2. Bridge classification
According to the scale of bridge construction (total length of bridge) or technical difficulty, it is divided into: extra large bridge, large bridge, medium bridge and small bridge culvert.
According to the roadway position of the superstructure, it is divided into: underpass bridge, underpass bridge and underpass bridge.
According to the structural system of the bridge (beam-arch-cable): beam bridge; Arch bridge; Rigid bridge; Combined system; suspension bridge
According to the materials used in the main load-bearing structure, it is divided into masonry bridge (including stone arch bridge and concrete arch bridge), reinforced concrete bridge, prestressed concrete bridge, steel bridge and steel-concrete composite bridge.
Bridges are divided into highway bridges, railway bridges, highway-rail bridges, agricultural bridges, pedestrian bridges and waterway bridges (aqueducts) according to their uses. Other special bridges (such as pipelines and cables, etc.). )
Crossing modes: fixed bridge, open bridge, pontoon bridge and overflow bridge.
The bridge is constructed as a whole according to the construction method-the superstructure is poured at one time; Segmented construction bridge-the superstructure is assembled by segments.
Bridge and culvert classification
Bridge classification: total length of porous bridge (m)
Single span (meter)
Extra large bridge L≥ 1000 Lk≥ 150 bridge100 ≤ l <100040 ≤ lk <150.
Medium bridge 30 ≤ l < 100 20 ≤ lk < 40
Small bridge 8 ≤ l < 30 5 ≤ lk < 20
Culvert -lk < 5
Note: 1. The total length of perforated bridge refers to the sum of the standard spans of perforated beam and perforated plate;
Arch bridge is the distance between the arch lines of abutment on both sides of the river; Other types of bridges are the length of the lanes of the deck system.
2. Both pipe culvert and box culvert are culverts, regardless of span or number of holes.
3. Composition of this bridge
From the load transfer function:
(1) Bridge span structure (superstructure): The part above the main girder is called superstructure (the arch bridge is above the arch foot)-it directly bears the service load.
(2) Pier, abutment and bearing (substructure): the lower part of bearing is called substructure; The force transfer device between the main girder and the pier is called the bearing. -transfer the load of the superstructure to the foundation, block the soil of the embankment, and ensure the temperature difference expansion of the bridge.
(3) Foundation-transfer the reaction force of the bridge structure to the foundation.
(4) Subsidiary structure
1.2 Names of various parts of the bridge —— Correctly describing the names of various parts of the bridge structure is the basis of bridge construction inspection and the necessary condition for recording, sorting and archiving.
1
Bridge span structure
1) clear span —— For the beam bridge, it is the clear distance between two adjacent piers (or abutments) at the design flood level, which is expressed by; For arch bridges, it is the horizontal distance between the lowest points of two arch foot segments of each arch span.
2) Total span-it is the sum of the net paths of each hole in the porous bridge, also known as the bridge aperture, which reflects the flood discharge and drainage capacity under the bridge.
3) Calculation of span-For bridges with supports, it refers to the distance between the centers of two adjacent supports of the bridge structure, which is expressed by. —— For an arch bridge, it is the horizontal distance between the centroids of two adjacent arch foot sections. Because the connecting line of the centroids of each segment of the arch ring (or arch rib) is called the arch axis, it is also the horizontal distance between the two ends of the arch axis. The mechanical calculation of bridge-span structure is based on this principle.
4) The total length of the bridge-referred to as the bridge length, is the distance L between the nodes behind the side walls or splayed walls of two abutments at both ends of the bridge. For bridges without abutments, the total length of the carriageway of the deck system.
5) Bridge height-referred to as bridge height for short, refers to the height difference between the bridge deck and the low water level, or the distance between the bridge deck and the pavement of the line under the bridge. Represented by H.
6) Clearance height under the bridge-refers to the distance between the designed flood level or the calculated navigable water level and the lowest edge of the bridge span structure, expressed in h, which should ensure safe flood discharge and should not be less than the clearance height specified for the navigation of the river.
7) Building height-refers to the distance between the elevation of the pavement (or rail top) on the bridge and the lowest edge of the bridge span structure, which is not only related to the system and span size of the bridge structure, but also varies with the height position of the accompanying vehicles on the bridge. The elevation of bridge deck (or rail top) determined in highway (or railway) alignment is relative to the elevation of navigable headroom.
