CN115455531A - Method for calculating internal and external temperature difference of underground hydraulic coal ash-doped concrete slab - Google Patents
Method for calculating internal and external temperature difference of underground hydraulic coal ash-doped concrete slab Download PDFInfo
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Abstract
The invention provides a method for calculating the internal and external temperature difference of an underground hydraulic coal ash-doped concrete slab, which comprises the following steps: step 1, analyzing and obtaining data; step 2, calculating the inside and outside temperature difference delta T of the underground hydraulic blended fly ash concrete slab nw ＝1.55t m +13.03α+7.14H+0.46C+0.96T 0 +0.38T g ‑0.56T a +0.02H×C‑0.10H×T 0 ‑0.01H×T g ‑0.02T 0 ×T g -24.18, wherein: t is t m The template removal time; alpha is the blending amount of the fly ash; h is the thickness of the concrete slab; c is the strength grade; t is 0 The concrete pouring temperature is adopted; t is a unit of g The water temperature effect value is the water age water temperature effect value; t is w The temperature of water is the temperature of water; t is a The air temperature value in the underground hydraulic cavern in the concrete slab casting period is obtained; step 3, determining the concrete lining of underground hydraulic engineering doped with fly ashAn internal and external temperature difference tolerance; and 4, analyzing and determining the heat preservation measures of the closed hole in winter.
Description
Technical Field
The invention belongs to the technical field of concrete temperature crack control, and particularly relates to a calculation method for the internal and external temperature difference of an underground hydraulic fly ash-doped concrete slab.
Background
The temperature difference between the inside and the outside refers to the difference between the highest temperature inside the concrete and the surface temperature of the concrete as defined in the design Specification for controlling the temperature of concrete dams (NB/T35092-2017). Concrete with different structures and different admixtures such as coal ash has obvious heat insulation temperature rise and difference of hydration process, which can cause obvious difference of temperature difference inside and outside the concrete.
Large-volume concrete such as a gravity dam, an arch dam and the like is embedded with a cooling water pipe to be cooled by water, and cooling water or low-temperature river water is introduced at the initial stage to reduce the highest temperature of the concrete; in the middle stage, river water can be introduced for cooling, and the temperature difference between the inside and the outside can be controlled. 8.1.5 regulations in design Specifications for controlling temperature of concrete dams (NB/T35092-2017)' analysis of stress of surface concrete and design of surface heat preservation should be carried out according to local climatic conditions, and allowable temperature difference between the inside and the outside of concrete is proposed. The stress analysis and surface heat preservation design of mass concrete such as concrete dams, and the like, are complicated due to the complex construction process, structure and temperature boundary conditions and the very complicated temperature evolution process, and belong to the problem of unstable temperature field. Thus, in article 6.4.2 it is clear that the "unstable temperature field can be calculated using the finite element method or the differential method, which can be calculated according to the method of appendix C of the present specification". The method of appendix C, which is also based on the heat transfer equation, is calculated by simplifying the boundary conditions etc. and using the difference method with the help of empirical parameters. Therefore, each calculation method is very complicated, and experimental studies such as concrete performance and the like need to be carried out to provide parameters.
The lining is a structure (figure 1) widely adopted by underground hydraulic engineering, and the relevant regulation and regulation of the underground hydraulic engineering (hydraulic tunnel, underground factory building and the like) has no regulation on the control of the internal and external temperature difference of lining concrete. For the opening section (or the section from the closed heat preservation door to the opening section), surface heat preservation design calculation is generally carried out according to large-volume concrete such as dams and the like. For the lining concrete in the underground tunnel, because the temperature in the tunnel is small relative to the amplitude of the natural environment, surface covering or wrapping heat preservation is usually not adopted, so that the research on the control of the temperature difference between the inside and the outside of the lining concrete in the tunnel or the design calculation is not available so far. However, like large-volume concrete, the internal and external temperature difference is still an important factor for generating temperature cracks (especially early surface cracks), and the lining thickness is small, and the surface geometric temperature gradient generated by the internal and external temperature difference is particularly large, so that the internal and external temperature difference is a main reason for generating the early surface cracks. Water cooling or other measures are adopted, so that the highest internal temperature is reduced, and the internal and external temperature difference is also reduced.
Therefore, the internal and external temperature difference control research is urgently needed for the underground hydraulic engineering fly ash-doped concrete lining concrete, and a simple, high-precision and rapid internal and external temperature difference calculation method is provided for workers to rapidly use for internal and external temperature difference control or winter cave closure heat preservation design on site.
