Methods and systems for controlling early-stage surface cracks in silica fume lining concrete of spillway tunnels

Abstract

This invention provides a method and system for controlling early-stage surface cracks in silica fume lining concrete of spillway tunnels. It considers the influence of factors such as concrete slump and the thickness of the polyurethane foam layer spraying on surface cracks, aiming to optimize, economically rationally, and effectively control early-stage surface temperature cracks in the lining structure concrete. The method for controlling early-stage surface cracks in silica fume lining concrete of spillway tunnels includes: Step 1, collecting relevant data on the spillway tunnel; Step 2, formulating a basic scheme for construction measures to control early-stage surface temperature cracks in the silica fume lining concrete of the spillway tunnel's tail section; Step 3, determining various parameters based on the basic scheme formulated in Step 2 and the data collected in Step 1, and substituting them into Formula 1 below to calculate the control value F for early-stage surface temperature cracks in the silica fume lining concrete of the tail section; Step 4, optimizing and determining the control measures scheme for early-stage surface temperature cracks in the silica fume lining concrete of the spillway tunnel based on the control value F.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lining structure concrete temperature crack control, and particularly relates to a method and system for controlling early surface cracks of a spillway tunnel silicon powder lining concrete. BACKGROUND

[0002] The silicon powder concrete lining structure Figure 1 ) is generally only used in the tail section of a spillway tunnel high flow area to increase the concrete impact resistance and service life. The silicon powder lining of the tail section of the spillway tunnel high flow area has a structural thickness much smaller than the planar size (length, width), and belongs to a concrete in an extremely strong constraint area, which is prone to temperature cracks under the action of temperature difference. In particular, the concrete has high strength (generally above C50), the surface heat dissipation is fast, the temperature rise and fall is rapid, and the concrete experiences hydration heat temperature rise, temperature drop, and enters the periodical change with the ambient temperature in a short time. Without effective measures, the temperature cracks, especially the early surface cracks, are prone to occur, and most of the cracks develop into penetrating temperature cracks from the surface cracks during the construction period (see Figure 2 ). For example, the measured results of the Three Gorges permanent ship lock underground water delivery tunnel show that the temperature rise amplitude of NY9 structure section 1d reaches 73.00% to 77.51% of the total temperature rise value; the highest temperature reaches 52.15℃ within 2.4d, and the maximum temperature rise is 28.40℃; the formwork is removed after 3d, and the temperature drop reaches 7.90℃ to 17.35℃ at the 7d age. The early surface geometry and time temperature gradient are very large. The surface concrete in the early stage is subjected to internal constraint and generates a large tensile stress, and the concrete generates surface temperature cracks at the early stage of about 5d age, and penetrates at the 7d age. The existence of the penetrating harmful cracks seriously affects the safety of the engineering structure, the construction progress and period, causes leakage and even penetration damage, durability and service life, engineering cost and appearance, and may induce the occurrence and development of other diseases.

[0003] The lining structure of the tail section of the spillway tunnel high flow area has a small thickness, fast temperature rise and fall, and the lining structure is a high-strength silicon powder lining, the hydration heat temperature rise is larger, the temperature difference is larger, and the early surface temperature cracks are more prone to occur.

[0004] The constraint conditions of different structure forms of circular curves and straight lines and combinations thereof are significantly different, and the performances of the concrete mixed with different additional materials (such as silicon powder) are obviously different. In addition, another important influencing factor is the concrete slump, which has a great influence on the control of temperature cracks, especially early surface temperature cracks, but is not considered in the temperature crack control design so far.

[0005] For the silicon powder lining of the tail section of the high flow spillway tunnel, the crack is extremely harmful, and the control of the early surface temperature cracks is very important, but the control is more difficult. For example, the concrete is poured in winter, the tail section is difficult to be tightly sealed and heat preserved at the tunnel outlet (generally only heat preservation structures can be installed in the tunnel,Figure 3 (The insulation structure still cannot insulate the opening), the winter ambient temperature is low, and the annual temperature variation is large; the side walls are vertical and the opening roof cannot be covered with geotextile or other insulation materials; therefore, according to the requirements for controlling early surface cracks in concrete, it is necessary to spray a polyurethane foam layer onto the concrete surface for insulation. Figure 4 However, the impact of polyurethane foam layers has been lacking in temperature crack control designs to date. Summary of the Invention

[0006] The purpose of this invention is to provide a method and system for controlling early surface cracks in silica fume lining concrete of spillway tunnels. It takes into account the influence of factors such as concrete slump and polyurethane foam layer spraying thickness on surface cracks, so as to optimize, economically and effectively control early surface temperature cracks in silica fume lining concrete of the tail section of high flow velocity spillway tunnels.

[0007] To achieve the above objectives, the present invention employs the following solution:

[0008] <Method>

[0009] like Figure 5 As shown, the present invention provides a method for controlling early surface cracks in silica fume lining concrete of spillway tunnels, comprising the following steps:

[0010] Step 1: Collect relevant information about the spillway tunnel;

[0011] Step 2: Draft a basic plan for construction measures to control early surface temperature cracks in the silica fume lining concrete of the tail section of the flood discharge tunnel.

