This project is a power plant chimney project of XX Group Co., Ltd. The chimney of Jiangsu Jiu Hao High-rise Building Anticorrosion Co., Ltd. is 240 meters high, with an outlet diameter of 6 meters. The cushion is C 10, the foundation is C30, the cylinder is C30, and the lining is refractory brick and acid-resistant cement.
The project is a high-rise structure with high construction height, great difficulty and complicated construction technology. However, Jiangsu Jiu Hao High-rise Building Anticorrosion Co., Ltd. has a group of professional chimney construction teams with rich theoretical and practical experience, which can fight hard, and both management and construction technology can meet the needs of this project.
Second, the construction goal
1. Duration: The total calendar duration is 120 days, and all the projects are completed.
2. Quality objective: the qualified rate of sub-item acceptance 100%, the excellent rate ≥90%, and the engineering sense ≥85%.
3. Cost objective: ensure the quality and safety of the project, and plan to save the project cost 17% through effective management means.
4. Safety objective: adhere to the policy of "safety first, prevention first", ensure that the frequency of general accidents is less than 1.5‰, the mortality rate is zero, and put an end to major safety accidents.
5. Environmental protection goal of civilized construction: strengthen the scientific management of the construction site, meet the requirements of environmental protection, establish the image of humanistic engineering, and create a municipal civilized construction site.
6. Scientific and technological progress goal: this project is listed as a professional scientific and technological demonstration project of this enterprise, and the benefit rate of scientific and technological progress reaches 1.5‰.
7. Service objective: Establish a satisfactory construction process for the owner, and track the project quality for three years.
Third, the construction deployment
1. Main construction technologies of Jiangsu Jiu Hao High-altitude Building Anticorrosion Co., Ltd.
1. 1 Adopt the whole formwork supporting construction of vertical shaft frame displacement.
1.2 same frequency construction of concrete pouring with lining thermal insulation layer.
2, the construction process
Construction preparation → excavation → cushion construction → equipment assembly → foundation slab concrete pouring → backfill soil → pipe body concrete pouring → lining pouring (min1.25m each section) → insulation layer masonry (min1.25m each section) → shell concrete pouring (min1.25m each section).
Four, the main construction technical scheme
1. Installation and construction of internal derrick, platform and lifting system
The whole construction process is shown in figure 1.
1. 1 Installation and construction of internal suspenders
The internal vertical lifting frame is1.25m high, which is erected by steel pipe scaffolding. The horizontal step of the standing pole is 1.5m, and the vertical step of the horizontal bar is 1. 15m. According to the proportion of the inner diameter of the chimney, the diameter of the inner frame gradually decreases with the size of the lining (see Annex I for the inner frame checking calculation). When erecting the steel pipe frame, both ends of the steel pipe should be inserted into the brick-lined masonry and placed on the brick masonry (see the following figure: Detail A). In the height direction, every 10m support, four surrounding steel pipes must extend to both ends and be anchored in the concrete of the pipe wall for 50mm, and be reinforced once together with the concrete wall to ensure the strength and stability of the parallel frame. During installation, the cement isolation concrete shall be wrapped at the end to prevent the steel pipe from being removed in the future (see the following figure: Detail B).
The vertical frame of chimney construction gradually increases with the construction of chimney wall, and the first installation height is 3 ~ 5m beyond 0.000. The bottom of the derrick is supported on the concrete foundation slab, and the uneven surface of the foundation concrete must be leveled with steel plates. When installing the derrick, the hanging cage is placed in the designated shaft in advance. During erection, all personnel must wear safety belts and non-slip insulating shoes. When steel pipes are uploaded in the same direction, they must be hoisted with hemp rope.
1.2 construction of operating platform
The operating platform has two layers, the lower layer is used for bricklaying and reinforcement, and the upper layer is used for hoisting and lifting plates, supporting formwork and pouring concrete. Spread a 50×300 wooden springboard on the operation platform. Wooden springboard and derrick steel pipe shall be firmly bound with brown rope or No.8 iron wire, and "jumping blindly" is not allowed. The wooden boards should be sewn tightly, and the big gap between the wooden springboard and the steel pipe should be sealed with narrow slats or iron sheets. The operating table rises with the derrick, and three sets of boards are prepared for turnover.
