Carbonization depth prediction method for extra-long highway tunnel lining structure considering coating protection

Abstract

The present invention provides a method for predicting the carbonization depth of an extra-long highway tunnel lining structure taking into account coating protection. The present invention takes coating protection factors into account, and the carbonization depth model established on this basis can accurately predict the carbonization depth of an extra-long highway tunnel lining structure with coating protection. In addition, the present invention also provides an idea of ​​considering other influencing factors, and obtains the influence coefficient of the influencing factors through experiments, so that the influence of other influencing factors on the carbonization depth can be combined to predict a more accurate carbonization depth. By adopting the method of the present invention, tunnel engineering practitioners can accurately and quickly predict the carbonization depth of the concrete of the extra-long highway tunnel lining structure, and evaluate the coating protection effect, thereby achieving reasonable and timely maintenance and ensuring the safety and reliability of the lining structure throughout its life cycle.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel lining structure durability prediction, and in particular relates to a method for predicting the carbonization depth of a super-long highway tunnel lining structure taking coating protection into consideration. Background Art

[0002] In recent years, with the continuous improvement of my country's development level, the demand for highway construction has also greatly increased. Highway tunnels are the best solution for highways crossing mountains, and have obvious advantages in optimizing routes, improving the environment, facilitating traffic, energy saving and environmental protection, etc. Extra-long tunnels generally have the characteristics of long distance, deep burial, large cross-section, and complex surrounding geological conditions. As a closed project in a geological body, the environment of extra-long tunnels is more severe than that of ordinary building structures, which poses a huge challenge to the durability of the tunnel during the operation stage.

[0003] Concrete structures are widely used in highway tunnel linings. The atmospheric environment of long highway tunnel linings is relatively harsh, with high concentrations of CO2 and NO x and SO x Acidic gases such as carbonization are extremely harmful to the durability of tunnel linings. In addition, the long length and good sealing of extra-long tunnels easily lead to the accumulation of harmful gases emitted by vehicles, making the concentration of harmful gases in the tunnel much higher than that in ordinary tunnels. At the same time, the tunnel lining structure is complex and has tensile stress areas, which easily cause concrete cracking, increase the permeability of the lining, and accelerate the deterioration of the lining durability. At present, there are few studies on carbonization that combine the characteristics of extra-long highway tunnels.

[0004] On the other hand, as a new type of protection technology, protective coating is not yet mature for the durability protection of tunnel linings, lacks relevant research, and is prone to ineffective protection or excessive protection, which does not meet economic requirements. Therefore, according to the characteristics of extra-long highway tunnels, accurately predicting the carbonization depth of extra-long highway tunnel lining structures under coating protection is of great significance for exploring the durability of extra-long highway tunnel linings. Summary of the invention

[0005] In view of the above-mentioned existing problems, the purpose of the present invention is to provide a method for predicting the carbonization depth of the lining structure of an extra-long highway tunnel taking into account coating protection, thereby achieving accurate prediction of the carbonization depth of the concrete of the lining structure of an extra-long highway tunnel and the coating protection effect, and providing support for the safety prediction and evaluation of the entire life cycle of highway tunnels.

[0006] The present invention is achieved through the following technical solutions:

[0007] The carbonization depth prediction method of the lining structure of a long highway tunnel considering coating protection includes:

[0008] Through rapid carbonation test, a preliminary carbonation depth model of concrete is established;

[0009] Carry out a rapid carbonation test in a standard rapid carbonation environment, and establish a carbonation depth model of concrete in the standard rapid carbonation environment based on the test results;

[0010] Combined with the preliminary carbonation depth model, the carbonation depth model in the standard rapid carbonation environment is transformed into the carbonation depth model of concrete in the natural carbonation environment;

[0011] The variables of influencing factors were introduced on the basis of the standard rapid carbonization environment to conduct rapid carbonization test, and the influence coefficient of influencing factors on the carbonation depth of concrete was obtained according to the test results and the preliminary carbonation depth model and the carbonation depth model of concrete in the standard rapid carbonization environment.

[0012] Based on the Alekseyev model, the coating outside the concrete is regarded as concrete of equivalent thickness, and a prediction model for the carbonization depth of concrete under coating protection is established.

[0013] The carbonation depth of the lining structure is predicted by combining the carbonation depth model of concrete in a natural carbonation environment, the influence coefficient of influencing factors on the carbonation depth of concrete, and the carbonation depth prediction model of concrete under coating protection.

