Method for analyzing sensitivity of humidity field of concrete dam before and after dismounting of surface insulation board

Abstract

The invention provides a method for analyzing the sensitivity of a humidity field of a concrete dam before and after dismounting a surface insulation board. The method comprises the following steps: S1, determining relevant parameters influencing the analysis of the humidity field; s2, determining corresponding humidity boundary conditions and humidity fields; s3, constructing a finite element analysis model of the concrete block; s4, humidity field simulation calculation is conducted, and corresponding concrete parameters are set according to the humidity environment where the concrete dam is located and the test result; and S5, simulating the influence of the humidity field of the concrete and the change of the humidity field of the concrete on the structural state of the concrete dam after the surface insulation board is removed when the surface insulation board of the concrete dam is not removed. According to the method, factors such as humidity loss caused by different humidity boundary conditions, hydration heat of concrete and continuous change of humidity along with time are considered, and the influence of humidity field change on the stress field and the working state of the concrete dam is obtained by analyzing and calculating the humidity field before and after the thermal insulation board on the surface of the concrete dam is dismantled.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of hydraulic engineering, and relates to a method for analyzing the humidity field sensitivity of a concrete dam before and after the removal of surface insulation boards, in particular to a method for numerically simulating and analyzing the humidity field changes of a concrete dam before and after the removal of surface insulation boards. BACKGROUND

[0002] Surface cracks of concrete dams have always been a key problem to be solved in the dam engineering field. During the construction process, surface insulation boards can slow down the dissipation of hydration heat, which is conducive to the progress of cement hydration. The causes of concrete structure cracking are complex, but for a concrete dam that has been poured, cracking is closely related to dry shrinkage deformation. After the surface insulation boards are removed, the water in the concrete begins to migrate to the surrounding. This migration of water causes the humidity distribution in the concrete to become uneven, which in turn triggers the drying shrinkage stress in the structure. Therefore, understanding the law of the change of the humidity of the concrete over time has practical guiding significance for solving the durability problem of hydraulic concrete structures.

[0003] At present, many studies have been conducted on the temperature changes of concrete dams before and after the removal of surface insulation boards. The setting of surface insulation boards can effectively reduce the temperature difference between the inside and outside of the concrete and the surface temperature gradient, alleviate the adverse effects of external environmental temperature on the concrete surface, and make the internal temperature more uniform. After the surface insulation boards are removed, temperature diffusion causes temperature to decrease, and the interaction between temperature and humidity cannot be ignored. However, the change of the humidity field of the dam before and after the removal of the formwork is an area that has not been fully focused on. The uneven change of humidity may affect the stability of the dam body, so it is particularly important to study the influence of the change of the humidity field of the dam caused by the removal of the surface insulation boards on the structural behavior of the concrete dam, and an effective method is needed to simulate and analyze the change of the humidity field of the dam. SUMMARY

[0004] The purpose of the present application is to provide a method for simulating and analyzing the humidity sensitivity of a concrete dam before and after the removal of surface insulation boards, in order to further effectively analyze the influence of the change of the humidity before and after the removal of the surface insulation boards on the structural behavior of the dam body.

[0005] To this end, the above-mentioned purpose of the present application is achieved by the following technical solution:

[0006] A method for analyzing the humidity field sensitivity of a concrete dam before and after the removal of surface insulation boards, comprising the following steps:

[0007] S1, determining the related parameters affecting the humidity field analysis;

[0008] S2, determining the corresponding humidity boundary conditions and humidity field according to the engineering conditions of a certain concrete dam;

[0009] S3, on the basis of considering the concrete dam engineering conditions, a finite element analysis model of the concrete block is constructed;

[0010] S4, humidity field simulation calculation is carried out, and corresponding concrete parameters are set according to the humidity environment of the concrete dam and the test results;

[0011] S5, the influence of the humidity field of the concrete and the change of the humidity field of the concrete after the surface insulation board is removed on the structural behavior of the concrete dam is simulated.

