CN109885914B - Design method for crack resistance K value of tunnel floor lining concrete temperature crack control - Google Patents
Design method for crack resistance K value of tunnel floor lining concrete temperature crack control Download PDFInfo
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Abstract
The invention provides a design method for controlling crack resistance K value of a temperature crack of a tunnel floor lining concrete, which comprises the following steps: collecting data for controlling and calculating the temperature crack of the lining concrete of the tunnel floor; step 2, analyzing and determining a temperature control anti-cracking target and an anti-cracking safety coefficient allowable value (K); step 3, designing a temperature control anti-cracking measure scheme, which comprises the following steps: step 3-1, analyzing variable quantity, and drawing up a plurality of temperature control anti-cracking construction measure schemes of lining concrete; step 3-2, calculating the minimum crack resistance safety coefficient K of each scheme in the concrete lining construction period by adopting a formulamin(ii) a Step 3-3. at KminAnd under the condition of not less than K, a measure scheme is optimized according to the principle of simplicity, practicability and economy for application. The method can be used for designing a temperature control anti-cracking scheme in a design stage, and can also be used for optimizing and improving construction temperature control measures in real time aiming at the change of problems, construction technologies, conditions and the like in the pouring construction process so as to realize a temperature control target.
Description
Technical Field
The invention belongs to the technical field of temperature control crack resistance of engineering structures, and particularly relates to a design method of crack resistance K value (safety coefficient) of temperature crack control of a tunnel floor lining concrete.
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 exception as long as effective measures are not taken, and most of the cracks generate penetrating temperature cracks during construction (see fig. 1 and 2).
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 no calculation methods for temperature stress and temperature controlled cracking are indicated. 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 crack resistance 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, can optimize the construction temperature control 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 the performance parameters of the concrete are not obtained through tests; and the method is not suitable for the rapid adjustment of the scheme in the preliminary design stage and construction. Particularly, the current relevant specifications have no requirement value of the crack resistance safety coefficient of the temperature control crack resistance design in the construction period, and the design specifications of a dam are all referred to when the temperature control crack resistance design of hydraulic tunnel lining concrete is adopted.
Some design units also provide a maximum temperature control value (hereinafter referred to as a strong constraint method) by referring to the temperature control standard of concrete in a strong constraint area of the dam, and a temperature control construction scheme is established by the construction units. 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 cannot be effectively realized. In particular, the temperature stress was not calculated and analyzed.
The above conditions are combined to show that the temperature control crack resistance in the construction period of the lining concrete of the current underground engineering has no clear requirements and technical standards; a simple high-precision design method is not available, the finite element method takes more time and cost, and the method cannot be suitable for the quick adjustment of the preliminary design stage without concrete test results and the scheme in construction; the strong constraint method has larger error and can not calculate the temperature stress; it is difficult to achieve the temperature crack control goal quickly and efficiently.
Disclosure of Invention
The invention is made to solve the above problems, and aims to provide a method for designing a temperature crack control crack resistance safety coefficient of lining concrete for an urban door opening type tunnel bottom plate structure as shown in fig. 3, which can be used for not only designing a temperature control crack resistance scheme in a design stage, but also optimizing and improving construction temperature control measures in real time to change found problems, construction technologies, conditions and the like in a pouring construction process to realize a temperature control target.