[0014] Preferably, the preliminary carbonization depth model of the concrete is:

[0015]

[0016] Where x is the carbonation depth of concrete, mm; k is the comprehensive carbonation rate coefficient of concrete, mm / d 0.5 ; t is time, year;

[0017] The carbonation depth model of concrete in the standard rapid carbonation environment is:

[0018]

[0019] Where k0 is the initial carbonization rate coefficient of the test concrete in a standard rapid carbonization environment.

[0020] Furthermore, the carbonization depth model of concrete in the natural carbonization environment is:

[0021]

[0022] In the formula, is the influence coefficient of CO2 concentration on the carbonation depth of concrete, and its value is as follows:

[0023]

[0024] In the formula, is the CO2 gas concentration in the air in the natural carbonization environment, %; is the CO2 gas concentration in the standard rapid carbonization environment, %.

[0025] Furthermore, the influencing factors are at least one of acidic harmful gases, bending stress, ambient temperature, ambient humidity, concrete water-cement ratio, concrete cement dosage and concrete compressive strength.

[0026] Furthermore, when the influencing factors include acidic harmful gases, a nitric acid concentration variable is introduced on the basis of the standard rapid carbonization environment to conduct a rapid carbonization test. According to the obtained results and the preliminary carbonization depth model, the k corresponding to different nitric acid concentrations is fitted, and the influence coefficient k corresponding to different nitric acid concentrations is obtained by dividing k by k0. A , the influence coefficient k is obtained by fitting A :

[0027]

[0028] In the formula, k A is the influence coefficient of nitric acid concentration on the carbonation depth of concrete; is the nitric acid concentration, mol / L;

[0029] The ratio of NO2 to CO2 in the atmosphere is used as the influencing parameter to determine k A To make corrections:

[0030]

[0031] In the formula, is the Henry constant of NO2 gas in aqueous solution; and are the concentration percentages of NO2 and CO2 in the air in a natural carbonization environment, %; p is the atmospheric pressure, kPa.

[0032] Furthermore, when the influencing factors include bending stress, the bending stress variable is introduced on the basis of the standard rapid carbonization environment to conduct rapid carbonization test. According to the obtained results and the preliminary carbonization depth model, the k corresponding to different bending stresses is fitted, and the influence coefficient k corresponding to different bending stresses is obtained according to k / k0. F , the influence coefficient of bending stress on the carbonation depth of concrete is obtained by fitting, and the expression is:

[0033] k F =0.96042+0.03983×exp(2.12694×f / f f )(0.3f f ≤f≤0.7f f )

[0034] In the formula, k Fis the influence coefficient of bending stress on the carbonation depth of concrete; f is the bending stress of the test concrete, MPa; f f is the ultimate flexural strength of the test concrete, MPa.

[0035] Furthermore, when the influencing factors include ambient temperature, the carbonization depth-time curve under temperature change is obtained by numerical simulation using COMSOL software. According to the carbonization depth-time curve under temperature change and the preliminary carbonization depth model, k corresponding to different temperatures is fitted, and the influence coefficient k corresponding to different temperatures is obtained by dividing k by k0. T , the influence coefficient k of ambient temperature on the carbonization depth of concrete is obtained by fitting T :

[0036] k T =-2.622×10 -4 ·T 2 +0.1829·T-30.075

[0037] When the influencing factor includes the ambient humidity, the carbonization depth-time curve under humidity change is obtained by numerical simulation using COMSOL software. According to the carbonization depth-time curve under humidity change and the preliminary carbonization depth model, k corresponding to different humidity is fitted, and the influence coefficient k corresponding to different humidity is obtained by dividing k by k0. RH , the influence coefficient k of ambient humidity on the carbonization depth of concrete is obtained by fitting RH :

[0038] k RH =84.083 RH 3 -217.297 RH 2 +182.576 RH-49.172

[0039] Wherein, T is the ambient temperature, °C, and RH is the ambient humidity,%.

[0040] Furthermore, when the influencing factors include the concrete water-cement ratio, the concrete water-cement ratio variable is introduced on the basis of the standard rapid carbonization environment to conduct a rapid carbonization test. According to the obtained results and the preliminary carbonization depth model, the k corresponding to different concrete water-cement ratios is fitted, and the influence coefficient k corresponding to different concrete water-cement ratios is obtained by dividing k by k0. W / C , the influence coefficient k of concrete water-cement ratio on concrete carbonization depth is obtained by fitting W / C :

[0041] k W / C =5.0881W / C-1.3456

[0042] When the influencing factors include the amount of concrete cement, the concrete cement amount variable is introduced on the basis of the standard rapid carbonization environment to conduct a rapid carbonization test. According to the obtained results and the preliminary carbonization depth model, the k corresponding to different concrete cement amounts is fitted, and the influence coefficient k corresponding to different concrete cement amounts is obtained by dividing k by k0. C , the influence coefficient k of concrete cement content on concrete carbonization depth is obtained by fitting C :

[0043]

[0044] Where W is the mass of water per unit volume, kg / m 3 ; C is the mass of concrete per unit volume, kg / m 3 ; W / C is the water-cement ratio;

[0045] When the influencing factors include the compressive strength of concrete, the Niu Ditao formula is used:

[0046]

[0047] Let f cu,k =30MPa Correct the above formula and we get

[0048]

[0049] Among them, f cu,k It is the standard value of the cube compressive strength of concrete, MPa.