A square hole of 0.9×0.9m is left in the center of the derrick for entering and leaving the bucket, and a small hole of 0.2×0.2m is left in the center for measuring the center line of the bucket during construction. Make a hole sealing plate of 1.2m× 1.2m, and use it to seal the hole after the bucket reaches the platform, so as to facilitate the placement of the trolley when unloading and ensure the safety when walking at ordinary times.
There is no outer ring platform on the derrick, and the person who fastens the steel wire flies only fastens it at the outer ladder. When shuttering and lifting formwork, everyone should stand in the bound ring wall reinforcement, and should not work outside. If it is necessary to deal with the surface quality problems of concrete, the personnel shall handle them on the external ladder.
A 3.8-meter-high external ladder is set at the position corresponding to the external ladder of the chimney, so that relevant personnel can safely board the platform through the external ladder of the chimney and the external ladder for relevant construction operations and quality inspection. As shown in the figure below.
Description:
1, field anti-slip reinforcement rod 2, 14mm steel wire rope 3, operation platform and protection platform.
4. Corner pulley 5, top pulley 6 and top sliding chamber rod
7. All kinds of distribution boxes and instruments are placed in the work shed, and the top is covered with asbestos tiles for rain and sun protection.
Set lightning rod, which is connected with the lightning protection system of steel pipe frame to prevent lightning strike.
Operating platform and external ladder diagram
1.3 construction of internal and external hoisting system
The vertical lifting equipment in the chimney adopts 5t hoist with φ 14 wire rope, which is loaded and unloaded by bucket. The bucket is round, welded with 6 mm thick steel plates, with a height of 700 mm, an inner diameter of 650 mm and an outer diameter of 750 mm at the bottom. The bottom plate is fixed with a pin shaft and can be rotated up and down to close the feeding or open the discharging. Regularly check the flatness of the bottom plate during the construction process, and put it down gently when installing steel bars, steel pipes and fasteners. , in order to avoid deformation of the bottom plate and slurry leakage.
Because there is a height difference between the existing ground and 0.000, it is necessary to build a small steel pipe gantry at 0.000. Gantry hoisting equipment adopts 3t hoist with diameter of φ 14 wire rope. The vertical lifting equipment of external gantry crane adopts 3t hoist, and the hanging plate is used for loading and unloading.
Steel bar, concrete, etc. It is transported to the hanging plate of the gantry by handcart or manually, lifted to the flue platform by the gantry, and then transported horizontally to the derrick in the chimney in the safe passage of the flue platform to complete the horizontal and vertical conversion. Lifting steel bars, bars, concrete, etc. Hoist it to the upper construction platform with the bucket in the derrick, and seal the hole with the platform sealing plate. Unload steel bars and steel pipes, and manually transport them to the parts that need to be bound. Unload the concrete from the handcart, push it to the concrete pouring position and pour it.
The crown block for lifting the inner derrick and the gantry is installed on the crown block at the top of the derrick. 4-8 diagonal rods are fixed on the crown block, and at least 8 fasteners are used for bearing. The moving load of the sliding bar is 2× 1.t=2.6t, so the dynamic load on each fastener is 2.6t/8 = 0.325t(3.25 kn), which can fully meet the bearing capacity. As shown below.
Vertical and plan views of the sky slider
Requirements for 5t winch: the hoisting speed is 30-440m/min (every 3-5min) or 60m/min (every 3min), the rope capacity of drum is at least120m, and the total rope length is at least 250m. Requirements for 3t winch: the lifting speed can be 30-440m/min (one round trip is 1 min).
The 3t hoist uses angle steel to bury anchor piles, and the 5t hoist uses 13mm steel wire rope to pull anchors on beams, plates and columns of flue leveling, and the beam and plate steel bars are removed to weld and anchor the hoist frame.
1.4 construction of protective shed
On the derrick in the chimney, a double-layer protective shed with a height of 5m is set to prevent objects from falling off during the upper construction and ensure the safety of the construction workers below. The shaft frame bears the full load of the operating table and is used for vertical transportation. A safe passage is arranged on the flue platform, and a double-layer protective shed is arranged at the top of the passage. The top of the outer gantry is provided with a double-layer protective shed. The spacing between the two layers of the double-layer protective shed is 500mm. As shown in figure 1.
