CN117468357A - Anti-cracking control method for pier body in high-cold freeze-thawing area - Google Patents
Anti-cracking control method for pier body in high-cold freeze-thawing area Download PDFInfo
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- CN117468357A CN117468357A CN202311512769.7A CN202311512769A CN117468357A CN 117468357 A CN117468357 A CN 117468357A CN 202311512769 A CN202311512769 A CN 202311512769A CN 117468357 A CN117468357 A CN 117468357A
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- 238000010257 thawing Methods 0.000 title claims abstract description 37
- 238000000034 method Methods 0.000 title claims abstract description 36
- 238000005336 cracking Methods 0.000 title claims abstract description 25
- 239000004567 concrete Substances 0.000 claims abstract description 69
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 35
- 239000007921 spray Substances 0.000 claims abstract description 25
- 238000010276 construction Methods 0.000 claims abstract description 24
- 239000002689 soil Substances 0.000 claims abstract description 16
- 238000012423 maintenance Methods 0.000 claims abstract description 14
- 238000005507 spraying Methods 0.000 claims abstract description 11
- 230000003020 moisturizing effect Effects 0.000 claims abstract description 8
- 238000011065 in-situ storage Methods 0.000 claims abstract description 4
- 239000011150 reinforced concrete Substances 0.000 claims abstract description 4
- 239000004746 geotextile Substances 0.000 claims description 21
- 238000004321 preservation Methods 0.000 claims description 14
- 230000001276 controlling effect Effects 0.000 claims description 13
- 239000000463 material Substances 0.000 claims description 13
- 229920000742 Cotton Polymers 0.000 claims description 12
- 239000004568 cement Substances 0.000 claims description 12
- 230000002265 prevention Effects 0.000 claims description 12
- 238000007789 sealing Methods 0.000 claims description 10
- 239000010410 layer Substances 0.000 claims description 9
- 239000002245 particle Substances 0.000 claims description 9
- 239000003795 chemical substances by application Substances 0.000 claims description 7
- 238000010438 heat treatment Methods 0.000 claims description 7
- 239000002985 plastic film Substances 0.000 claims description 7
- 229920006255 plastic film Polymers 0.000 claims description 7
- 239000003513 alkali Substances 0.000 claims description 6
- 239000010881 fly ash Substances 0.000 claims description 6
- 239000004575 stone Substances 0.000 claims description 6
- 238000000889 atomisation Methods 0.000 claims description 5
- 238000005266 casting Methods 0.000 claims description 5
- 238000005086 pumping Methods 0.000 claims description 5
- 230000000694 effects Effects 0.000 claims description 4
- 239000004033 plastic Substances 0.000 claims description 4
- RBTBFTRPCNLSDE-UHFFFAOYSA-N 3,7-bis(dimethylamino)phenothiazin-5-ium Chemical compound C1=CC(N(C)C)=CC2=[S+]C3=CC(N(C)C)=CC=C3N=C21 RBTBFTRPCNLSDE-UHFFFAOYSA-N 0.000 claims description 3
- 238000009825 accumulation Methods 0.000 claims description 3
- 230000000740 bleeding effect Effects 0.000 claims description 3
- 239000003638 chemical reducing agent Substances 0.000 claims description 3
- 238000004140 cleaning Methods 0.000 claims description 3
- HOOWDPSAHIOHCC-UHFFFAOYSA-N dialuminum tricalcium oxygen(2-) Chemical compound [O--].[O--].[O--].[O--].[O--].[O--].[Al+3].[Al+3].[Ca++].[Ca++].[Ca++] HOOWDPSAHIOHCC-UHFFFAOYSA-N 0.000 claims description 3
- BCAARMUWIRURQS-UHFFFAOYSA-N dicalcium;oxocalcium;silicate Chemical compound [Ca+2].[Ca+2].[Ca]=O.[O-][Si]([O-])([O-])[O-] BCAARMUWIRURQS-UHFFFAOYSA-N 0.000 claims description 3
- 239000004744 fabric Substances 0.000 claims description 3
- 238000002955 isolation Methods 0.000 claims description 3
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims description 3
- 239000000395 magnesium oxide Substances 0.000 claims description 3
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 claims description 3
- 229960000907 methylthioninium chloride Drugs 0.000 claims description 3
- 239000000843 powder Substances 0.000 claims description 3
- 230000001105 regulatory effect Effects 0.000 claims description 3
- 239000004576 sand Substances 0.000 claims description 3
- 238000005204 segregation Methods 0.000 claims description 3
- 239000003469 silicate cement Substances 0.000 claims description 3
- 239000002344 surface layer Substances 0.000 claims description 3
- 229910021534 tricalcium silicate Inorganic materials 0.000 claims description 3
- 235000019976 tricalcium silicate Nutrition 0.000 claims description 3
- 230000002093 peripheral effect Effects 0.000 claims 1
- 230000006978 adaptation Effects 0.000 abstract description 2
- 229910000831 Steel Inorganic materials 0.000 description 9
- 239000010959 steel Substances 0.000 description 9
- 239000012528 membrane Substances 0.000 description 5
- 239000000654 additive Substances 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 238000009415 formwork Methods 0.000 description 3
- 230000000996 additive effect Effects 0.000 description 2
- 230000036571 hydration Effects 0.000 description 2
- 238000006703 hydration reaction Methods 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 230000002787 reinforcement Effects 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- 239000011358 absorbing material Substances 0.000 description 1