[0012] Step 3: Based on the basic scheme proposed in Step 2 and the data collected in Step 1, determine the parameters and substitute them into the following Formula 1 to calculate the early-stage surface temperature crack control value F of the silica fume lining concrete in the Longluo tail section:

[0013] F=16.84H-369.14H / L-0.1C×D+0.05E-0.06T a +0.21T0+1.09t m -14.36β-0.64H×C×D-0.40×

[0014] H×T0+0.05C×H×T0×D+0.42 (Formula 1)

[0015] In the formula: D is the concrete slump (m); H is the concrete thickness of the lining structure (m); L is the length of the long side of the lining structure (m); C is the 90-day design age strength grade of the lining structure concrete (MPa), such as C 90 40, then C = 40; E is the deformation modulus of the surrounding rock (GPa); T aT0 is the ambient temperature (°C) during the concrete pouring period of the lining structure; T0 is the concrete pouring temperature; β is the silica fume content, such as 7%, then β = 0.07; t0 m Let L be the formwork removal time (d) for silica fume lining concrete; where L is the length of the longer side, and for flat plate structures, the larger of the width and length is taken, such as... Figure 6 For a city gate-shaped cross-section bottom slab, the width is 16m and the joint length is 9m, then L = 16m; the side arches are cast separately, the side wall height is 14.87m and the joint length is 9m, then L = 14.87m; for a city gate-shaped cross-section structure ( Figure 1 In the case of integral casting of the side arch, due to symmetry, the height of the side arch is calculated as 1 / 2 of the side arch, that is, the vertical side wall is 14.87m + 1 / 2 of the arch arc length is 9.57m = 24.44m, which is greater than the joint length, so L = 24.44m;

[0016] Step 4: Optimize and determine the early surface temperature crack control measures for the silica fume lining concrete of the spillway tunnel based on the control value F and the surface insulation coefficient α related to the thickness of the polyurethane foam layer.

[0017] Preferably, the method for controlling early surface cracks in silica fume lining concrete of spillway tunnels provided by the present invention includes the following specific cases for real-time optimization control of early surface temperature cracks in step 4:

[0018] (1) If F≤0.1℃, then the basic scheme proposed in step 2 is suitable and can be used for construction;

[0019] (2) When F > 0.1℃, two situations should be distinguished: winter pouring (December to March of the following year) and pouring in other seasons. Temperature control measures should be strengthened for each situation, and the optimized measures should be used for construction.

[0020] Preferably, in the method for controlling early surface cracks in silica fume lining concrete of flood discharge tunnels provided by the present invention, in step 4, for winter pouring, a certain thickness h of sprayed polyurethane foam layer for insulation should be added based on the basic scheme proposed in step 2; first, different thicknesses h are proposed and substituted into formula 2 to calculate the surface insulation coefficient α for crack control, and the thickness h of the polyurethane foam layer is optimized and determined under the condition of satisfying formula 3.

[0021] α = 1.0 + 0.08h (Formula 2)

[0022] F-0.26(α-1)T a ≤0.1 (Formula 3)

[0023] For pouring in other seasons, water cooling and temperature control measures should be taken.

[0024] For the case where the tail section of the spillway tunnel is poured using a steel formwork trolley, if there is no insulation covering, h = 0, then α = 1.0. If the silica fume lining concrete of the tail section of the spillway tunnel is poured in winter, it is difficult to tightly seal the tunnel entrance for insulation because the tail section is located at the tunnel exit (generally, insulation structures can only be installed inside the tunnel). Figure 3 (The insulation structure still cannot insulate the opening), and geotextiles cannot be used to cover the vertical sidewalls and the top of the opening for insulation. Instead, polyurethane foam layers of varying thicknesses need to be sprayed onto the concrete surface for insulation. Figure 4 For polyurethane foam layer construction, see [link / reference]. Figure 7 The process involves turning on the polyurethane spraying machine and using a spray gun to evenly spray rigid polyurethane foam onto the concrete surface of the vertical sidewalls and ceiling, forming a polyurethane foam insulation layer. The thickness of the insulation layer is controlled during the spraying process according to the insulation design requirements.

[0025] Preferably, in the method for controlling early surface cracks in silica fume lining concrete of flood discharge tunnels provided by the present invention, in step 4, for pouring in other seasons, water cooling measures are added based on the basic scheme proposed in step 2, and different water temperatures are proposed, and water temperature that satisfies formula 4 is selected for water cooling.

[0026] F+0.04T g +0.014H×T g -0.008T0×T g ≤0.1 (Formula 4)

[0027] In the formula, T g =35℃-T w , representing the temperature effect value (°C) with and without water cooling, where T is taken as the temperature effect value without water cooling. w =35℃, under water cooling conditions T w The water temperature is in °C.

[0028] Specifically, the method for controlling early surface cracks in silica fume lining concrete of flood discharge tunnels provided by the present invention includes, in step 1, relevant information about the flood discharge tunnel, such as: project overview of the flood discharge tunnel, hydrological and meteorological conditions, design of the tail lining structure, technical requirements for silica fume lining concrete and its temperature control design, and technical information on temperature control during pouring construction.

[0029] Furthermore, in steps 3 and 4, when the lining concrete adopts the strength grade designed for 28 days, it needs to be converted to the strength grade designed for 90 days according to the specifications; if measures such as sealing the opening and insulation are used during construction, which increases the air temperature in the underground cavern, then T a The increased air temperature inside the tunnel should be adopted. Additionally, the thickness of the lining concrete is generally small, and the cooling water pipes are arranged in a single row.

[0030] <System>

[0031] Furthermore, the present invention also provides a control system for early surface cracks in silica fume lining concrete of spillway tunnels, comprising:

[0032] The data acquisition department obtains relevant data and information about the spillway (especially the silica fume lining concrete of the Longluowei section);

[0033] The drafting department drafted a basic plan for construction measures to control early surface temperature cracks in the silica fume lining concrete of the tail section of the flood discharge tunnel.