[0050] Preferably, the carbonization depth prediction model of concrete under coating protection is:

[0051]

[0052] In the formula, x coat is the carbonation depth of concrete under coating protection, mm; k is the comprehensive carbonation rate coefficient, mm / d 0.5 ; t is time, year; S is the equivalent concrete thickness of the coating, mm:

[0053]

[0054] x is the carbonation depth of concrete without coating protection.

[0055] Preferably, the influencing factors include acidic harmful gases, bending stress, ambient temperature, ambient humidity, concrete water-cement ratio, concrete cement content and concrete compressive strength. The carbonization depth of the lining structure is predicted by combining the carbonization depth model of concrete in a natural carbonization environment, the influence coefficient of the influencing factors on the carbonization depth of concrete and the carbonization depth prediction model of concrete under coating protection. Specifically, the carbonization depth is obtained by solving the following equation:

[0056]

[0057] Among them, k T k is the influence coefficient of ambient temperature on the carbonation depth of concrete; RH k is the influence coefficient of ambient humidity on the carbonation depth of concrete; A k is the influence coefficient of acidic harmful gas on the carbonation depth of concrete; F is the influence coefficient of bending stress on the carbonation depth of concrete; k is the influence coefficient of CO2 concentration on the carbonation depth of concrete; W / C k is the influence coefficient of concrete water-cement ratio on concrete carbonation depth; C is the influence coefficient of concrete cement content on concrete carbonization depth; The influence coefficient of concrete compressive strength on concrete carbonation depth; k0 is the initial carbonation rate coefficient of the test concrete in a standard rapid carbonation environment; t is time, years; T is ambient temperature, RH is ambient humidity, and NO in the air 2 and CO2 concentration percentage; f is the bending stress of the test concrete, MPa; f f is the ultimate flexural strength of the test concrete, MPa; W is the mass of water per unit volume, kg / m 3 ; C is the mass of concrete per unit volume, kg / m 3 ; W / C is water-cement ratio; f cu,k is the compressive strength of concrete; x coat is the carbonization depth under coating protection, mm; k is the comprehensive carbonization rate coefficient, mm / d 0.5 ; S is the equivalent concrete thickness of the coating, mm; x is the carbonation depth of the concrete without coating protection, mm.

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] The present invention provides an algorithm for predicting the carbonization depth of concrete in the lining structure of a super-long highway tunnel when considering the effects of coating protection and other influencing factors. Since the coating surface is very dense, the diffusion coefficient of CO2 gas in the coating is very low. The coating blocks most of the CO2 molecules outside the concrete surface, which greatly reduces the CO2 gas concentration on the concrete surface, and can play a certain role in delaying the carbonization of concrete, affecting the carbonization depth of concrete. Therefore, the present invention takes the coating protection factor into consideration, and the carbonization depth model established on this basis can accurately predict the carbonization depth of the lining structure of a super-long highway tunnel with coating protection. In addition, the present invention also provides an idea of ​​considering other influencing factors, and obtains the influence coefficient of the influencing factor through experiments, so that the influence of other influencing factors on the carbonization depth can be combined, and a more accurate carbonization depth can be predicted. Using the method of the present invention, tunnel engineering practitioners can accurately and quickly predict the carbonization depth of the concrete lining structure of a super-long highway tunnel, and evaluate the coating protection effect, thereby achieving reasonable and timely maintenance and ensuring the safety and reliability of the lining structure throughout its life cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 The present invention is a flowchart of a method for predicting the carbonization depth of a lining structure of an extra-long highway tunnel taking coating protection into consideration in an embodiment of the present invention.

[0061] Figure 2 This is the regression result of carbonization depth for rapid carbonization test.

[0062] Figure 3 Illustration of the carbonization protection mechanism of coating on concrete.

[0063] Figure 4 The bending stress influence coefficient and acidic harmful gas influence coefficient curves obtained for the rapid carbonization test.