- 238000009435 building construction Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 210000000695 crystalline len Anatomy 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 230000008014 freezing Effects 0.000 description 1
- 238000007710 freezing Methods 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 239000004570 mortar (masonry) Substances 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 239000002861 polymer material Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000004886 process control Methods 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 239000011435 rock Substances 0.000 description 1
- 230000001932 seasonal effect Effects 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Classifications
-
- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01D—CONSTRUCTION OF BRIDGES, ELEVATED ROADWAYS OR VIADUCTS; ASSEMBLY OF BRIDGES
- E01D21/00—Methods or apparatus specially adapted for erecting or assembling bridges
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
- C04B28/04—Portland cements
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
- C04B40/02—Selection of the hardening environment
- C04B40/0263—Hardening promoted by a rise in temperature
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
- C04B40/04—Preventing evaporation of the mixing water
-
- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01D—CONSTRUCTION OF BRIDGES, ELEVATED ROADWAYS OR VIADUCTS; ASSEMBLY OF BRIDGES
- E01D19/00—Structural or constructional details of bridges
- E01D19/02—Piers; Abutments ; Protecting same against drifting ice
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
- E04G21/00—Preparing, conveying, or working-up building materials or building elements in situ; Other devices or measures for constructional work
- E04G21/24—Safety or protective measures preventing damage to building parts or finishing work during construction
- E04G21/246—Safety or protective measures preventing damage to building parts or finishing work during construction specially adapted for curing concrete in situ, e.g. by covering it with protective sheets
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Structural Engineering (AREA)
- Ceramic Engineering (AREA)
- Architecture (AREA)
- Materials Engineering (AREA)
- Civil Engineering (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Inorganic Chemistry (AREA)
- Mechanical Engineering (AREA)
- Health & Medical Sciences (AREA)
- Toxicology (AREA)
- On-Site Construction Work That Accompanies The Preparation And Application Of Concrete (AREA)
Abstract
The invention discloses a pier body anti-cracking control method for a high-cold freeze-thawing area, wherein a foundation is connected below the pier body, and a pile foundation extending into the interior of a freeze-thawing soil body is arranged below the foundation; the pier body is a cast-in-situ reinforced concrete member, the top of the pier body is provided with horizontal transverse pipes and horizontal longitudinal pipes which are distributed in a net shape, spraying pipes are arranged above the horizontal transverse pipes and the horizontal longitudinal pipes, and the spraying pipes are arranged according to the shape of the periphery of the top of the pier body and are provided with spray heads at intervals. According to the invention, through the demarcation and integral assembly of the pier body templates, the convenient construction of the pier body templates is ensured, and the templates are used for moisturizing and template maintenance in the follow-up process; through maintenance in two processes, temperature cracks of concrete due to high and cold and freeze thawing can be greatly built through temperature control in different stages; through the setting of shower and shower nozzle, do benefit to and carry out controllable real-time spray to the pier shaft, further guaranteed concrete humidity, and spray water temperature is controllable, do benefit to and guarantee adaptation local environment.
Description
Technical Field
The invention relates to the field of underground building construction, in particular to a pier body cracking prevention control method in a high-cold freeze-thawing area.
Background
Along with the popularization of traffic, more and more high-altitude areas also enter road and bridge construction. However, in high altitude areas such as the Sichuan-Tibetan area, the temperature difference is large, the temperature is low, and freezing and thawing seasons and soil bodies exist, which also cause difficulty in construction in the area. For bridge construction, the construction of the pier body is important, and how to ensure the durability of the pier body and the size of cracks in construction and use are important control links in construction; the preparation method is generally carried out by water retention agent and general maintenance, but the conventional material proportion, additive and control means and experience are not applicable in alpine regions; a complete set of anti-cracking process and control indexes needs to be re-established.
Disclosure of Invention
The invention provides an anti-cracking control method for pier bodies in a high-cold freeze-thawing area, which is used for solving the problem of setting up the whole process control of material proportioning, additive selection, formwork support, maintenance, spraying and the like of the pier bodies in the high-cold freeze-thawing area.
