Construction method of high-cold high-altitude gravity dam overhanging bracket concrete anti-cracking

Abstract

The application discloses a kind of high-cold high-altitude gravity dam cantilever bracket concrete anti-cracking construction methods, belong to the technical field of hydropower engineering construction.The method is based on pre-embedded cantilever beam, inclined strut, support scaffold and formwork system, sets up enclosure layer and thermal insulation layer on the outside of bracket to form local closed curing cavity;Bracket is divided into root, middle and end along the cantilever direction, and temperature and environmental monitoring points are laid out;Pre-cooling concrete is poured in layers and blocks, and according to the partition monitoring value, spray, insulation and wind opening degree are adjusted;After meeting the preset conditions, gradually open cavity and unload wind from the end to the root, and according to the order of end, middle and root, partition dismantling and subsequent maintenance are carried out.The application can reduce the water loss rate of cantilever bracket concrete surface and the temperature difference between inside and outside in high-cold high-altitude environment, slow down the effect of sudden cooling and drying, and inhibit the generation of early temperature cracks and drying shrinkage cracks.

Description

Technical Field

[0001] This invention relates to the field of gravity dam construction technology for hydropower stations, specifically to a method for preventing cracking of cantilevered corbel concrete in high-altitude and cold-climate gravity dams. Background Technology

[0002] In high-altitude and cold regions, the air is dry, solar radiation is strong, the temperature difference between day and night is large, and the wind speed fluctuates significantly. Cantilevered corbels have characteristics such as strong root restraint, large end exposure, and significant changes in structural thickness, which make the concrete surface prone to rapid water loss and make it difficult to balance the temperature difference between the interior and the surface, resulting in a high risk of early temperature cracks and drying shrinkage cracks.

[0003] Existing corbel construction schemes mainly focus on the erection of the load-bearing platform, the fixing of formwork, and the organization of pouring operations. However, there is still a lack of specific methods for preventing cracking of the corbel components themselves in high-altitude and cold environments, which involves "local microenvironment curing - gradual exposure - controlled formwork removal".

[0004] Existing construction methods have established seven core processes: "H-beam pre-embedding → scaffolding erection → scaffolding acceptance → rebar and embedded part installation → formwork assembly → surface acceptance and pouring → formwork and scaffolding dismantling." These methods employ a combined support system of "20a H-beam cantilever beams + coupler-type steel pipe scaffolding," 16℃ pre-cooled concrete, surface cooling with mist cannons, and green dense mesh netting enclosure, providing a solid engineering foundation for this invention. However, these measures have not yet been organized into a construction method scheme with crack prevention as its core and capable of independent protection. Summary of the Invention

[0005] To address the shortcomings of cantilever corbel concrete in harsh environments (strong winds, low humidity, large temperature differences) at high altitudes and cold regions, which are prone to early-stage temperature cracks and shrinkage cracks due to strong root constraints, large end exposure, and significant variations in structural thickness, this invention provides a crack-prevention construction method for cantilever corbel concrete in gravity dams at high altitudes and cold regions.

[0006] In a first aspect, the present invention provides a method for preventing cracking of concrete cantilever corbels in high-altitude and cold-climate gravity dams, comprising the following steps:

[0007] An insulation layer is covered on the outside of the corbel template, and an enclosure layer is set on the outside of the support system around the corbel. The insulation layer and the enclosure layer form a partially closed curing cavity that covers the outside of the corbel.

[0008] The cow leg is divided into a root constraint zone, a middle transition zone, and an end free zone along the cantilever direction, and monitoring points for monitoring temperature and the environment of the curing chamber are set up in each zone.

[0009] Temperature-controlled concrete was used to pour the corbels in layers and blocks, and the opening of the spray humidification, heat preservation coverage and windbreak layer were adjusted in conjunction with the monitoring values ​​of each zone during the pouring and curing stages.

[0010] After meeting the preset temperature difference and strength conditions, a gradual opening and air unloading process is implemented from the end free area to the root constrained area;

[0011] The demolding and subsequent maintenance are carried out in the order of the end free zone, the middle transition zone, and the root constraint zone.