[0012] While the above technical solutions are adopted, the application can also adopt or combine the following technical solutions:

[0013] As a preferred technical solution of the application: in step S1, the parameters related to the humidity field analysis include: humidity diffusion coefficient, surface humidity transfer coefficient, self-drying effect.

[0014] As a preferred technical solution of the application: the humidity diffusion coefficient is determined by the following formula:

[0015]

[0016] In the above formula, D is the humidity diffusion coefficient of the concrete; D1 is the humidity diffusion coefficient in the saturated state, when h=1.0, D1 is the maximum value of D(h); h c is the relative humidity when D(h)=0.5D1, h is the relative humidity. α0, n are empirical coefficients, usually 0.05, 15.

[0017] As a preferred technical solution of the application: the surface humidity transfer coefficient is determined by the following formula:

[0018] f=A(0.253+0.06v a )(h-h c )

[0019] In the formula, f is the surface humidity transfer coefficient; A is an empirical coefficient related to the water-cement ratio of the concrete; v a is the wind speed; h c is the environmental humidity.

[0020] As a preferred technical solution of the application: in step S2, the humidity field differential equation adopts a non-steady humidity field differential equation, as shown below:

[0021]

[0022] In the formula: D(h) is the humidity diffusion coefficient of the concrete, Q is the humidity content in the concrete, h is the relative humidity, t is the time, x, y, z represent the three directions of the coordinate axis.

[0023] The humidity field satisfies the second Fick's law and the mass conservation law.

[0024] As a preferred technical solution of the present application: in step S2, the humidity boundary condition is the concrete structure and atmospheric contact boundary condition, the concrete surface absolute humidity boundary condition and the concrete humidity boundary condition.

[0025] As a preferred technical solution of the present application: in step S4, the SAPTIS finite element analysis software independently developed by the China Institute of Water Resources and Hydropower Research is used for humidity field simulation calculation.

[0026] As a preferred technical solution of the present application: in step S5, the surface insulation board information includes the influence of the surface insulation board removal time, the removal area and the removal range on the dam deformation field and the stress field.

[0027] The present application provides a kind of humidity sensitivity simulation analysis method before and after the removal of surface insulation board of concrete dam, and the method for studying the influence of the change of concrete humidity field caused by the removal of surface insulation board on the structural behavior of concrete dam is proposed, considering different humidity boundary conditions, humidity loss caused by hydration heat of concrete itself and humidity continues to change with time and other factors, the humidity field before and after the removal of surface insulation board of concrete dam is analyzed and calculated by self-developed finite element simulation analysis software, and the influence of humidity field change on the stress field and working behavior of concrete dam is obtained. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The flow chart of the humidity field sensitivity analysis method of concrete dam before and after the removal of surface insulation board provided by the present application.

[0029] Figures 2-4 It is the cloud chart of the humidity field of concrete dam after the removal of surface insulation board changes with time.

[0030] Figure 5 It is the schematic diagram of the humidity field simulation results before and after the removal of surface insulation board of concrete dam. DETAILED DESCRIPTION

[0031] The present application is further described in detail with reference to the drawings and specific examples.

[0032] The present application uses the finite element simulation calculation method of humidity field to simulate the overall humidity distribution before and after the removal of surface insulation board of concrete dam. By analyzing the relationship between humidity and strain, the deformation parameters at different depths and positions of concrete dam can be calculated. These parameters are then input into the pre-constructed finite element model to simulate the stress state of concrete dam during the drying shrinkage process after the removal of surface insulation board. This method can effectively perform numerical simulation of the deformation caused by concrete drying shrinkage. The detailed ideas of the present application are described in detail as follows:

[0033] Reference Figure 1 The application provides a sensitive analysis method for a concrete dam humidity field before and after surface insulation board removal, mainly comprising the following steps:

