse and damage caused by temperature changes, channel frost heaving and other reasons. Generally, 2 to 3cm are reserved. In the treatment of expansion joints, the filling materials of the expansion joints should be reasonably selected according to the design requirements, and the expansion joints should be properly processed to effectively prevent the channels from breaking due to horizontal expansion and contraction and the channels from leaking. Currently commonly used filling materials include asphalt mortar, asphalt grease, polyvinyl chloride grease, etc. When filling, first clean the concrete surfaces inside and on both sides of the expansion joint, then fill the prepared filler into the joint, tamp it with a wooden rod, and leave 15mm outside and plaster it with cement mortar.
5. Conclusion
During the construction process, fluctuations in raw material quality have a great impact on the quality of concrete. For example, fluctuations in cement strength directly affect the strength of concrete; The diameter or diameter will change the gradation of concrete and affect the workability of concrete; errors in weighing ingredients during construction will cause variations in the mix ratio, thus affecting the quality of concrete; processes such as concrete mixing, transportation, pouring and maintenance Changes will also cause changes in the workability, strength and durability of concrete. In order to ensure the quality of concrete, strict control and management of concrete raw materials and construction techniques should be carried out. For this reason, the concrete mix must be inspected frequently. The quality of materials used should be strictly checked. The mix ratio of concrete should be strictly controlled, and water cannot be added at will during the mixing process. The slump should be checked at least three times per shift. If the slump is not within the allowed range, the cause should be checked in time and dealt with, and the inspection results should be recorded. During the concrete pouring period, concrete strength test blocks should be randomly sampled according to the amount of pouring, three blocks in each group. The production and maintenance methods of the test blocks should be the same as the construction conditions. After the test blocks are made, they should be registered and numbered. When the maintenance period expires, it will be sent to the relevant unit for testing, and the test results will be included in the construction files for filing.