[0012] Preferably, the outer side of the corbel is provided with a cantilever support system consisting of pre-embedded cantilever beams, diagonal braces and supporting scaffolding. The insulation layer covers the outer side of the corbel template, and the enclosure layer is set on the periphery of the support system. The insulation layer and the enclosure layer form the locally closed curing cavity.

[0013] Preferably, the monitoring points include temperature sensors embedded in the concrete, temperature sensors attached to the concrete surface, and temperature and humidity sensors and wind speed sensors installed in the curing chamber. Each sensor is independently deployed according to a zone and transmits data in real time.

[0014] Preferably, the partially enclosed curing cavity is composed of a protective net, a windbreak membrane, and an insulation layer covering the outside of the template. The windbreak membrane is located inside or outside the protective net and its opening degree can be adjusted in stages.

[0015] Preferably, the root constraint zone, the middle transition zone, and the end free zone are arranged sequentially and continuously along the cantilever direction of the corbel, and the set curing time of the root constraint zone is greater than that of the middle transition zone, and the set curing time of the middle transition zone is greater than that of the end free zone.

[0016] Preferably, the progressive cavity opening and unloading is carried out in two to five stages. After each stage of cavity opening, a stable observation period is set. Only after the monitoring values ​​of the current cavity opening area and the adjacent areas meet the preset safety threshold can the next stage of cavity opening be entered. The preset safety threshold includes the maximum internal and external temperature difference, the maximum cooling rate, the minimum relative humidity, and the maximum local wind speed limit corresponding to each zone.

[0017] Preferably, when any monitoring value exceeds the preset safety threshold, the opening or demolding operation of the corresponding partition and subsequent partitions is suspended, and the previous stage of heat preservation and moisture retention is restored. After the monitoring value falls back to the safe range, the decision on whether to continue the opening or demolding operation is reassessed.

[0018] Preferably, the temperature of the temperature-controlled concrete is controlled between 12°C and 18°C ​​when it is poured into the formwork, and the thickness of each layer in the layered and block-casting process is controlled between 30cm and 50cm.

[0019] Preferably, the spray humidification process is performed by a combination of a fog cannon and distributed spray pipes installed on the supporting scaffolding, wherein the fog cannon is used for large-scale cooling of the warehouse surface, and the distributed spray pipes are used for localized and precise humidification of each zone.

[0020] Preferably, the supporting scaffold is a coupler-type steel pipe scaffold, which is erected on pre-embedded I-beam cantilever beams and diagonal braces, with the angle between the diagonal braces and the cantilever beams being 30° to 60°.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] The construction method provided by this invention involves covering the outside of the corbel formwork with an insulation layer and setting up an enclosure layer on the outside of the support system, thereby forming a partially closed curing cavity between the two. This effectively blocks strong winds, low humidity, and drastic temperature differences in high-altitude and cold regions, reduces the rate of moisture evaporation from the concrete surface, and provides a controllable space for temperature and humidity regulation.

[0023] By dividing the corbel along the cantilever direction into a root restraint zone, a middle transition zone, and an end free zone, the differences in restraint degree and exposure conditions in different parts were identified, avoiding the problems of insufficient root curing or excessive end curing under a uniform curing method. Temperature and curing chamber environment monitoring points were set up in each zone, enabling real-time sensing of the internal and surface temperatures of the concrete in each area, as well as the humidity and wind speed within the chamber, providing data support for zoned control.

[0024] By using temperature-controlled concrete for layered and segmented pouring, and by adjusting the spray humidification, insulation coverage, and windbreak opening based on the monitoring values ​​of each zone during the pouring and curing stages, the peak heat of hydration and temperature gradient can be reduced, achieving dynamic control throughout the entire process from pouring to curing, and suppressing temperature difference cracks and drying shrinkage cracks.

[0025] After meeting the preset temperature difference and strength conditions, the cavity is opened and the air is unloaded gradually from the free zone at the end to the constrained zone at the root, so that the concrete surface environment gradually transitions from closed to the outside, avoiding sudden cooling and drying and sudden change in tensile stress caused by one-time cavity opening.