In order to achieve the purpose, the invention adopts the following scheme:
the invention provides a method for designing a crack resistance K value of a tunnel floor lining concrete temperature crack control, which is characterized by comprising the following steps of:
collecting data for controlling and calculating the temperature crack of lining concrete of a bottom plate of an urban tunnel;
step 2, analyzing and determining a temperature control anti-cracking target and an anti-cracking safety coefficient allowable value (K);
step 3, designing a temperature control anti-cracking measure scheme, comprising the following substeps:
step 3-1, analyzing variable quantity, and drawing up a plurality of temperature control anti-cracking construction measure schemes of lining concrete;
step 3-2, calculating the minimum crack resistance safety coefficient K of each scheme in the concrete lining construction period by adopting the following formulamin：
Kmin＝6.1566－1.4763×H+0.062×W－0.103×L－0.0069×C－0.0241×E－0.0367×T0+0.0072×Tg+0.0966×Ta－0.0673×(Ta－Tmin)－3.505/H+0.013×(Ta－Tmin)/H+0.2538×H2+1.1966/H2－0.0384×(Ta－Tmin)/H2+0.0004×E2－0.0026×W2－0.019×H×T0+0.0011×H×Tg-0.003 XE XH-0.0004 Xdate +0.0408cos (2 π (date-120)/365) (equation 1)
In the above formula: kminThe minimum crack resistance safety factor in the construction period of lining concrete for the bottom plate of the urban door opening type tunnel; h is the thickness (m) of the lining concrete structure; w is the width of the bottom plate (m); l is the parting length (m); e is the deformation modulus (GPa) of the surrounding rock; c is the strength grade (MPa) of the lining concrete designed according to the age of 90 days; t is0The pouring temperature (DEG C) of lining concrete is adopted; t isaThe temperature (DEG C) of air in the tunnel when the lining concrete is cast and constructed; t isminThe winter lowest temperature (DEG C) in the hole; t isg＝35-TwThe temperature effect value (. degree. C.) is shown for both water-cooling and non-water-cooling conditions, and T is taken without water-coolingwAt 35 ℃, T in the presence of cooling waterwThe water temperature (DEG C); date is the number of days (d) from 1 month to 1 day when pouring;
substituting lining thickness and width of bottom plate of tunnel with city gate, concrete strength grade, deformation modulus of surrounding rock, casting temperature, air temperature in tunnel during casting construction, lowest temperature in tunnel in winter, water cooling, water temperature and days at 1 month and 1 day distance during casting into public city gate tunnelFormula 1, namely the minimum anti-cracking safety coefficient K of the construction period of pouring the lining concrete of the bottom plate of the urban door opening type tunnel corresponding to the period (season) can be obtainedmin；
Step 3-3. at KminAnd under the condition of not less than K, a measure scheme is optimized according to the principle of simplicity, practicability and economy for application. Namely, satisfy KminIn the scheme of more than or equal to K, an optimization measure scheme is selected according to the safe, economic, reasonable, simple and feasible principle.
Preferably, the method for designing the crack resistance K value of the temperature crack control of the tunnel floor lining concrete provided by the invention can also have the following characteristics: in step 1, the collected data for calculation includes: the design data of the lining structure, in particular the temperature control anti-cracking design and calculation result, the lining thickness and the width of the bottom plate of the urban door opening type tunnel and the concrete strength grade; environmental data, in particular the deformation modulus of the surrounding rock under geological conditions, the annual change rule of the air temperature in the tunnel and the annual change rule of the water temperature; concrete pouring construction data, in particular to a concrete pouring construction temperature control measure scheme, a pouring temperature, the air temperature in a tunnel during pouring construction (pouring month and day), whether water is used for cooling or not, the water temperature and the like.
Preferably, the method for designing the crack resistance K value of the temperature crack control of the tunnel floor lining concrete provided by the invention can also have the following characteristics: in the step 2, a temperature control anti-cracking target and an anti-cracking safety coefficient allowable value (K) are determined according to design specifications, the grade of a lining structure, the damage of a crack in a running period, safety and anti-seepage requirements.
Preferably, the method for designing the crack resistance K value of the temperature crack control of the tunnel floor lining concrete provided by the invention can also have the following characteristics: according to the design of the hydraulic and hydroelectric engineering and the related underground engineering and the construction specification, the related regulations of temperature control crack resistance of underground hydraulic lining concrete, the operating characteristics and the working performance requirements of the underground hydraulic engineering, considering the construction period temperature crack control, and referring to the research and experience of temperature crack control in the construction period of the underground hydraulic lining concrete of more than 10 large-scale hydraulic and hydroelectric engineering in the last 20 years, such as three gorges, lineage, etc., the underground hydraulic engineering door-hole type tunnel floor lining concrete temperature control crack resistance grading target and the crack resistance safety coefficient allowable value (K) are suggested to be as shown in the following table 1:
TABLE 1 temperature-controlled crack-resistant grading target for lining concrete of bottom plate of urban door opening type tunnel and allowable value of crack-resistant safety coefficient (K)
Note: when [ K ] is "without limitation" means KminThe calculation result of (A) is that any value meets the condition of being more than or equal to (K).