[0064] Figure 5 The carbonization depth-time curve under temperature change obtained by numerical simulation.

[0065] Figure 6 The carbonization depth-time curve under humidity changes obtained by numerical simulation. DETAILED DESCRIPTION

[0066] In order to further understand the present invention, the present invention is described below in conjunction with embodiments. These descriptions are only to further explain the features and advantages of the present invention and are not intended to limit the claims of the present invention.

[0067] like Figure 1 The method for predicting the carbonization depth of the lining structure of a super-long highway tunnel considering coating protection of the present invention comprises the following steps:

[0068] Step 1: Establish a preliminary carbonation depth model of concrete.

[0069] According to the classic carbonization model, a preliminary carbonization depth model of concrete is established:

[0070]

[0071] Where x is the carbonation depth of concrete (mm); k is the comprehensive carbonation rate coefficient of concrete (mm / d 0.5 );t is time (year).

[0072] Step 2: Establish a carbonization depth model for the transformation from rapid carbonization process to natural carbonization process.

[0073] The carbonation depth model of C30 concrete in a rapid carbonation test in a standard rapid carbonation environment (20% CO2, 20°C, 70% RH) is:

[0074]

[0075] Where k0 is the initial carbonization rate coefficient of the test concrete in a standard rapid carbonization environment, and K0 = 1.644 mm / d 0.5 .

[0076] Combined with the preliminary carbonization depth model in step 1, the carbonization depth model in the natural carbonization environment can be obtained as follows:

[0077]

[0078] In the formula, is the influence coefficient of CO2 concentration on carbonization depth, and its value is as follows:

[0079]

[0080] In the formula, is the CO2 gas concentration in the natural carbonization environment (%),

[0081] Step 3: Calculate the influence coefficient of acidic harmful gas and bending stress on carbonization depth.

[0082] Considering the effect of acidic gas corrosion, the CO2 concentration influence coefficient of the carbonation depth model is modified: In order to simulate the effect of acidic gas (mainly NO2) in the tunnel atmosphere on the carbonation process of concrete, nitric acid (HNO3), the product of the reaction of NO2 and water, is used as the medium, and the carbonation test surface of the specimen is immersed in HNO3 solutions of different concentrations, so as to study the carbonation characteristics of lining concrete in tunnel atmospheres with different acidic gas concentrations, and at the same time avoid acidic gas or solution corrosion loading device affecting the stress state of the specimen. HNO3 solution is divided into three concentrations, namely 0.01 mol·L -1, 0.05mol·L -1 , 0.1 mol·L -1 Before the carbonization test (0 day) and at 7, 14, and 21 days of carbonization, the specimens were taken out of the integrated laboratory and the test surface was immersed in HNO3 solution of corresponding concentration for 1 day. After drying, the rapid carbonization test was continued. That is, the nitric acid concentration variable was introduced to conduct the rapid carbonization test on the basis of the standard rapid carbonization environment. According to the obtained results and the preliminary carbonization depth model, the k corresponding to different nitric acid concentrations was fitted, and the k corresponding to different nitric acid concentrations was obtained according to k / k0. A , fitting parameter k A We can get:

[0083]

[0084] In the formula, k A is the influence coefficient of nitric acid concentration on carbonization depth; is the nitric acid concentration, mol / L.

[0085] The ratio of NO2 to CO2 in the atmosphere is used as the influencing parameter to determine k A To make corrections:

[0086]

[0087] In the formula, is the Henry constant of NO2 gas in aqueous solution, which is approximately 1.3845×10-5mol / (L·Pa) at 20°C; and are the percentages of NO2 and CO2 concentrations in the air in the natural environment respectively; p is the atmospheric pressure, kPa.

[0088] Based on the standard rapid carbonization environment, the bending stress variable was introduced to conduct rapid carbonization test. According to the obtained results and the preliminary carbonization depth model, the k corresponding to different bending stresses was fitted, and the influence coefficient k corresponding to different bending stresses was obtained according to k / k0. F , the influence coefficient of bending stress on carbonization depth is obtained by fitting, and the expression is:

[0089] k F =0.96042+0.03983×exp(2.12694×f / f f )(0.3f f ≤f≤0.7f f )

[0090] In the formula, k F is the influence coefficient of bending stress on carbonation depth; f is the bending stress of the test concrete, MPa; f f is the ultimate flexural strength of the test concrete, MPa.

[0091] Step 4: Calculate the influence coefficients of temperature, humidity, water-cement ratio, cement dosage, compressive strength and other factors on carbonation depth.