Disclosure of Invention
The invention aims to provide a calculation method for the internal and external temperature difference of an underground hydraulic coal ash-doped concrete plate, which is beneficial to optimally controlling the temperature crack of the underground hydraulic coal ash-doped concrete plate and quickly carrying out internal and external temperature difference control or winter closed hole heat preservation design.
In order to achieve the purpose, the invention adopts the following scheme:
as shown in fig. 2, the invention provides a method for calculating the temperature difference between the inside and the outside of an underground hydraulic coal ash-doped concrete slab, which is characterized by comprising the following steps:
step 2, calculating the inside and outside temperature difference delta T of the underground hydraulic doped fly ash concrete slab according to the data obtained in the step 1 nw (℃)：
△T nw ＝1.55t m +13.03α+7.14H+0.46C+0.96T 0 +0.38T g -0.56T a +0.02H×C-0.10H×T 0 -0.01H×T g -0.02T 0 ×T g -24.18 (equation 1)
In the formula: t is t m A formwork removal time (d); alpha is the blending amount of the fly ash, for example, alpha = if the blending amount is 20 percent0.2; h is the thickness (m) of the concrete slab; c is the design age strength grade (MPa) of the fly ash concrete slab 90d, such as C 90 40, then C =40; t is 0 Concrete pouring temperature (DEG C); t is g The water temperature effect value (DEG C) in the water passing age and T g ＝35-T w ，T w Temperature of water passage (taking T when water passage cooling is not performed) w ＝35℃)；T a The temperature value (DEG C) in the underground hydraulic cavern in the concrete slab casting period is shown;
step 3, determining the allowable value [ Delta T ] of the temperature difference between the inside and the outside of the underground hydraulic blended fly ash concrete lining nw 】；
Step 4. According to Delta T nw And [ Delta T ] nw Analysis and determination of winter sealing hole heat preservation measures.
Preferably, the method for calculating the internal and external temperature difference of the underground hydraulic fly ash-doped concrete slab provided by the invention can also have the following characteristics: in the step 1, relevant data of underground hydraulic engineering fly ash doped concrete lining temperature crack control are analyzed, and the method comprises the following steps: collecting and analyzing data such as underground hydraulic engineering lining project outline, hydrological weather and the like; collecting and analyzing concrete temperature control design technical requirement data.
In step 2, it must be pointed out that when the lining concrete adopts the strength grade designed for the 28-day age, the strength grade designed for the 90-day age needs to be converted according to the specification; if the curtain is adopted for heat preservation in the construction period, the air temperature of the underground cavern is increased, and T is a The increased air temperature in the cavern should be used. In addition, the thickness of the lining is generally small, the water-cooling water pipes are arranged in a single row, namely, each formula is suitable for the situation that the water-cooling water pipes are arranged in a single row. Because the lining concrete in the underground tunnel does not adopt covering heat preservation and the temperature of the surface concrete drops and rapidly reaches the air temperature in the tunnel, the surface temperature of the concrete after the form removal is similar to the air temperature in the tunnel, namely the air temperature T in the tunnel in the concrete pouring period a . The calculated internal and external temperature difference is slightly larger, and the calculated value is safer to control.
Preferably, the method for calculating the internal and external temperature difference of the underground hydraulic fly ash-doped concrete slab provided by the invention can also have the following characteristics: if step (ii)1, the design allowable internal and external temperature difference is provided in the obtained data, and then [ Delta T ] is obtained in step 3 nw The design allows the temperature difference between the inside and the outside; if the allowable internal and external temperature difference is not designed and the relevant specifications of the hydraulic and hydroelectric engineering do not stipulate the allowable internal and external temperature difference, then the value [ Delta T ] is obtained nw -25 ℃; for the particularly important flood discharging tunnel, the allowable internal and external temperature difference [ Delta T ] can be obtained for the concrete slab with the thickness far smaller than the plane size (the thickness is smaller than 20 percent of the plane size, and the concrete slab belongs to a strong constraint area) by referring to the experience of hydraulic and hydroelectric engineering nw 】＝20～22℃。
Preferably, the method for calculating the internal and external temperature difference of the underground hydraulic fly ash-doped concrete slab provided by the invention can also have the following characteristics: step 4 comprises the following substeps:
step 4.1 comparative analysis of internal and external temperature difference Delta T nw Whether or not the allowable value [ Delta T ] is exceeded nw 】；
Step 4.2 if Δ T nw ≤【△T nw The heat preservation measure for closing the hole opening is not needed; if Δ T nw ＞【△T nw And C, sealing the hole and preserving heat.
