CN109977484B - Rapid design method for temperature control and crack control temperature stress control of circular section lining concrete - Google Patents

Rapid design method for temperature control and crack control temperature stress control of circular section lining concrete Download PDF

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CN109977484B
CN109977484B CN201910162326.7A CN201910162326A CN109977484B CN 109977484 B CN109977484 B CN 109977484B CN 201910162326 A CN201910162326 A CN 201910162326A CN 109977484 B CN109977484 B CN 109977484B
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段亚辉
樊启祥
方朝阳
郑斌
罗刚
冉景江
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Wuhan University WHU
China Three Gorges Projects Development Co Ltd CTG
Wuchang University of Technology
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China Three Gorges Projects Development Co Ltd CTG
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Abstract

A method for quickly designing temperature control anti-cracking temperature stress control of circular section lining concrete is characterized in that a maximum temperature control anti-cracking temperature stress value in the construction period of the circular section lining concrete is calculated according to a formula by determining a temperature control anti-cracking target, an allowable temperature stress value and a variable quantity of the circular section lining concrete.

Description

Rapid design method for temperature control and crack control temperature stress control of circular section lining concrete
Technical Field
The invention belongs to the technical field of temperature control and crack prevention of concrete, and relates to a rapid design method for temperature control and crack prevention temperature stress control of lining concrete with a circular section.
Background
Cracks are one of the major diseases of concrete. According to the leading cause of crack generation, the crack can be divided into structural crack caused by external load action and non-structural crack caused by deformation change action. The deformation effect comprises temperature, dry shrinkage and wet swelling, surrounding rock deformation and the like, wherein 80 percent of the deformation effect is temperature cracks. In recent years, the construction of water conservancy and hydropower engineering is developed at a high speed, the scale and section size of underground water conservancy project are larger and larger, and the environmental conditions such as geology and the like are more and more complicated. As the height of the dam is increased, the drainage flow rate is higher and higher, and the concrete strength grade is higher. The large-section high-strength underground hydraulic lining concrete generates a large number of cracks without any effective measures, and most of the cracks generate penetrating temperature cracks in the construction period.
Underground structural engineering works in a wet environment and a dry environment and a wet environment alternately for a long time, the safety of the engineering structure, the construction progress period, leakage and even infiltration damage caused by existence of harmful cracks, durability, service life, engineering cost and attractiveness are seriously influenced, and other diseases can be induced to occur and develop.
The existing design specifications generally lack clear and specific regulations on the control of the underground engineering lining concrete temperature cracks and the calculation method thereof, and have no clear temperature control standard. For example, the structural member required to be crack-controlled in use is required to be subjected to crack resistance or crack width checking calculation according to the hydraulic concrete structure design specification of 4.1.2(3), and the temperature stress calculation is required to be carried out according to the regulation of 4.1.8 when the temperature change has great influence on the building during the construction and operation of the building, and the construction measures are preferably adopted to eliminate or reduce the temperature stress. In the case of a reinforced concrete structural member which is allowed to develop cracks in use, the influence of crack development, which causes a reduction in the rigidity of the member, should be considered in calculating the temperature stress. But does not indicate a calculation method of temperature stress and temperature control crack prevention. As for the design Specification of Hydraulic engineering Tunnel (DL/T5195-2004), 11.2.6 requirements only require that the influence of stress and grouting pressure generated by temperature change, concrete drying and expansion on the lining be solved by construction measures and constructional measures. Special studies should be made for the temperature stress generated in high-temperature areas.
The temperature control and crack prevention design calculation of part of underground engineering lining concrete (such as high-flow-rate flood discharging tunnels, power generation tunnel water diversion sections and the like) which requires crack control in use during construction is mainly carried out by adopting a finite element method at present. After the structural design is finished, a construction temperature control anti-cracking scheme and a field construction highest temperature control standard are provided through simulation calculation analysis of temperature and temperature stress of a large number of schemes. By doing so, the precision is higher, and can optimize the construction scheme moreover. But the concrete mixing proportion and a large number of performance parameter tests need to be carried out firstly, and the test and the simulation calculation need to take more time; but also needs to spend more funds; the method can not be carried out when the construction mixing proportion is not determined and no concrete performance test is carried out; and the method is not suitable for the rapid adjustment of the scheme in the preliminary design stage and construction. Particularly, the requirements of temperature control anti-cracking safety coefficient of the prior relevant specifications without a temperature control anti-cracking design in the construction period are the design specifications of a reference dam when the temperature control anti-cracking design of hydraulic tunnel lining concrete is adopted.