[0026] The formwork is removed and subsequently cured in sections according to the order of the end free zone, the middle transition zone, and the root constrained zone. This allows the weakest constrained area to release deformation first, and the strongest constrained area to be removed last, reducing the concentration of tensile stress in the root area during early-age stages. In summary, this invention can comprehensively reduce the risk of early cracking in cantilevered corbel concrete in high-altitude and cold environments. Attached Figure Description

[0027] Figure 1 This is a flowchart of the construction method steps of the present invention.

[0028] Figure 2 This is a schematic diagram of the overall structure of the dam body corbel of the present invention.

[0029] Figure 3 for Figure 2 A side view of the construction process of the cantilevered corbel in section A.

[0030] Figure 4 This is a schematic diagram of the construction layout from the frontal view of the cantilevered corbel of the present invention.

[0031] Figure 5 This is a schematic diagram of the partially sealed maintenance cavity of the cantilevered cow leg according to the present invention.

[0032] Figure 6 This is a schematic diagram of the cow leg zoning and monitoring point layout of the present invention.

[0033] Figure label:

[0034] 1-Dam body, 2-Corner, 3-Cantilevered I-beam, 4-Diagonal brace, 5-Supporting scaffold, 6-Formwork, 7-Insulation layer, 8-Enclosure layer, 9-Windbreak membrane, 10-Partially enclosed curing cavity, 11-Root constraint zone, 12-Middle transition zone, 13-End free zone, 14-Monitoring point. Detailed Implementation

[0035] The present invention will now be described in further detail with reference to specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0036] This embodiment provides a method for partial sealing and curing of the concrete cantilever corbel of a gravity dam in high-altitude and cold regions, as well as a progressive cavity-opening method for crack prevention. The project is located at an altitude of 3,500 meters, with an average annual temperature of 2.5℃, a maximum diurnal temperature difference of 25℃, an average annual relative humidity of 45%, and extreme wind speeds of up to 15 meters per second in winter.

[0037] Example 1

[0038] This explanation uses the cantilevered corbel 2 of a gravity dam in a high-altitude area as an example. Figures 1-6 As shown, the project is located at an altitude of 3,500 meters, with an average annual temperature of 2.5℃, a maximum diurnal temperature range of 25℃, an average annual relative humidity of 45%, and extreme wind speeds of up to 15 meters per second in winter.

[0039] Figure 3This is a schematic diagram of the construction structure for partial sealing and progressive opening for crack prevention in this invention. The corbel 2 and the dam are constructed synchronously. As shown in the diagram, 20a I-beams are pre-embedded in the upper dam body 1 concrete as cantilevered I-beam beams 3. These cantilevered I-beam beams 3 are arranged at 1.5-meter intervals along the length of the corbel 2, with a single beam length of 6.5 meters. Of this, 2.0 meters are embedded in the dam body 1, and 4.5 meters are exposed and cantilevered. The tail end of the cantilevered I-beam beam 3 is anchored to the dam body 1 concrete using 10mm diameter U-shaped round steel bars, with a single anchorage length of 40cm. Each cantilevered I-beam beam 3 is equipped with two U-shaped round steel bars. 20a I-beams are installed at the lower part of the cantilevered I-beam beam 3 as diagonal braces 4. The diagonal braces 4 are 4.5 meters long, with their upper end connected to the outer end of the cantilevered I-beam beam 3 and their lower end connected to the pre-embedded parts in the dam body 1. The angle between the diagonal brace 4 and the vertical plane is 45°. A coupler-type steel pipe support scaffolding 5 is erected above the cantilevered I-beam 3. The uprights of the support scaffolding 5 are spaced 1.2 meters apart, and the horizontal bars are spaced 1.5 meters apart. A protective netting, consisting of white safety netting and green dense mesh netting, is hung on the openable side of the scaffolding. An operable roller shutter-type windbreak membrane 9 is installed inside the dense mesh netting. The outer formwork 6 of the corbel 2 is a combined steel formwork 6. The outer side of the formwork 6 is covered with an insulation layer 7, which is an insulation blanket made of double-layer polyethylene foam material with a thickness of 3 cm. The cavity between the dense mesh netting, the windbreak membrane 9, the insulation blanket, and the formwork 6 together constitutes a partially enclosed curing cavity 10 covering the outer side of the corbel 2.

