CN110188464B - Method for determining water cooling control curve in concrete arch dam construction period - Google Patents
Method for determining water cooling control curve in concrete arch dam construction period Download PDFInfo
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- CN110188464B CN110188464B CN201910459949.0A CN201910459949A CN110188464B CN 110188464 B CN110188464 B CN 110188464B CN 201910459949 A CN201910459949 A CN 201910459949A CN 110188464 B CN110188464 B CN 110188464B
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- 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
- C04B40/0075—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability making use of a decrease in temperature
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02B—HYDRAULIC ENGINEERING
- E02B7/00—Barrages or weirs; Layout, construction, methods of, or devices for, making same
- E02B7/02—Fixed barrages
- E02B7/04—Dams across valleys
- E02B7/08—Wall dams
- E02B7/12—Arch dams
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
- G06F30/23—Design optimisation, verification or simulation using finite element methods [FEM] or finite difference methods [FDM]
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Abstract
The invention belongs to the technical field of dam safety control, and particularly relates to a method for determining a water cooling control curve in a concrete arch dam construction period, which comprises the following steps: determining the cooling time of the pouring bin; determining the stress development process of the concrete, wherein the ratio of the strength to the stress in the stage from the highest temperature to the arch sealing target temperature is required to be a fixed value or is linearly adjusted, and the value is required to meet the specification requirement; a simulation method is adopted to inversely calculate a dam temperature change curve according to a stress curve, and the curve ensures that the ratio of the strength to the stress is constant or linearly changed in the cooling process; by adopting the curve and combining intelligent water supply, intelligent temperature control is realized. The invention avoids the temperature rise phenomenon in the water cut-off stage caused by the current three-stage water supply mode, reduces the fluctuation degree of the concrete temperature stress and the anti-cracking safety coefficient, and is beneficial to temperature control and anti-cracking control.
Description
Technical Field
The invention belongs to the technical field of dam safety control, and particularly relates to a method for determining a water cooling control curve in a concrete arch dam construction period.
Background
Temperature control anti-cracking is an important task in the construction process of the arch dam and is mainly realized through various temperature control measures. The temperature control measures specifically comprise concrete precooling, surface heat preservation, water cooling and other modes. The precooling of the concrete means that one or more materials in the concrete raw materials are cooled, so that the pouring temperature is reduced, the maximum temperature of the dam is further reduced, and under the condition of certain arch sealing temperature, the temperature load and the temperature stress are correspondingly reduced. The concrete precooling measures mainly include water cooling, air cooling, vacuum vaporization and the like. Surface heat preservation is an effective measure for preventing external temperature from flowing backwards or surface temperature difference from being too large. The water cooling is the most main temperature control measure, and is characterized in that a large number of cooling water pipes are arranged according to a certain height interval and a certain horizontal interval in the concrete pouring process of the dam, and heat is taken out by controlling the water temperature and the flow of the water, so that the temperature change process of the concrete is controlled, the stress control is realized, and the anti-cracking target is achieved.
The early stage concrete pouring is only carried out with one stage of water supply, after the concrete reaches a certain age, the water supply is cooled to the arch sealing temperature, the arch sealing grouting is carried out, and the later stage gradually develops into two-stage water supply and three-stage water supply. The first-stage cooling is mainly used for reducing the temperature peak value formed by the hydration heat of the concrete, the water is introduced in the middle stage to prevent the temperature from rising back and further reduce the temperature, and the water is introduced in the second stage before joint grouting, so that the concrete temperature is mainly reduced to the arch sealing temperature. However, the method has defects in temperature control, particularly in the stage of water cut-off and temperature control during two-stage cooling, temperature rise is easy to occur, the difficulty in keeping the temperature at a constant level is high, and the temperature drop amplitude in the later stage is increased; meanwhile, the stress curve is not smooth, large fluctuation exists, the concrete crack resistance safety coefficient is high and low, and the water cooling and crack resistance are safe and unfavorable, so that further improvement is needed.
The ideal temperature control curve proposed by Liu Youzhi in the patent is an ideal temperature control curve model which is obtained by researching temperature fields and temperature stress distribution rules of various dam types and performing simulation calculation on the basis of the existing specifications and temperature control practical experience, wherein the ideal temperature control curve model has the minimum temperature stress under the same temperature control standard condition. Because the influence factors of the temperature stress of dam concrete are numerous, including structural characteristics, constraint degree, pouring temperature, heat preservation measures, water distribution, material heating value and speed, environmental conditions and the like, the temperature stress of each position of each bin is different, and an ideal temperature control curve model with the minimum temperature stress is very difficult to obtain and has low practicability.
Disclosure of Invention
Aiming at the defects of the water-through cooling control curve, the invention provides a practical water-through cooling control curve which is easy to realize intelligent control, and solves the problems of large fluctuation of the existing three-section stress and safety coefficient and easy temperature rise.