In order to achieve the above purpose, the invention adopts the following technical scheme:
a control method for preventing cracking of pier shaft in a high-cold freeze thawing area comprises the steps that a foundation is connected below the pier shaft, and a pile foundation extending into the freeze thawing soil body is arranged below the foundation; the pier body is a cast-in-situ reinforced concrete member, the top of the pier body is provided with horizontal transverse pipes and horizontal longitudinal pipes which are distributed in a net shape, spraying pipes are arranged above the horizontal transverse pipes and the horizontal longitudinal pipes, and the spraying pipes are arranged according to the shape of the periphery of the top of the pier body and are provided with spray heads at intervals;
the control method for preventing the pier body from cracking in the high-cold freeze-thawing area comprises the following specific steps:
firstly, after pile foundation and foundation construction are completed, chiseling and cleaning the top of the foundation, and then erecting a scaffold to support a pier shaft template; the pier body is divided into a pier body lower part and a pier body upper part, and the pier body lower part is a straight line section and a partial arc section; the upper part of the pier body is an arc section;
step two, pouring the pier body into an integrated pouring mode, and controlling the proportion of each material of the poured concrete according to the characteristics of the high-cold freeze-thawing soil body;
the proportion of each material of the concrete is controlled: the cement adopts low-heat silicate cement, the specific surface area is not less than 250m/kg, and the content of magnesium oxide is controlled within the range of 4.0-5.0 percent; the mud content of the crushed stone is not more than 0.8%, the crushing value is 6-8%, the content of needle-like and flaky particles is not more than 8%, the maximum particle size is 31.5, and the content of particles below 0.075mm is controlled to be less than or equal to 1.5%; the alkali activity is strictly controlled below 0.1%;
and step three, in addition, the concrete admixture is added in the concrete pouring process: adding 5% of an internal curing agent, wherein the 28-day shrinkage ratio of the water reducer is not more than 110%, and the 28-day shrinkage ratio of the air entraining agent added during winter construction is not more than 115%; fly ash: the loss on ignition is less than 3% in the freeze thawing environment, and the 2-grade fly ash accounts for 5-8%; the fineness modulus of the sand is 2.6-2.9, the stone powder content is 3-5%, and the methylene blue content is 0.8-1.0%; the mud content is not more than 3%, and the mud block content is not more than 1%; the alkali content in the alkali-aggregate control cement is not more than 0.6 percent of Na 2 O equivalent, active aggregate content not more than 1%, tricalcium silicate not more than 40%, tricalcium aluminate not more than 12%;
step four, wrapping cotton quilts outside the section template to be poured, wrapping plastic cloth on the template travelling platform outside the cotton quilts, and wrapping the cotton quilts inside the template travelling platform
A warm air gun is arranged at the part, a suspension thermometer is arranged, and when the temperature of the template before pouring is lower than 5 ℃, a warm air blower is started for heating;
covering a plastic film on the top surface of the concrete for moisturizing after pouring, and sequentially covering an electric blanket and a cotton quilt outside the plastic film, and starting the electric blanket to heat when the difference between the temperature of the surface layer of the pier top concrete and the ambient temperature is more than 20 ℃;
the method comprises the steps of entering a maintenance period, not removing a mold in the whole maintenance period of the pier body, not removing the cover of the pier body, moisturizing by using a mold plate, assisting an industrial humidifier to ensure the environment humidity, and heating by using a warm air blower when the difference between the surface temperature of concrete and the environment temperature is more than 20 ℃;
step six, curing for at least 4 days with a template after pouring, curing the pier skin by using a steam curing shed and a steam curing system after demolding, and curing for at least 6 months by adopting a water energy curing film and geotextile wrapping curing process after steam curing is removed;
step seven, after the pier body is disassembled and steam curing is completed, the water energy curing film is tightly attached to the concrete surface, then a layer of geotextile is wrapped around the pier body, a spray pipe and a spray head are arranged on the pier top, a water retaining sleeve bag is arranged on the outer side of the pier body, a humidity sensor is arranged in the sleeve bag, when the humidity is less than 50%, the spray system is automatically started, and when the humidity is greater than 95%, the spray system is automatically closed; thus, the anti-cracking control construction of the pier body in the high-cold freeze-thawing area is completed.
Further, at the pier body boundary between the lower part of the pier body and the upper part of the pier body, the templates are correspondingly divided into an upper template and a lower template, and the upper template and the lower template are manufactured respectively and then integrally installed.
Further, the relative pressure bleeding rate when pumping the concrete for 10 seconds is not more than 40%, so that the stability and pumpability of the concrete are ensured; control of slump: the water-cement ratio is controlled to be about 0.45, the water consumption is not more than 180kg/m < 3 >, and the minimum cement consumption is 320kg/m < 3 >; the slump of the main body structure is controlled to be 160-200mm.