[0040] Depend on Figure 3-5 It can be seen that the outer side of the corbel 2 consists of the template 6 and the supporting scaffold 5 in sequence. The space between the template 6 and the scaffold is the partially enclosed curing cavity 10 on the outer side of the corbel 2. The partially enclosed curing cavity 10 is covered with an insulation blanket on the side closer to the template 6. The side of the supporting scaffold 5 closer to the curing cavity is the inner side, and the side farther away from the curing cavity is the outer side. The inner side of the scaffold is equipped with a windbreak membrane 9, and the outer side is equipped with a protective net.

[0041] In this embodiment, the windproof film 9 can also cover the top surface, and the opening can be adjusted from the side. Preferably, the scaffold board located at the bottom of the corbel 2 is also covered with a film in advance, so that the whole structure forms a sealed curing chamber.

[0042] like Figure 1 As shown, the construction method of the present invention includes the following core steps performed in sequence.

[0043] In step S1, the pre-embedded cantilever support and curing chamber are constructed according to the above structure. The internal net dimensions of the curing chamber are: 4.5 meters in length along the cantilever direction, 3.0 meters in width (matching the width of bracket 2), and a height ranging from 1.2 meters to 2.5 meters depending on the thickness of bracket 2. The degree of closure of the curing chamber is adjusted by the opening of the windbreak membrane 9, and can be controlled to be completely closed, semi-closed, or gradually opened.

[0044] like Figure 6As shown, in step S2, the corbel 2 is divided into three zones along the cantilever direction. The root restraint zone 11 is located 0 to 1.5 meters from the connection surface of the dam body 1; this zone is rigidly connected to the dam body 1 and has the strongest restraint. The middle transition zone 12 is located 1.5 to 3.0 meters from the connection surface of the dam body 1; this zone has a moderate degree of restraint. The end free zone 13 is located 3.0 to 4.5 meters from the connection surface of the dam body 1; this zone is the free end and has the largest exposed area. Monitoring points 14 are set up in each zone: two internal concrete temperature sensors are installed in each zone, buried at the center of the cross-section, with depths of 10 cm from the surface and the center of the cross-section, respectively; two concrete surface temperature sensors are installed, attached to the inner concrete surface of the formwork 6; and one temperature and humidity sensor and one wind speed sensor are installed in each zone within the curing chamber, installed on the inner side of the scaffold 20 cm from the concrete surface. Based on the design strength grade C40, the pouring volume of approximately 85 cubic meters, and external environmental parameters, control thresholds for each zone are set, as shown in the table below.

[0045] Table 1 Initial settings of control parameters for each zone

[0046]

[0047] In step S3, pre-cooled concrete is used for pouring. The concrete outlet temperature is controlled between 12℃ and 14℃, and the placement temperature is controlled between 14℃ and 16℃, with an average placement temperature of approximately 15℃. The concrete is pumped into the placement chamber and constructed in two layers: a lower construction layer and an upper construction layer. The lower construction layer corresponds to the lower part of bracket 2, approximately 0.8 meters, and the upper construction layer corresponds to the upper part, approximately 1.0 meter. Each construction layer is poured continuously in layers and blocks, with three blocks poured within each layer, each block approximately 1.0 meter wide. The thickness of each layer is controlled between 30 cm and 50 cm, preferably approximately 40 cm. During the pouring process, two mist cannons are placed above the placement chamber surface, each with an airflow of 15,000 cubic meters per hour and a mist particle size of less than 50 micrometers, for large-area cooling and humidification. Simultaneously, three distributed spray pipes are installed along the cantilever direction of the corbel 2 on the inner side of the scaffolding. The spray pipes are 20 mm diameter PVC pipes, with an atomizing nozzle installed every 50 cm. The nozzle flow rate is 5 liters per hour, used for localized and precise humidification. The fog cannon and spray pipes are operated in conjunction to maintain the relative humidity of the curing chamber surface above 85%, and the concrete surface temperature rises by no more than 5°C from the initial temperature. The opening of the windbreak membrane 9 is adjusted to the minimum, leaving only a gap of about 10 cm at the top for ventilation, and the local wind speed in the curing chamber is controlled to within 0.5 meters per second.