[0034] The control value calculation department determines each parameter based on the basic scheme proposed in the planning department and the data collected by the data acquisition department, and substitutes them into the following formula 1 to calculate the early surface temperature crack control value F of the silica fume lining concrete in the tail section:

[0035] F=16.84H-369.14H / L-0.1C×D+0.05E-0.06T a +0.21T0+1.09t m -14.36β-0.64H×C×D-0.40×

[0036] H×T0+0.05C×H×T0×D+0.42 (Formula 1)

[0037] Where: D is the concrete slump; H is the concrete thickness of the lining structure; L is the length of the long side of the lining structure; C is the 90-day design strength grade of the lining structure concrete; E is the deformation modulus of the surrounding rock; T a T0 is the ambient temperature during the concrete pouring period of the lining structure; T0 is the concrete pouring temperature of the lining structure; β is the silica fume content; t0 is the ambient temperature during the concrete pouring period of the lining structure. m For the formwork removal time of silica fume lining concrete;

[0038] The optimization and determination department optimizes and determines the early surface temperature crack control measures for the silica fume lining concrete of the spillway tunnel based on the control value F and the surface insulation coefficient α related to the thickness of the polyurethane foam layer.

[0039] The control unit is communicatively connected to the data acquisition unit, the drafting unit, the control value calculation unit, and the optimization determination unit, and controls their operation.

[0040] Preferably, the early surface crack control system for silica fume lining concrete in spillway tunnels provided by the present invention specifically includes the following cases for real-time optimization control of early surface temperature cracks in the optimization determination section:

[0041] (1) If F≤0.1℃, then the basic scheme proposed by the drafting department is appropriate and can be used for construction;

[0042] (2) F > 0.1℃, it should be divided into two cases: winter pouring (December to March of the following year) and pouring in other seasons. The construction temperature control measures should be strengthened respectively, and the optimized measures should be used for construction.

[0043] Preferably, in the optimization and determination section of the early surface crack control system for silica fume lining concrete of the flood discharge tunnel provided by the present invention, for winter pouring, a certain thickness h of sprayed polyurethane foam layer for insulation should be added on the basis of the basic scheme; first, different thicknesses h are proposed and substituted into Formula 2 to calculate the surface insulation coefficient α of crack control, and the thickness h of the polyurethane foam layer is optimized and determined under the condition of satisfying Formula 3.

[0044] α = 1.0 + 0.08h (Formula 2)

[0045] F-0.26(α-1)T a ≤0.1 (Formula 3)

[0046] For pouring in other seasons, water cooling and temperature control measures should be taken.

[0047] Preferably, the early surface crack control system for silica fume lining concrete of the flood discharge tunnel provided by the present invention, in the optimization determination section, for the pouring situation in other seasons, adds water cooling measures on the basis of the basic scheme, and proposes different water temperatures, and selects water temperature that satisfies Formula 4 for water cooling.

[0048] F+0.04T g +0.014H×T g -0.008T0×T g ≤0.1 (Formula 4)

[0049] In the formula, T g =35℃-T w , representing the temperature effect value (°C) with and without water cooling, where T is taken as the temperature effect value without water cooling. w =35℃, under water cooling conditions T w The water temperature is in °C.

[0050] Preferably, the early surface crack control system for silica fume lining concrete in the spillway tunnel provided by the present invention includes an input display unit that is communicatively connected to the control unit, used to allow users to input operation commands and display them accordingly.

[0051] The method and system for controlling early surface cracks in silica fume lining concrete of spillway tunnels provided by this invention demonstrates the reliability of the water cooling effect in formulas 1 in step 3 and 4 in step 4 as follows: Taking a large-scale domestic hydraulic tunnel project as an example, based on the silica fume lining structure of the tail section of a high-velocity spillway tunnel (… Figure 1A total of 111 schemes under different temperature control conditions were analyzed. The temperature control and crack prevention effects and parameters of the lining concrete throughout the process were listed in Table 1. The parameters of 60 schemes with a crack resistance safety factor K greater than 1.0 were listed in Table 2. Statistical analysis of these data was then performed to obtain calculation formulas 1 and 4, which confirmed that the calculation results were basically consistent with the actual measurements.

[0052] Table 1. 111 Temperature Control Measures for High-Strength Silica Powder Lined Concrete

[0053]

[0054]

[0055]

[0056]

[0057] Table 2. Sixty Temperature Control Measures for High-Strength Silica Powder Lined Concrete (K>1.0)

[0058]

[0059]

[0060]

[0061] The role and effect of invention

[0062] The present invention relates to a method and system for controlling early surface cracks in silica fume lining concrete of spillway tunnels. It proposes for the first time a high-precision scientific calculation method and formula for controlling the early surface temperature crack value F of silica fume lining concrete in the Longluowei section. It also proposes for the first time that the influence of concrete slump and polyurethane foam layer spraying thickness on surface cracks should be considered. Based on this, the control measures for early surface temperature cracks in silica fume lining concrete of spillway tunnels are optimized and determined, thereby effectively controlling early surface temperature cracks in silica fume lining concrete in the Longluowei section of high flow velocity spillway tunnels.