Preferably, the method for calculating the internal and external temperature difference of the underground hydraulic fly ash-doped concrete slab provided by the invention can also have the following characteristics: in step 4.2, if [ Delta T ] nw 】＜△T nw ≤【△T nw At +2.0 ℃, a simple curtain-hanging heat preservation measure for closing the opening is adopted, and ventilation holes or gaps are allowed to exist; if Δ T nw ＞【△T nw And +2.0 ℃, a strict hole opening sealing heat preservation measure is adopted, and a ventilation gap is basically not allowed to exist.
Preferably, the method for calculating the internal and external temperature difference of the underground hydraulic fly ash-doped concrete slab provided by the invention can also have the following characteristics: as shown in fig. 3, the simple curtain-type hole-closing thermal insulation measure is a hole-closing manner in which a hole is covered with thin geotextile, plastic film and the like with small thickness in a hanging manner, and the combination of the strips/blocks is not tight, so that a ventilation hole or a gap exists; as shown in fig. 4, the strict sealing hole insulation measure means that a thick insulation quilt, a cotton felt and the like are adopted to strictly fix the whole sealing hole, and the sealing structure forms a whole without ventilation gaps.
In addition, the step 2 is used for calculating the inside and outside temperature difference Delta T of the underground hydraulic fly ash doped concrete slab nw The reliability of (equation 1) is confirmed by the following method: taking a domestic large hydraulic tunnel as an example, a three-dimensional finite element method is adopted to carry out temperature and temperature stress simulation calculation on 175 schemes of different thicknesses, different strength grades and different fly ash mixing amount of lining concrete on the side wall of the tunnel-type section under the conditions of different pouring temperatures, different template dismantling times and different water cooling temperatures, the temperature control anti-cracking effect and the internal and external temperature difference of the lining concrete in the whole process are collated and analyzed and listed in the table 1, then statistical analysis is carried out on the data, and the calculation result is confirmed to be basically consistent with the actual measurement condition.
TABLE 1 simulation calculation result of inside and outside temperature difference of lining concrete of side wall with urban door opening-shaped section
Action and Effect of the invention
The invention relates to a method for calculating the internal and external temperature difference of an underground hydraulic coal ash-doped concrete slab, which firstly provides a high-precision scientific calculation method suitable for the internal and external temperature difference of the underground hydraulic coal ash-doped concrete slab, calculates the internal and external temperature difference according to factors such as the template dismantling time, the coal ash doping amount, the thickness and the strength of a lining structure, the pouring temperature, water cooling and water temperature thereof, the internal and external temperature in a hole in the pouring period and the like, and quickly determines the heat preservation measures of a closed hole opening required to be taken in low-temperature seasons based on the comparative analysis of the internal and external temperature difference allowable values.
Drawings
FIG. 1 is a sectional view (unit: m) of a gate-opening type lining structure of a hydraulic tunnel according to the present invention;
FIG. 2 is a flow chart of a method for calculating the internal and external temperature difference of a hydraulic blended fly ash concrete slab in the ground according to the invention;
FIG. 3 is a schematic view of a simple insulation structure for sealing a hole in winter to insulate heat and prevent cross wind according to the present invention;
FIG. 4 is a schematic view of a strictly closed hole insulation structure according to the present invention;
FIG. 5 is a sectional view of a 1.0m thick lining structure of an upper flat section of a white crane beach spillway tunnel according to the present invention;
FIG. 6 is a sectional view of a lining structure with a thickness of 2.5m on the upper flat section of the flood discharging tunnel of the white crane beach according to the present invention.
Detailed Description
The concrete embodiment of the method for calculating the internal and external temperature difference of the underground hydraulic fly ash doped concrete slab related to the invention is explained in detail below by taking concrete lining at different parts of a flood discharge tunnel project of a hydropower station of a white crane beach as an example with reference to the attached drawings.
