CN109885915B - Method for rapidly calculating maximum temperature tensile stress of circular section lining concrete in construction period - Google Patents
Method for rapidly calculating maximum temperature tensile stress of circular section lining concrete in construction period Download PDFInfo
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- CN109885915B CN109885915B CN201910105183.6A CN201910105183A CN109885915B CN 109885915 B CN109885915 B CN 109885915B CN 201910105183 A CN201910105183 A CN 201910105183A CN 109885915 B CN109885915 B CN 109885915B
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Abstract
The invention provides a maximum temperature tensile stress of a circular section lining concrete in a construction periodThe quick calculation method comprises the following steps: step 1, collecting data for temperature control and crack prevention calculation of the lining concrete with the circular section; step 2, calculating the maximum temperature tensile stress sigma of the circular section lining concrete in the construction periodmax＝0.1672H+0.15R+0.0718C‑0.003E+0.1431T0+0.0758Tg‑0.1958Ta+0.0299H×E+0.244△T‑0.0022C×Tg‑0.0062H×Tg-0.838. The method has simple calculation formula, can quickly calculate the maximum temperature tensile stress of the circular section lining structure concrete in any period in the construction period, has small calculation error, and can carry out real-time quick calculation on the temperature tensile stress in the construction period aiming at the change of problems, construction technology, conditions and the like in the casting construction process.
Description
Technical Field
The invention belongs to the technical field of temperature control and crack prevention of engineering structure concrete, and particularly relates to a method for quickly calculating maximum temperature tensile stress of a circular section lining concrete in a construction period.
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, in the specification of "hydraulic concrete structure design regulation" at 4.1.2(3), "structural members required to be crack-controlled in use should be subjected to crack prevention or crack width checking calculation", and in the specification of 4.1.8, "during construction and operation of a building, if the temperature change has a great influence on the building, temperature stress calculation should be performed, and construction measures should be 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, 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. Especially, the prior relevant specifications have no requirement value of the anti-cracking safety coefficient of the temperature control anti-cracking design in the construction period, and the design specifications of the dam are all referred to when the temperature control anti-cracking design of the hydraulic tunnel lining concrete is adopted.
Most design units propose 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 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 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 present invention is made to solve the above problems, and an object of the present invention is to provide a method for rapidly calculating a maximum temperature tensile stress during a concrete construction period of a circular cross-section lining structure as shown in fig. 3, which can be used for optimizing and improving a construction temperature control measure in real time to achieve a temperature control goal in a casting construction process for finding a problem and changing a construction technology, conditions, and the like.
In order to achieve the purpose, the invention adopts the following scheme:
the invention provides a method for quickly calculating the maximum temperature tensile stress of a circular section lining concrete in a construction period, which is characterized by comprising the following steps of:
step 1, collecting data for temperature control and crack prevention calculation of the lining concrete with the circular section;
step 2, calculating the maximum temperature tensile stress sigma of the circular section lining concrete in the construction periodmax：
σmax＝0.1672H+0.15R+0.0718C-0.003E+0.1431T0+0.0758Tg-0.1958Ta+0.0299H×E+0.244△T-0.0022C×Tg-0.0062H×Tg-0.838 (equation 1),
in the above 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 a circular section lining concrete structure; 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; 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 (DEG C); 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 (. degree. C.) was measured.
Substituting the thickness and the inner radius of the circular 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 into the formula 1, and calculating to obtain the maximum temperature tensile stress of the circular section lining concrete in the construction period corresponding to the period.
Preferably, the method for rapidly calculating the maximum temperature tensile stress of the circular cross-section lining concrete in the construction period provided by the invention can also have the following characteristics: in step 1, the collected data for calculation includes: the lining structure design data, in particular the temperature control anti-cracking design and calculation result, the lining thickness and the inner radius, and the concrete strength grade; environmental data, especially geological condition surrounding rock deformation modulus, air temperature annual change rule in the tunnel and water temperature annual change rule; concrete pouring construction data, in particular to a concrete pouring construction temperature control measure scheme, a pouring temperature, an air temperature in a hole during pouring construction, whether water is introduced for cooling, a water temperature and the like.
Preferably, the method for rapidly calculating the maximum temperature tensile stress of the circular cross-section lining concrete in the construction period provided by the invention further comprises the following steps: step 3, analyzing the maximum temperature tensile stress sigmamaxAnd (3) influencing the temperature control anti-cracking target and adopting corresponding control measures.