8) allowable building height-also known as allowable building height. Obviously, the building height of the bridge cannot be greater than its allowable building height, otherwise the navigation requirements under the bridge cannot be guaranteed.
9) Clear height-is the vertical distance from the lower edge of vault section to the lowest point of the lower edge of two adjacent arch foot sections, expressed by.
10) Calculate lift-it is the vertical distance from the centroid of vault section to the connecting line between two adjacent vaults, which is expressed by.
1 1) Rise-span ratio-it is the ratio of the calculated rise of arch ring (or arch rib) to the calculated path (), also known as arch vector, and it is an important index reflecting the mechanical characteristics of arch bridge.
Characteristics of 1.3 bridge structure system
1. beam bridge
Beam bridge is a kind of structure with no horizontal reaction force under vertical load. Because the direction of external force (dead load and live load) is almost perpendicular to the axis of load-bearing structure, compared with other structural systems of the same span, the bending moment generated in the beam is the largest.
The most widely used highway bridge is the assembled concrete beam (reinforced concrete, prestressed concrete) bridge. Beam bridge has simple structure, convenient construction and low requirements for foundation bearing capacity, but its common span is below 25m. Beam bridges are divided into simply supported slab (beam) bridges, simply supported (ribbed) beams, continuous beams and continuous rigid frames. (respective characteristics)
The bending moment of midspan section is the largest, and the shear force of fulcrum section is the largest.
Applicable materials: concrete is the main material in compression area, and steel bar or prestressed steel bar is the main material in tension area.
Construction method: prefabricated installation or integral casting.
Classification of beam bridges: simply supported beam bridge, continuous beam bridge, cantilever beam bridge and T-shaped rigid frame bridge.
2. Arch bridge
The main load-bearing structure of arch bridge is arch ring or arch rib. Under the vertical load of arch bridge, the pier or abutment will bear both vertical force and horizontal thrust. The horizontal thrust will significantly offset the bending moment in the main arch ring (or arch rib) caused by load. Compared with the beam bridge with the same span, the bending moment and deformation of the arch are much smaller. In view of the fact that the load-bearing structure of arch bridge is mainly compressed, masonry materials (such as stone and concrete) or reinforced concrete with strong compression resistance can usually be used for construction. However, the requirements for the deformation and bearing capacity of the foundation are higher. The arch bridge has great spanning capacity and beautiful appearance. When conditions permit, it is often economical and reasonable to build arch bridges.
Classification of arch bridges:
1. According to the materials used in the main arch ring, it can be divided into masonry arch bridge and reinforced concrete arch bridge.
2. According to the arch structure, it can be divided into solid arch bridge and hollow arch bridge;
3. According to the type of arch axis used in the main arch ring, arch bridges can be called arc arch bridges, parabolic arch bridges and catenary arch bridges.
4. Three-hinged arch, two-hinged arch or non-hinged arch are classified according to the structural stress diagram.
5. According to the section form of the main arch ring, it can be divided into slab arch bridge, rib arch bridge, hyperbolic arch bridge and box arch bridge.
3. Rigid frame bridge
The main load-bearing structure of rigid frame bridge is a rigid frame structure in which beams or slabs are connected with columns or vertical walls. Beam-column joints have great stiffness. Under the vertical load, the beam is mainly bent, and there is also horizontal reaction at the foot of the column, and its stress state is between the beam bridge and the arch bridge. For the same span and under the same load, the mid-span bending moment of rigid frame bridge is smaller than that of general beam bridge. According to this feature, in the span of rigid frame bridge, the height of the building can be made smaller. In cities, when encountering line interchanges or crossing navigable rivers, this bridge type can reduce the line elevation as much as possible to improve the longitudinal slope and reduce the earthwork volume of dikes. Such as the underpass bridge.
4. Combined system
1) beam and arch combination
Beam and arch are the main load-bearing structures, which cooperate with each other and bear the force together. When the boom hangs the beam upwards, the bending moment in the beam is significantly reduced; At the same time, the arch is connected with the beam, and the horizontal thrust of the arch is transferred to the beam, and the beam is still in tension except for the bending moment. This composite system bridge can span a larger span than the general simply supported beam bridge, and the pier and abutment have no thrust. The requirements for foundation are the same as those for general simply supported beam bridges.