< temperature control data of concrete lining for flood discharge tunnel engineering of white crane beach hydropower station >
The installed capacity of the white crane beach hydropower station is 16000MW, and is the junction project of the 2 nd hydropower station (next to the three gorges) all over the world. The energy-saving water diversion and power generation system is composed of main buildings such as a barrage, a flood discharge and energy dissipation building, a water diversion and power generation system and the like. The flood discharge facility comprises 6 surface holes of a dam, 7 deep holes and 3 flood discharge tunnels on the left bank. 3 flood discharge holes are arranged on the left bank, a non-pressure flood discharge hole type is adopted, and each flood discharge hole type consists of a water inlet (a gate chamber), a non-pressure gentle slope section, a dragon falling tail section and an outlet trajectory flip bucket, a 1# and a 2# flood discharge hole dragon falling tail reverse arc is directly connected with the trajectory flip bucket, a 3# hole is limited by terrain conditions, and a lower horizontal section with the gradient of 8% is connected with the tail end of the reverse arc and then connected with the outlet trajectory flip bucket.
The tunnel body section of the flood discharge tunnel comprises a flood discharge tunnel non-pressure section and a flood discharge tunnel falling tail section, which are all of an urban portal cross section and are divided into four basic lining types with the thickness of 1.0m, 1.2m, 1.5m and 2.5m according to the characteristics of different lining thicknesses, surrounding rocks and the like. The maximum allowable temperature for the flood tunnel lining concrete design is shown in table 2.
Table 2 unit of maximum temperature allowed during construction of flood tunnel lining concrete: c
| Engineering site | 5-9 months | 3. Months 4, 10 and 11 | 12. 1, 2 months |
| Upper flat section 1.0m | 38 | 36 | 34 |
| Upper flat section 1.5m | 40 | 38 | 36 |
| Upper flat section 2.5m | 42 | 40 | 38 |
| Dragon falling tail 1.2m | 40 | 38 | 36 |
| Dragon falling tail 1.5m | 42 | 40 | 38 |
Carry out temperature control to the concrete at the overall process of concrete placement and maintenance, avoid the concrete fracture, the design requirement temperature control measure includes:
(1) The mixing proportion of the concrete is optimized, and the crack resistance of the concrete is improved.
(2) Reasonably arranging concrete construction procedures and construction progress and striving to improve the construction management level.
(3) And controlling the highest temperature in the concrete. The effective measures comprise the reduction of the concrete pouring temperature, the reduction of the hydration heat temperature rise of the cementing material, the initial water supply and the like. And (3) the water cooling time is required to reach the surface temperature of the concrete to the air temperature of the tunnel, and generally 10-20 days is required. Controlling the pouring temperature of the lining concrete to be 20 ℃ within 4-9 months; the temperature of 10 months to the next year and 3 months is 18 ℃. The concrete transporting tool should have heat insulation and sun shading measures, so that the exposure time of concrete is shortened, and the temperature rise in the concrete transporting and pouring process is reduced. Concrete pouring in high-temperature time is avoided as much as possible, and pouring in low-temperature seasons, morning and evening and night with low air temperature is fully utilized.
< embodiment I > calculation of internal and external temperature difference of lining concrete with thickness of 1.0m on upper flat section of flood discharge tunnel poured in summer
Concrete is lined on the upper flat section of the flood discharge tunnel, the lining with the thickness of 1.0m is arranged in the surrounding rock area of type II, annular construction parting joints are arranged at intervals of 12m along the axial direction of the flood discharge tunnel on the cross section of the shape of the urban portal, and the lining structure is adoptedThe bottom plate and the side wall are C 90 40 low heat concrete with crown of C 90 30 low heat concrete, doped with 25% fly ash, as shown in fig. 5. Pouring concrete by stages 3: side walls, a rear arch and a bottom plate. The basic data of temperature control are the same as above. And (5) moisturizing and maintaining for 90 days by adopting normal-temperature tap water, and introducing water for cooling to control the internal temperature of the concrete.
According to the temperature control data, a construction unit plans a lining concrete pouring temperature control measure: summer T 0 Pouring at 20 ℃ T w =22 deg.C (calculate T) g Cooling with water at 35-22=13 deg.C for 10d, and removing mould time t m =3d. The temperature in the tunnel chamber is 14-26 ℃ per year under the condition of heat preservation without a closed tunnel opening according to the monitoring data of the temperature in the diversion tunnel chamber.