[0034] The humidity field is analyzed. First, a concrete block grid model file is constructed according to symmetry through ANSYS APDL, and then a humidity field module is developed based on a temperature field analysis module in SAPTIS software. According to a non-steady humidity field differential equation, each calculation parameter of the humidity field is set, including relative humidity, humidity diffusion coefficient, humidity self-reduction term and surface moisture transfer coefficient. Then, corresponding initial humidity and humidity boundary conditions are applied according to the environmental conditions of the concrete dam. The initial relative humidity of the humidity field is 100%, and the third type of boundary condition is applied around, and the symmetric surface is applied with an absolute humidity boundary condition. The values of the above calculation parameters can be selected according to indoor or field humidity test data.

[0035] The humidity diffusion coefficient calculation formula in the above can be expressed as:

[0036]

[0037] In the formula, D is the humidity diffusion coefficient of concrete, D1 is the humidity diffusion coefficient in the saturated state, when h = 1.0, D1 is the maximum value of D(h), α0 = D0 / D1, wherein D0 is the minimum value of D(h), and h is the pore relative humidity when D(h) = 0.5D1; n is a curve fitting parameter. c

[0038] Meanwhile, according to related references, the diffusion coefficient of concrete in the saturated state has a certain functional relationship with the strength of the concrete, and D1 is estimated by the following formula:

[0039]

[0040] In the formula: D 1,0 = 3.6 × 10 -6 m 2 / h; f cko = 10 Mpa; f ck = f cm - 8 Mpa, wherein: f cm is the average compressive strength.

[0041] The surface humidity transfer coefficient f is related to the water-cement ratio of concrete, the temperature difference between inside and outside, temperature, wind speed and other factors. In particular, the wind speed and the water-cement ratio have an important influence on the surface humidity transfer coefficient. The following gives a commonly used empirical formula:

[0042] f = A (0.253 + 0.06v a )(h-h​c )

[0043] wherein:

[0044] f - surface humidity transfer coefficient, m / h;

[0045] A - empirical coefficient related to the water-cement ratio of concrete;

[0046] v a - wind speed, m / s;

[0047] h c - ambient humidity, %.

[0048] After obtaining the humidity change of the calculation node within each incremental step, the dry shrinkage strain is calculated according to the corresponding formula. The dry shrinkage strain of the concrete is calculated by the following formula:

[0049] ε sh = k sh h

[0050] wherein: k sh is the shrinkage coefficient of concrete.

[0051] This process accumulates the calculated dry shrinkage strain value to the total strain.

[0052] The strain increment of the concrete under complex stress within Δt n can be described as follows:

[0053]

[0054] wherein, the arrays respectively represent the elastic strain increment, the temperature strain increment, the dry shrinkage strain increment, the autogenous shrinkage strain increment and the creep strain increment.

[0055] The temperature load and humidity load obtained in SAPTIS are directly substituted into the nonlinear analysis module to calculate the stress.

[0056] The overall equilibrium equation is obtained by solving the stress field by using the finite element method:

[0057] [K]{Δδ n} = {ΔP n} L + {ΔP n} C + {ΔP n} T + {ΔP n} 0 + {ΔP n} S

[0058] {ΔP n}L —Increment in nodal load caused by external loads;

[0059] {ΔP n} C —Incremental load at nodal points caused by creep;

[0060] {ΔP n} T —Increment in nodal load caused by temperature;

[0061] {ΔP n} 0 —Increment in nodal load caused by self-generated volumetric deformation;

[0062] {ΔP n} S —Nodal loads caused by drying shrinkage.

[0063] The relationship between stress increment and strain increment is as follows:

[0064]

[0065] {ε}=[B]{δ} e

[0066] Find the displacement increments {Δδ} of each node. n After that, the stress increment can be obtained, and the stress at the corresponding moment can be obtained by accumulation.