[0048] In step S4, after pouring, the formwork 6 and the curing chamber remain in working condition. During curing with the formwork in place, zoned linkage control is implemented according to the thresholds set in Table 1. When the temperature difference between the inside and outside of the root restraint zone 11 approaches 18℃, an additional 2cm thick insulation blanket is added outside the insulation blanket to reduce the temperature difference to below 12℃. When the relative humidity of the middle transition zone 12 is below 75%, the corresponding zone's spray pipes are automatically activated, spraying once every 10 minutes for 2 minutes each time, until the humidity rises back to above 85%. When the local wind speed in the end free zone 13 exceeds 2.5 meters per second, the opening of the windbreak membrane 9 is reduced or restored to a closed state, and the spraying frequency is increased simultaneously. If necessary, temporary windbreak measures are added outside the enclosure layer 8 to reduce the local wind speed inside the chamber to a preset safe range. The actual curing days for the root restraint zone 11 with the formwork in place are 14 days, for the middle transition zone 12 it is 10 days, and for the end free zone 13 it is 7 days. During the maintenance period, monitoring data were collected four times a day, at 6:00, 12:00, 18:00, and 24:00, recording the temperature difference between the inside and outside of each zone, the surface cooling rate, the relative humidity inside the cavity, and the wind speed, forming a maintenance log. The following is a set of typical monitoring data.

[0049] Table 2 Typical monitoring data on day 3 of curing with formwork

[0050]

[0051] In step S5, a gradual opening and unloading of the cavity is implemented. The concrete in the end free zone reaches 75% of its design strength on day 7, with an actual strength of 32.5 MPa. The internal and external temperature difference is less than 15°C for 12 consecutive hours, meeting the cavity opening conditions. First, a primary cavity opening is implemented in the end free zone. Specifically, the lower roller shutter of the windbreak membrane in this section is raised by 30 cm, and approximately 0.5 square meters of the bottom dense mesh netting in this section is removed, resulting in an opening area of ​​approximately 25% of the total area of ​​the end free zone. After 24 hours of stable observation, monitoring data shows that the surface cooling rate of the end free zone is 2.1°C per hour, the internal and external temperature difference is 12.5°C, the relative humidity is 75%, and the wind speed is 1.8 m / s. All indicators are within the preset safety range, thus proceeding to the secondary cavity opening. The secondary cavity opening involves completely rolling up the windbreak membrane in the end free zone and completely removing the dense mesh netting. Simultaneously, the lower roller shutter of the windbreak membrane in the middle transition zone is raised by 20 cm, resulting in an opening area of ​​approximately 20% of the total area of ​​the middle transition zone. After a second 24-hour stable observation, monitoring data showed that the surface cooling rate in the central transition zone was 2.0℃ per hour, the internal and external temperature difference was 14.2℃, the relative humidity was 80%, and the wind speed was 1.5 m / s, meeting the requirements. Subsequently, the third-stage opening process began, where the windbreak membrane in the central transition zone was completely rolled up and the dense mesh netting was fully removed. Simultaneously, the lower part of the windbreak membrane in the root constraint zone was raised by 15 cm, opening the cavity to approximately 15% of the total area of ​​the root constraint zone. After another 24-hour stable observation, monitoring data showed that the surface cooling rate in the root constraint zone was 1.5℃ per hour, the internal and external temperature difference was 15.1℃, the relative humidity was 85%, and the wind speed was 1.0 m / s, meeting the requirements. Finally, the fourth-stage opening process began, where the windbreak membrane in the root constraint zone was completely rolled up and the dense mesh netting was fully removed, completely opening the curing cavity and connecting it to the external environment. The entire gradual opening process lasted 4 days, completed in four stages, with a 24-hour stable observation period between each adjacent stage. If, at any stage, the surface cooling rate exceeds 3.0°C per hour, the internal and external temperature difference exceeds 20°C, or the relative humidity falls below 65%, the opening process is paused and the previous closed state is restored. The process is repeated once the conditions are met. In this embodiment, no pause was required.