2. Reinforced concrete structure of chimney
24-hour shift work system is adopted, and 50 people, including rebar workers, carpenters, welders, electricians, concrete workers and mechanical operators, participate in daily work to ensure the progress of the project.
Quality requirements for barrel construction: In the construction project, it is necessary to ensure that the verticality deviation of the barrel center is not more than 60mm, the thickness error of the barrel wall is less than 20mm, and the radius error of any section of the barrel is not more than 0% of the radius of 65438 and not more than 30mm. The deviation of the center line of the flue is not more than15mm, the deviation of the elevation in the flue is less than 20mm, the local unevenness of the inside and outside of the pipe wall and the back is not more than 1% of the section and not more than 30mm, and the height and width of the flue are not more than 30mm and not less than-20mm. ..
2. 1 displacement formwork construction
2. 1. 1 displacement template structure
The outer mold of the barrel body is made of iron sheets with a thickness of 2mm and a thickness of 1 1,000× 000 m, and each iron sheet is divided in proportion during processing. Each set of templates has 1m edges on both sides. Divided into two points, each section is1.25m high. Using the iron sheet coated with engine oil as the external mold can make the external surface of the chimney smooth and beautiful, support the mold quickly, make the proportion of the cylinder body consistent, and reduce the flat-fell seam between the templates.
The internal model adopts the combination of brick-lined wooden wedge and internal steel formwork: firstly, the chimney lining is laid, and the internal steel formwork is placed between the lining and the steel bar; then, the undeformed Chinese fir is processed into wedge-shaped wooden strips with the same thickness as the air insulation layer, which are placed between the internal steel formwork and the brick masonry as measuring materials to form the air insulation layer. Wedge battens are finished on a 3 cm thick wood planer. Because the air insulation layer is 100 mm and 50 mm, there are two kinds of wedges, one is 75 mm and 25 mm, and the other is 30 mm and 20 mm. In construction, the bricklaying time is generally 6 ~ 3 hours, and there is still a certain preparation time for internal formwork erection. Therefore, the time interval between bricklaying and internal formwork erection is generally 4 ~ 7 hours, and the speed of concrete pouring is extremely slow, so the strength of mortar can bear the construction load of internal formwork erection and concrete pouring.
According to the practical experience of our company for many years, the external formwork is processed into four groups with 2mm-thick iron sheets according to the grid scale of the chimney outer wall, and the grid formwork is set aside on both sides of each group, and the upper interval of each group of plates is 2m, that is, every other plate is welded with φ 14 steel bar hooks for lifting the formwork. First, drill holes on two iron sheets with an electric drill, and then fix them with anchor screws, which are upward from the inside to the outside, so that the inside is flush with the surface of the iron sheets, and are connected by electric welding and spot welding. On each piece of iron, 250 mm away from the joint, two rows of joints passing through the steel wire rope are welded, so that the formwork can be fastened with the steel wire rope, and the outer formwork can be fastened when pouring concrete. Install 18-28 elevator bracket and 18-28 elevator (1t) on the vertical steel bar and operation platform. After the concrete reaches the formwork removal strength of 1.2n/m㎡, the external formwork will be lifted uniformly by the elevator section by section.
Internal and external templates are bound or welded with φ 12 steel bars on the wall reinforcement to ensure the clear distance between internal and external templates and the thickness of internal and external protective layers. The length of the reinforcement is the same as the wall thickness of the first part. The spacing along the circumferential direction is @250mm, and four layers are set in the height direction.
As shown in Figure 2, φ25 steel bar is welded into a tripod, and tied to the vertical steel bar with circular steel bar with three or four No.8 iron wires. The load shared by each elevator is (considering the dynamic load factor 1.4):
1.4×(4 1× 1.35×0.00 127×7.85× 103+ 18×36× 18/ 100)28
= 1.4×638.03/28 = 3 1.9× 10-2KN
This force is quite small, and the 1t elevator and the lifting frame welded with φ25 steel bars can bear it completely.