Preferably, the method for rapidly calculating the maximum temperature tensile stress of the circular cross-section lining concrete in the construction period provided by the invention can also have the following characteristics: the step 3 specifically comprises the following substeps: step 3-1, analyzing the temperature control anti-cracking data of the lining structure, particularly analyzing and knowing a temperature control anti-cracking target and crack control indexes, concrete strength and allowable tensile stress value, and an original temperature control measure scheme and allowable tensile stress value; step 3-2, comparing and analyzing tensile stress values: the calculated maximum temperature tensile stress sigmamaxComparing the temperature control measure scheme with the allowable tensile stress value and the allowable concrete tensile stress value, and analyzing and checking whether the requirements are met; step 3-3, real-time improvement and optimization of the measure scheme: according to the comparative analysis result, if the tensile stress is rich (the tensile stress is small), optimizing and lightening the temperature control measures (if water cooling is not carried out), and if the tensile stress exceeds the control value, strengthening the temperature control measures (if cooling by adopting cooling water and water cooling is strengthened, and the pouring temperature is reduced).
Preferably, the method for rapidly calculating the maximum temperature tensile stress of the circular cross-section lining concrete in the construction period provided by the invention can also have the following characteristics: in step 2, when the lining concrete adopts the strength grade designed for 28-day age, the strength designed for 90-day age is required according to the specificationDegree grade; 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 2 is obtained based on the intensive research and analysis of the circular cross-section lining concrete structure and related parameters thereof. The structure of the pressurized-segment circular cross-section lining of the stream luo-ferry spillway tunnel shown in fig. 3 and related parameters thereof are taken as an example for explanation: based on the circular section lining structure and related parameters thereof, and combined with similar domestic engineering, a three-dimensional model as shown in figure 4 is established, and finite element method simulation calculation is carried out on various possible conditions (125 schemes). The basic parameters and calculation schemes are shown in Table 1 below, and the maximum temperature tensile stress sigma is shown in each scheme during the concrete lining construction periodmaxAlso listed in table 1:
TABLE 1 calculation scheme of temperature stress and maximum temperature tensile stress of lining concrete with circular section
Maximum temperature tensile stress σ for the lining concrete construction period of Table 1maxStatistical analysis and study were performed to obtain results consistent with equation 1 above.
Action and Effect of the invention
The method for quickly calculating the maximum temperature tensile stress of the circular section lining concrete in the construction period has a simple calculation formula, and can comprehensively and reasonably reflect the influences of main factors such as the thickness and the center line radius of a portal lining structure, the concrete strength grade, the surrounding rock performance (deformation modulus), 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 carried out 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 during the concrete lining construction period, has small calculation error, and can be completely used for temperature stress calculation of actual engineering, particularly preliminary design and real-time rapid calculation analysis during on-site construction.
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 round cross-section lining concrete according to an embodiment of the present invention;
FIG. 4 is a three-dimensional finite element model diagram of a lining structure with a circular cross section according to an embodiment of the present invention;
FIG. 5 is a flow chart of a method for rapidly calculating maximum temperature tensile stress during construction of a circular cross-section lining concrete according to an embodiment of the present invention;
fig. 6 is an annual temperature change curve diagram of the cavern of the spillway tunnel according to the embodiment of the invention.
Detailed Description
The concrete embodiment of the method for rapidly calculating the maximum temperature tensile stress in the construction period of the circular cross-section lining concrete is explained in detail by using a calculation example of the temperature stress of the circular cross-section lining concrete of the pressure section of the flood discharge tunnel of the Xiluou 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 the figure3, the pressed section is a circular section, the types of lining and surrounding rock are listed in the following 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.
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 2 flood discharge Tunnel Lining and surrounding rock Classification
(2) Temperature control anti-cracking design requirement
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 temperature in the tunnel is calculated by adopting the formula 2)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 2.0m3H, cooling water temperature of 20 ℃ (normal temperature water), and concrete placementWhen building, water is introduced and cooled 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 concrete temperature control and crack prevention 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 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 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 concrete surface cracks caused by cold air poured into the tunnel are avoided.
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 flood discharge tunnels on the left bank and the right bank and the overtemperature condition of the pressure section lining concrete, and the results are listed in the following tables 3-6.