[0092] (1) Ambient temperature influence coefficient k T :According to the carbonization depth-time curve under temperature change obtained by numerical simulation with COMSOL software, the k corresponding to different temperatures is fitted according to the obtained results and the preliminary carbonization depth model, and the influence coefficient k corresponding to different temperatures is obtained by dividing k by k0 T , fitting according to the quadratic function, we get

[0093] k T =-2.622×10 -4 ·T 2 +0.1829·T-30.075

[0094] (2) Environmental humidity influence coefficient k RH :According to the numerical simulation results of COMSOL software, the carbonization depth-time curve under humidity changes is obtained. According to the obtained results and the preliminary carbonization depth model, the k corresponding to different humidity is fitted, and the influence coefficient k corresponding to different humidity is obtained by dividing k by k0 RH , fitting according to the cubic function, we get

[0095] k RH =84.083 RH 3 -217.297 RH 2 +182.576 RH-49.172

[0096] (3) Concrete water-cement ratio influence coefficient k W / C :Based on the standard rapid carbonization environment, the concrete water-cement ratio variable was introduced to conduct rapid carbonization test. According to the obtained results and the preliminary carbonization depth model, the k corresponding to different concrete water-cement ratios was fitted. The influence coefficient k corresponding to different concrete water-cement ratios was obtained by dividing k by k0. W / C , fitting

[0097] k W / C =5.0881W / C-1.3456

[0098] Where W is the mass of water per unit volume, kg / m 3 ; C is the mass of concrete per unit volume, kg / m 3 ; W / C is the water-cement ratio.

[0099] (4) Concrete cement consumption influence coefficient k C (When C=300kg / m 3 When k C=1): Based on the standard rapid carbonization environment, the concrete cement dosage variable is introduced to conduct rapid carbonization test. According to the obtained results and the preliminary carbonization depth model, the k corresponding to different concrete cement dosages is fitted. The influence coefficient k corresponding to different concrete cement dosages is obtained by dividing k by k0. C , fitting is:

[0100]

[0101] (5) Concrete compressive strength influence coefficient Here we use the Niu Ditao formula:

[0102]

[0103] According to the test data, let f cu,k =30MPa Correct the above formula and we get

[0104]

[0105] Among them, f cu,k It is the standard value of the cube compressive strength of concrete, MPa.

[0106] Step 5: Establish a carbonization depth model under coating protection.

[0107] The carbonization protection mechanism of the coating on concrete can be summarized as follows: since the coating surface is very dense and the diffusion coefficient of CO2 gas in the coating is very low, the coating blocks most of the CO2 molecules outside the concrete surface, greatly reducing the CO2 gas concentration on the concrete surface.

[0108] Based on the Alekseyev model, the carbonation depth prediction model of concrete under coating protection was established by considering the coating as concrete with equivalent thickness:

[0109]

[0110] In the formula, x coat is the carbonization depth under coating protection, mm; k is the comprehensive carbonization rate coefficient, mm / d 0.5 ; S is the equivalent concrete thickness of the coating, mm:

[0111]

[0112] Where x is the carbonation depth of uncoated protective concrete under the same conditions, mm.

[0113] Therefore, after determining the value of the carbonization coefficient k without protection, the carbonization depth under coating protection can be calculated.

[0114] Since the rapid carbonization test has a limited time period, the carbonization effect under the coating protection is not obvious. At this time, the carbonization depth of the specimen can be estimated by the pH value. The method is as follows: The pH value of the simulated pore solution of the rapid carbonization test specimen is analyzed, and it can be found that the pH value corresponding to the carbonization depth is in the range of 10.58 to 11.79. Therefore, the depth corresponding to the overall average pH of 11 is taken as the carbonization depth x at 28 days of carbonization. coat .

[0115] Step 6: Establish the final carbonization depth prediction model for the extra-long highway tunnel lining structure taking into account coating protection, and calculate the predicted value of carbonization depth.

[0116]

[0117] Example

[0118] Most of the secondary lining of the Qinling Zhongnanshan Tunnel is made of C25 cast-in-place concrete. 3 The material composition of concrete is: 175kg water, 372kg cement, 580kg sand, 730kg crushed stone. According to the on-site test data, the annual average temperature in the tunnel is set to 30℃ and the average humidity is 65%. The CO2 concentration is 0.2%, and the acid gas concentration is equivalent to the NO2 concentration of 20ppm. Due to the uncertainty of the surrounding rock pressure, the distribution of the lining stress is relatively complex and difficult to calculate. The maximum bending stress is taken as 0.7f f .