2) Cable-stayed bridge (beam-cable combination)
Cable-stayed bridge is a typical structural system composed of suspended cable structure and beam structure. It consists of main girder, cable and bridge tower. The characteristics of cable structure and beam structure are fully utilized. The beam structure directly bears the bending moment and shear force caused by the load outside the bridge deck, and the stay cables on both sides of the bridge tower provide elastic support for the beam structure after being tensioned, and at the same time bear the tensile force caused by the load, and the vertical component of the tensile force is transmitted to the foundation and foundation through the bridge tower; The horizontal component of tension caused by the load in the stay cable makes the bridge structure bear axial pressure, which is equivalent to prestressing the beam structure.
5. suspension bridge
Suspension bridge is also called suspension bridge. It is characterized in that the main load-bearing structure of the bridge consists of the tower body, high-strength flexible cables and slings suspended on the tower body, stiffening beams and anchor ingots. The load on the bridge span is borne by the stiffening beam and transmitted to the cable through the sling. The main cable is the main load-bearing structure, but it only bears tension. The cable itself is geometrically deformed, but it can be combined by bridge tower, anchorage structure and acting load to form a balanced structural system with a certain geometric shape in space. The tension of the main cable is transmitted to the foundation and foundation through the pressure on the bridge tower and the tension of the anchor structure. This type of bridge gives full play to the tensile properties of high-strength steel cables, which makes its structure lighter in self-weight and can span a super-long span unmatched by any other bridge type with a small building height.
Overview of Bridge Construction Methods and Selection of Construction Methods
Bridge construction is divided into foundation construction, pier construction and superstructure construction. Foundation construction includes enlarged foundation, pile and pipe pile foundation, open caisson foundation, underground continuous wall foundation and composite foundation. Pier construction includes stone pier, cast-in-place pier and precast pier. The construction of superstructure can be divided into cast-in-place method and prefabricated installation method according to the location of component production; According to the structure formation mode, it is divided into cantilever construction method and swivel construction method based on pier; Based on the end point of bridge shaft, hole-by-hole construction method, jacking construction method and lifting floating transportation method; According to the transverse bridge direction, the transverse construction method is adopted.
Support structure and main construction equipment of bridge
Pile driving and drilling equipment: pile driver, pile driver, grouting machine, etc.
Earthmoving equipment: backhoe, bulldozer, etc.
Measuring equipment (measuring instruments): theodolite, etc
Steel bar and steel plate processing equipment: electric welding machine, cutting machine, etc.
Lifting equipment: gantry, hanging basket, bridge erecting machine, etc.
Vertical construction equipment: scaffolding, universal bars, steel sheet piles, etc.
Concrete construction equipment: mixer, vibrator, concrete pump, etc.
Prestressing equipment: jack, upsetter, threading machine, etc.
Means of transportation: cars, trains, tractors, etc.
Drainage equipment: water pump, well point, etc.
Special construction equipment: guide equipment, moving formwork roller, etc.
Main contents of bridge and culvert construction survey:
1, check all the pile positions and leveling points delivered by the design unit and their measurement data;
2. Establish a construction control network that meets the accuracy requirements and carry out adjustment calculation;
3, supplement the construction needs of bridge and culvert centerline piles and leveling points;
4. Determine the longitudinal and transverse center lines of the pier and the position of the foundation pile;
5. Carry out elevation measurement and construction lofting of buildings, and move the design elevation and necessary geometric dimensions to the site;
6. Carry out necessary construction deformation observation and precision control on related structures;
7. Determine and check the position and elevation of the construction site, so as to provide a basis for evaluating the project quality;
8. Carry out completion measurement for the completed project.
Open excavation to expand foundation construction
First, expand the infrastructure process.
1, measurement and positioning, 2, foundation lofting, 3, excavation and drainage, 4, basement inspection and treatment (plane position, size, basement elevation, soil uniformity, foundation stability, bearing capacity, basement treatment and drainage), 5, formwork binding, 6, concrete pouring, maintenance, 7, formwork removal, 8, backfill soil.
Second, expand the foundation excavation.
Land foundation excavation is divided into unsupported and supported; Among them, the supporting excavation is divided into straight baffle, transverse baffle, frame, anchor pile, diagonal support, anchor rod, concrete supporting pit wall, steel sheet pile and reinforced concrete casing.