Furthermore, the pier adopts pumping concrete to cast integrally and once; conveying the concrete entering the bottom of the pier body by using a hose or a stringing barrel, wherein the height of a discharge hole from the concrete surface is controlled to be 1m so as to avoid concrete segregation; when the stacking height of the discharged material of the guide pipe is more than 30cm, layering and vibrating by using an inserted vibrating rod; the casting speed is controlled to be not more than 3m and not less than 1m per hour.
Further, when the vibrator is inserted, the moving distance is not more than 1.5 times of the action radius of the vibrator, the distance between the vibrator and the side mould is kept between 50 and 100mm, the lower concrete layer of the vibrator is inserted between 50 and 100mm, and the vibrating rod is slowly lifted after each vibration is finished.
Further, during casting construction, the highest temperature in the concrete is ensured not to exceed 65 ℃, the temperature difference between the internal temperature and the surface temperature of the concrete and the temperature difference between the surface temperature and the environment temperature are not more than 20 ℃, and the temperature difference between the curing water temperature and the surface temperature of the concrete is not more than 15 ℃; and the temperature of the spray water changes along with the change of the outside air temperature.
Further, the steam curing system comprises a heat preservation sealing system, a steam atomization system and an intelligent temperature and humidity control system; the heat preservation sealing system adopts a novel multilayer heat preservation film, so that the isolation and the sealing of the pier body and the surrounding environment can be realized; the intelligent temperature and humidity control system is a core part of the pier body construction maintenance system and consists of a temperature and humidity controller, a sensor and a heating and humidifying system, and the temperature and humidity of a maintenance area are intelligently controlled and regulated by the controller; the steam atomization system introduces steam into the heat preservation system through a pipeline which is arranged according to the temperature change rule and the fluidity in the sealed space, and continuously conveys the steam.
Further, when the mould is disassembled, the mould is disassembled from top to bottom, and a mode of disassembling and covering is adopted, so that a layer of template is disassembled to immediately wrap geotextile; the thickness of the geotextile is not less than 2mm, and the geotextile is bound and fixed every 2 m; the geotextile at the pier top is pressed on the geotextile at the pier side, and the lap joint length is not less than 20cm.
Further, backfilling the foundation pit after the concrete reaches the design strength; backfilling with undisturbed soil and tamping; the foundation pit backfilling is needed to be symmetrically performed and the vibration is dense; the top surface should form an outward 2% slope after backfilling of the pit and no water accumulation should be formed.
The beneficial effects of the invention are as follows:
1) According to the invention, through the demarcation and integral assembly of the pier body templates, the convenient construction of the pier body templates is ensured, the templates are used for moisturizing and template maintenance subsequently, and the templates are used for cracking prevention control further;
2) According to the invention, through two-process curing, namely template curing and pier coating curing, temperature cracks of the concrete caused by high and cold and freeze thawing can be greatly built through temperature control at different stages;
3) According to the invention, through the targeted design of new material proportion, additives, pouring process and the like, the temperature control under special environment is more facilitated to be ensured;
4) The invention is beneficial to controllable real-time spraying of the pier body through the arrangement of the spray pipe and the spray head, further ensures the concrete humidity, ensures the controllable spraying water temperature and is beneficial to ensuring the adaptation to the local environment.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention; the primary object and other advantages of the invention may be realized and attained by means of the instrumentalities and particularly pointed out in the specification.
Drawings
FIG. 1 is a schematic view of a pier body and its connection structure;
FIG. 2 is a front view of the pier body structure;
FIG. 3 is a side view of a pier body construction;
fig. 4 is a schematic view of a shower pipe, a shower head and a connection structure thereof.
Reference numerals: 1-pile foundation, 2-lower foundation, 3-upper foundation, 4-pier shaft, 41-pier shaft lower part, 42-pier shaft upper part, 43-pier shaft boundary line, 5-support, 6-freeze thawing soil body, 7-horizontal transverse pipe, 8-horizontal longitudinal pipe, 9-spray pipe and 10-spray head.
Detailed Description
Taking the construction of a Sichuan area as an example, the altitude of the project is 3900m-4600m, and the bridge pier adopts a round-end bridge pier; pier height 12.0m, vertical face diameter 6.4m, side face diameter 2.7m, pier body slope ratio 45:1, adopting hyperboloid ball-type shock-absorbing and isolating support, support 5 height 50cm (without mortar height), support pad height 27cm. The frost heaving environment of the bridge is D3, and pier bodies and foundations below 1 meter on the ground adopt C45 concrete. The poor geology is sandy soil liquefaction, and the special rock soil is loose soil and seasonal frozen soil. The construction area of the project has the advantages of low air temperature, long winter, long sunshine, small annual temperature difference, large daily temperature difference, strong radiation, large wind power, hydro-thermal synchronization, large evaporation capacity and distinct seasons in the plateau climate area.