[0119] Step 1: If Figure 2 , based on the classic carbonization model, a preliminary concrete carbonization model is established:

[0120]

[0121] Where x is the carbonation depth of concrete (mm); k is the comprehensive carbonation rate coefficient of concrete (mm / d 0.5 ); t is time (year)

[0122] Step 2: Establish a carbonation model for the transformation of rapid carbonation process into natural carbonation process. The carbonation depth model of C25 concrete under standard carbonation test (20% CO2, 20℃, 70% RH) is:

[0123]

[0124] Where k0 is the initial carbonization rate coefficient of the test concrete in a standard rapid carbonization environment, and K0 = 1.644 mm / d 0.5 .

[0125] Combined with the preliminary carbonization depth model in step 1, the carbonization depth model in the natural carbonization environment can be obtained as follows:

[0126]

[0127] In the formula, is the influence coefficient of CO2 concentration on carbonization depth, and its value is as follows:

[0128]

[0129] In the formula, is the CO2 gas concentration in the natural carbonization environment (%),

[0130] Step 3: Calculate the influence coefficients of acidic harmful gases and bending stress on carbonization depth. Considering the effect of acidic gas erosion, the CO2 concentration influence coefficient of the carbonization depth model is corrected: Figure 4 , a rapid carbonization test was carried out under nitric acid conditions, and the fitting parameter k of the obtained results A We can get:

[0131]

[0132] The ratio of NO2 to CO2 in the atmosphere is used as the influencing parameter to determine k A To make corrections:

[0133]

[0134] In the formula, is the Henry constant of NO2 gas in aqueous solution, which is approximately 1.3845×10-5mol / (L·Pa) at 20°C; is the concentration percentage of NO2 and CO2 in the air; p is the atmospheric pressure.

[0135] like Figure 4 , based on the rapid carbonization test, the influence coefficient of bending stress on carbonization depth is given, and the expression is:

[0136] k F =0.96042+0.03983×exp(2.12694×f / f F )=1.1371

[0137] Where kF is the influence coefficient of bending stress on carbonation depth; f is the bending stress of the test concrete (MPa); f f is the ultimate flexural strength of the test concrete (MPa).

[0138] Step 4: Calculate the influence coefficients of temperature, humidity, water-cement ratio, cement dosage, compressive strength and other factors on carbonation depth.

[0139] (1) Ambient temperature influence coefficient k T :like Figure 5 According to the carbonization depth-time curve obtained by numerical simulation, a quadratic function is fitted to obtain

[0140] k T =-2.622×10 -4 ·T 2 +0.1829·T-30.075=1.2750

[0141] (2) Environmental humidity influence coefficient k RH :like Figure 6 According to the carbonization depth-humidity curve obtained from the numerical simulation results, a cubic function is fitted to obtain

[0142] k RH =84.083·RH3-217.297·RH2+182.576·RH-49.172=0.7857

[0143] (3) Concrete water-cement ratio influence coefficient k W / C :Combining the natural carbonization test and the rapid carbonization test, we can get

[0144] k W / C =5.0881W / C-1.3456=1.0458

[0145] (4) Concrete cement consumption influence coefficient k C : Perform linear fitting on the experimental data and get

[0146] k C =537.9222 / C-0.49423=0.9518

[0147] (5) Concrete compressive strength influence coefficient Modify the Niu Ditao formula, and we get

[0148]

[0149] Step 5: Establish a carbonization depth model under coating protection.

[0150] like Figure 3 The carbonization protection mechanism of the coating on concrete can be summarized as follows: since the coating surface is very dense and the diffusion coefficient of CO2 gas in the coating is very low, the coating blocks most of the CO2 molecules outside the concrete surface, greatly reducing the CO2 gas concentration on the concrete surface.

[0151] Based on the Alekseyev model, the carbonation depth prediction model of concrete under coating protection was established by considering the coating as concrete with equivalent thickness:

[0152]

[0153] In the formula, x coat is the carbonization depth under coating protection (mm); k is the comprehensive carbonization rate coefficient (mm / d 0.5 ); S is the equivalent concrete thickness of the coating (mm):

[0154]

[0155] Where x is the carbonation depth of uncoated protective concrete under the same conditions (mm).

[0156] Step 6: Establish the final carbonization depth prediction model for the extra-long highway tunnel lining structure taking into account coating protection, and calculate the predicted value of carbonization depth.

[0157]

[0158] According to the above parameter values, the comprehensive carbonization rate coefficient of the concrete lining structure of the Qinling Zhongnanshan Tunnel can be calculated as k = 0.2911 mm / d 0.5 The predicted value of carbonization depth of concrete after 10 years of operation is 17.59mm, and the predicted value of carbonization depth under coating protection is 0.99mm.