[0052] After the progressive cavity opening was completed, the formwork was removed in sections. First, the side formwork in the free zone at the ends was removed. At the time of removal, the concrete strength was 38.2 MPa, and the concrete age was 9 days. After observing for 24 hours without cracks or abnormal deformation, the side formwork in the middle transition zone was removed. At this point, the concrete strength was 41.5 MPa, and the concrete age was 12 days. After another 24 hours of observation, the side formwork, bottom formwork, and local supports in the root restraint zone were removed. At this point, the concrete strength was 46.3 MPa, and the concrete age was 16 days. Immediately after removal, subsequent curing was implemented: the concrete surface was covered with two layers of damp burlap, and water was sprayed four times a day, at 8:00, 12:00, 16:00, and 20:00, with approximately 2 liters of water per square meter each time, keeping the surface continuously moist. Simultaneously, during windy or low-temperature periods (wind speed greater than 8 m / s or temperature below 0°C), a plastic film was added for wind protection and insulation. Curing continued until day 28, and the final concrete strength test value was 52.6 MPa, meeting the C40 design strength requirements. No temperature cracks or obvious shrinkage cracks were found during on-site inspection and ultrasonic testing.

[0053] In another implementation, relevant parameters can be adjusted for different engineering conditions. For more severe environments with altitudes above 4000 meters and average annual temperatures below 0°C, the pre-cooled concrete placement temperature can be reduced to 12°C, the curing days in the root constraint zone can be extended to 21 days, the number of progressive cavity opening stages can be increased to 5, and the observation period for each stage can be extended to 36 hours. The windbreak membrane can adopt an electric roller shutter structure, linked with the monitoring system, to achieve automatic graded opening and closing. Monitoring parameters can be expanded to include concrete maturity calculations and strain gauge readings. Cavity opening control conditions are automatically generated by a risk assessment model based on monitoring data. For example, a fuzzy logic controller can be used to comprehensively judge the coupling state of four parameters: temperature difference, cooling rate, humidity, and wind speed. When the comprehensive risk index is below 0.3, the next stage of cavity opening is allowed.

[0054] Table 3 Recommended values ​​of main construction parameters under different altitude conditions

[0055]

[0056] The pre-embedded cantilevered I-beams are embedded in the dam body and anchored with U-shaped round steel bars. The lower end of the diagonal brace is welded to the pre-embedded steel plate in the dam body, and the upper end is bolted to the outer end of the cantilevered I-beam. Coupler-type steel pipe scaffolding is erected above the cantilevered I-beams, with adjustable bases at the bottom of the uprights. Dense mesh netting is hung on the outside of the scaffolding, and a windproof membrane is placed inside the dense mesh netting and can be raised and lowered via a roller shutter. Insulation blankets cover the outside of the formwork, allowing direct contact between the formwork and the concrete surface. The curing chamber encloses the entire corbel, and monitoring sensors are arranged in corresponding positions within the chamber according to zones.

[0057] The specific embodiments of the present invention described above are also applicable to the concrete construction of cantilevered corbels, large-volume cantilever blocks, or similar strongly constrained locally extended components in factory buildings, gate piers, and other parts in high-altitude and cold environments. By constructing locally closed curing cavities, implementing differentiated control in three zones, multi-level progressive cavity opening and air unloading, and separating the formwork from the end to the root in a zoned demolding sequence, effective crack prevention of cantilevered corbel concrete in high-altitude and cold environments is achieved, with crack control significantly superior to traditional overall curing methods.