Preferably, the method for designing the crack resistance K value of the temperature crack control of the tunnel floor lining concrete provided by the invention can also have the following characteristics: in the step 3-1, in different temperature control crack resistance design stages, analyzing design parameters which are related to temperature control crack resistance and can be changed in the stage under the condition of meeting the standard requirement; in the structural design stage, the lining thickness and the concrete strength are main variable quantities; in the construction stage, the pouring temperature, the water cooling and the water temperature thereof and the heat preservation of the closed hole in winter (the lowest temperature in winter is increased) are mainly variable. Because the winter sealing hole heat preservation (improving the winter minimum temperature) is an economic and effective measure which must be taken, the proposed construction measure scheme mainly comprises the combination of pouring temperature, water cooling and water temperature.
Preferably, the method for designing the crack resistance K value of the temperature crack control of the tunnel floor lining concrete provided by the invention can also have the following characteristics: in step 3-2, when the lining concrete adopts the strength grade designed in the 28-day age, the strength grade is converted into the strength grade designed in the 90-day age 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 isaAnd TminAn elevated temperature of the air in the hole should be used. In addition, the thickness of the lining concrete is generally smaller, the water-cooling water pipes are arranged in a single row, namely, the formula is suitable for the situation that the water-cooling water pipes are arranged in the single row.
In addition, the formula 1 proposed in the step 3-2 is based on the deep research and study on the bottom plate structure of the urban door opening type tunnel and the related parameters thereofAnalysis is carried out, and the structure of the bottom plate of the pressureless city gate cave tunnel of the brook ferry hydropower station shown in fig. 3 and relevant parameters are taken as an example for explanation: based on the bottom plate structure of the urban door opening type tunnel and relevant parameters thereof, and combined with similar projects in China, a three-dimensional model as shown in figure 4 is established, and finite element method simulation calculation is carried out on various possible conditions (127 schemes). The basic parameters and calculation schemes are shown in the following table 2, and the minimum crack resistance safety factors K in the concrete lining construction period of each schememinAlso listed in table 2:
TABLE 2 calculation scheme of temperature stress of lining concrete of bottom plate of urban door opening type tunnel and minimum crack resistance safety factor Kmin
Minimum crack resistance safety factor K for urban door opening type tunnel floor lining concrete construction period of table 2minThe calculated value is subjected to statistical analysis and deep research, and the obtained result is consistent with the formula 1.
Action and Effect of the invention
The design method for the crack resistance control safety coefficient of the tunnel floor lining concrete temperature crack provided by the invention has a simple calculation formula, and can comprehensively and reasonably reflect the influences of main factors such as the structure size of the lining, the strength grade of concrete, the performance (deformation modulus) of surrounding rock, the pouring temperature, the annual change of the temperature of air in the tunnel, the temperature of air in the tunnel in the pouring period (pouring season), whether water cooling is conducted or not, the water temperature and the like. And can quicklyQuickly calculating the minimum anti-crack safety coefficient K of the floor structure lining concrete construction period of the gate-hole type tunnel in any seasonminSmall calculation error and can be completely used for anti-cracking safety coefficient K of practical engineeringminAnd (3) calculating and temperature control anti-cracking measure scheme design, in particular to preliminary design and real-time rapid design and calculation in the field construction period.
Drawings
FIG. 1 is a diagram of a concrete crack lining a flood discharging tunnel of a three-plate creek power station in the background art;
FIG. 2 is a diagram of a concrete crack lining an underground water transport tunnel of a permanent ship lock of the three gorges hydro-junction in the background art;
FIG. 3 is a schematic structural view of a bottom plate lining concrete of an urban door opening tunnel according to an embodiment of the present invention;
FIG. 4 is a three-dimensional finite element model diagram of a lining structure of a bottom plate of an urban door opening type tunnel according to an embodiment of the present invention;
FIG. 5 is a flow chart of a design method for controlling crack resistance K value of a temperature crack of a tunnel floor lining concrete according to an embodiment of the present invention;
fig. 6 is an annual temperature change curve of the actual measurement spillway tunnel cavern according to the embodiment of the invention.
Detailed Description
The concrete implementation of the method for designing the crack resistance K value of the temperature crack control of the tunnel floor lining concrete according to the invention is explained in detail by using the calculation example of the temperature stress of the urban door tunnel lining concrete at the non-pressure section of the flood discharge tunnel of the river luo-crossing hydropower station in combination with the attached drawing.