Underwater foundation excavation is divided into earth-rock cofferdam, wooden cage cofferdam or bamboo cage cofferdam, steel sheet pile cofferdam and boxed cofferdam.
Matters needing attention in foundation pit construction
1. Observe whether there are cracks on the edge of the pit wall; 2. Set the berm; 3. The static load is 0.5m away from the pit edge, and the dynamic load is1.0m; From the pit; 4. Set intercepting ditch; 5. Observe whether the edge of the pit wall is loose; 6. 30cm artificial excavation at the bottom of the pit.
Inspection and treatment of substrate
1, base inspection
1) Check the plane position, size and elevation of the basement; 2) Check the uniformity, foundation stability and bearing capacity of the foundation soil; 3) check the substrate treatment and drainage; 4) Check the construction log and relevant experimental data.
The main construction technology of bored piles: leveling the site (cofferdam and platform on water) → positioning and burying the liners → positioning the drilling rig → drilling and hole-forming inspection → hole cleaning → hanging the reinforcing cage → lowering the conduit → hole cleaning and sediment test → pouring underwater concrete → removing and pulling out the liners → digging the pile head → pile quality inspection → maintenance and cleaning.
1 Level the site
1) Dry land leveling and compaction; Pile location lofting; Preparatory work for the building
2) Site preparation in water
(1) If the island building site is shallow water, island building should be selected.
(2) When the cofferdam site is deep water, cofferdam and other technologies can be adopted, and fixed platforms such as steel pipe pile platform and double-wall cofferdam can be adopted; Only satellite platforms can be used.
2 embedded linings
The role of the pile casing is to fix the pile position, guide the pile head, isolate the groundwater, protect the orifice and raise the water level.
Jacket top: 2.0m above the construction water level and 0.5m above the ground.
Casing burial depth:1.0m; Under clay and silt; Underground in 2.0m sandy soil; 1.0m below the bottom of Tudao River bed.
Pad thickness: steel 4 ~ 8 mm; Reinforced concrete: 8~ 10cm
(1) The pile casing is rolled with 4mm thick steel plate, and its inner diameter is 200 ~ 400 mm larger than the designed diameter of the bored pile. The pile casing is manually cleared and sunk. The joint of casing is guaranteed to withstand tension and pressure.
② The top of the gasket should be at least 0.3m higher than the ground.
(3) The center line of the pile casing should coincide with the center line of the pile. The allowable deviation between the buried center position of the pile casing and the pile position is ≤20mm or less, the inclination deviation of the pile casing is not more than 65438 0%, and the buried pile casing must enter the undisturbed soil by 20cm.
(4) After the pile casing is buried, insert φ 12 steel bar in the center of the pile position to facilitate the alignment of the pile frame.
(5) After the liners are buried, clay should be backfilled around them and compacted to prevent slurry leakage during drilling.
3 Mud
1) Mud pit
Mud pools are set in the non-isolated area of the machine, one on each abutment side, each mud pool is about 150m3, and each pool is 1.5 ~ 2.0m deep. The pool body is in the form of concrete pouring, and safety warning signs and enclosure measures are set. Set a mud pump of 15KW on the mud pool for recycling. Mud in the casing is pumped to the circulating pool by the mud pump, and the water level in the casing is kept at a certain head without slurry leakage.
(2) Mud preparation
Mechanism of wall protection: liquid support of pore wall soil; Forming a hole wall with stable mud skin.
Other functions: suspending drilling slag, lubricating drilling tools, and discharging slag by positive circulation.
Soil quality: bentonite, the PH value of water is between 7 and 8, and it contains no impurities.
Chemical treatment agent: inorganic matter: soda ash, etc. Promote particle dispersion and prevent coagulation and sedimentation;
Organic matter: tannin solution, glue copy solution, etc. To reduce viscosity.
Purification: gravity precipitation method; Hole cleaning method of vibrating screen.
3) Mud circulation
The circulation route is: pile hole → circulation pool → sedimentation pool → mud pool → pile hole.
Excess mud, waste mud and sediment generated in the construction process should be transported outside by closed transport means such as tank cars and discarded at designated places to prevent environmental pollution.
Precautions:
① Prepare enough high-quality clay or bentonite for mud preparation before drilling.
(2) Mud is composed of water, clay (or bentonite) and additives, and its performance indicators should comply with the provisions of JTJ04 1-2000. Drilling mud should be tested frequently, and mud that does not meet the requirements must be adjusted in time.