[0063] Furthermore, this invention uses Formula 2 to determine whether the basic scheme is suitable based on the control value F. In the case where the basic scheme is unsuitable (F > 0.1℃), it is divided into two cases: winter pouring and pouring in other seasons. Different construction measures are adopted. For winter pouring, the thickness h of the urethane foam layer is optimized and determined under the condition of satisfying Formula 3. For other seasons, water cooling measures are added on the basis of the basic scheme, and different water temperatures are proposed. The water temperature that satisfies Formula 4 is selected for water cooling.

[0064] In summary, the present invention is simple to implement, highly accurate, and can quickly calculate the early surface temperature crack control value F of the silica fume lining concrete in the tail section of the dragon's tail section. Based on formulas 2 to 4, it can design surface temperature crack control construction measures in real time, which is conducive to taking early temperature crack control construction measures in a real time, reasonably and effectively. Attached Figure Description

[0065] Figure 1 The following is a cross-sectional view of a 0.8m thick lining structure involved in the background technology of this invention (unit: m in the figure) (the top arch is cast integrally, and the bottom slab is cast separately);

[0066] Figure 2 This is a diagram showing the concrete cracks in the underground water conveyance tunnel lining of the permanent ship lock at the Three Gorges Dam, which is related to the background technology of this invention.

[0067] Figure 3 The diagram illustrates the simple winter sealing and insulation measures for preventing drafts in openings, as per the present invention.

[0068] Figure 4 This invention relates to a thermal insulation measure involving spraying polyurethane foam layers onto the vertical sidewalls and tunnel ceiling of the Longluowei section.

[0069] Figure 5 The flowchart is a method for controlling early surface cracks in silica fume lining concrete of spillway tunnels, which is involved in this invention.

[0070] Figure 6 The cross-sectional view of the 1.0m thick silicon powder lining structure involved in this invention (unit: m in the figure) (the side and top arches are cast separately, and the bottom plate is cast separately);

[0071] Figure 7 This invention relates to the construction drawing of spraying polyurethane foam insulation layer onto silica fume lining concrete in a flood discharge tunnel. Detailed Implementation

[0072] The following, in conjunction with the attached diagram, illustrates the sidewall of a flood discharge tunnel, specifically a gate-type tunnel at the tail end of a hydroelectric power station. Figure 1 Taking silica fume lining concrete as an example, the specific implementation scheme of the present invention will be described in detail.

[0073] <Basic Data on the Longluowei Gate-Type Lining of the Flood Discharge Tunnel of a Hydropower Station>

[0074] (1) Overview

[0075] A certain hydropower station is a large (Class I) type, and its spillway tunnels are Class I structures. All four spillway tunnels utilize a pressurized-to-unpressurized connection, with their axes arranged in a spatial curve with a "dragon's tail" configuration. They are arranged on the left and right banks; spillway tunnels #1 and #2 are on the left bank, and #3 and #4 are on the right bank. All tunnels use a pressurized-to-unpressurized connection, with a gate chamber in the middle section. The lower section and outlet are designed using a "dragon's tail" and a cantilever design, respectively. The "dragon's tail" section of the spillway tunnel has a complex shape, consisting from top to bottom of an upper straight slope section, an irregular curve section, a sloping section, a reverse arc section, and a lower straight slope section. The "dragon's tail" section is an unpressurized section with a circular arch and straight wall cross-section. Figure 1 The lining thickness (Table 3) is 0.8m, 1.0m, and 1.5m respectively, and the cross-sectional dimensions after lining are 14m × 19m (width × height). The bottom slab and sidewalls are C. 90 60 impact-resistant silica fume concrete, with C grade within 2m below the arch top and arch initiation point. 90 25. Concrete. The structural concrete is poured in two stages, following the sequence of "first the side arches, then the bottom slab," with standard sections divided into 9m blocks. The side arches are poured separately using steel formwork trolleys. The 0.8m thick lining structure cross-section is shown below. Figure 1 As shown in the diagram (the lining thickness is marked as follows: 80cm for the bottom slab; 85cm for the side and top arches because a 5cm thick mortar layer was sprayed onto the side and top arches initially, and the actual lining concrete thickness is also 80cm), the cross-sectional dimensions remain unchanged after lining of other thicknesses. All concrete contains 7% silica fume, and formwork is removed after 48 hours. Concrete slump is as follows: bottom slab is three-graded conventional concrete with a slump of 70mm; side walls are pumped two-graded concrete with a slump of 145mm; and top arches are two-graded pumped concrete with a slump of 170mm.

[0076] During the design phase, based on initial excavation data and information provided by the design institute, the design unit determined the average annual temperature inside the tunnel to be 23.0℃, with an annual temperature variation of ±3.0℃. Regarding construction conditions, the tender documents specify that the concrete should be refrigerated at 14℃ at the outlet, achieving a pouring temperature of 18℃.

[0077]

[0078] In the formula: T a Let τ be the air temperature (°C) inside the cave at time τ; τ be the time (days) from January 1st; τ0 be the time (days) from the highest temperature inside the cave to January 1st, and take τ0 = 210 days.

[0079] Table 3 Classification of Lining and Surrounding Rock of Unpressurized Gate-Type Tunnels

[0080]

[0081] (2) Temperature control and crack prevention design technical requirements

[0082] Based on relevant design specifications, concrete mix design optimization and performance tests, and finite element method calculation results, the design institute determined the temperature control standards and pouring temperatures for the silica fume lining concrete in the Longluowei section of the flood discharge tunnel, as listed in Table 4.