< xi Luo Du hydropower station basic data >
(1) Overview
The hydropower station is a large (I) type, and the flood discharge tunnel is a level I building. As shown in FIG. 3, the pressureless section is an urban door opening type tunnel, various surrounding rock properties and lining types thereof are listed in the following Table 3, and the length of the parting of the lining structure is 9 m. Wherein the section of the lining structure with the thickness of 1.0m is shown in figure 3, and the section size is unchanged after lining with the rest thicknesses. Floor lining concrete design strength grade of C9040 normal concrete; the side wall is C9040 pumping concrete; c25 is formed by the water lines of the top arch and the side wall being more than 1.0 m. According to the measurement data in the initial excavation stage and the data provided by a design institute, the design unit takes the average temperature in the tunnel per year as 23.0 ℃, the annual variation of the temperature as +/-3.0 ℃, and the following normalized cosine formula is adopted for calculation. 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 ℃.
In the formula: t isaAir temperature (. degree. C.) at time τ inside the hole; τ is the time (day) 1 day from 1 month; tau is0Taking tau as the time (day) between the highest temperature in the tunnel and 1 month and 1 day0Day 210.
TABLE 3 non-pressure section city gate tunnel lining and surrounding rock classification
(2) Temperature-controlled anti-cracking measures and design specifications
According to the related design specifications, the concrete mixing proportion optimization and performance tests thereof, and the finite element method calculation results, the design institute determines the temperature control standard of the lining concrete of the non-pressure section of the spillway tunnel and the pouring temperature to be listed in the following table 4.
TABLE 4 temperature control Standard for non-pressure section lined concrete
The following scheme is recommended during summer construction: the non-pressure section has the concrete pouring temperature of 18 ℃, the water pipe interval of 1.0m, the water pipe length of 100m and the cooling water flow of 2.0m3And h, cooling the concrete at the temperature of 14-20 ℃, and introducing water for cooling for 7 days when the concrete is poured. In winter construction, natural warehousing concrete can be adopted for pouring under the condition that the concrete pouring temperature can be lower than 18 ℃.
(3) Temperature-controlled anti-cracking 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 concrete temperature control anti-cracking scheme for 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 water is kept moist for 1h, uninterrupted curing is carried out when the temperature exceeds 25 ℃, and the curing time of the pressure section, the side 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 and the overtemperature conditions of the non-pressure sections of the left and right bank flood discharging tunnels (limited to space, only 2010 of the peak period) and are listed in the following tables 5 and 6.
Table 52010 statistics table of internal highest temperature of lining concrete of flood discharge tunnel
Statistical table of concrete pouring temperature of lining concrete of flood discharging tunnel on left bank and right bank in 62010 years
As can be seen from the upper tables 5 and 6, the temperature control effect of the lining concrete of the non-pressure section of the flood discharge tunnel is overall good, the pouring temperature overtemperature proportion is higher, the highest temperature overtemperature (design allowable value) proportion is lower, and the control effect of the right bank is better. The pouring temperature of lining concrete of the right bank is 4.30 percent of the overtemperature proportion of the bottom plate, and the overtemperature of the side wall is not higher, and is 2.86 percent on average; the highest temperature in the concrete is not overtemperature.
(5) Lining concrete crack conditions
The lining concrete crack condition of the gate tunnel type tunnel of the flood discharge tunnel non-pressure section is listed in the following table 7 according to the structure section and the construction section statistics:
TABLE 7 left and right bank flood discharge tunnel non-pressure section city gate tunnel type tunnel lining concrete crack condition
According to the structural characteristics of the flood discharge tunnel, the lining concrete construction process and the statistical conditions of the cracks in the upper table 7, the following knowledge can be obtained through comprehensive analysis:
(A) the side arch lining concrete has more cracks. The bottom plate of the non-pressure section is only provided with 2 bins with cracks. Estimates are associated with side wall (side crown) dimensions larger than the floor. In addition, the right bank of the bottom plate of the non-pressure section is cast and leveled with concrete, cracks are less than those of the left bank, and the influence is small.
(B) Compared with flood discharging holes on two banks, the holes on the left bank No. 1 and the right bank No. 2 have more cracks than those on the right bank No. 3 and No. 4, and are related to that the highest temperature and over-temperature proportion of the lining concrete on the left bank is large (including the influence of higher water cooling temperature) and the lining concrete on the top arch of the falling tail section of the right bank is separately poured.