Claims

1. A method for preventing cracking of cantilever corbel concrete in high-altitude, cold-climate gravity dams, characterized in that... This includes the following steps performed in sequence: An insulation layer (7) is covered on the outside of the template (6) of the cow leg (2), and an enclosure layer (8) is set on the outside of the support system of the cow leg (2). A partially closed curing cavity (10) covering the outside of the cow leg (2) is formed between the insulation layer (7) and the enclosure layer (8). The cow leg (2) is divided into the root restraint zone (11), the middle transition zone (12) and the end free zone (13) along the cantilever direction, and monitoring points (14) are set up in each zone to monitor the temperature and the environment of the curing chamber. Temperature-controlled concrete was used to pour the corbel (2) in layers and blocks. During the pouring and curing stages, the opening of the spray humidification, heat preservation coverage and windbreak layer was adjusted in conjunction with the monitoring values ​​of each zone. After meeting the preset temperature difference and strength conditions, a gradual opening and air unloading process is implemented from the end free area (13) to the root constraint area (11); The demolding and subsequent maintenance are carried out in the order of the end free zone (13), the middle transition zone (12), and the root constraint zone (11).

2. The construction method according to claim 1, characterized in that, The outer side of the corbel (2) is provided with a cantilever support system consisting of a pre-embedded cantilever beam, a diagonal brace (4) and a supporting scaffold (5). The insulation layer (7) covers the outer side of the template (6) of the corbel (2). The enclosure layer (8) is set on the periphery of the support system. The insulation layer (7) and the enclosure layer (8) form the local closed curing cavity (10).

3. The construction method according to claim 2, characterized in that, The partially enclosed curing cavity (10) is composed of a protective net, a windbreak membrane (9) and a heat insulation layer (7) covering the outside of the template (6). The windbreak membrane (9) is located on the inside or outside of the protective net 8, and the opening degree of the windbreak membrane (9) can be adjusted in stages.

4. The construction method according to claim 1, characterized in that, The monitoring point (14) includes a temperature sensor embedded in the concrete, a temperature sensor attached to the concrete surface, and a temperature and humidity sensor and a wind speed sensor installed in the curing chamber. Each sensor is independently deployed according to the zone and transmits data in real time.

5. The construction method according to claim 1, characterized in that, The root constraint area (11), the middle transition area (12) and the end free area (13) are arranged sequentially along the cantilever direction of the cow leg (2), and the set curing time of the root constraint area (11) is greater than that of the middle transition area (12), and the set curing time of the middle transition area (12) is greater than that of the end free area (13).

6. The construction method according to claim 1, characterized in that, The progressive cavity opening and unloading is carried out in two to five stages. After each stage of cavity opening, a stable observation period is set. Only after the monitoring values ​​of the current cavity opening area and the adjacent areas meet the preset safety thresholds can the next stage of cavity opening be entered. The preset safety thresholds include the maximum internal and external temperature difference, the maximum cooling rate, the minimum relative humidity, and the maximum local wind speed limit for each zone.

7. The construction method according to claim 1, characterized in that, When any monitoring value exceeds the preset safety threshold, the opening or demolding operation of the corresponding zone and subsequent zones is suspended, and the previous stage of heat preservation and moisture retention is restored. After the monitoring value falls back to the safe range, the decision on whether to continue the opening or demolding operation is reassessed.

8. The construction method according to claim 1, characterized in that, The temperature of the temperature-controlled concrete is controlled between 12°C and 18°C ​​when it is poured into the formwork, and the thickness of each layer in the layered and block-casting process is controlled between 30cm and 50cm.

9. The construction method according to claim 1, characterized in that, The spray humidification process is performed by a combination of a fog cannon and a distributed spray pipe installed on the supporting scaffold (5). The fog cannon is used for large-scale cooling of the warehouse surface, and the distributed spray pipe is used for localized and precise humidification of each zone.

10. The construction method according to claim 2, characterized in that, The supporting scaffold (5) adopts a coupler-type steel pipe scaffold, which is erected on the pre-embedded I-beam cantilever beam and diagonal brace (4). The angle between the diagonal brace (4) and the cantilever beam is 30° to 60°.

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