[0067] In SAPTIS software, surface insulation boards are added or removed as needed for each dam section. When the surface insulation boards are not removed, simulation is performed by setting the surface humidity transfer coefficient to 0. After the surface insulation boards are removed, the corresponding parameters are obtained through experiments, and the above operation is repeated to perform simulation.

[0068] refer to Figures 2 to 4 It presents the time-varying process of the humidity field distribution of concrete blocks in a concrete dam. Among them: Figure 2 This represents the distribution of the internal humidity field of the concrete over a period of 1 day. Based on the initial conditions, the relative humidity of the concrete is 100%. Figure 3 This indicates the distribution of the concrete humidity field over 30 days. Figure 4 This indicates the distribution of internal humidity field in concrete over 60 days. As time progresses, the humidity in the concrete continues to diffuse, with different colors representing different humidity values.

[0069] refer to Figure 5 The graph shows the humidity change curves before and after the removal of the surface insulation board from the concrete. The horizontal axis represents time, the vertical axis represents humidity, and different marked points represent the relative humidity at different times.

[0070] The above specific embodiments are used to explain and illustrate the present invention, and are only preferred embodiments of the present invention, not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A method for analyzing the humidity field sensitivity of concrete dams before and after the removal of surface insulation boards, characterized in that: Includes the following steps: S1. Determine the relevant parameters affecting humidity field analysis; S2. Based on the conditions of a concrete dam project, determine the corresponding humidity boundary conditions and humidity field; S3. Based on the engineering conditions of concrete dams, construct a finite element analysis model of the concrete blocks; S4. Perform humidity field simulation calculations and set corresponding concrete parameters based on the humidity environment of the concrete dam and the test results. S5. Simulate the effect of the humidity field of concrete on the structural behavior of concrete dam when the surface insulation board is not removed, and the change of the concrete humidity field after the surface insulation board is removed.

2. The method for analyzing the humidity field sensitivity of concrete dams before and after the removal of surface insulation boards according to claim 1, characterized in that: In step S1, the parameters affecting the humidity field analysis include: humidity diffusion coefficient, surface humidity transfer coefficient, and self-drying effect.

3. The method for analyzing the humidity field sensitivity of concrete dams before and after the removal of surface insulation boards according to claim 2, characterized in that: The humidity diffusion coefficient is determined by the following formula: In the above formula, D is the moisture diffusion coefficient of concrete; D1 is the moisture diffusion coefficient under saturated conditions, and when h = 1.0, D1 is the maximum value of D(h); h c The relative humidity is D(h) = 0.5D1, where h is the relative humidity; α0 and n are empirical coefficients, usually taken as 0.05 and 15, respectively.

4. The method for analyzing the humidity field sensitivity of concrete dams before and after the removal of surface insulation boards according to claim 2, characterized in that: The surface humidity transfer coefficient is determined by the following formula: f=A(0.253+0.06v a )(hh c ) In the formula, f is the surface moisture transfer coefficient; A is an empirical coefficient related to the water-cement ratio of concrete; v a Wind speed; h c This refers to ambient humidity.

5. The method for analyzing the humidity field sensitivity of concrete dams before and after the removal of surface insulation boards according to claim 1, characterized in that: In step S2, the differential equation for the humidity field is: In the formula: D(h) is the concrete humidity diffusion coefficient, Q is the humidity content in the concrete, h is the humidity, and x, y, and z represent the three directions of the coordinate axis.

6. The method for analyzing the humidity field sensitivity of concrete dams before and after the removal of surface insulation boards according to claim 1, characterized in that: In step S2, the humidity boundary conditions are the boundary conditions for the concrete structure in contact with the atmosphere, the boundary conditions for the concrete surface to be completely dry, and the boundary conditions for the concrete humidity.

7. The method for analyzing the humidity field sensitivity of concrete dams before and after the removal of surface insulation boards according to claim 1, characterized in that: In step S5, the surface insulation board information includes the impact of the time, area, and scope of surface insulation board removal on the deformation and stress fields of the dam.

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