Some design units propose a maximum temperature control value (hereinafter referred to as a strong constraint method) by referring to a temperature control standard of concrete in a strong constraint area of the dam, and a temperature control construction scheme is established by a construction unit. The construction unit generally calculates the highest temperature of the concrete of the lining structure according to the concrete mixing ratio, the transportation distance and mode, the air temperature and the like to the planned concrete mixing (whether to refrigerate or not and measures thereof) and the pouring construction temperature control (such as water cooling) scheme, and provides a construction scheme meeting the design standard. Firstly, the temperature control standard of dam concrete cannot be suitable for a thin-wall lining structure, and the influence of differences of concrete strength, surrounding rock performance, lining thickness, structure size and the like is not reflected; secondly, the error of the construction unit for calculating the highest temperature inside the lining concrete is large, and the value of a large number of coefficients is strong in man-made property; the temperature difference between the two aspects may cause the formulated construction schemes to be far apart, and the temperature crack control target is difficult to achieve effectively. In particular, the temperature stress was not calculated and analyzed.
The above conditions are combined to show that the temperature control and crack prevention are realized in the construction period of the lining concrete of the current underground engineering, and no clear requirements and technical standards are provided; the existing design calculation method has the defects of more time and cost, and is not suitable for the initial design stage without concrete test results and the rapid adjustment of the scheme in construction; the strong constraint method has larger error and can not calculate the temperature stress; it is difficult to effectively achieve the temperature crack control goal.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a rapid design method for temperature control and anti-cracking temperature stress control of circular section lining concrete, which can rapidly calculate the temperature control and anti-cracking temperature stress aiming at the found problems and the change of construction technology and conditions in the pouring construction process, and can be used for optimizing and improving construction temperature control measures in real time to realize the temperature control and anti-cracking targets.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a rapid design method for temperature control and crack prevention temperature stress control of circular section lining concrete is used for calculating the temperature control and crack prevention tensile stress safety coefficient of the lining concrete in practical engineering, and comprises the following steps:
s1, determining a temperature control anti-cracking target of the lining concrete with the circular section;
s2, determining the allowable temperature stress value of the lining concrete with the circular section;
s3, determining the variable quantity of lining concrete of the circular section;
and S4, calculating the maximum temperature tensile stress of the circular section lining concrete in the construction period according to the parameters determined in the S1-S3.
The temperature control anti-cracking target and the allowable temperature stress value of the circular section lining concrete are determined according to the design specification, the grade of the lining structure, the damage of the crack in the operation period, the safety and the anti-seepage performance.
The calculation formula of the temperature control anti-cracking maximum stress in the construction period of the circular section lining concrete is as follows: sigmamax＝0.45H+0.145R+0.028C+0.069E-0.0017E2+0.325T0+0.14Tg-0.194Ta+0.24△T-0.0147(H×Tg)+0.021(H×E)-0.009(T0×Tg)-2.655 (1)
In the formula: sigmamaxThe maximum temperature tensile stress (MPa) is used in the construction period of the lining concrete with the circular section;
h is the thickness (m) of the lining concrete structure;
r is the inner radius (m) of the lining concrete structure;
e-deformation modulus (GPa) of surrounding rock;
c, strength grade (MPa) of lining concrete designed according to the age of 90 days;
T0-lining concrete pouring temperature (° c);
Ta-air temperature (deg.C) in the tunnel during the construction of the cast-in-place concrete;
the delta T is the annual variation of the air temperature in the tunnel, namely the highest temperature in summer to the lowest temperature in winter;
Tg＝35-Twthe temperature effect value (DEG C) represents the cooling conditions with and without water, and T is taken when cooling without water is carried outwCalculation of T at 35 ℃ g0; when cooling with water, TwThe water temperature (DEG C);
replacing the thickness and the inner radius of the circular section lining structure, the concrete strength grade, the surrounding rock deformation modulus, the pouring temperature, the air temperature in the tunnel during pouring construction, the annual variation of the air temperature in the tunnel, whether water cooling is conducted or not and the water temperature in the tunnel into the formula (1), thereby obtaining the maximum temperature tensile stress (MPa) of the circular section lining concrete during the construction period corresponding to the period.
When the strength grade designed for 28-day age is adopted in the lining concrete with the circular section, the strength grade designed for 90-day age needs to be converted according to the specification.
The circular section lining concrete adopts the curtain to keep warm, the air temperature of the underground cavern is increased, then TaThe increased temperature of the air in the hole is adopted.
When the thickness of the lining concrete with the circular cross section is smaller, the water-cooling water pipes are arranged in a single row.
A method for quickly designing temperature control anti-cracking temperature stress control of circular section lining concrete is characterized in that a maximum temperature control anti-cracking temperature stress value in the construction period of the circular section lining concrete is calculated according to a formula by determining a temperature control anti-cracking target, an allowable temperature stress value and a variable quantity of the circular section lining concrete.
Drawings
The invention is further illustrated by the following examples in conjunction with the accompanying drawings:
FIG. 1 is a schematic representation of the present invention lining a concrete crack.
Fig. 2 is a schematic structural view of the round cross-section lining concrete of the present invention.
FIG. 3 is a schematic diagram of the three-dimensional finite element structure of FIG. 2.