(C) According to the details of the general investigation of the cracks, the harder the surrounding rock, the more complete the temperature cracks. The lining is a hard and complete II-type surrounding rock area of the surrounding rock, and is a main occurrence area of temperature cracks although the lining thickness is small; the lining concrete with large thickness in the IV-type surrounding rock area generally has few temperature cracks. The harder the surrounding rock, the stronger the restraint to the lining concrete.
(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 above also lists the results of a large number of finite element method simulation calculations for the no-pressure-section bottom plate. Such as: III 1 type surrounding rock area F2 type 1.0m thick lining casting 7 months and 1 day in summer, casting at 18 ℃ in the construction stage and water cooling at 22 ℃ in the calculation scheme 25 sigmamax3.05MPa, and the minimum crack resistance safety factor is 1.69; in the construction stage, the minimum anti-cracking safety coefficient of the calculation scheme 2 is 1.78 by pouring at 18 ℃ and water cooling at 12 ℃, and the minimum anti-cracking safety coefficient of the calculation scheme 7 is 1.60 by pouring at 18 ℃ and water cooling; IV-type surrounding rock area F4 type 1.5m thick lining casting in 7 months and 1 day in summer, casting at 18 ℃ in the construction stage and water cooling at 12 ℃ in the calculation scheme 38 of sigmamax2.43MPa, and the minimum cracking safety factor is 2.17.
< embodiment I > flood discharge tunnel non-pressure section city gate tunnel type tunnel III 1 class surrounding rock area F2 type lining with thickness of 1.0m
A III 1 type surrounding rock area F2 type lining with the thickness of 1.0m is a structural section with the largest quantity and larger temperature control crack resistance difficulty in the gate tunnel type tunnel of the flood discharge tunnel non-pressure section.
As shown in fig. 5, the method for designing the crack resistance K value for controlling the temperature crack of the tunnel floor lining concrete provided by this embodiment includes the following steps:
step 1, collecting data for controlling and calculating the temperature crack of lining concrete of a bottom plate of the tunnel with the city gate hole:
lining structure design data, lining structure section and concrete strength grade; environmental data, deformation modulus of surrounding rock under geological conditions, annual change rule of air temperature in the tunnel, annual change rule of water temperature and other basic data.
Step 2, analyzing and determining a temperature control anti-cracking target and an anti-cracking safety coefficient allowable value (K):
the river luodie spillway tunnel is a first-level building, the flow rate is high, the damage of cracks in the operation period is large, similar engineering experience is referred, and according to the table 1, the temperature control anti-cracking target of the lining concrete is anti-cracking in level 1, and the allowable value (K) of the anti-cracking safety coefficient is 1.6.
Step 3, designing a temperature control anti-cracking measure scheme, comprising the following substeps:
step 3-1, analyzing variable quantity, and drawing up a plurality of temperature control anti-cracking construction measure schemes of lining concrete;
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. For casting in summer 7 months, the bidding document can provide refrigerated commercial concrete at the outlet of the machine at 14 ℃, and the casting temperature is 18 ℃. According to construction conditions, 3 temperature control schemes of 18 ℃ pouring temperature, no water cooling, 12 ℃ refrigerating water cooling and 22 ℃ normal temperature water cooling are planned.
Step 3-2, calculating the minimum crack resistance safety coefficient K of each scheme in the concrete lining construction period by adopting the following formulamin：
In the design stage, the air temperature Ta in the hole in the casting period of 7 months and 1 day is calculated to be 25.63 ℃ according to the formula 2, and the lowest air temperature T in winter min20 ℃. According to the above data, H is 1.0m, W is 15.2m, L is 9m, C is 40, E is 20GPa, T018 ℃ and date 181 d. The 3 proposed temperature control schemes (Tg calculated as 0 deg.C, 23 deg.C, 13 deg.C, respectively) and the above parameters were substituted into the above (equation 1) to calculate: non-aerated Water Cooling protocol Kmin2.28; 12 ℃ refrigeration water through-water cooling scheme Kmin2.47; water cooling scheme K for water at normal temperature of 22 DEG Cmin2.39, which are all larger than 1.6, and the margin is large.