As shown in fig. 1 to 3, in the method for controlling cracking prevention of the pier body in the high-cold freeze-thawing area, a foundation is connected below the pier body 4, and the foundation comprises an upper foundation 3 and a lower foundation 2 as an expansion foundation; pile foundations 1 extending into the freeze-thawing soil body 6 are arranged below the foundation; the pier body 4 is a cast-in-situ reinforced concrete member, the top of the pier body 4 is provided with horizontal transverse pipes 7 and horizontal longitudinal pipes 8 which are distributed in a net shape, spraying pipes 9 are arranged above the horizontal transverse pipes 7 and the horizontal longitudinal pipes 8, and the spraying pipes 9 are arranged according to the shape of the periphery of the top of the pier body 4 and are provided with spray heads 10 at intervals;
the method for controlling cracking prevention of the pier body in the high-cold freeze-thawing area is further described with reference to fig. 1 to 4, and comprises the following specific steps:
firstly, after the pile foundation 1 and a foundation are constructed, chiseling and cleaning the top of the foundation, and then erecting a scaffold to support a pier shaft 4 template; the pier body 4 is divided into a pier body lower part 41 and a pier body upper part 42, and the pier body lower part 41 is a straight line section and a partial arc section; the upper part 42 of the pier body is an arc-shaped section;
in this embodiment, at the boundary line 43 between the pier body lower part 41 and the pier body upper part 42, the templates are correspondingly divided into upper and lower templates, which are manufactured separately and then integrally installed.
The pier body 4 template is processed into an assembled steel die by adopting a 6mm thick steel plate, and a shaping steel die is adopted: the panel adopts a 6mm steel plate, the vertical ribs adopt common 10# channel steel with the interval of 400mm, the transverse ribs adopt common 14# channel steel with the interval of 500mm; the formwork reinforcement adopts channel steel bolt hoops, and is reinforced by screw rods, so that the formwork reinforcement is required to have enough strength, rigidity and stability. The templates are transported to the vicinity of pier positions by adopting automobiles, assembled into a whole on site, supported by installing trusses and integrally hung by adopting a crane
When the template is assembled integrally, the staggering is less than 1mm, and the joint is less than 1mm. During installation, the steel template is fixed by using a cable rope, and the inclination angles of the steel template in two vertical directions are corrected by using a total station. The templates are subjected to trial assembly, and the quality of the connecting bolt holes and the connecting positions is timely trimmed in the trial assembly process; after the trial assembly is completed, the welding quality, the plane size, the surface flatness and the like of the trial assembly are checked in detail; in particular, it is necessary to check that the joint or misalignment between each of the templates should not be greater than 1mm.
Step two, pouring the pier body 4 into an integrated pouring mode, and controlling the proportion of each material of the poured concrete according to the characteristics of the alpine freeze-thawing soil body 6;
the proportion of each material of the concrete is controlled: the cement adopts low-heat silicate cement, the specific surface area is not less than 250m/kg, and the content of magnesium oxide is controlled within the range of 4.0-5.0 percent; the mud content of the crushed stone is not more than 0.8%, the crushing value is 6-8%, the content of needle-like and flaky particles is not more than 8%, the maximum particle size is 31.5, and the content of particles below 0.075mm is controlled to be less than or equal to 1.5%; the alkali activity is strictly controlled below 0.1%;
and step three, in addition, the concrete admixture is added in the concrete pouring process: adding 5% of an internal curing agent, wherein the 28-day shrinkage ratio of the water reducer is not more than 110%, and the 28-day shrinkage ratio of the air entraining agent added during winter construction is not more than 115%; fly ash: the loss on ignition is less than 3% in the freeze thawing environment, and the 2-grade fly ash accounts for 5-8%; the fineness modulus of the sand is 2.6-2.9, the stone powder content is 3-5%, and the methylene blue content is 0.8-1.0%; the mud content is not more than 3%, and the mud block content is not more than 1%; the alkali content in the alkali-aggregate control cement is not more than 0.6 percent of Na 2 O equivalent, active aggregate content not more than 1%, tricalcium silicate not more than 40%, tricalcium aluminate not more than 12%;
in the embodiment, the pier adopts pumping concrete for integral one-time pouring; the concrete entering the bottom of the pier body 4 is conveyed by a hose or a stringing barrel, and the height of a discharge hole from the concrete surface is controlled to be 1m so as to avoid concrete segregation; when the stacking height of the discharged material of the guide pipe is more than 30cm, layering and vibrating by using an inserted vibrating rod; the casting speed is controlled to be not more than 3m and not less than 1m per hour.