FIG. 4 is a graph showing the annual temperature change of the cavern of the spillway tunnel in the practical application of the invention.
Detailed Description
As shown in fig. 1 to 4, a rapid design method for temperature control and crack prevention temperature stress control of a circular cross-section lining concrete is used for calculating the temperature control and crack prevention tensile stress safety coefficient of the lining concrete in actual engineering, and comprises the following steps:
s1, determining a temperature control anti-cracking target of the lining concrete with the circular section;
preferably, the thickness and the inner radius of the round section lining, the concrete strength grade, the deformation modulus of the geological condition surrounding rock, the annual change rule of the air temperature in the tunnel, the annual change rule of the water temperature, the concrete, the pouring temperature, the air temperature in the tunnel during pouring construction and the water cooling working condition are recorded according to engineering actual data.
S2, determining the allowable temperature stress value of the lining concrete with the circular section;
s3, determining the variable quantity of lining concrete of the circular section;
and S4, calculating the maximum temperature tensile stress of the circular section lining concrete in the construction period according to the parameters determined in the S1-S3.
In the preferred scheme, the temperature control anti-cracking target and the allowable temperature stress value of the circular section lining concrete are determined according to the design specification, the grade of lining structures, the damage of cracks in the operation period, the safety and the anti-seepage performance.
In an optimized scheme, a calculation formula of the temperature control anti-cracking maximum tensile stress in the construction period of the circular section lining concrete is as follows: sigmamax＝0.45H+0.145R+0.028C+0.069E-0.0017E2+0.325T0+0.14Tg-0.194Ta+0.24△T-0.0147(H×Tg)+0.021(H×E)-0.009(T0×Tg)-2.655 (1)
In the formula: sigmamaxIs a lining with a circular cross sectionMaximum temperature tensile stress (MPa) in the construction period of building concrete;
h is the thickness (m) of the lining concrete structure;
r is the inner radius (m) of the lining concrete structure;
e-deformation modulus (GPa) of surrounding rock;
c, strength grade (MPa) of lining concrete designed according to the age of 90 days;
T0-lining concrete pouring temperature (° c);
Ta-air temperature (deg.C) in the tunnel during the construction of the cast-in-place concrete;
the delta T is the annual variation of the air temperature in the tunnel, namely the highest temperature in summer to the lowest temperature in winter;
Tg＝35-Twthe temperature effect value (DEG C) represents the cooling conditions with and without water, and T is taken when cooling without water is carried outwCalculation of T at 35 ℃ g0; when cooling with water, TwThe water temperature (DEG C);
in the preferred scheme, the thickness and the inner radius of the circular section lining structure, the concrete strength grade, the surrounding rock deformation modulus, the pouring temperature, the air temperature in the tunnel during pouring construction, the annual variation of the air temperature in the tunnel, whether water cooling is carried out or not and the water temperature are substituted into the formula (1), so that the maximum temperature tensile stress (MPa) of the circular section lining concrete in the construction period corresponding to the period is obtained.
In a preferred embodiment, when the strength grade designed for 28-day-old lining concrete is adopted, the strength grade designed for 90-day-old lining concrete needs to be converted according to specifications.
In the preferred scheme, the circular section lining concrete adopts a curtain to preserve heat, the air temperature of the underground cavern is increased, and then T is obtainedaThe increased temperature of the air in the hole is adopted.
In a preferable scheme, when the thickness of the lining concrete with the circular cross section is smaller, the water-passing cooling water pipes are arranged in a single row.
In the following practical application, various possible situations are calculated on the basis of the pressure section circular section structure of the flood discharge tunnel and related parameters thereof and by combining similar projects. Basic parameters and metersThe calculation scheme is shown in table 1, and the maximum temperature tensile stress sigma in the concrete lining construction period of each schememaxThe results of the calculations are shown in Table 1.
TABLE 1 calculation scheme of temperature stress and maximum tensile stress of lining concrete with circular section
Figure GDA0003008473730000051
Figure GDA0003008473730000061
Figure GDA0003008473730000071
Figure GDA0003008473730000081
Figure GDA0003008473730000091
Maximum temperature tensile stress σ for the lining concrete construction period of Table 1maxAnd (4) carrying out statistical analysis on the calculated value to obtain the formula (1).
In the case of the example-1,
the spillway tunnel is a main building (I level), the pressure section is a circular section, and the types of lining and surrounding rock are listed in Table 2. The inner diameter of the lining section is 7.5m, and the designed strength grade C of lining concrete90And 40, the length of the structural section seam is 9 m. According to the measurement data in the initial excavation and the data provided by a design institute, the average temperature of a design unit is 23.5 ℃ for many years, the annual variation of the temperature is 3.0 ℃, and the cosine formula (2) is adopted for calculation according to the specification. The construction conditions and the bidding documents can provide the refrigerated commercial concrete with the temperature of 14 ℃ at the machine outlet, and the pouring temperature is 18 ℃. Two kinds of water can be provided for water cooling, namely, cooling water at 12 ℃; secondly, normal temperature tap water, 22 ℃ in summer and 12 ℃ in winter.