[0159] The present invention solves the problem of predicting the carbonation depth of concrete in the lining structure of a super-long highway tunnel under the condition of coating protection, taking into account the simultaneous effects of factors such as temperature, humidity, water-cement ratio, concrete compressive strength, cement dosage, carbon dioxide concentration, acidic harmful gases and bending stress. It achieves accurate prediction of the carbonation depth of concrete in the lining structure of a super-long highway tunnel and the protective effect of coatings, providing support for the prediction and evaluation of the safety of highway tunnels throughout their life cycle.

[0160] The above-mentioned related explanations and descriptions of the embodiments are for the convenience of those skilled in the art to understand and apply the present invention. It is obvious that those familiar with the art can easily make various modifications to these contents and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above-mentioned related explanations and descriptions of the embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A method for predicting carbonization depth of lining structure of extra-long highway tunnel considering coating protection, characterized in that: include: Through rapid carbonation test, a preliminary carbonation depth model of concrete is established; Conduct a rapid carbonization test in a standard rapid carbonization environment, and establish a carbonization depth model of concrete in the standard rapid carbonization environment based on the test results; Combined with the preliminary carbonation depth model, the carbonation depth model in the standard rapid carbonation environment is transformed into the carbonation depth model of concrete in the natural carbonation environment; The variables of influencing factors were introduced on the basis of the standard rapid carbonization environment to conduct rapid carbonization test, and the influence coefficient of influencing factors on the carbonation depth of concrete was obtained according to the test results and the preliminary carbonation depth model and the carbonation depth model of concrete in the standard rapid carbonization environment. Based on the Alekseyev model, the coating outside the concrete is regarded as concrete of equivalent thickness, and a prediction model for the carbonization depth of concrete under coating protection is established. The carbonization depth of lining structure is predicted by combining the carbonization depth model of concrete in natural carbonization environment, the influence coefficient of influencing factors on the carbonization depth of concrete and the carbonization depth prediction model of concrete under coating protection; The preliminary carbonation depth model of the concrete is: Where x is the carbonation depth of concrete, mm; k is the comprehensive carbonation rate coefficient of concrete, mm / d 0.5 ; t is time, year; The carbonation depth model of concrete in the standard rapid carbonation environment is: Where k0 is the initial carbonization rate coefficient of the test concrete in a standard rapid carbonization environment; The carbonation depth model of concrete in the natural carbonization environment is: In the formula, is the influence coefficient of CO2 concentration on the carbonation depth of concrete, and its value is as follows: In the formula, is the CO2 gas concentration in the air in the natural carbonization environment, %; is the CO2 gas concentration in the standard rapid carbonization environment, %; The prediction model of carbonization depth of concrete under the coating protection is: In the formula, is the carbonation depth of concrete under coating protection, mm; is the comprehensive carbonization velocity coefficient, mm / d 0.5 ; t is time, year; is the equivalent concrete thickness of the coating, mm: x is the carbonation depth of concrete without coating protection.

2. The carbonization depth prediction method for the lining structure of a super-long highway tunnel considering coating protection according to claim 1 is characterized in that: The influencing factors are at least one of acidic harmful gases, bending stress, ambient temperature, ambient humidity, concrete water-cement ratio, concrete cement dosage and concrete compressive strength.

3. The carbonization depth prediction method for the lining structure of a super-long highway tunnel considering coating protection according to claim 2 is characterized in that: When the influencing factors include acidic harmful gases, the nitric acid concentration variable is introduced on the basis of the standard rapid carbonization environment to conduct rapid carbonization tests. According to the obtained results and the preliminary carbonization depth model, the k corresponding to different nitric acid concentrations is fitted, and the influence coefficient corresponding to different nitric acid concentrations is obtained by dividing k by k0. , the influence coefficient is obtained by fitting : In the formula, is the influence coefficient of nitric acid concentration on the carbonation depth of concrete; is the nitric acid concentration, mol / L; The ratio of NO2 and CO2 in the atmosphere is used as the influencing parameter To make corrections: In the formula, is the Henry constant of NO2 gas in aqueous solution; and are the percentage concentrations of NO2 and CO2 in the air in a natural carbonization environment, respectively; p is the atmospheric pressure, kPa.

4. The carbonization depth prediction method for the lining structure of a super-long highway tunnel considering coating protection according to claim 2 is characterized in that: When the influencing factors include bending stress, the bending stress variable is introduced on the basis of the standard rapid carbonization environment to conduct rapid carbonization test. According to the obtained results and the preliminary carbonization depth model, the k corresponding to different bending stresses is fitted, and the influence coefficient corresponding to different bending stresses is obtained according to k / k0. k F , the influence coefficient of bending stress on the carbonation depth of concrete is obtained by fitting, and the expression is: In the formula, k F is the influence coefficient of bending stress on the carbonation depth of concrete; f is the bending stress of the test concrete, MPa; f f is the ultimate flexural strength of the test concrete, MPa.