③ The top surface of mud in casing should always be at least 1.0m higher than the water level outside casing.
(4) When short temporary liners are used, mud should be filled in the borehole to stabilize the borehole.
4. Pore-forming structure
(1) pore-forming operation procedure
1) Before the construction, the full-time builder shall be arranged to take charge of on-site operation, and written requirements shall be put forward, including detailed requirements such as drilling depth, inspection method, concrete mixture ratio, shortest time for completing one pile and the next pile, and construction progress. The written request will be copied to the supervision engineer, and after approval, the construction of bored piles can be started.
2) Assign experienced construction personnel for drilling. Before drilling, make a comprehensive technical disclosure to the construction personnel, so that the construction personnel can have a comprehensive understanding of the geology and hydrology of the drilling area.
3) Record carefully when drilling. The drilling operation shall be carried out continuously in shifts, and the drilling situation and matters needing attention of the next shift shall be explained when filling in the drilling construction record.
4) Pay attention to the stratum changes at any time, take slag samples from the stratum changes, record them in the record table after identification, and check them with the geological profile. At the same time, adjust the performance index of mud in time according to the formation change. In the process of drilling, if it is found that the geological conditions of the drilling location are obviously different from those described on the design drawings, a written report should be written to solicit instructions from the supervision engineer, or the original design can be changed according to the actual situation, but detailed design calculations and geological data must be provided to the supervision engineer. Without the approval of the supervision engineer, the next step shall not be carried out.
5) The hole position must be accurate (meet the quality standard), and the drilling can be accelerated only after all the guiding parts such as slow drilling or drill bits enter the stratum.
6) The rig base should be balanced firmly, and the pulley should be on the same vertical line with the center hole and casing center in the rig floor. After the rig is in place, it is necessary to further check whether the rig platform is level and whether the platform and top are stable. If the level below is unstable, adjust it immediately to ensure that there is no displacement or subsidence during drilling. When using positive circulation drilling, decompression drilling should be adopted, that is, the main hook of the drilling rig is always stressed, and the force is 20% of the gravity of drilling tools (drill bit and drill pipe).
7) Before lowering the drilling tools, do a good job of inspection. During drilling, pay attention to the footage of the first and second drill pipes to ensure that the drilling tools are perpendicular to the hole center. At the same time, tighten the drilling tools, drill holes evenly, and assign special personnel to operate.
8) During drilling, it is necessary to change the drilling parameters according to the change of formation, and designate special personnel to operate during the whole drilling process. When drilling in clay, choose a sharp bottom bit with medium speed, large pump capacity and dilute mud; The camera can't be too fast. If it is too fast, the drill pipe is easy to break and the mud is not easy to be crushed.
(2) Selection of drilling rig
According to the geological conditions, choose the appropriate drilling machine or hole-forming method.
Impact method, grasp method and rotation method.
1) Cross bit and tubular bit for impact drilling rig.
Key points of impact drilling construction
Drilling after the concrete of adjacent holes reaches 2.5MPa; Small opening stroke; Hole depth is the normal impact of drill bit after high stroke.
Cohesive soil, weathered layer, gravel, etc. , medium and low stroke:1~ 2m; Sandy pebbles, etc. Medium stroke: 2 ~ 3m bedrock, boulder and dense pebble bed; high stroke: 3 ~ 5m 1.5m and above, the cross bit caliper is divided into two grades, and the tubular bit caliper above 0.7m is divided into two to four grades (graded reaming).
2) punch holes and grab the drill holes.
3) drilling with a rotary drilling rig
4) Kato drilling rig has impact type, grab type and rotary drilling type bits, which can be used for cast-in-place piles for protecting the wall of pressure liners, with pile diameter1.0 ~ 2.0m ~ 2.0m.
5) Common drilling accidents: hole collapse, drilling slurry leakage, bending hole, drilling paste, shrinkage hole, plum blossom hole, drilling sticking and drilling drop.
(3) Borehole inspection
(1) After drilling, use theodolite, measuring rope and other instruments to check the hole and submit it to the supervision engineer. Without the supervision engineer's inspection and approval, concrete shall not be poured into the hole.
(2) The diameter and depth of the hole must meet the requirements of the drawings. When defects are found in the inspection, report to the supervision engineer and put forward suggestions for remedial measures. Construction is not allowed to continue until it is approved.