Figure GDA0003008473730000092
In the formula: t isaThe temperature of the air at the time tau in the hole;
τ is the time (day) 1 day from 1 month;
τ0taking tau as the time (day) between the highest temperature in the tunnel and 1 month and 1 day0Day 210.
TABLE 2 flood discharge Tunnel Lining and surrounding rock Classification
Figure GDA0003008473730000093
Figure GDA0003008473730000101
(2) Temperature control anti-cracking design and technical requirements thereof
The design institute determines that the pressure section lining concrete of the flood discharge tunnel adopts C according to the related design specifications, the concrete mixing proportion optimization and the performance test thereof and the calculation result of the finite element method (the air temperature in the tunnel adopts the formula (2) for calculation)90And 40, the length of the pouring section is 9m, the pouring temperature of the bottom arch with the pressing section is not more than 18 ℃, the highest temperature is not more than 37 ℃, the pouring temperature of the top arch with the pressing section is not more than 18 ℃, and the highest temperature is not more than 38 ℃. In winter construction, natural warehousing concrete can be adopted for pouring under the condition that the concrete pouring temperature can be lower than 18 ℃. The following scheme is recommended during summer construction: the pressure section is pressed, the concrete pouring temperature is 18 ℃, the distance between water pipes is 1.0m, the length of the water pipes is 100m, and the cooling water flow is 2.0m3And h, cooling the water at 20 ℃ (normal temperature water), and starting to pass water when the concrete is poured, and cooling the water for 15 days.
(3) Temperature control and crack control construction scheme for lining concrete
According to the design requirements, the construction scheme plans that the whole flood discharge tunnel is basically poured according to 9m bins, and the temperature control anti-cracking scheme for the lining concrete construction is as follows:
firstly, adopting precooled concrete, and making the outlet temperature reach 12-14 ℃.
And the temperature rise in the concrete transportation and pouring process is reduced. The transportation capacity is increased, and the pouring blank on the concrete bin surface can be effectively covered in time; the movable canvas sunshade is arranged at the top of the carriage of the concrete transport vehicle, and the foaming heat preservation device and the like are arranged on the box body of the concrete transport vehicle.
And thirdly, reinforcing management and accelerating construction speed. Through strengthening management, waiting time for unloading or unloading and warehousing time is reduced, repeated material transfer and warehousing and the like are avoided, and concrete pouring and covering time is not more than 1 h.
And fourthly, reasonably arranging the construction progress of the concrete. The concrete pouring time is arranged to be carried out in low-temperature seasons and at low morning and evening temperatures as much as possible. Preparation before pouring is carried out in high-temperature time periods in the daytime, and pouring is carried out as much as possible from 16 pm to 10 am of the next day.
Air conditioning in the storehouse. The steel mould trolley is provided with an air conditioner for summer construction in the bin, so that the pouring environment temperature in the bin is reduced, the temperature control is facilitated, and the heatstroke prevention and cooling effects can be achieved.
Sixthly, surface maintenance. After the concrete is demoulded, the flowing water maintenance is started, a phi 35mm plastic pipe is adopted, small holes with the phi of about 1mm are drilled every 20-30 cm, the small holes are hung on the formwork or the exposed reinforcing steel bar head, and the water flow is about 15L/min. Uninterrupted flowing water curing is carried out in the daytime, interrupted flowing water curing is carried out at night (20: 00-6: 00), namely flowing water is carried out for 1h, the moisture is kept for 1h, uninterrupted curing is carried out when the temperature exceeds 25 ℃, and the curing time of the pressure section, the side top arch and the non-pressure section is not less than 28 d.
And cooling with water. The flow rate of the cooling water is 35L/min, and the difference between the concrete temperature and the water temperature is not more than 22 ℃. The cooling water pipe adopts the PE pipe, is on a parallel with the water flow direction and snakelike arranges in the middle part of every pouring block, and single water pipe length is not more than 100m, and perpendicular interval is 1.0 m. Introducing cold water (about 14-20 ℃) for 48 hours into the tail of the dragon falling off from the right bank in a high-temperature season, and then normally heating the water for 7 days; the cold season is usually warm water.
Special heat preservation of concrete in winter. In winter, the exposed surface of the concrete is covered by the heat-insulating material with good heat-insulating effect, so that cracks are prevented from being generated on the surface of the concrete. The tunnel portal can adopt a door curtain hanging mode, and cold air is prevented from being poured into the tunnel to cause cracks on the surface of concrete.
And ninthly, the switching time is shortened. The field shift system is implemented, so that equipment operators have to shift shifts on the field, and the shift time cannot exceed 30 min; the pouring can not be stopped when eating, the eating must be staggered in batches, and the continuity of the concrete pouring in the bin needs to be ensured.