Table 32010 years flood discharge tunnel lining concrete internal highest temperature statistical table
Table 42010 years statistical table of concrete pouring temperature of left and right bank flood discharging tunnel lining
Table 52011 statistics table of internal highest temperature of flood discharging tunnel lining concrete of left and right banks in year
Statistical table of concrete pouring temperature of lining concrete of flood discharging tunnel on left bank and right bank in 62011 years
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 crack condition is lined on the round section of the flood discharge tunnel with the pressure section, the bottom arch concrete has no crack, and the statistics of the concrete crack of the side top arch are listed in the following table 7:
TABLE 7 left and right bank flood discharge tunnel pressure section circular section lining concrete crack condition
According to the characteristics of the pressure section structure of the flood discharge tunnel, the construction process of lining concrete and the statistical condition of the cracks of the upper 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 above also lists a number of finite element method simulation calculations. Such as: pouring lining with the thickness of 1.0m in the II-type surrounding rock area within 8 months and 1 day in summer, and designing the sigma of the phase calculation scheme 49max2.06MPa, and the minimum crack resistance safety factor is 1.88; sigma of the calculation scheme 5 at the construction stagemax4.4MPa, and the minimum cracking safety factor 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 cracking safety factor is 1.41.
< example I > flood discharge tunnel has a lining with thickness of 1.0m and type E1 surrounding rock zone type II with pressure section and circular section
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.
As shown in fig. 5, the method for rapidly calculating the maximum temperature tensile stress during the construction period of the circular cross-section lining concrete provided by this embodiment includes the following steps:
step 1, collecting data for temperature control and crack prevention calculation of the lining concrete with the circular cross section:
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, annual change rule of water temperature and other basic data.
Step 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 a formula 2aAbout.25 ℃. Scheme 1 was drawn up: constructing in summer, pouring at 18 ℃, cooling by water at 12 ℃, substituting the related parameters of E1 type lining of the round section class II surrounding rock area into a formula 1 to calculate sigmamax1.85 MPa. Scheme 2 was drawn up: summer construction, pouring at 16 ℃ and cooling with water at 16 ℃, and calculating to obtain sigmamax＝1.73MPa。
Step 3, analyzing the maximum temperature tensile stress sigmamaxThe method specifically comprises the following substeps of influencing a temperature control anti-cracking target and taking corresponding control measures:
and 3-1, analyzing and calculating temperature control anti-cracking data of the lining structure, particularly analyzing and knowing a temperature control anti-cracking target and crack control indexes, concrete strength and an allowable tensile stress value, and an original temperature control measure scheme and an allowable tensile stress value. The flood discharge tunnel has high flow rate, and concrete is lined to prevent harmful temperature cracks. Strength of concrete C9040, according to the design specification of a concrete structure, the standard value of the axial tensile strength is 2.39MPa, and the design value is 1.71 MPa.
Step 3-2, comparing and analyzing the tensile stress value, and calculating the maximum temperature tensile stress sigmamaxAnd comparing the temperature control measure scheme with the allowable tensile stress value and the allowable concrete tensile stress value, and analyzing and checking whether the requirements are met. Sigma of design phase finite element method calculation scheme 49 (pouring at 16 ℃ and water cooling at 16 ℃), andmax2.06MPa, and the minimum crack resistance safety factor is 1.88. The actual construction scheme is pouring at 18 ℃, water cooling at 12 ℃ and sigmamaxThe standard value of the tensile strength of the core is 1.85MPa, less than 2.06MPa and less than the standard value of the axial tensile strength, and therefore, the construction scheme is designed to meet the requirement.
And 3-3, according to the comparison and analysis result, the calculated tensile stress is equivalent to the calculated value of the original finite element method, so that the temperature control scheme is reasonable.
Calculating and analyzing the temperature stress of the lining concrete in real time in the 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, 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 design calculation must be carried out again in real time during the construction.
The construction is carried out by pouring in 8 months and 1 day in summer according to the design method, and the temperature T in the holeaPouring at 18 deg.C and cooling with water at 12 deg.C at 25.99 deg.C to obtain sigmamax4.15 MPa. Pouring at 16 ℃ and cooling with water at 16 ℃ to obtain sigmamax3.93 MPa. According to the construction stage of pouring at 16 ℃, water cooling at 16 ℃ and the sigma of the finite element method simulation calculation scheme 5max4.4MPa, and the minimum cracking safety factor is 1.22. The result shows that the construction scheme of 18 ℃ pouring and 12 ℃ water cooling has smaller crack resistance safety coefficient, still has crack risk, needs further enhanced temperature control, reduces pouring temperature, water cooling water temperature, enhances heat preservation of the hole in winter, improves the temperature in the hole and the like.
< example two > flood discharge tunnel with pressure section circular section III 2 type surrounding rock area E3 type lining
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.
In the design stage, pouring construction is carried out for 1 day in 8 months in summer, and the temperature T in the holeaPouring at 25 deg.C, pouring at 18 deg.C, cooling with water at 12 deg.C, and calculating to obtain sigmamax1.35 MPa; summer construction, pouring at 16 ℃ and cooling with water at 16 ℃, and calculating to obtain sigmamax1.13 MPa. The standard value of the tensile strength of the axle center is 2.39MPa, so the design construction scheme meets the requirements.