As shown in fig. 2, the method for calculating the internal and external temperature difference of the underground hydraulic blended fly ash concrete lining provided by this embodiment includes the following steps:
Step 2, calculating the inside and outside temperature difference Delta T of the underground hydraulic blended fly ash concrete lining nw Pouring H =1.0m, side wall C =40MPa and T in summer 0 ＝20℃、T g ＝13℃、t m Δ T is calculated by substituting =3d, ta =26 ℃ into (formula 1) nw ＝12.32℃。
Step 3, determining the allowable value [ Delta T ] of the temperature difference between the inside and the outside of the underground hydraulic blended fly ash concrete lining nw [ MEANS FOR solving PROBLEMS ] is provided. Because the design does not provide the allowable internal and external temperature difference, the white crane beach flood discharge tunnel belongs to a particularly important project, and the allowable internal and external temperature difference [ Delta T ] is taken according to the step 3 nw 】＝20～22℃。
And 4, analyzing and providing required heat preservation measures. Due to the calculation of DeltaT nw =12.32 ℃, less than [ Delta T ] nw =20 to 22 ℃. Due to the fact thatHere, 1.0m thick side wall C of flood discharge tunnel is poured in summer 90 40 concrete lining does not require insulation.
< example two > calculation of inside and outside temperature difference of lining concrete with 2.5m thickness in upper flat section of flood discharge tunnel poured in winter
The upper flat section of the flood discharge tunnel is lined with concrete, the V-type surrounding rock area is lined with concrete in the thickness of 2.5m, the urban portal section is provided with annular construction joints every 12m along the axial direction of the flood discharge tunnel, and the bottom plate and the side wall of the lining structure are C 90 40 low heat concrete with crown of C 90 30 low heat concrete, doped with 25% fly ash, as shown in fig. 6. Pouring concrete by stages 3: side walls, a rear arch and a bottom plate. The basic data of temperature control are the same as above. And (5) moisturizing and maintaining for 90 days by adopting normal-temperature tap water, and introducing water for cooling to control the internal temperature of the concrete.
According to the temperature control data, a construction unit plans a lining concrete pouring temperature control measure: winter T 0 Pouring at 18 ℃ without water cooling to calculate T g =0.0 ℃, and the mold stripping time t m =3d. The temperature in the tunnel chamber is 14-26 ℃ per year under the condition of heat preservation without a closed tunnel opening according to the monitoring data of the temperature in the diversion tunnel chamber.
As shown in fig. 2, the method for calculating the temperature difference between the inside and the outside of the underground hydraulic engineering doped fly ash concrete lining provided by this embodiment includes the following steps:
Step 2, calculating the inside and outside temperature difference Delta T of the underground hydraulic blended fly ash concrete lining nw Pouring 2.5m lining at 18 ℃ 2 months in winter, cooling without water, H =2.5m, side wall C =40MPa, T 0 ＝18℃、T g ＝0.0℃、t m ＝3d、T a Substituting the temperature of =14 ℃ into the formula (1) to calculate Delta T nw ＝26.92℃。
Step 3, determining the allowable value [ Delta T ] of the temperature difference between the inside and the outside of the underground hydraulic blended fly ash concrete lining nw [ solution ] A. Because the design does not provide allowable internal and external temperature difference, the white crane beach spillway tunnel belongs to a particularly important project, and the allowable internal and external temperature difference [ Delta T ] is taken according to the step 3 nw 】＝20～22℃。
And 4, analyzing and providing required heat preservation measures. Due to the calculation of DeltaT nw =26.92 ℃, is greater than [ Delta T ] nw 26.92-22 =4.92 ℃, belonging to Δ T nw ＞【△T nw And +2.0 ℃, the figure 4 is adopted in low-temperature seasons to strictly seal the hole mouth for heat preservation.
By combining the calculation and analysis, the lining side wallboard concrete with small structural thickness is poured in summer, the air temperature in the cavern is high, and the internal and external temperature difference is small; and in winter, the lining concrete with large thickness is poured, the temperature in the cavern is low, the temperature difference between the inside and the outside is large, and the heat preservation of the opening of the cavern needs to be performed in low-temperature seasons. For the upper flat section of the flood discharge tunnel, strict hole opening sealing heat preservation measures in a figure 4 need to be adopted.
In actual engineering, lining concrete at an upper flat section (namely, an entrance to a cave) of a flood discharging cave of a white crane beach is poured at 18 ℃ in summer and is kept at 15 ℃ in winter, the cave is strictly sealed and kept at a temperature according to a graph shown in a figure 4, the highest temperature and the maximum internal surface temperature difference in the concrete are both greatly reduced, the temperature in the cave is obviously improved in winter, and the temperature in the cave is actually measured at the lowest 18 ℃ in winter, so that the effect of no temperature crack of the lining concrete is realized (the temperature and temperature crack control effect is detailed and shown in the Yangxian, the section of Suohui, the shaking of the royal sea, the Yang union, the Kangxu rising, and the intelligent closed-loop control research on the moisture preservation and maintenance of the concrete [ J ]. The Qinghua university notice (Nature science edition), 2021,61 (07): 671-680 ]. The calculation analysis result is consistent with the actual engineering situation.