And (c) reinforced concrete temperature measurement. In order to verify whether the temperature of the concrete in the construction period meets the temperature control requirement, a resistance thermometer or a thermocouple which is pre-embedded in the concrete is adopted to measure the temperature of the concrete, and the result is analyzed; in the concrete pouring process, measuring the outlet temperature of the concrete, the pouring temperature of the concrete and the air temperature every 4 hours, and recording the outlet temperature, the pouring temperature and the air temperature; and in the temperature measurement process, the condition exceeding the temperature control standard is found and reported in time.
(4) Temperature observation result of lining concrete
Statistical analysis is carried out on the temperature control results of the pressure section lining concrete of the left bank flood discharge tunnel and the right bank flood discharge tunnel and the overtemperature condition of the pressure section lining concrete, and the results are listed in tables 3-6.
Table 32010 years flood discharge tunnel lining concrete internal highest temperature statistical table
Figure GDA0003008473730000111
Figure GDA0003008473730000121
Table 42010 years statistical table of concrete pouring temperature of left and right bank flood discharging tunnel lining
Figure GDA0003008473730000122
Table 52011 statistics table of internal highest temperature of flood discharging tunnel lining concrete of left and right banks in year
Figure GDA0003008473730000123
Figure GDA0003008473730000131
Statistical table of concrete pouring temperature of lining concrete of flood discharging tunnel on left bank and right bank in 62011 years
Figure GDA0003008473730000132
The observation result of the internal temperature of the concrete shows that: compared with the design standard, the casting temperature overtemperature phenomenon of the left bank and the right bank in 2010 and 2011 is respectively 56.6% and 13.33%; in addition, the water temperature for water cooling also generally exceeds the design standard; therefore, the maximum temperature also has a certain overtemperature phenomenon, which is 45.28% and 16.67%, respectively.
(5) Lining concrete crack conditions
The concrete cracks are lined on the pressure section round section of the flood discharge tunnel, the bottom arch concrete has no cracks, and the statistics of the cracks of the side top arch concrete are listed in table 7.
TABLE 7 Overall situation of pressure-section circular section lining concrete cracks of left and right bank flood discharge tunnels
Figure GDA0003008473730000133
Figure GDA0003008473730000141
According to the characteristics of the pressure section structure of the flood discharge tunnel, the construction process of lining concrete and the crack statistical conditions of the table 7, the following knowledge can be obtained through comprehensive analysis:
(a) the pressure section side top arch lining concrete has more cracks, and the bottom plate has no cracks. The estimation is related to the fact that the dimension of the side wall (side crown) is larger than that of the bottom plate, and the maintenance condition of the bottom plate is better. This result is consistent with the finite element method simulation calculation conclusion. Therefore, the temperature control and crack prevention of similar large tunnel lining concrete should be focused on the side crown arch in future. This is also the reason why the above design calculation formula is done only for the dome arch.
(b) Compared with the flood discharging tunnels on the two banks, the holes on the left bank No. 1 and the right bank No. 2 have more cracks than the holes on the right bank No. 3 and the right bank No. 4, and are related to the fact that the highest temperature and overtemperature proportion of the lining concrete on the left bank is large (including the influence of higher water temperature of water cooling).
(c) According to the details of the general investigation of the cracks, the harder the surrounding rock, the more complete the temperature cracks. The pressure sections of the flood discharge tunnel are E1 type linings of II type surrounding rock areas with hard and complete surrounding rocks, and the pressure sections are main generation areas of temperature cracks although the thickness of the linings is small; the lining concrete with large thickness in the IV-type surrounding rock area generally has few temperature cracks.
(6) Finite element method simulation calculation result
The design technical requirements are provided according to the simulation calculation result of the finite element method in the design phase. In addition, table 1 also lists a number of finite element method simulation calculations. Such as: pouring 1.0m thick lining in II-type surrounding rock area within 8 months and 1 day in summer, and designing the sigma of the stage calculation scheme 49max2.06MPa, and the minimum temperature control anti-cracking safety coefficient is 1.88; sigma of the calculation scheme 5 at the construction stagemax4.4MPa, and the minimum temperature control anti-cracking safety coefficient is 1.22. III 2 type surrounding rock area E3 type 1.0m thickness lining is poured 8 months in summer and 1 day in summer, and the sigma of the scheme 21 is calculated in the construction stagemax3.8MPa, and the minimum temperature control anti-cracking safety coefficient is 1.41.
In the case of the example-2,
e1 type lining with thickness of 1.0m for class II surrounding rock area with pressure section of flood discharge tunnel
A lining with the thickness of 1.0m in a class II surrounding rock area is a structural section with the largest difficulty in medium temperature control and crack prevention of a pressure section round section of the whole flood discharge tunnel.