In the embodiment, the relative pressure bleeding rate when pumping the concrete for 10 seconds is not more than 40%, so that the stability and pumpability of the concrete are ensured; control of slump: the water-cement ratio is controlled to be about 0.45, and the water consumption is not more than 180kg/m 3 Minimum cement dosage 320kg/m 3 The method comprises the steps of carrying out a first treatment on the surface of the The slump of the main body structure is controlled to be 160-200mm.
In the embodiment, when the vibrator is inserted, the moving distance is not more than 1.5 times of the action radius of the vibrator, the distance between the vibrator and the side mould is kept between 50 and 100mm, the concrete at the lower layer of the person is inserted between 50 and 100mm, and the vibrating rod is slowly lifted after each vibration is finished.
When in pouring construction, the highest temperature in the concrete is ensured not to exceed 65 ℃, the difference between the temperature in the concrete and the surface temperature is ensured not to be more than 20 ℃, and the difference between the temperature of curing water and the temperature of the concrete surface is ensured not to be more than 15 ℃; and the temperature of the spray water changes along with the change of the outside air temperature.
Step four, wrapping cotton quilts outside the section template to be poured, wrapping plastic cloth on the template travelling platform outside the cotton quilts, and wrapping the cotton quilts inside the template travelling platform
A warm air gun is arranged at the part, a suspension thermometer is arranged, and when the temperature of the template before pouring is lower than 5 ℃, a warm air blower is started for heating;
covering a plastic film on the top surface of the concrete for moisturizing after pouring, and sequentially covering an electric blanket and a cotton quilt outside the plastic film, and starting the electric blanket to heat when the difference between the temperature of the surface layer of the pier top concrete and the ambient temperature is more than 20 ℃;
the method comprises the steps of entering a curing period, not removing a mold in the full curing period of a pier body 4, covering and not removing the pier body 4, moisturizing by using a template, and ensuring the environment humidity by using an industrial humidifier, wherein when the difference between the surface temperature of concrete and the environment temperature is more than 20 ℃, a warm air blower is adopted to heat the environment temperature;
and step six, curing for at least 4 days with a template after pouring, curing the pier skin after demolding by using a steam curing shed and a steam curing system for at least 4 days, and curing for at least 6 months by adopting a water energy curing film and geotextile wrapping curing process after steam curing is removed.
The steam curing system comprises a heat preservation sealing system, a steam atomization system and an intelligent temperature and humidity control system; the heat preservation sealing system adopts a novel multilayer heat preservation film, so that the isolation and sealing of the pier body 4 and the surrounding environment can be realized; the intelligent temperature and humidity control system is a core part of the pier body 4 construction maintenance system and consists of a temperature and humidity controller, a sensor and a heating and humidifying system, and the temperature and humidity of a maintenance area are intelligently controlled and regulated by the controller; the steam atomization system introduces steam into the heat preservation system through a pipeline which is arranged according to the temperature change rule and the fluidity in the sealed space, and continuously conveys the steam.
Step seven, after the pier body 4 is disassembled and steam curing is completed, the water energy curing film is tightly attached to the concrete surface, then a layer of geotextile is wrapped around the pier body, a spray pipe 9 and a spray head 10 are arranged at the pier top, a water-retaining sleeve bag is arranged at the outer side of the pier body 4, a humidity sensor is arranged in the sleeve bag, when the humidity is less than 50%, the spray system is automatically started, and when the humidity is greater than 95%, the spray system is automatically closed; thus, the anti-cracking control construction of the pier body in the high-cold freeze-thawing area is completed.
Wherein, the water energy conservation membrane can form internal circulation in the closed space in the membrane to play a role in absorbing and retaining water. Because of the good sealing performance of the plastic film, the wet curing time is prolonged, the plastic shrinkage is reduced, and the generation of concrete cracks is controlled. After the water energy curing film is covered, the relative humidity of the concrete surface is increased, the hydration degree of the cementing material is improved, and the early shrinkage cracking phenomenon of the concrete is improved. The water absorbing material of the curing membrane is changed into transparent crystalline lens after being absorbed and expanded, liquid water is stored in the polymer material to form a small reservoir, and then the liquid water permeates to the surface of the concrete through capillary action, and meanwhile, steam water generated by the concrete in hydration heat is continuously absorbed, so that sufficient water can be kept in the water energy curing membrane, and the curing membrane is favorable for improving the engineering quality of the concrete. The water energy curing film has the following excellent properties; 1, adjusting relative humidity, wherein a curing film controls water to be dispersed into air during curing, and the surface of concrete is kept moist; 2, effectively preserving heat, increasing early strength, curing the film like a bed of cotton quilt, wherein the temperature in the film is higher than the external temperature during curing; 3 effectively inhibit microcracks, and the maintenance film has good heat preservation and moisture preservation effects and can effectively inhibit the generation of microcracks
When the mould is disassembled, the mould is disassembled from top to bottom, and a mode of disassembling and covering is adopted, so that a layer of template is disassembled to immediately wrap geotextile; the thickness of the geotextile is not less than 2mm, and the geotextile is bound and fixed every 2 m; the geotextile at the pier top is pressed on the geotextile at the pier side, and the lap joint length is not less than 20cm.