5. The method for predicting carbonization depth of a super-long highway tunnel lining structure considering coating protection according to claim 2 is characterized in that: When the influencing factors include ambient temperature, the carbonization depth-time curve under temperature change is obtained by numerical simulation using COMSOL software. According to the carbonization depth-time curve under temperature change and the preliminary carbonization depth model, k corresponding to different temperatures is fitted, and the influence coefficient corresponding to different temperatures is obtained by dividing k by k0. , the influence coefficient of ambient temperature on the carbonization depth of concrete is obtained by fitting : When the influencing factor includes ambient humidity, the carbonization depth-time curve under humidity change is obtained by numerical simulation using COMSOL software. According to the carbonization depth-time curve under humidity change and the preliminary carbonization depth model, k corresponding to different humidity is fitted, and the influence coefficient corresponding to different humidity is obtained by dividing k by k0. , the influence coefficient of ambient humidity on the carbonization depth of concrete is obtained by fitting : Where T is the ambient temperature, °C, and RH is the ambient humidity,%.

6. The method for predicting carbonization depth of a lining structure of a super-long highway tunnel considering coating protection according to claim 2 is characterized in that: When the influencing factors include the concrete water-cement ratio, the concrete water-cement ratio variable is introduced on the basis of the standard rapid carbonization environment to conduct a rapid carbonization test. According to the obtained results and the preliminary carbonization depth model, the k corresponding to different concrete water-cement ratios is fitted, and the influence coefficient corresponding to different concrete water-cement ratios is obtained by dividing k by k0. , the influence coefficient of concrete water-cement ratio on concrete carbonization depth is obtained by fitting : When the influencing factors include the amount of concrete cement, the concrete cement amount variable is introduced on the basis of the standard rapid carbonization environment to conduct a rapid carbonization test. According to the obtained results and the preliminary carbonization depth model, the k corresponding to different concrete cement amounts is fitted, and the influence coefficient corresponding to different concrete cement amounts is obtained by dividing k by k0. , the influence coefficient of concrete cement content on concrete carbonization depth is obtained by fitting : Where W is the mass of water per unit volume, kg / m 3 ; C is the mass of concrete per unit volume, kg / m 3 ; W / C is the water-cement ratio; When the influencing factors include the compressive strength of concrete, the Niu Ditao formula is used: set up hour , modify the above formula to get in, It is the standard value of the cube compressive strength of concrete, MPa.

7. The method for predicting carbonization depth of a lining structure of a super-long highway tunnel considering coating protection according to claim 1 is characterized in that: The influencing factors include acidic harmful gases, bending stress, ambient temperature, ambient humidity, concrete water-cement ratio, concrete cement content and concrete compressive strength. The carbonation depth of the lining structure is predicted by combining the carbonation depth model of concrete in a natural carbonation environment, the influence coefficient of influencing factors on the carbonation depth of concrete and the carbonation depth prediction model of concrete under coating protection. Specifically, the carbonation depth is obtained by solving the following equation: in, is the influence coefficient of ambient temperature on the carbonation depth of concrete; is the influence coefficient of environmental humidity on the carbonation depth of concrete; is the influence coefficient of acidic harmful gas on the carbonation depth of concrete; k F is the influence coefficient of bending stress on the carbonation depth of concrete; is the influence coefficient of CO2 concentration on the carbonation depth of concrete; is the influence coefficient of concrete water-cement ratio on concrete carbonation depth; is the influence coefficient of concrete cement content on concrete carbonization depth; The influence coefficient of concrete compressive strength on concrete carbonation depth; k0 is the initial carbonation rate coefficient of the test concrete in a standard rapid carbonation environment; t is time, years; T is ambient temperature, RH is ambient humidity, and are the percentages of NO2 and CO2 concentrations in the air, respectively; f is the bending stress of the test concrete, MPa; f f is the ultimate flexural strength of the test concrete, MPa; W is the mass of water per unit volume, kg / m 3 ; C is the mass of concrete per unit volume, kg / m 3 ; W / C is the water-cement ratio; is the compressive strength of concrete; is the carbonization depth under coating protection, mm; is the comprehensive carbonization velocity coefficient, mm / d 0.5 ; is the equivalent concrete thickness of the coating, mm; is the carbonation depth of concrete without coating protection, mm.

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