(1) Collecting and calculating temperature control anti-cracking data of circular section lining structure
Lining structure design data, lining thickness, inner radius and concrete strength grade; environmental data, deformation modulus of surrounding rock under geological conditions, annual change rule of air temperature in the tunnel and annual change rule of water temperature; etc. as described above.
(2) Analyzing and determining a temperature control anti-cracking target and determining allowable temperature stress [ sigma ] of lining concrete with a circular sectionmaxValue.
The stream luo-ferry flood discharge tunnel is a first-level building according to the design specification of hydraulic tunnels, has high flow velocity and great damage to cracks in the operation period, and needs to be designed to prevent cracking by referring to similar engineering experience. According to the design Specifications of Hydraulic concrete Structure and the design Specifications of Hydraulic reinforced concrete Structure, the circular section lining C90The standard value of the axial tensile strength of 40 pumping concrete is 2.39 MPa.
(3) Design stage temperature control anti-cracking measure scheme design
(3.1) variable quantity analysis and planning of temperature control and crack prevention construction measures for lining concrete with circular section
Because the size of the lining structure and the strength grade of concrete are determined, and the opening of the hole must be closed in winter for heat preservation, the variable quantity is only the pouring temperature and the water cooling temperature. The temperature control anti-cracking design is carried out by taking pouring in 8 months and 1 day in summer as a representative. The bidding document can provide the refrigerated commercial concrete with the temperature of 14 ℃ at the machine outlet, and the pouring temperature is 18 ℃. According to construction conditions, 4 temperature control measures of 18 ℃ pouring temperature, no water cooling, 12 ℃ refrigerating water cooling, 22 ℃ normal temperature water cooling, and 16 ℃ pouring plus 16 ℃ water cooling are planned.
(3.2) calculating the maximum temperature tensile stress sigma of the circular section lining concrete in the construction periodmax
Since the lining thickness of 1.05m includes the sandblasting paste layer of 0.05m and the finite element method in the table is to take the thickness of 1.0m, the lining thickness of 1.0m is taken for comparison with the finite element method calculation value. Pouring the concrete in 8 months and 1 day in summer, and calculating T by the formula (2)aAbout.25 ℃. Calculating related parameters of E1 type lining of class II surrounding rock zone of the circular section by substituting formula (1) into sigmamax＝2.67MPa、2.05MPa、2.29MPa、1.89MPa。
(3.3) in calculating σmax≤【σmaxOn the premise of the technology, a measure scheme is optimized according to the principle of simplicity, practicability and economy for construction application. In the 4 proposed schemes, pouring at 18 ℃, cooling water at 12 ℃ and pouring at 18 ℃, cooling water at 22 DEG CThe scheme of 3 temperature control measures of normal temperature water cooling, 16 ℃ pouring and 16 ℃ water cooling meets the requirement of calculating sigmamax≤【σmax2.39MPa, according to the principle of safety, economy, reasonability, simplicity and feasibility, and in combination with the technical design requirements, a 18 ℃ pouring and 22 ℃ normal-temperature water cooling scheme is selected as a construction temperature control measure scheme.
(4) The calculated values of the tensile stress are compared and analyzed. For the scheme of pouring at 16 ℃ and water cooling at 16 ℃, the design stage finite element method scheme 49 calculates sigmamaxThe calculated value of the formula (1) is 1.89MPa, the error is-8.25 percent, the precision is high, and the engineering design requirement is met.
Pouring at 18 ℃ and water cooling at 12 ℃ adopted in actual construction, wherein sigma ismaxThe standard value of the tensile strength of the core is 2.05MPa and the standard value of the tensile strength of the core is 2.39MPa, so that the design construction scheme meets the requirement.
(4) Real-time temperature control anti-cracking scheme optimization design in construction process
In construction, the tunnel excavation is communicated with the outside, so that the temperature in the tunnel rapidly drops to approach the change of the outside temperature. In total, from 10 months to 11 months in 2009 to 2012, the temperature measurement was performed 300 times for the spillway tunnels (left and right banks), and the results are collectively shown in fig. 4. With day 1 of 2010 as the date axis for day one. Wherein the abscissa is time (days); the ordinate is temperature (. degree. C.). Fitting cosine function by least square method
Figure GDA0003008473730000161
In the formula: t isaTemperature in the hole (. degree. C.);
τ is the time (day) 1 day from 1 month.
Due to the change of the temperature in the tunnel, a temperature control anti-cracking scheme must be redesigned in real time in the construction process.
And (3) calculating the temperature T in the hole according to the design method, pouring construction is carried out in 8 months and 1 day in summer, and the formula (3)a25.99 ℃ and the winter minimum temperature Tmin12.59 ℃. Planning to substitute all parameters into a formula (1), and calculating a 18-DEG C pouring + 12-DEG C water cooling scheme sigmamin4.35 MPa; pouring at 16 DEG C+16 ℃ water cooling scheme sigmamin4.19 MPa; pouring at 18 ℃, cooling by water at 8 ℃ and preserving heat at 14 ℃ (namely strictly closing the opening of the hole and keeping the lowest temperature in the hole from T in winterminIncrease to T at 12.59 ℃min14 ℃ solution σmin3.14 MPa. Each scheme sigmaminThe calculated values are all larger than the standard value of the axial tensile strength by 2.39MPa, and stricter temperature control measures must be adopted.