2. 1.2 Installation of displacement formwork
Internal model installation: Before installing the internal model, the chimney lining brick masonry shall be built first, and the center line and radius shall be measured at the same time, so as to control the internal model installation radius and fix the formwork. After placing the inner steel formwork, add a set of wooden wedges between the lining and the steel formwork (the thickness of a set of wooden wedges is the same as that of the air insulation layer), and support the inner steel formwork with wood. Wedges are arranged in the circumferential direction according to the spacing of 100mm, and wooden supports are arranged up and down according to the joint position of the iron sheet of the internal mold. The concrete will be removed after pouring.
External mold installation: After the external mold installation and correction meet the specified size requirements, the clear distance between the internal and external molds and the protective layer between the external mold and the main mold shall be controlled with temporary chocks with designed wall thickness. The wooden frame should be placed every other iron sheet, and when concrete is poured into the temporary wooden frame, the wooden frame will be gradually removed. After the installation of outer formwork is completed, each formwork of outer ring shall be fastened with 18 6.5mm steel wire rope and rope tightener. Outside the template should be tied up, the gap should be blocked tightly, to prevent Zhang Mo and slurry leakage. Internal formwork shall be firmly supported. Prevent deformation.
Template hoisting color is 18 ~ 25 hoisting frame, which is hoisted by elevator.
The error rate difference between the center of the displacement formwork and the geometric center of the chimney is less than 5 mm, and the lower edge of the formwork overlaps with the poured concrete by about 100 mm. After each demolition, the mortar on the surface of the formwork shall be removed and coated with release agent.
Check the determination of the center position of the barrel. Laser centering instrument is mainly used. After the centering and rechecker are leveled with the total station, turn on the laser transmitter, and the laser will be leveled on the top grid plate. Then, check the radius with the laser point as the center. Check the verticality of the chimney with a 20kg vertical ball which is convenient for construction operation every 5m. The vertical ball is hung on the zigzag frame for centering, and the vertical ball is hung with wheels.
2.2 Reinforcement construction
Vertical steel bar and ring steel bar are bound and lapped, the lap length is 45d, and iron wires are tied at the middle and both ends of the joint. Any horizontal annular steel bar with a diameter greater than 12 mm shall be placed in advance according to the curvature of the cylinder in which it is located and processed into an arc for later use. The steel bar below φ 12mm only needs hooks at both ends, and its arc can be bent when binding. When binding reinforcement, the vertical reinforcement should be bound first, and then the ring reinforcement should be bound.
The ring steel bar at the top of each barrel should be positioned first, based on the edge of the poured concrete formwork, according to the upward scale, and at the same time, considering the thickness of the protective layer. After hanging the position with a wire hammer, it should be bound and fixed, and then the ring steel bar below should be bound based on this ring steel bar.
After measuring the radius with a steel ruler, the vertical reinforcement of the cylinder shall be evenly distributed from the center of the cylinder according to the drawing requirements. The vertical steel bars shall be staggered in each horizontal section according to the head, the number of which shall not exceed 25% of the total steel bars, and the number of welded joints shall not exceed 50% of the total steel bars. When changing the diameter or quantity of longitudinal reinforcement, it should be evenly distributed on the whole circumference of the barrel wall. The circumferential reinforcement of the cylinder should be arranged on the outer side of the longitudinal reinforcement, and the allowable deviation of the spacing is 20 mm All steel bar intersections should be bound with 22 # tie wire.
The steel protective layer should be controlled by wood, and the radius measured from the center line should be bound by binding wire, and it should be kept within the length range of at least 0.5 per meter along the perimeter of the formwork. The thickness of the concrete protective layer and the circumferential reinforcement of the cylinder wall should be 30mm, and the deviation of the cylinder protective layer should not exceed+10/0mm and-5mm.
Longitudinal reinforcement higher than the formwork shall be temporarily fixed by binding two annular reinforcement. After each layer of concrete is poured, there must be at least one stirrup on it.
2.3 concrete construction
2.3. 1 concrete material
Easy-to-mark 42.5 ordinary portland cement shall be adopted, and the cement mixture ratio test must be carried out when entering the site, and there are quality certificates such as variety label, material origin and factory date. The coarse aggregate is Baoquan 5 ~ 5 ~ 31.5mm igneous gravel, and weathered ones cannot be used.