In the embodiment, backfilling the foundation pit after the concrete reaches the design strength; backfilling with undisturbed soil and tamping; the foundation pit backfilling is needed to be symmetrically performed and the vibration is dense; the top surface should form an outward 2% slope after backfilling of the pit and no water accumulation should be formed.
The foregoing is merely a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that would occur to those skilled in the art within the scope of the present invention are intended to be included in the scope of the present invention.
Claims (9)
1. A pier shaft anti-cracking control method in a high-cold freeze thawing area is characterized in that a foundation is connected below a pier shaft (4), and a pile foundation (1) extending into a freeze thawing soil body (6) is arranged below the foundation; the pier body (4) is a cast-in-situ reinforced concrete member, the top of the pier body (4) is provided with horizontal transverse pipes (7) and horizontal longitudinal pipes (8) which are distributed in a net shape, spraying pipes (9) are arranged above the horizontal transverse pipes (7) and the horizontal longitudinal pipes (8), and the spraying pipes (9) are arranged according to the peripheral shape of the top of the pier body (4) and are provided with spray heads (10) at intervals;
the control method for preventing the pier body from cracking in the high-cold freeze-thawing area comprises the following specific steps:
firstly, after a pile foundation (1) and a foundation are constructed, chiseling and cleaning the top of the foundation, and then erecting a scaffold to support a pier body (4) template; the pier body (4) is divided into a pier body lower part (41) and a pier body upper part (42), and the pier body lower part (41) is a straight line section and a partial arc section; the upper part (42) of the pier body is an arc-shaped section;
step two, pouring the pier body (4) into an integrated pouring mode, and controlling the proportion of each material of the poured concrete according to the characteristics of the high-cold freeze-thawing soil body (6);
the proportion of each material of the concrete is controlled: the cement adopts low-heat silicate cement, the specific surface area is not less than 250m/kg, and the content of magnesium oxide is controlled within the range of 4.0-5.0 percent; the mud content of the crushed stone is not more than 0.8%, the crushing value is 6-8%, the content of needle-like and flaky particles is not more than 8%, the maximum particle size is 31.5, and the content of particles below 0.075mm is controlled to be less than or equal to 1.5%; the alkali activity is strictly controlled below 0.1%;
and step three, in addition, the concrete admixture is added in the concrete pouring process: adding 5% of an internal curing agent, wherein the 28-day shrinkage ratio of the water reducer is not more than 110%, and the 28-day shrinkage ratio of the air entraining agent added during winter construction is not more than 115%; fly ash: the loss on ignition is less than 3% in the freeze thawing environment, and the 2-grade fly ash accounts for 5-8%; the fineness modulus of the sand is 2.6-2.9, the stone powder content is 3-5%, and the methylene blue content is 0.8-1.0%; the mud content is not more than 3%, and the mud block content is not more than 1%; the alkali content in the alkali-aggregate control cement is not more than 0.6 percent of Na 2 O equivalent, active aggregate content not more than 1%, tricalcium silicate not more than 40%, tricalcium aluminate not more than 12%;
step four, wrapping a cotton quilt outside the section template to be poured, wrapping plastic cloth outside the template travelling platform, arranging a warm air gun inside the cotton quilt, configuring a hanging thermometer, and starting a warm air blower to heat when the temperature of the template is lower than 5 ℃ before pouring;
covering a plastic film on the top surface of the concrete for moisturizing after pouring, and sequentially covering an electric blanket and a cotton quilt outside the plastic film, and starting the electric blanket to heat when the difference between the temperature of the surface layer of the pier top concrete and the ambient temperature is more than 20 ℃;
the method comprises the steps of entering a curing period, not removing a mold in the full curing period of a pier body (4), not removing a cover of the pier body (4), moisturizing by using a template, and ensuring the environment humidity by using an industrial humidifier, wherein when the difference between the surface temperature of concrete and the environment temperature is more than 20 ℃, a warm air blower is used for heating the environment temperature;
step six, curing for at least 4 days with a template after pouring, curing the pier skin by using a steam curing shed and a steam curing system after demolding, and curing for at least 6 months by adopting a water energy curing film and geotextile wrapping curing process after steam curing is removed;
step seven, after the pier body (4) is disassembled and steam curing is completed, the water energy curing film is tightly attached to the concrete surface, then a layer of geotextile is wrapped around the pier body, a spray pipe (9) and a spray head (10) are arranged at the pier top, a water-retaining sleeve bag is arranged at the outer side of the pier body (4), a humidity sensor is arranged in the sleeve bag, when the humidity is less than 50%, the spray system is automatically started, and when the humidity is greater than 95%, the spray system is automatically closed; thus, the anti-cracking control construction of the pier body in the high-cold freeze-thawing area is completed.