The above embodiments are merely illustrative of the technical solutions of the present invention. The method for calculating the temperature difference between the inside and the outside of the underground hydraulic fly ash-mixed concrete slab is not limited to the contents described in the above embodiments, but is subject to the scope defined by the claims. Any modification, supplement or equivalent replacement by a person skilled in the art on the basis of this embodiment is within the scope of the invention as claimed in the claims.
Claims (5)
1. The method for calculating the internal and external temperature difference of the underground hydraulic doped fly ash concrete slab is characterized by comprising the following steps of:
step 1, analyzing and obtaining related data of temperature crack control of an underground hydraulic doped fly ash concrete lining;
step 2, calculating the inside and outside temperature difference delta T of the underground hydraulic doped fly ash concrete slab according to the data obtained in the step 1 nw ：
△T nw ＝1.55t m +13.03α+7.14H+0.46C+0.96T 0 +0.38T g -0.56T a +0.02H×C-0.10H×T 0 -0.01H×T g -0.02T 0 ×T g -24.18 (equation 1)
In the formula: t is t m Removing time for the template; alpha is the blending amount of the fly ash; h is the thickness of the concrete slab; c, designing age strength grade for the fly ash-doped concrete slab 90 d; t is 0 The concrete pouring temperature; t is a unit of g The water temperature effect value is the water age water temperature effect value; t is a The air temperature value in the underground hydraulic cavern in the concrete slab casting period is obtained;
step 3, determining the allowable value [ Delta T ] of the temperature difference between the inside and the outside of the underground hydraulic blended fly ash concrete lining nw 】；
Step 4. According to Delta T nw And [ Delta T ] nw Analysis and determination of winter sealing hole heat preservation measures.
2. The method for calculating the internal and external temperature difference of the underground hydraulic fly ash-doped concrete slab according to claim 1, wherein the method comprises the following steps:
wherein, if the data obtained in step 1 provides the design allowable internal and external temperature difference, then [ Delta T ] is obtained in step 3 nw The design allows the temperature difference between the inside and the outside; if the allowable internal and external temperature difference is not designed and the relevant specifications of the hydraulic and hydroelectric engineering do not stipulate the allowable internal and external temperature difference, then the value [ Delta T ] is obtained nw -25 ℃; for particularly important projects, and for concrete slabs with a thickness less than 20% of the plane dimension, a certain internal and external temperature difference [ Delta T ] is taken nw 】＝20～22℃。
3. The method for calculating the internal and external temperature difference of the underground hydraulic fly ash-doped concrete slab according to claim 1, wherein the method comprises the following steps:
wherein, step 4 comprises the following substeps:
step 4.1 comparative analysis of internal and external temperature difference Delta T nw Whether or not the allowable value [ Delta T ] is exceeded nw 】；
Step 4.2 if Δ T nw ≤【△T nw The heat preservation measure for closing the hole opening is not needed; if Δ T nw ＞【△T nw Closing the hole and preserving heat.
4. The method for calculating the internal and external temperature difference of the underground hydraulic fly ash-doped concrete slab according to claim 1, wherein the method comprises the following steps:
wherein, in step 4.2, if [ Delta T ] nw 】＜△T nw ≤【△T nw At +2.0 ℃, a simple curtain-hanging heat preservation measure for closing the opening is adopted, and ventilation holes or gaps are allowed to exist; if Δ T nw ＞【△T nw And +2.0 ℃, a strict hole opening sealing heat preservation measure is adopted, and a ventilation gap is basically not allowed to exist.
5. The method for calculating the internal and external temperature difference of the underground hydraulic fly ash-doped concrete slab according to claim 4, wherein the method comprises the following steps:
the simple curtain-hanging hole-sealing heat-insulating measure is a hole-sealing mode that a hole is fully covered with geotextile and plastic films with small thicknesses in a hanging mode, and all the geotextile and the plastic films are not tightly combined, so that ventilation holes or gaps exist;
the strict hole sealing heat preservation measure is that a thick heat preservation quilt and a cotton felt are adopted to strictly fix a sealing hole mode of the integral sealing hole, a sealing structure forms an integral body, and no ventilation gap exists.
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