Step 3-3. at KminAnd under the condition of not less than K, a measure scheme is optimized according to the principle of simplicity, practicability and economy for application. According to the 3 scheme calculation results, the scheme K is cooled without watermin2.28, meets the requirement, and is most economical, simple and practical. Therefore, construction is recommended.
The real-time temperature control anti-cracking measure scheme in the construction process is specifically designed as follows:
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, temperature measurements were performed over 300 times for the spillway tunnels (left and right banks), and the results are summarized in fig. 6. With day 1 of 2010 as the date axis for day one. Wherein the abscissa is time (days); the ordinate is temperature (. degree. C.). And (3) performing cosine function fitting by adopting a least square method to obtain:
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, the calculation must be redesigned in real time during construction.
According to the design method, pouring construction is carried out 7 months and 1 day in summer, and the temperature T in the hole is calculated according to a formula 3aAt 25.23 deg.C, and the winter lowest temperature Tmin12.59 ℃. Calculating 3 schemes of water-tight cooling, water-tight cooling at 12 ℃ and water-tight cooling at 22 ℃ under the condition of pouring the concrete at 18 ℃ to obtain Kmin1.59, 1.78, 1.70. The crack resistance safety coefficient of the cast concrete at 18 ℃ under the condition of water-free cooling is slightly less than 1.6, and the crack resistance safety coefficients of cast concrete at 18 ℃ and water cooling at 12 ℃ and cast concrete at 18 ℃ and water cooling at 22 ℃ are all more than 1.6.
According to the calculation result of the three schemes, a 18 ℃ pouring and 22 ℃ water cooling scheme Kmin1.78, meets the requirement, and is most economical, simple and practical. Therefore, construction is recommended.
< example II > flood discharge tunnel non-pressure section city gate tunnel type tunnel III 2 type surrounding rock area F4 type lining
(1) The basic data are the same as above. In order to reduce space, summer temperature control calculation results in a design stage and a construction real-time control stage are only briefly introduced.
(2) Analyzing and determining temperature control anti-cracking target and anti-cracking safety coefficient allowable value (K)
The river luodie spillway tunnel is a first-level building, the flow rate is high, the damage of cracks in the operation period is large, similar engineering experience is referred, and according to the table 1, the temperature control anti-cracking target of concrete is lined with 1-level anti-cracking, and the allowable value (K) of the anti-cracking safety coefficient is 1.6.
(3) Design stage temperature control crack resistance scheme design
And according to the construction conditions, 3 temperature control measures of 18 ℃ of pouring temperature, no water cooling, 12 ℃ of refrigerating water cooling and 22 ℃ of normal temperature water cooling are drawn up.
In the design stage, the air temperature in the tunnel in the 7-month and 1-day pouring period is calculated by the formula 2 to be 25.63 ℃, and the lowest air temperature T in winter min20 ℃. According to the above data, H is 1.5m, W is 15.2m, L is 9m, C is 40, E is 5GPa, T018 ℃ and date 181 d. The 3 proposed temperature control schemes (Tg 0 deg.C, 23 deg.C, 13 deg.C, respectively) and the above parameters were substituted into equation 1 to calculate: non-aerated Water Cooling protocol Kmin2.54; 12 ℃ refrigeration water through-water cooling scheme Kmin2.74; water cooling scheme K for water at normal temperature of 22 DEG Cmin2.65, both greater than 1.6. According to the 3 scheme calculation results, the scheme K is cooled without watermin2.54, meets the requirement, and is most economical, simple and practical. Therefore, construction is recommended.
In the construction real-time control stage, pouring construction is carried out in 1 day in 7 months in summer, and the temperature T in the holeaAt 25.23 deg.C, and the winter lowest temperature Tmin12.59 ℃. Similarly, the anti-crack safety coefficient K of 3 schemes of cooling without water, cooling with 12 ℃ and cooling with 22 ℃ normal temperature water at the pouring temperature of 18 ℃ is calculated by the formula 1min1.97, 2.17 and 2.08, the requirement of 1.6 is met. The scheme of cooling without water is poured at 18 ℃, so that the requirement is met, and the method is most economical, simple and practical. Therefore, construction is recommended.