(5) Stress achievement calculation error and design solution analysis
According to the construction stage of pouring at 16 ℃, water cooling at 16 ℃ and the sigma of the finite element method simulation calculation scheme 5minThe calculated value of the formula (1) is 4.35MPa, the error is-1.1 percent, and the calculation value of the stress has high precision.
In actual construction, a scheme of 18 ℃ pouring and 12 ℃ water cooling is adopted, the stress exceeds the standard value of axial tensile strength by 2.39MPa, the risk of cracks exists, the temperature control needs to be further enhanced, the pouring temperature is reduced, the water cooling temperature is enhanced, the heat preservation of a hole opening in winter is enhanced, the air temperature in the hole is increased, and the like.
In the case of example-3,
the E3 type lining of the III 2 type surrounding rock area of the pressure section of the flood discharge tunnel, the temperature control anti-cracking target of the lining concrete and the allowable temperature stress value are the same.
In the design stage, pouring construction is carried out for 1 day in 8 months in summer, and the temperature T in the hole is calculated by formula (2)aAt 25 ℃, the 18 ℃ pouring non-aerated water cooling scheme sigma is calculated by adopting the formula (1)max2.22 MPa; 18 ℃ pouring and 12 ℃ water cooling scheme sigmamax1.55 MPa; 16 ℃ pouring and 16 ℃ water cooling scheme sigmamax1.39 MPa. The tensile strength of the cast iron core is less than the standard value of the axial tensile strength and is 2.39MPa, and a 18-DEG C casting non-water cooling scheme is recommended.
In the construction real-time control stage, pouring construction is carried out in 8 months and 1 day in summer, and the temperature T in the hole is calculated by formula (3)aAt 25.99 ℃, the 18 ℃ pouring +12 ℃ water cooling scheme sigma is calculated by adopting a formula (1)max3.85 MPa. 16 ℃ pouring and 16 ℃ water cooling scheme sigmamaxThe standard value of the axial tensile strength of the steel sheet is 3.69MPa and is 2.39 MPa. The temperature control anti-cracking measure scheme adopted in actual construction is pouring at 18 ℃, water cooling at 14-20 ℃ and temperature stressThe axial tensile strength greater than the standard value of 2.39MPa is liable to cause temperature cracking. The temperature control measures need to be enhanced, and the method is recommended to adopt 16 ℃ pouring, 16 ℃ water cooling and 14 ℃ heat preservation (namely strictly closing the opening of the hole and keeping the lowest temperature in the hole in winter from TminIncrease to T at 12.59 ℃min14 deg.c), calculating the temperature stress sigmamaxThe axial tensile strength was 2.63MPa, which was slightly higher than the axial tensile strength standard value of 2.39 MPa.
And (4) stress achievement calculation error and design scheme analysis. For the scheme of pouring at 16 ℃ and water cooling at 16 ℃ in the construction stage, the finite element method scheme 21 calculates the value sigmamaxThe calculated value of the formula (1) is 3.69MPa, the error is-2.9 percent, and the error is small, so that the calculation precision requirement of engineering design is met. However, in the actual construction scheme, the casting is carried out at 18 ℃ and the water cooling is carried out at 14-20 ℃, the temperature stress is 2.39MPa higher than the standard value of the axial tensile strength, and temperature cracks are easy to occur.
4. Formula (1) calculation precision and design temperature control anti-cracking scheme rationality analysis
Compared with the finite element method calculation result. Lining of type II surrounding rock area E1 type 1.0m thickness, pouring at 16 ℃, cooling by introducing water at 16 ℃, and designing the sigma of the stage finite element method calculation scheme 49max2.06MPa, the calculated value of the formula (1) is 1.89MPa, and the error is-8%; in the construction stage, the sigma of the finite element method simulation calculation scheme 5maxThe calculated value of formula (1) is 4.19MPa with an error of-4.8% when it is 4.4 MPa. III 2 type surrounding rock area E3 type lining, 16 ℃ pouring and 16 ℃ water cooling calculation scheme 21 in construction stage, sigma calculated by finite element method simulationmaxThe calculated value of formula (1) is 3.69MPa under 3.8MPa with an error of-2.9%. And errors are small, and the requirement of engineering design calculation accuracy is met.