The specific technical scheme is as follows:
the method for determining the water cooling control curve in the construction period of the concrete arch dam comprises the following steps:
1. determining the temperature control time of concrete in each bin according to the dam concrete pouring and arch sealing progress, namely the time from the dam concrete pouring to the temperature reduction to the arch sealing temperature;
2. determining the stress development process of dam concrete according to the concrete strength development process and the total temperature control time, wherein the ratio of the strength to the stress of the dam concrete in the stage from the highest temperature to the arch sealing target temperature is required to be a fixed value or linearly adjusted, and the value is required to meet the specification requirement and is generally more than 1.8;
3. establishing a dam structure finite element model, and inversely calculating a dam temperature change process curve according to a stress curve by adopting a simulation analysis method to obtain temperature control curves of different structure areas and different material partitions, wherein the temperature curve ensures that the ratio of the strength to the stress (namely the crack resistance safety coefficient) is constant or linearly changed in the cooling process of the concrete.
4. By adopting the curve and combining intelligent water supply, intelligent temperature control can be realized, the temperature of the dam is continuously reduced, the temperature rise is avoided, and meanwhile, the anti-cracking safety risk of the concrete is controllable.
And 2, inversely calculating a temperature control curve according to the stress change curve, or directly drawing up the temperature change curve, and determining the stress change curve in a trial calculation mode or other modes to ensure that the anti-cracking safety coefficient is basically constant.
The invention has the beneficial effects that:
the invention avoids the temperature rise phenomenon in the water cut-off stage caused by the current general three-stage water supply mode, reduces the fluctuation degree of the concrete temperature stress and the anti-cracking safety coefficient, keeps basic stability and is beneficial to temperature control and anti-cracking control.
Drawings
FIG. 1 is a graph of concrete strength versus stress development according to the present invention;
FIG. 2 is a graph showing stress development and temperature control of the concrete according to the present invention.
Detailed Description
The present invention is described in detail below with reference to the attached drawings, but it should be noted that these embodiments do not limit the present invention, and those skilled in the art should be able to make functional, methodological, or structural equivalents or substitutions according to these embodiments within the scope of the present invention.
The concrete temperature control curve is based on the specification and the prior practical experience to determine the cooling time and the crack resistance safety coefficient;
the cooling time is generally between 90 and 120 days and is determined according to dam concrete pouring, arch sealing progress and the like. The length of the dam sections can be shortened to about 50d, and the length of the restriction area at the bottom of the dam body can be prolonged to about 200 d;
the crack resistance safety coefficient is 2.0 at the early age, namely the highest temperature, 1.8 at the arch sealing temperature, and the middle age is determined according to the linear interpolation of the ages;
determining a concrete stress development process curve according to the dam concrete strength development process and the determined safety coefficient, as shown in figure 1;
the temperature control curve comprises a highest temperature, an arch sealing temperature and cooling time, wherein the highest temperature and the arch sealing temperature mainly depend on a basic temperature difference and are obtained through specification or numerical analysis; the cooling time is determined according to the cooling time; in addition, the initial temperature of dam concrete, namely the pouring temperature, is determined according to the highest temperature, the concrete adiabatic temperature rise, the burying of a cooling water pipe, the initial water flowing condition and the like;
through the concrete stress development process, combining the highest temperature of the temperature control curve, the sealing arch temperature and the cooling time, and adopting a finite element simulation analysis method, the concrete temperature control curves of different parts and different material partitions are obtained through inverse calculation, as shown in FIG. 2;
and calculating to obtain the arrangement mode, the cooling water flowing water temperature, the cooling water flowing water amount and the like of the cooling water pipes matched with different parts, different material partitions, different seasons and the like of the dam concrete by adopting a simulation analysis method based on the temperature control curve.
Claims (1)
1. The method for determining the water cooling control curve in the construction period of the concrete arch dam is characterized by comprising the following steps of:
(1) determining the temperature control time of concrete in each bin according to the dam concrete pouring and arch sealing progress, namely the time from the dam concrete pouring to the temperature reduction to the arch sealing temperature;
(2) determining the stress development process of dam concrete according to the concrete strength development process and the total temperature control time, wherein the ratio of the strength to the stress of the dam concrete in the stage from the highest temperature to the arch sealing target temperature is required to be a fixed value or is linearly adjusted, and the value is required to meet the specification requirement;
(3) establishing a dam structure finite element model, and inversely calculating a dam temperature change process curve according to a stress curve by adopting a simulation analysis method to obtain temperature control curves of different structure areas and different material partitions, wherein the temperature curve ensures that the ratio of the strength to the stress is constant or linearly changed in the cooling process of the concrete;
(4) and (4) by adopting the curve obtained in the step (3) and combining intelligent water supply, intelligent temperature control can be realized, the temperature of the dam is continuously reduced, the temperature is prevented from rising again, and meanwhile, the anti-cracking safety risk of the concrete is controllable.
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