[0083] Table 4 Temperature Control Standards for Unpressurized Section Lining Concrete

[0084]

[0085] For the summer construction of the silica fume lining concrete in the Longluowei section, the following temperature control measures are recommended: concrete pouring temperature 18℃, water pipe spacing 1.0m, water pipe length 100m, cooling water flow rate 2.0m. 3 The cooling water temperature is 14-20℃, and water is supplied starting when the concrete is poured, with cooling lasting for 7 days. For winter construction, if the concrete temperature can be kept below 18℃, natural placement of the concrete can be used.

[0086] (3) Construction plan for temperature control of lining concrete

[0087] Based on the above design requirements, the construction plan outlines that the entire spillway tunnel will be poured in 9m sections. The specific plan for temperature control and crack resistance during the lining concrete construction is as follows:

[0088] ① Pre-cooled concrete is used, and the outlet temperature reaches 12℃~14℃.

[0089] ② Reduce temperature rise during concrete transportation and pouring. Increase transportation capacity to ensure timely coverage of the concrete pouring surface; install movable canvas sunshades on the top of concrete transport trucks, and install foam insulation devices on the concrete transport vehicle bodies, etc.

[0090] ③ Strengthen management and accelerate construction speed. By strengthening management, reduce waiting time for unloading or unloading into the storage area, avoid multiple transfers of materials into the storage area, and ensure that the concrete pouring and covering time does not exceed 1 hour.

[0091] ④ Arrange the concrete construction schedule reasonably. Concrete pouring should be scheduled during the cold season, when temperatures are lower in the morning and evening. Preparations for pouring should be made during the hottest part of the day, and pouring should ideally be scheduled between 4 PM and 10 AM the following morning.

[0092] ⑤ Air conditioning inside the silo. Air conditioning is installed on the steel formwork trolley for use during summer construction inside the silo, in order to reduce the ambient temperature during pouring, which is beneficial for temperature control and also helps to prevent heatstroke and cool down.

[0093] ⑥ Surface curing. Water curing begins immediately after concrete demolding. Use φ35mm plastic pipes with small holes (approximately φ1mm) drilled every 20-30cm. Hang the pipes on the formwork or exposed rebar ends, with a water flow rate of approximately 15L / min. Continuous water curing is implemented during the day, while intermittent water curing is implemented at night (20:00-6:00), i.e., water flows for 1 hour, followed by 1 hour of moistening. When the temperature exceeds 25℃, continuous curing is maintained. The curing time for the pressurized sections, the top arch, and the unpressurized sections should not be less than 28 days.

[0094] ⑦ Water cooling. The cooling water flow rate is 35L / min, and the temperature difference between the concrete and the water should not exceed 22℃. PE pipes are used for the cooling water, arranged in a serpentine pattern parallel to the water flow direction in the middle of each poured block. The length of a single pipe should not exceed 100m, and the vertical spacing should be 1.0m. During the high-temperature season, the right bank section should be circulated with chilled water (approximately 14-20℃) for 48 hours, followed by 7 days of warm water; during the low-temperature season, warm water should be used normally.

[0095] ⑧ Special insulation for concrete in winter. A curtain can be used at the tunnel entrance to prevent cold air from flowing back into the tunnel and causing cracks on the concrete surface. For the tunnel entrance section with the curtain, in winter, a high-quality insulation material can be used to cover the exposed concrete surface or a 15mm thick foam layer can be sprayed to prevent cracks from forming on the concrete surface.

[0096] ⑨ Shorten shift handover time. Implement an on-site shift handover system, so equipment operators must hand over shifts on-site, and the handover time must not exceed 30 minutes; pouring must not be stopped during mealtimes, and meals must be staggered in batches to ensure the continuity of concrete pouring in the silo.

[0097] ⑩ Strengthen concrete temperature measurement. To verify whether the concrete temperature meets the temperature control requirements during construction, use resistance thermometers or thermocouples embedded in the concrete to measure the concrete temperature and analyze the results; during the concrete pouring process, measure the concrete outlet temperature, concrete pouring temperature, and air temperature every 4 hours and record them; if any temperature exceeds the temperature control standard during the temperature measurement process, report it in a timely manner.

[0098] <Example 1> Left Bank No. 1 and No. 2 Dragon Tail Gate-shaped Cross Section ( Figure 1 Early surface crack control of 0.8m thick edge and top arch lining

[0099] The 0.8m thick F1-type lining in the Class II surrounding rock area is the most challenging structural section for temperature control and crack prevention in the portal-shaped cross-section of the No. 1 and No. 2 spillway sections on the left bank. The portal-shaped lining of the No. 1 and No. 2 spillway sections on the left bank was poured in two phases: first, the side arches were poured (monolithic casting), followed by the bottom slab. Early surface crack control measures included... Figure 1Taking the 0.8m thick lining section of Longluowei as an example, concrete was poured on August 1st in summer, and the formwork removal time was 48 hours. The side arch is cast integrally, with a large circumferential length, making it the most difficult part to prevent cracking. The side arch is a combination of vertical sidewalls and a circular arch lining, a symmetrical structure, with a circumferential length of 24.44m (half the length). The specific crack control measures are designed as follows.

[0100] Step 1. Collect relevant data on the spillway, focusing on data related to temperature crack control of the silica fume concrete in the Longluowei section. This includes: collecting and analyzing the project overview of the spillway; hydrological and meteorological data; the structural design of the Longluowei lining; the technical requirements for the silica fume lining concrete and its temperature control design; the temperature control technology for concrete pouring construction; and other specific data as described above.