The particle size is less than 40mm, the silt content is less than 1%, the aggregate is sheepfold sand (fineness modulus MX= 1.2 1), and the silt content is less than 3%. Water is the tap water of the factory. The water-cement ratio of concrete is not greater than 0.5. In order to ensure the engineering quality, speed up the construction progress and ensure the construction safety, Shanfeng brand SF-2 high-efficiency early strength agent with cement content of 0.6% was added to the concrete.
concrete pouring
Before pouring concrete, the template size must be rechecked, and the elevation, position and quantity of various embedded parts should be checked in detail, and concrete can be poured only after it is confirmed.
A 500L forced mixer is set on site to mix concrete, which is transported to the outer gantry by trolley, lifted to the flue platform, pushed to the derrick, and lifted from the inner derrick to the platform for pouring. Concrete should be poured in layers evenly along the circumferential section in two ways from one point, and then poured in reverse after the intersection of the two ways, and layered continuously. Each layer should be poured in layers by vibrating dense concrete with a 50-type vibrator, and the height of each layer is about 250-300mm. When pouring concrete, the pouring direction should be changed symmetrically to prevent the formwork from tilting and twisting in one direction. When vibrating concrete, don't touch steel bars and templates. The insertion depth of vibrator in the previous layer of concrete should not exceed 50 mm When lifting the formwork, the concrete shall not be vibrated. For the treatment of construction joints, loose stones should be removed first, washed clean, and then a 20-30 mm thick 1: 2 cement mortar layer should be laid, and then the upper concrete should be poured. When concrete and steel bars are polluted by oil, they should be cleaned up.
Make a set of concrete test blocks every 5m high for the cylinder, and mark the sampling date to test the concrete strength for 28 days. When pouring for the first time, several groups of test blocks are made to test the strength for one day, two days and three days respectively for construction reference. The production, maintenance and inspection of concrete test blocks shall be carried out by specialized personnel. The concrete surface and all joints must be smooth, without honeycomb pits and obvious construction joints.
Maintenance and form removal
The removal of the formwork outside the barrel shall be carried out when the concrete strength reaches the capacity of bearing the upper load without deformation, and the concrete strength shall not be less than 0.8Mpa. The load-bearing formwork at Yandaokou shall be removed only after the concrete strength reaches 70% of the design label. After form removal, the surface shall be repaired in time, watered and maintained, and kept moist frequently for not less than 7 days and nights. Tube wall concrete can also be cured with film curing agent. Maintenance water, because the water pressure is not high, it is necessary to install a pressurized water pump, use φ50-60 water pipe to send the water to the top of the derrick, and connect it with the derrick height. From the top of the pipeline, use a hose to introduce water into the φ 25mm rubber spray pipe around the external ladder, and spray holes are drilled on the spray pipe with the interval of120-150mm φ 3-5mm for spray maintenance.
3. Structure of chimney accessories
Before pouring concrete, the embedded parts of the ladder and signal platform of reinforced concrete chimney should be fixed in the external reinforcement by binding and welding. The allowable deviation of the embedding position of the ladder is 20mm, and the allowable deviation of the embedding signal station is 10mm. The threads of embedded parts shall be properly protected and shall not be defiled, and the threads of embedded parts shall be buttered to prevent concrete slurry from entering. When installing metal parts, the exposed parts should be coated with antirust agent before installation, and then the external parts should be connected after installation, and finally the antirust agent should be brushed. The bolts of chimney accessories shall be tightened and shall not be missed. Ladders and fences should be aligned up and down, and the concrete strength should reach at least 1.2N/m㎡ when installing accessories. All parts of the chimney arrester should be welded firmly, and its grounding electrode should be buried when the foundation pit is backfilled. After the lightning arrester is installed, check the grounding resistance, and its value should not be greater than 10 ohm required by the design.
4, lining masonry construction
Using the construction method of internal masonry and external sliding, it is necessary to ensure the quality of lining masonry and the accuracy of insulation layer position. The upper surface of the annular cantilever supporting the lining shall be leveled with 1:2 cement mortar, and the horizontal deviation shall not be greater than 20mm. The lining of layered masonry is not allowed to stay straight, and the mortar in masonry must be full. Plumpness of horizontal mortar joint: ordinary clay brick should not be less than 80%; Clay refractory bricks and acid-resistant bricks shall not be less than 90%. Vertical mortar joint should be squeezed and grouted to make its mortar full.