4. Borehole cleaning
(1) After the hole-forming inspection is completed, clean the hole immediately. The hole-cleaning method adopts mud replacement hole-cleaning method in combination with the geological conditions of this project. When cleaning the hole, the water level in the hole should be kept above 1m outside the hole.
② First hole cleaning: after drilling to the designed depth, stop the footage, lift the drilling tool slightly away from the bottom of the hole 10~20cm, keep the mud circulating normally, idle the drilling disc regularly, and grind the residual mud at the bottom of the hole into mud for discharge. The hole cleaning time is about 30 minutes.
③ Second hole cleaning: After the first hole cleaning, pull out the drilling tool and measure the hole depth. Then take the time to place the reinforcing cage and concrete conduit, and then carry out the second hole cleaning, which generally takes 0.5~ 1 hour.
④ After the second hole cleaning, the sediment thickness at the bottom of the hole is ≤20cm, the mud index 1. 15~ 1.20, the viscosity 18~24s, and the sand content is about 4%.
⑤ After hole cleaning, keep the head height in the hole and pour concrete within 30 minutes. If it exceeds 30 minutes, the mud index must be measured again. If the allowable value in the specification is exceeded, the hole should be cleaned again.
The purpose of hole cleaning is to reduce precipitation and improve the bearing capacity of hole bottom; Sediment thickness: columnar ≯10cm; Friction column ≯30cm.
Hole cleaning methods: slag pumping, mud suction and slurry changing.
Key points of construction: clear holes in time to prevent mud precipitation; Replenish fresh water and fresh mud to keep the water level. Before pouring the column pile, flush it with water for 3 ~ 5min minutes, and the water pressure is 0.05MPa.
Manufacture of reinforcing cage
(2) Requirements for fabrication of reinforcing cage
A, before making reinforcement cage, remove the dirt and rust on the surface of reinforcement, and accurately control the blanking length. The fabrication of long pile skeleton shall be carried out in sections, and the length of sections shall be subject to the length of materials (generally 9m), so as to ensure no deformation during hoisting. At the same time, the joints shall be staggered, and the number of joints in the same section shall not be greater than 50%. In order to ensure that the skeleton is not deformed during hoisting, a reinforcing hoop is added at 2m in the skeleton, and the problem is solved by hoisting with multiple hoisting points.
B, reinforcing cage is made of ring mould, and the production site is kept flat.
C. E50 covered electrode shall be selected for the welding of reinforcing cage, with the weld width not less than 0.7d and the thickness not less than 0.3d.. ..
D, reinforcing cage welding process, slag should be removed in time. All steel hoops and main bars at both ends of the cage shall be spot-welded and welded firmly. Other reinforcing cages are also fixed by spot welding.
E, reinforcing cage main reinforcement connection adopts single-sided welding, the weld length is ≥ 10d, and the number of joints in the same section is ≤50% staggered.
F, each reinforcing cage is provided with a reinforcing bar positioning control piece up and down, and each reinforcing cage is provided with four pieces along the circumference. The thickness of protective layer is 50 mm.
G, forming reinforcing cage lying on the flat and clean ground, stacking layer should not be more than 2.
Reinforcement cage placement
(1) The elevation of the reinforcing cage shall be calculated by the elevation of the top of the mouth guard pipe, and the design elevation of the pile top must be guaranteed when placing, with an allowable error of100 mm. ..
(2) When lowering the reinforcing cage, carefully aim at the center of the hole, slowly and gradually sink through positive and negative rotation to prevent collision, and fix it immediately after placing it at the design elevation.
(3) The reinforcing cage is installed in the hole. When welding the upper and lower reinforcing cages or reinforcing cages, the reinforcing cage must be kept in a vertical state, and both sides of the reinforcing cage must be symmetrically welded when welding.
(4) After the fabrication of the hole-butted reinforcing cage is completed, the intermediate acceptance procedure shall be strictly implemented, and the next reinforcing cage can be installed only after it is qualified. Check the number of steel skeleton segments before hoisting to prevent the steel skeleton length from failing to meet the design requirements.
⑤ When lifting the conduit, the reinforcing cage must be prevented from being pulled up. When pouring concrete, measures must be taken to observe and measure the possible movement of the reinforcing cage and deal with it in time.