2. The method for controlling cracking prevention of a pier body in a high-cold freeze-thawing area according to claim 1, wherein the templates are correspondingly divided into upper and lower templates at a pier body parting line (43) of a pier body lower part (41) and a pier body upper part (42), and the upper template and the lower template are manufactured respectively and then integrally installed.
3. The method for controlling the cracking prevention of the pier body in the high-cold freeze-thawing area according to claim 1, wherein the relative pressure bleeding rate of the concrete pumped for 10 seconds is not more than 40%, so that the stability and pumpability of the concrete are ensured; control of slump: the water-cement ratio is controlled to be about 0.45, and the water consumption is not more than 180kg/m 3 Minimum cement dosage 320kg/m 3 The method comprises the steps of carrying out a first treatment on the surface of the The slump of the main body structure is controlled to be 160-200mm.
4. The method for controlling cracking prevention of pier bodies in high-cold freeze-thawing areas according to claim 1, wherein the pier adopts pumping concrete for integral one-time pouring; the concrete entering the bottom of the pier body (4) is conveyed by a hose or a string cylinder, and the height of a discharge hole from the concrete surface is controlled to be 1m so as to avoid concrete segregation; when the stacking height of the discharged material of the guide pipe is more than 30cm, layering and vibrating by using an inserted vibrating rod; the casting speed is controlled to be not more than 3m and not less than 1m per hour.
5. The method for controlling the cracking prevention of pier bodies in high-cold freeze-thawing areas according to claim 1, wherein when the personnel vibrator is inserted, the moving distance is not more than 1.5 times of the action radius of the vibrator, the distance from a side mould is kept between 50 and 100mm, the distance from the lower layer of concrete of the personnel is inserted between 50 and 100mm, and a vibrating rod is slowly lifted after each vibration is finished.
6. The method for controlling the cracking prevention of the pier body in the high-cold freeze-thawing area according to claim 1, wherein the highest temperature in the concrete is not more than 65 ℃ during casting construction, the difference between the temperature in the concrete and the surface temperature, the difference between the surface temperature and the environment temperature is not more than 20 ℃, and the difference between the temperature of curing water and the surface temperature of the concrete is not more than 15 ℃; and the temperature of the spray water changes along with the change of the outside air temperature.
7. The method for controlling the cracking prevention of the pier body in the high-cold freeze-thawing area according to claim 1, wherein the steam curing system comprises a heat preservation sealing system, a steam atomizing system and an intelligent temperature and humidity control system; the heat preservation sealing system adopts a novel multilayer heat preservation film, so that isolation and sealing between the pier body (4) and the surrounding environment can be realized; the intelligent temperature and humidity control system is a core part of a pier body (4) construction maintenance system and consists of a temperature and humidity controller, a sensor and a heating and humidifying system, and the temperature and humidity of a maintenance area are intelligently controlled and regulated by the controller; the steam atomization system introduces steam into the heat preservation system through a pipeline which is arranged according to the temperature change rule and the fluidity in the sealed space, and continuously conveys the steam.
8. The method for controlling the cracking prevention of the pier body in the high-cold freeze-thawing area according to claim 1, wherein when the mold is disassembled, the mold is disassembled from top to bottom, and a layer of mold plates are disassembled and covered simultaneously to immediately wrap geotextiles; the thickness of the geotextile is not less than 2mm, and the geotextile is bound and fixed every 2 m; the geotextile at the pier top is pressed on the geotextile at the pier side, and the lap joint length is not less than 20cm.
9. The method for controlling cracking prevention of pier bodies in high-cold freeze-thawing areas according to claim 1, wherein the foundation pit backfilling is carried out after the concrete reaches the design strength; backfilling with undisturbed soil and tamping; the foundation pit backfilling is needed to be symmetrically performed and the vibration is dense; the top surface should form an outward 2% slope after backfilling of the pit and no water accumulation should be formed.
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| CN116768557A (en) * | 2022-03-07 | 2023-09-19 | 江苏省建筑科学研究院有限公司 | Low-temperature-rise high-crack-resistance large-volume concrete, preparation method and application |
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| KR100832848B1 (en) * | 2007-06-01 | 2008-05-28 | 원용석 | Method for constructing pier and concrete permanent form applied to it |
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