[0101] Based on the above information, the lining thickness H = 0.8m; the integral casting circumferential length of the side arch is 24.44m, and the joint length is 9.0m, so the long side length of the structure L = 24.44m; the concrete strength C of the side arch lining... 90 60, then C = 60; concrete slump 145mm, D = 0.145m; silica fume content 7%, then β = 0.07; surrounding rock is Class II, E = 30GPa; pouring temperature T0 = 18℃; demolding time 48h, i.e. t m =2.0d; Ambient temperature T during the concrete pouring period of the lining structure a Take the maximum value during the pouring period, and calculate [△T] accordingly. nb The value is slightly lower, leaning towards safety. Here, based on pouring on August 1st in summer, τ = 210d, substituting into formula 5, we calculate T. a =26℃.

[0102] Step 2. Develop a basic plan for controlling early-stage surface temperature cracks in the silica fume lining concrete of the Longluowei section. Based on the above information, the specific parameters are as described above, where the concrete pouring temperature T0 = 18℃.

[0103] Step 3. Calculate the control value F for early surface temperature cracking of silica fume lining concrete in the Longluowei section. That is, substitute the proposed construction measures for controlling early surface temperature cracking of silica fume lining concrete in the Longluowei section and the parameters in the above data into Formula 1 to calculate the control value F, and get F = 1.89℃.

[0104] Step 4. Optimize and determine the early surface temperature crack control measures for silica fume lining concrete.

[0105] According to the above calculations, F = 1.89℃ is greater than 0.1℃, which falls under case (2). In this embodiment, the silica fume lining concrete was poured on August 1st in summer, which falls under the case of pouring in seasons other than winter. Water cooling temperature control measures should be adopted. That is, water cooling measures are added to the construction measures plan proposed in step 2, and different water temperatures are proposed so that the conditions of formula 4 are met. According to the actual engineering conditions, it is proposed to use 12℃ cooling water for water cooling, then T w =12℃, T g =23℃, substituting into formula 4, we get:

[0106] F+0.04Tg+0.014H×Tg-0.008T0×Tg=-0.25℃≤0.1℃

[0107] That is, after the above optimization, it is recommended to use a pouring temperature of T0 = 18℃ and T... w A temperature control scheme using 12℃ cooling water is provided for construction and can effectively control early surface temperature cracks in silica fume lining concrete.

[0108] <Example 2> Early surface crack control of 1.0m thick side-top arch lining in Class III2 surrounding rock zone of the left bank No. 1 and No. 2 dragon tail gate section (winter pouring of the gate section)

[0109] To illustrate the characteristics of surface temperature crack control in lining concrete poured in different tunnel sections and seasons, this study focuses on the F3 type 1.0m thick side-top arch in the Class III2 surrounding rock area of ​​the left bank No. 1 and No. 2 tunnel portal sections poured in winter. Figure 6 Design of surface temperature crack control measures for silica fume lining concrete. The tunnel entrance section refers to the structural section from the curtain insulation to the tunnel exit.

[0110] The annual temperature variation is increasing, and the annual temperature variation is calculated using formula 6.

[0111]

[0112] The symbols in the formula have the same meaning as before.

[0113] The 1.0m thick F3 type lining in the Class III2 surrounding rock area is a common structural section in the portal-shaped cross-section of the left bank spillway tunnels No. 1 and No. 2. The portal-shaped cross-section lining of the left bank spillway tunnels No. 1 and No. 2 was poured in two phases: first, the side arches were poured (monolithic casting), followed by the bottom slab. Crack control measures were designed to... Figure 6 The lining structure is 1.0m thick (i.e.) Figure 1Taking the Longluowei section as an example (with changes in thickness but no change in structure and internal cross-section after lining), concrete was poured on February 1st in winter, and the formwork was removed after 48 hours. Other data is the same as above. The side-top arch is cast integrally, with a large circumferential length, making it a difficult part to prevent cracking. The side-top arch is a combination of vertical sidewalls and a circular arch lining, a symmetrical structure, with a circumferential length of 24.44m (half the length). The specific design of early surface crack control measures is as follows:

[0114] Step 1. Collect relevant data on the spillway, focusing on data related to temperature crack control in the silica fume concrete of the Longluowei section. Specific data are as described above.

[0115] Based on the above data, H = 1.0m; C = 60; D = 0.145m; L = 24.44m; E = 9GPa; Ta = 13℃; silica fume content 7%, β = 0.07; winter pouring temperature T0 = 16℃; demolding time 48h, i.e., t m =2.0d.

[0116] Step 2. Develop a construction plan for controlling early-stage surface temperature cracks in the silica fume lining concrete of the Longluowei section. Based on the above information, the specific parameters are as described above, where the winter concrete pouring temperature T0 = 16℃.

[0117] Step 3. Calculate the control value F for early surface temperature cracking of silica fume lining concrete in the Longluowei section. That is, substitute the proposed construction measures for controlling early surface temperature cracking of silica fume lining concrete in the Longluowei section and the parameters in the above data into Formula 1 to calculate the control value F, and get F = 0.48℃.

[0118] Step 4. Optimize and determine the early surface temperature crack control measures for silica fume lining concrete. According to the above calculation, F = 0.48℃, which is greater than 0.1℃, belonging to case (2), and it is poured in winter.