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 holeaPouring at 18 deg.C and cooling with water at 12 deg.C at 25.99 deg.C to obtain sigmamax3.65 MPa. Pouring at 16 ℃ and cooling with water at 16 ℃ to obtain sigmamax3.43 MPa. 16 ℃ pouring and 16 ℃ water cooling calculation scheme 21 in construction stage, and sigma calculated by finite element method simulationmax3.8MPa, and the minimum cracking safety factor is 1.41. The construction scheme that the casting at the temperature of 16 ℃ and the water cooling at the temperature of 16 ℃ basically meet the requirements, but the risk of cracks is low.
< comparative 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 formula 1 is 1.73MPa, and the error is-16%; in the construction stage, the sigma of the finite element method simulation calculation scheme 5maxThe calculated value of formula 1 is 3.93MPa under 4.4MPa with an error of-10.7%. 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 3.43MPa with an error of-9.7% at 3.8 MPa. And errors are small, and the requirement of engineering design calculation accuracy is met.
Comparison with temperature crack inspection results:
the stress result calculated by the formula 1 shows that lining concrete of the II-type and III-type surrounding rock areas have certain crack risks, and the stress of the lining of the II-type and III-type surrounding rock areas is much larger than that of the lining of the III-type and III-type surrounding rock areas, so that more concrete cracks are formed. Consistent with the conclusion of (C) of the results of the temperature fracture inspection of table 6, "harder the surrounding rock, more complete the temperature fracture".
The calculation formula is simple, and the influences of main factors such as the thickness and the inner radius of the lining structure, the concrete strength grade, the surrounding rock performance (deformation modulus), 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 is used for cooling, the water temperature and the like can be comprehensively and reasonably reflected. The method can quickly calculate the maximum temperature tensile stress of the concrete in the construction period of pouring the circular section structure lining side wall concrete at any time interval, has small calculation error, and can be completely used for temperature crack control design of actual engineering, particularly preliminary design and real-time quick design in the field construction period.
The protection scope of the invention is not limited to the hydraulic tunnel circular section lining side wall concrete structure, and can be completely applied to similar engineering, 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 to the 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 rapidly calculating the maximum temperature tensile stress during the construction of the circular cross-section 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 (4)
1. A method for quickly calculating the maximum temperature tensile stress of a circular section lining concrete in a construction period is characterized by comprising the following steps:
step 1, collecting data for temperature control and crack prevention calculation of the lining concrete with the circular section;
step 2, calculating the maximum temperature tensile stress sigma of the circular section lining concrete in the construction periodmax：
σmax=0.1672H+0.15R+0.0718C-0.003E+0.1431T 0 +0.0758T g -0.1958T a +0.0299H×E+0.244△T-0.0022C×T g -0.0062H×T g -0.838，
In the above formula: h is round section lining concrete knotThe thickness of the structure; r is the inner radius of a circular section lining concrete structure; e is the deformation modulus of the surrounding rock; c is the strength grade of the lining concrete with the circular section designed according to the age of 90 days; t is0The temperature for casting the circular section lining concrete; t isaThe air temperature in the tunnel is measured when the circular section lining concrete is cast; delta T is the annual variation of the temperature of the gas in the tunnel; t isg=35-TwThe temperature effect values of the water and water cooling are shown, and T is taken without water coolingw=35 ℃ C, T in the case of water coolingwThe temperature of water passage.
2. The method for rapidly calculating the maximum temperature tensile stress of the circular cross section lining concrete in the construction period according to claim 1, wherein the method comprises the following steps:
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, the thickness and the inner radius of a circular section lining section and 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 a 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 rapidly calculating the maximum temperature tensile stress during the construction period of the circular cross-section lining concrete according to claim 1, further comprising the following steps of:
step 3, analyzing the maximum temperature tensile stress sigmamaxAnd (3) influencing the temperature control anti-cracking target and adopting corresponding control measures.
4. The method for rapidly calculating the maximum temperature tensile stress of the circular cross section lining concrete in the construction period according to claim 1, wherein the method comprises the following steps:
in step 2, when the strength grade designed for 28-day age is adopted in the lining concrete with the circular cross section, the strength grade designed for 90-day age needs to be converted according to the specification; during construction period, for example, miningThe temperature of the air in the underground cave is increased by using the curtain for heat preservation, and T isaIncreasing the air temperature in the rear tunnel should be used.
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