And comparing with the temperature crack inspection result. In actual construction, lining concrete of II and III 2 type surrounding rock areas is poured at 18 ℃ and cooled by water at 14-20 ℃. The calculated stress result of the formula (1) shows that temperature stress is 2.39MPa higher than the standard value of the axial tensile strength, and temperature cracks are easy to occur. And the stress of the lining of the class II surrounding rock area is much larger than that of the class III 2 surrounding rock area, and more concrete cracks are formed. Table 6 results of temperature crack inspection, 65% to 86% of the circular cross-section lining concrete side crown had temperature cracks. And (c) conclusion "the harder the surrounding rock the more complete temperature fractures". The calculation stress result is completely consistent with the temperature crack inspection result.
To sum up, the calculation and analysis of the examples show that the method has a simple calculation formula, and can comprehensively and reasonably reflect the influences of main factors such as the thickness and the inner radius of the lining structure, the strength grade of concrete, the performance (deformation modulus) of surrounding rock, the pouring temperature, the annual change of the air temperature in the tunnel, the air temperature in the tunnel during the pouring period, whether water cooling is conducted or not, the water temperature and the like. The method can rapidly calculate the maximum temperature tensile stress of the circular section structure poured at any time period in the concrete lining construction period, has small calculation error, and can be completely used for temperature crack control design of actual engineering, particularly preliminary design and real-time rapid design in the field construction period.
The above-described embodiments are merely preferred embodiments of the present invention, and should not be construed as limiting the present invention, and features in the embodiments and examples in the present application may be arbitrarily combined with each other without conflict. The protection scope of the present invention is defined by the claims, and includes equivalents of technical features of the claims. I.e., equivalent alterations and modifications within the scope hereof, are also intended to be within the scope of the invention.

Claims (5)

1. A rapid design method for temperature control and crack prevention temperature stress control of circular section lining concrete is used for calculating temperature control and crack prevention tensile stress of the lining concrete in actual engineering, and is characterized by comprising the following steps:
s1, determining a temperature control anti-cracking target of the lining concrete with the circular section;
s2, determining the allowable temperature stress value of the lining concrete with the circular section;
s3, determining the variable quantity of lining concrete of the circular section;
s4, calculating the maximum temperature tensile stress of the circular section lining concrete in the construction period according to the parameters determined in the S1-S3;
the calculation formula of the tensile stress when determining the minimum temperature control anti-cracking safety coefficient of the circular section lining concrete is as follows:
σmax=0.45H+0.145R+0.028C+0.069E-0.0017E2+0.325T0+0.14Tg-0.194Ta+0.24△T-0.0147(H× Tg) +0.021(H×E)-0.009(T0×Tg) -2.655 （1）
in the formula: sigmamaxThe maximum temperature tensile stress (MPa) is used in the construction period of the lining concrete with the circular section;
h is the thickness (m) of the lining concrete structure;
r is the inner radius (m) of the lining concrete structure;
e-deformation modulus (GPa) of surrounding rock;
c, strength grade (MPa) of lining concrete designed according to the age of 90 days;
T0-lining concrete pouring temperature (° c);
Ta-air temperature (deg.C) in the tunnel during the construction of the cast-in-place concrete;
the delta T is the annual variation of the air temperature in the tunnel, namely the highest temperature in summer to the lowest temperature in winter;
Tg=35-Twthe temperature effect value (DEG C) represents the cooling conditions with and without water, and T is taken when cooling without water is carried outw=35 ℃ calculation of Tg= 0; when cooling with water, TwThe water temperature (DEG C);
replacing the thickness and the inner radius of the circular section lining structure, the concrete strength grade, the surrounding rock deformation modulus, the pouring temperature, the air temperature in the tunnel during pouring construction, the annual variation of the air temperature in the tunnel, whether water cooling is provided or not and the water temperature in the tunnel into the formula (1), thereby obtaining the maximum temperature tensile stress of the circular section lining concrete during the construction period corresponding to the period.
2. The temperature control anti-cracking temperature stress control rapid design method of the circular cross section lining concrete as claimed in claim 1, which is characterized in that: the temperature control anti-cracking target and the allowable temperature stress value of the circular section lining concrete are determined according to the design specification, the grade of the lining structure, the damage of the crack in the operation period, the safety and the anti-seepage performance.
3. The temperature-control anti-cracking temperature stress control rapid design method for the lining concrete with the circular cross section as claimed in any one of claims 1-2, is characterized in that: when the strength grade designed for 28-day age is adopted in the lining concrete with the circular section, the strength grade designed for 90-day age needs to be converted according to the specification.
4. The temperature-control anti-cracking temperature stress control rapid design method for the lining concrete with the circular cross section as claimed in any one of claims 1-2, is characterized in that: the circular section lining concrete adopts the curtain to keep warm, the air temperature of the underground cavern is increased, then TaThe increased temperature of the air in the hole is adopted.
5. The temperature-control anti-cracking temperature stress control rapid design method for the lining concrete with the circular cross section as claimed in any one of claims 1-2, is characterized in that: when the thickness of the lining concrete with the circular cross section is smaller, the water-cooling water pipes are arranged in a single row.
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