[0119] For winter pouring, a sprayed polyurethane foam layer for insulation should be added to the construction measures proposed in step 2. The thickness h of the polyurethane foam layer is determined by formula 3. In formula 3, F is the value calculated in step 3. That is, different thicknesses h are proposed and substituted into formula 2 to calculate the surface insulation coefficient α. The thickness h of the polyurethane foam layer is then optimized and determined under the condition of satisfying formula 3. The proposed thickness of the urethane foam layer is h = 2.0 cm. Substituting it into formula 2, α = 1.16 is obtained; then, substituting it into formula 3, F - 0.26(α-1)T is calculated. a = -0.06℃, less than 0.1℃.

[0120] Therefore, based on the principles of simplicity and cost-effectiveness, and according to the above calculations, it is recommended that the silica fume lining concrete of the Longluowei section be poured at 16℃ in winter, with a 2.0cm thick polyurethane foam layer sprayed for insulation, as the preferred construction measure for construction application.

[0121] <Practical Engineering Temperature Control Crack Prevention Effects and Experience>

[0122] The actual flood discharge tunnel at the Longluowei section of the project was kept warm in winter by sealing the tunnel entrance with curtains. Figure 3 Strict temperature control measures, such as refrigerated concrete pouring and water cooling, were implemented to effectively control the penetrating temperature cracks in the lining concrete. Since this temperature control scheme also met the requirements for controlling early surface cracks in the silica fume lining concrete, a 2.0cm thick polyurethane foam layer was further sprayed for insulation in winter on the opening sections in addition to the curtain insulation, effectively controlling early surface cracks as well.

[0123] According to the above-mentioned method of the present invention, the early surface temperature crack control of silica fume lining concrete in the tail section of the flood discharge tunnel is as follows: for the tunnel section poured in summer, water cooling temperature control measures should be adopted; for the tunnel entrance section poured in winter with large temperature changes, it is even more required to cover and insulate in winter; for the tail section, it is advisable to use a 2.0cm thick polyurethane foam layer for insulation.

[0124] <Example 3>

[0125] Furthermore, this embodiment three provides a control system for early surface cracks in silica fume lining concrete of a flood discharge tunnel that can automatically implement the above-mentioned method of the present invention. The system includes a data acquisition unit, a drafting unit, a control value calculation unit, an optimization determination unit, an input display unit, and a control unit.

[0126] The data acquisition unit performs the tasks described in step 1 above to acquire relevant data and information about the spillway. For example, the input display unit displays prompts to allow the user to import or input relevant data and information about the spillway (focusing on the silica fume lining of the Longluo tail section).

[0127] The drafting department is responsible for implementing the content described in step 2 above, and for drafting the basic plan for construction measures to control early surface temperature cracks in the silica fume lining concrete of the flood discharge tunnel tail section.

[0128] The control value calculation unit performs the work described in step 3 above, determines each parameter based on the basic scheme proposed in the planning unit and the data collected by the data acquisition unit, and substitutes them into formula 1 to calculate the early surface temperature crack control value F of the silica fume lining concrete in the tail section of Longluo.

[0129] The optimization and determination unit is used to perform the content described in step 4 above, and optimizes and determines the early surface temperature crack control measures for the silica fume lining concrete of the flood discharge tunnel based on the control value F and the surface insulation coefficient α related to the thickness of the polyurethane foam layer.

[0130] The input display unit is used to allow users to input operation commands and displays the corresponding information. For example, the input display unit can display relevant data information on the spillway (focusing on the lining of the tail section) acquired by the data acquisition unit, the basic scheme proposed by the planning unit, the F-value calculated by the control value calculation unit, the calculation data and judgment results of various proposed thickness h and water temperature by the optimization determination unit, and the final optimized scheme. It can also display the aforementioned information in association at the corresponding positions in the two-dimensional or three-dimensional model of the spillway.

[0131] The control unit is communicatively connected to the data acquisition unit, the drafting unit, the control value calculation unit, the optimization determination unit, and the input display unit, and controls their operation.

[0132] The above embodiments are merely illustrative examples of the technical solution of the present invention. The method and system for controlling early surface cracks in silica fume lining concrete of spillway tunnels involved in this invention are not limited to the content described in the above embodiments, but are defined by the scope of the claims. Any modifications, additions, or equivalent substitutions made by those skilled in the art based on these embodiments are within the scope of protection claimed by the claims of this invention.

Claims

1. A method for controlling early-stage surface cracks in silica fume lining concrete of spillway tunnels, characterized in that, Includes the following steps: Step 1: Collect relevant information about the spillway tunnel; Step 2: Draft a basic plan for construction measures to control early surface temperature cracks in the silica fume lining concrete of the tail section of the flood discharge tunnel. Step 3: Based on the basic scheme proposed in Step 2 and the data collected in Step 1, determine the parameters and substitute them into the following Formula 1 to calculate the early-stage surface temperature crack control value F of the silica fume lining concrete in the Longluo tail section: F=16.84H-369.14H / L-0.1C×D+0.05E-0.06T a +0.21T0+1.09t m -14.36β-0.64H×C×D-0.40×H×T0+0.05C×H×T0×D+0.42 (Formula 1) Where: D is the concrete slump; H is the concrete thickness of the lining structure; L is the length of the long side of the lining structure; C is the 90-day design strength grade of the lining structure concrete; E is the deformation modulus of the surrounding rock; T a T0 is the ambient temperature during the concrete pouring period of the lining structure; T0 is the concrete pouring temperature of the lining structure; β is the silica fume content; t0 is the ambient temperature during the concrete pouring period of the lining structure. m For the formwork removal time of silica fume lining concrete; Step 4: Optimize and determine the construction measures for controlling early surface temperature cracks in the silica fume lining concrete of the flood discharge tunnel tail section based on the control value F and the surface insulation coefficient α related to the thickness of the polyurethane foam layer. In step 1, the relevant data for the spillway includes: an overview of the spillway project, hydrological and meteorological conditions, design of the lining structure of the Longluowei section, technical requirements for the silica fume lining concrete and its temperature control design, and technical data on temperature control during pouring construction. In step 4, the following specific situations are considered for optimizing and determining the construction measures to control early surface temperature cracks: (1) If F≤0.1℃, then the basic scheme proposed in step 2 is suitable and can be used for construction; (2) When F > 0.1℃, it should be divided into two cases: winter pouring and pouring in other seasons. The construction temperature control measures should be strengthened for each case, and the optimized measures should be used for construction. In step 4, for winter pouring, a certain thickness of sprayed polyurethane foam layer for insulation should be added based on the basic scheme proposed in step 2; first, different thicknesses of h should be proposed and substituted into formula 2 to calculate the surface insulation coefficient α for crack control, and then the thickness of polyurethane foam layer h should be optimized and determined under the condition of satisfying formula 3. α = 1.0 + 0.08h (Formula 2) F-0.26(α-1)T a ≤0.1 (Formula 3) For pouring in other seasons, water cooling and temperature control measures should be taken.