The minimum crack resistance safety coefficient is calculated by combining the finite element method 18 ℃ pouring +12 ℃ water cooling scheme 38, the minimum crack resistance safety coefficient is 2.17, the calculated value is equal to the calculated value of the formula 1, and the calculation precision of the formula 1 is very high. It is reasonable to recommend a construction scheme.
< comparative analysis >
Compared with the finite element method calculation result:
the III 1 type surrounding rock area F2 type 1.0m lining is poured 7 months and 1 day in summer, 3 schemes of water-tight cooling pouring at 18 ℃, water cooling pouring at 12 ℃ and water cooling pouring at 18 ℃ and water cooling at 22 ℃ are poured in the construction stage, and the calculated values of the finite element method and the formula 1 in each scheme are listed in Table 8; the F4 type 1.5m thick lining of the IV type surrounding rock area is poured 7 months and 1 day in summer, the scheme of pouring at 18 ℃ and water cooling at 12 ℃ is adopted in the construction stage, and the calculated values of the finite element method and the formula 1 are also listed in the following table 8; the errors and relative errors are also listed in table 8 below. As can be seen from Table 8, the maximum error is only 0.01, and the maximum relative error is only 0.6%, which completely meets the calculation accuracy requirement of engineering design.
TABLE 8 comparison of formula 1 of each temperature control measure scheme with the calculated value of the finite element method
Comparison with results of temperature crack inspection:
in actual engineering, a recommended 18 ℃ pouring +22 ℃ water cooling scheme is finally adopted. According to the actual temperature in the tunnel in the construction period, the minimum anti-cracking safety coefficient of the actual temperature control measure scheme of the project is calculated by using a formula 1, the anti-cracking safety coefficients of the actual construction scheme conditions of pouring concrete in the III 1 and IV type surrounding rock areas at 18 ℃ and cooling by water at 22 ℃ are all larger than 1.6, and the possibility of temperature cracks is very low. And the cracking resistance safety coefficient of the lining of the III type 1 surrounding rock area is smaller than that of the IV type surrounding rock area, but the possibility of cracking of the concrete lining of the III type 1 surrounding rock area is also very small. Compared with the temperature crack inspection results in the table 7, the calculation results in the formula 1 are very consistent with the results in the table 7 on the basis that only the surrounding rock areas of the type II and type III 1 of the 1# hole have two cracks and the rest have no cracks, and on the basis that the surrounding rock is harder and the temperature cracks are more complete and the calculation results in the formula 1 are very consistent with the results in the table 7.
The calculation formula is simple, and the influences of main factors such as the structure size of the lining, 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 pouring, whether water cooling is conducted or not, the water temperature and the like can be comprehensively and reasonably reflected. The minimum crack resistance safety factor and the design temperature control crack resistance scheme in the construction period of the floor structure lining concrete of the cast door-hole type tunnel in any period can be rapidly calculated, the calculation error is small, and the method can be completely used for temperature crack control design calculation in actual engineering, particularly for preliminary design and real-time rapid design calculation in the field construction period.
The protection scope of the invention is not limited to the lining concrete structure of the bottom plate of the hydraulic tunnel and the tunnel portal type tunnel, and can be completely applied to similar projects, particularly underground engineering structures and other linings by proper adjustment and deformation. It will be apparent to those skilled in the art that certain modifications may be made in the present invention without departing from the scope or spirit of the invention. It is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.