Allowable added value of lining mortar joint thickness and mortar joint quantity
Project lining type and mortar joint thickness
Thickness allowance of mortar joint (mm)
The allowable added value (mm) on a surface of 5 square meters is 10.
Allow to increase the number of mortar joints (places)
1 Ordinary clay brick and diatomite brick 8 +47
2 Clay refractory bricks and acid-resistant bricks 4 +25
When the lining thickness is 1/2 bricks, it should be laid along the bricks and staggered by half a brick. When the lining thickness is 1 brick, it should be laid together with the top brick and staggered by a quarter brick. Brick joints on the lining surface shall be smooth, and the roughness of the lining surface in one circle shall not exceed 1% of the lining radius in the radial direction, and the maximum shall not exceed 50 mm. The thickness of the insulation layer between the liner and the cylinder shall be 100 mm and 50 mm respectively. In order to maintain the stability of the lining, two top bricks are selected from the lining in the direction of the cylinder wall per square meter, and a temperature seam of 10mm is left between the top bricks and the cylinder wall. At the same time, a circle of anti-settling belt with a longitudinal spacing of 2.0m is set on the outer surface of the inner lining, and a temperature seam of 10mm is left between the anti-settling belt and the cylinder wall. Pay attention to the dosage of mortar when laying to avoid mortar falling into the air insulation layer.
5, chimney decoration construction
The concrete outer surface of the upper part of the 95m- 120m chimney is coated with red and white marker rings, which are designed with durable coating or paint. The logo ring is 5m wide, and the elevation mark is115m, which is red above the steel platform. The decorative groove of the cylinder is painted white and will be hung on the external cantilever beam by professional construction personnel. When painting, the concrete surface should be dry, the water content within 20 mm depth should not be greater than 6%, and the floating ash and oil stain on the surface should be removed. The preparation and construction of anticorrosive coatings should be carried out in accordance with the current relevant national standards.
6, the demolition of the shaft frame construction
Should have professional command, demolition should be carried out by skilled workers. Demolition shall be carried out layer by layer from top to bottom, and construction shall be carried out layer by layer in ascending order. Firstly, the upper platform is transferred to the lower platform and laid, then the steel pipe frame above is removed, and the overhead slide bar frame is reserved, and the removed pipe fittings are put down by the bucket. When removing one part, other parts should be prevented from falling. The balustrade ladder shall be dismantled as a whole, and the bearing columns and cross bars shall not be dismantled first, and can only be dismantled after all the structures undertaken by it are dismantled. For the original pipe fittings anchored in concrete, if they cannot be removed, they must be cut off, and then the steel pipe holes should be blocked with fine stone concrete; Pumpable, after pumping with C35 fine stone concrete block. Remove the left brick hole and plug it with bricks and M7.5 mortar. No leakage is allowed.
7, settlement observation construction
Settlement observation points should be buried at the elevation of 0.44m outside the pipe wall, and four observation points should be set on two mutually perpendicular straight lines. When the concrete strength reaches 1.2N/m㎡, the formwork shall be removed and settlement observation points shall be set. After installation, observation should be started and recorded in detail. After the completion of the project, filing inspection and continuous observation should be carried out.
8, special climate construction
8. 1 rainy day construction
In order to ensure the construction progress of the project, the construction was still carried out under the condition that it was not very rainy. All personnel put on raincoats and insulated water shoes. Cover all electrical equipment with plastic sheets to prevent rain. On the construction platform, set up temporary shelter from the rain. As shown in the previous figure 1.
8.2 Lightning weather
The area belongs to strong lightning area, and the measures must be practical. The lightning rod is installed on the sliding bar frame at the top of the inner derrick to connect the down lead to the underground grounding outside the chimney. A lightning rod is arranged on the rain cover, and the lightning rod is connected with the lightning protection system of the inner derrick. In case of lightning weather, all construction personnel shall enter the shelter in time and come out for construction after the weather is stable.
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