2. The method for controlling early-stage surface cracks in silica fume lining concrete of spillway tunnels according to claim 1, characterized in that: in, In step 4, for pouring in other seasons, water cooling measures are added to the basic plan proposed in step 2, and different water temperatures are proposed. Water cooling is carried out by selecting the water temperature that satisfies Formula 4. F+0.04T g +0.014H×T g -0.008T0×T g ≤0.1 (Formula 4) In the formula, T g =35℃-T w T represents the temperature effect value under cooling conditions with and without water flow; w This refers to the water temperature for cooling.

3. A control system for early-stage surface cracks in silica fume lining concrete of spillway tunnels, capable of implementing the method for controlling early-stage surface cracks in silica fume lining concrete of spillway tunnels as described in claim 1 or 2, characterized in that... include: The data acquisition department obtains relevant data and information about the spillway tunnel; The drafting department drafted a basic plan for construction measures to control early surface temperature cracks in the silica fume lining concrete of the tail section of the flood discharge tunnel. The control value calculation department determines each parameter based on the basic scheme proposed in the planning department and the data collected by the data acquisition department, and substitutes them into the following formula 1 to calculate the early surface temperature crack control value F of the silica fume lining concrete in the tail section: F=16.84H-369.14H / L-0.1C×D+0.05E-0.06T a +0.21T0+1.09t m -14.36β-0.64H×C×D-0.40×H×T0+0.05C×H×T0×D+0.42 (Formula 1) Where: D is the concrete slump; H is the concrete thickness of the lining structure; L is the length of the long side of the lining structure; C is the 90-day design strength grade of the lining structure concrete; E is the deformation modulus of the surrounding rock; T a T0 is the ambient temperature during the concrete pouring period of the lining structure; T0 is the concrete pouring temperature of the lining structure; β is the silica fume content; t0 is the ambient temperature during the concrete pouring period of the lining structure. m For the formwork removal time of silica fume lining concrete; The optimization and determination department optimizes and determines the construction measures for controlling early surface temperature cracks in the silica fume lining concrete of the tail section of the flood discharge tunnel based on the control value F and the surface insulation coefficient α related to the thickness of the polyurethane foam layer. The control unit is communicatively connected to the data acquisition unit, the drafting unit, the control value calculation unit, and the optimization determination unit, and controls the operation of these units.

4. The early surface crack control system for silica fume lining concrete in spillway tunnels according to claim 3, characterized in that: in, In the optimization and determination section, the following situations are specifically divided into optimization and determination of early surface temperature crack control construction measures: (1) If F≤0.1℃, then the basic scheme proposed by the drafting department is appropriate and can be used for construction; (2) When F > 0.1℃, it should be divided into two cases: winter pouring and pouring in other seasons. The temperature control measures should be strengthened for construction and optimized for construction.

5. The early surface crack control system for silica fume lining concrete in spillway tunnels according to claim 4, characterized in that: in, In the optimization and determination section, for winter pouring, a certain thickness h of sprayed polyurethane foam layer for insulation should be added on the basis of the basic scheme; first, different thicknesses h are proposed and substituted into Formula 2 to calculate the surface insulation coefficient α for crack control, and then the thickness h of polyurethane foam layer is optimized and determined under the condition of satisfying Formula 3. α = 1.0 + 0.08h (Formula 2) F-0.26(α-1)T a ≤0.1 (Formula 3) For pouring in other seasons, water cooling and temperature control measures should be taken.

6. The early surface crack control system for silica fume lining concrete in spillway tunnels according to claim 5, characterized in that: in, In the optimization and determination section, for pouring in other seasons, water cooling measures are added to the basic plan, and different water temperatures are proposed. Water cooling is carried out by selecting the water temperature that satisfies Formula 4. F+0.04T g +0.014H×T g -0.008T0×T g ≤0.1 (Formula 4) In the formula, T g =35℃-T w T represents the temperature effect value under cooling conditions with and without water flow; w This refers to the water temperature for cooling.

7. The early surface crack control system for silica fume lining concrete in spillway tunnels according to claim 3, characterized in that, Also includes: The input display unit is connected in communication with the control unit and is used to allow users to input operation commands and display the corresponding commands.

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