The above embodiments are merely illustrative of the technical solutions of the present invention. The method for designing the crack resistance K value of the temperature crack control of the tunnel floor lining concrete is not limited to the contents described in the above embodiments, but is subject to the scope defined by the claims. Any modification or supplement or equivalent replacement made 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 (6)
1. A method for designing a crack resistance K value of a tunnel floor lining concrete temperature crack control is characterized by comprising the following steps:
collecting data for controlling and calculating the temperature crack of the lining concrete of the tunnel floor;
step 2, analyzing and determining a temperature control anti-cracking target and an anti-cracking safety coefficient allowable value (K);
step 3, designing a temperature control anti-cracking measure scheme, comprising the following substeps:
step 3-1, analyzing variable quantity, and drawing up a plurality of temperature control anti-cracking construction measure schemes of lining concrete;
step 3-2, calculating the minimum crack resistance safety coefficient K of each scheme in the concrete lining construction period by adopting the following formulamin：
Kmin＝6.1566－1.4763×H+0.062×W－0.103×L－0.0069×C－0.0241×E－0.0367×T0+0.0072×Tg+0.0966×Ta－0.0673×(Ta－Tmin)－3.505/H+0.013×(Ta－Tmin)/H+0.2538×H2+1.1966/H2－0.0384×(Ta－Tmin)/H2+0.0004×E2－0.0026×W2－0.019×H×T0+0.0011×H×Tg－0.003×E×H－0.0004×date+0.0408cos(2π(date-120)/365)
In the above formula: kminThe minimum crack resistance safety factor is set for the construction period of lining concrete of the tunnel floor; h is the thickness of the lining concrete structure; w is the width of the bottom plate; l is the length of the parting; e is the deformation modulus of the surrounding rock; c is the strength grade of the lining concrete designed according to the age of 90 days; t is0Pouring temperature for lining concrete; t isaThe air temperature in the tunnel when the lining concrete is cast; t isminThe lowest winter temperature in the hole; t isg＝35-TwThe temperature effect values of the water and water cooling are shown, and T is taken without water coolingwAt 35 ℃, T in the presence of cooling waterwThe temperature of water is the temperature of water; date is the number of days from 1 month to 1 day when pouring;
step 3-3. at KminAnd under the condition of not less than K, a measure scheme is optimized according to the principle of simplicity, practicability and economy for application.
2. The method for designing the crack resistance K value of the temperature crack control of the tunnel floor lining concrete according to claim 1, is characterized in that:
wherein, in step 1, the collected data for calculation includes: the lining structure comprises lining structure design data of temperature control anti-cracking design and calculation results, tunnel bottom plate lining thickness and bottom plate width, concrete strength grade, environment data of geological condition surrounding rock deformation modulus, air temperature annual change rule in a tunnel and water temperature annual change rule, and concrete pouring construction data of concrete pouring construction temperature control measure scheme, pouring temperature, air temperature in the tunnel during pouring construction, water cooling and water temperature.
3. The method for designing the crack resistance K value of the temperature crack control of the tunnel floor lining concrete according to claim 1, is characterized in that:
in the step 2, a temperature control anti-cracking target and an anti-cracking safety coefficient allowable value (K) are determined according to design specifications, the grade of a lining structure, the damage of a crack in a running period, safety and anti-seepage requirements.
4. The method for designing the crack resistance K value of the temperature crack control of the tunnel floor lining concrete according to claim 1, is characterized in that:
for different positions, different building grades and different anti-cracking grades, a temperature control anti-cracking target and an anti-cracking safety coefficient allowable value (K) of the tunnel floor lining concrete are shown in the following table:
when [ K ] is not limited, KminThe calculation result of (A) is that any value meets the condition of being more than or equal to (K).
5. The method for designing the crack resistance K value of the temperature crack control of the tunnel floor lining concrete according to claim 1, is characterized in that:
in the step 3-1, in different temperature control crack resistance design stages, analyzing design parameters which are related to temperature control crack resistance and can be changed in the stage under the condition of meeting the standard requirement; in the structural design stage, the thickness of a lining and the strength of concrete are taken as main variable quantities; in the construction stage, the pouring temperature, the water cooling and the water temperature thereof, and the heat preservation and temperature control measures of the closed hole in winter are taken as main variable.
6. The method for designing the crack resistance K value of the temperature crack control of the tunnel floor lining concrete according to claim 1, is characterized in that:
wherein, in step 3-2, when the strength grade designed for 28-day-old lining concrete is adopted, the strength grade needs to be converted into 90-day-old lining concrete according to the specificationThe strength grade of the design; if the curtain is adopted for heat preservation in the construction period, the air temperature of the underground cavern is increased, and T isaAnd TminAn elevated temperature should be used.
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| CN110532649B (en) * | 2019-08-12 | 2021-07-20 | 武昌理工学院 | Temperature control anti-cracking temperature stress control design method for concrete of end free lining plate |
| CN113191043B (en) * | 2021-04-13 | 2022-04-29 | 武昌理工学院 | Hydraulic tunnel lining concrete temperature crack control strong constraint method and temperature control system |
| CN114592887B (en) * | 2022-03-14 | 2023-05-09 | 中国水利水电科学研究院 | Design method for joint-joining process of expansion joint of lining of water delivery tunnel |
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