A method for predicting the leakage of water from a water-sealed cavern sealing plug

Abstract

This invention discloses a method for predicting the leakage of water from the sealing plug of a water-sealed cavern, relating to the field of seepage control technology in underground water-sealed cavern engineering. The method includes: calculating the spatiotemporal temperature distribution and effective cooling difference during the hydration heat process and subsequent cooling process of the concrete sealing plug; introducing a stress relaxation coefficient to calculate net shrinkage strain, thereby obtaining real-time tensile stress and tensile strength; comparing the two, determining the occurrence of opening cracks when the tensile stress exceeds the tensile strength, and calculating the equivalent crack width; establishing a seepage prediction calculation model based on the cubic law of fluid mechanics and obtaining the seepage volume; finally, converting the seepage volume into a capacitance value to establish a time curve, and comparing it with acceptance standards. This invention upgrades empirical seepage control measures into a quantifiable and predictable guidance system, providing a scientific basis for temperature control and precise timing of grouting during sealing plug construction.

Description

Technical Field

[0001] This invention relates to the field of seepage control technology in underground water-sealed cavern engineering, specifically to a method for predicting the leakage of water through the sealing plug of a water-sealed cavern. Background Technology

[0002] A water-sealed underground cavern is a deep underground engineering structure that uses the hydrostatic pressure of groundwater to seal and store liquid or gaseous media. Its core principle lies in maintaining a consistently higher groundwater pressure within the surrounding rock than the pressure of the stored medium inside the cavern, thus creating a stable "water seal" effect. The sealing plug, as the final crucial barrier against water leakage, directly determines the stability of the water seal system and the long-term safety of the project. Sealing plugs are typically made of cast concrete. During the cooling process after construction, the concrete shrinks due to the release of heat from hydration. The surrounding hard rock strongly constrains this shrinkage, easily inducing tensile stress within the concrete. When this tensile stress exceeds the tensile strength limit of the concrete, micro-cracks will appear at the interface between the sealing plug and the rock mass or in weak points of the concrete. These cracks directly connect the water pressure surface and the backwater surface, forming the main permeable channels and leading to leakage problems.

[0003] Currently, the industry relies heavily on empirical measures for seepage control treatment of sealing plugs, lacking a quantifiable and predictable technical system. This makes it difficult to accurately predict the timing and width of cracks during the cooling process, and also to anticipate whether the seepage volume meets acceptance standards (typically requiring Q≤0.1Lu, i.e., a maximum allowable seepage volume of 0.1L / min). Consequently, temperature control and seepage control during construction lack a scientific basis. Excessive seepage not only increases the cost of replenishing or draining water during operation but may also lead to the failure of the water seal system, causing storage medium leakage, groundwater pollution, and other safety hazards, severely impacting the structural integrity, functional stability, and economic lifespan of the underground water-sealed cavern project. Therefore, developing a method to accurately predict the seepage volume of sealing plugs in water-sealed caverns, providing scientific guidance for temperature control, seepage control treatment, and grouting timing during construction, has become an urgent technical problem to be solved in the field of underground water-sealed cavern engineering. Summary of the Invention

[0004] To address the problem of leakage caused by micro-cracks induced by hard rock mass during the cooling and shrinkage process of underground water-sealed cavern sealing plugs, this invention provides a method for predicting the leakage volume of water-sealed cavern sealing plugs. The aim is to upgrade traditional empirical seepage control measures into a quantifiable and predictable guidance system. By accurately predicting the seepage volume and development process of cracks, it provides a scientific basis for temperature control, timing of grouting, and seepage control treatment during the sealing plug construction process. The specific technical solution is as follows: A method for predicting the leakage of water from a water-sealed cavern sealing plug includes the following steps: Step S1: Calculate the spatiotemporal temperature distribution of the concrete sealing plug during the early hydration heat release process and the later cooling process, and obtain the effective temperature drop difference ΔT(t) at any time t. Step S2: Introduce the stress relaxation coefficient and calculate the net shrinkage strain generated by the concrete during the later cooling process based on the effective temperature drop difference ΔT(t). Thus, the real-time tensile stress at any time t can be obtained. And the real-time tensile strength f(t); Step S3, compare the real-time tensile stress And the real-time tensile strength f(t); like When the value is greater than f(t), it is determined that an opening crack has occurred between the concrete sealing plug and the rock mass, and the equivalent crack width at this moment is calculated. ; Step S4: Based on the cubic law of fluid dynamics, establish a seepage prediction calculation model, and calculate the equivalent crack width. Substitute the data into the model to calculate the amount of water seepage Q through the crack between the concrete seal and the rock mass; Step S5: Convert the calculated seepage volume Q into a capacitance value. And establish a time curve The seepage control performance of the sealing plug was evaluated by comparing it with the seepage volume acceptance standard, and the evaluation results were obtained.

[0005] In a preferred implementation, the formula for calculating the effective temperature drop difference ΔT(t) in step S1 is:

[0006] in, This represents the highest core temperature of the concrete at its peak. Let t be the real-time temperature of the concrete at any time t after it has reached its peak temperature.

[0007] In a preferred implementation, the spatiotemporal temperature distribution is simulated using finite element analysis software coupled with the thermal conductivity equation and the hydration heat release equation of concrete, wherein the thermal conductivity equation is:

[0008] Where ρ, c, and λ are the density, specific heat capacity, and thermal conductivity of concrete, respectively. The rate of change of temperature over time. For thermal conduction gradient; This represents the cumulative heat of hydration released. The equation for the cumulative release of heat of hydration is:

[0009] in, For the final total heat output, This is the heating rate coefficient.

[0010] In a preferred implementation, the net shrinkage strain in step S2 The calculation formula is:

[0011] in, is the linear expansion coefficient of concrete. It is a self-contracting term. As compensation; Real-time tensile stress in step S2 The calculation formula is:

[0012] in, Let be the real-time effective elastic modulus of concrete at time t. This represents the constraint coefficient of the rock mass.

[0013] In a preferred implementation, the formula for calculating the real-time tensile strength f(t) in step S2 is as follows:

[0014]

[0015] Where E(t) is the instantaneous elastic modulus, The elastic modulus of concrete after 28 days of standard curing. It is the growth factor of the elastic modulus. The tensile strength (MPa) of concrete after 28 days of standard curing.

[0016] In a preferred implementation, the equivalent crack width in step S3 The calculation formula is:

[0017] in, Where L is the constraint coefficient of the rock mass, and L is the constraint length. This represents net shrinkage strain.

[0018] In a preferred implementation, the formula for calculating the seepage volume Q in step S4 is:

[0019] in, The rate of water seepage per second through the crack between the sealing plug and the surrounding rock mass, assuming a water head of 1m. It is the acceleration due to gravity. The density of water, The dynamic viscosity of water, Due to head difference, This is the seepage path length. This represents the total length of the crack.

[0020] In a preferred implementation, the Lv-ratio value in step S5 The calculation formula is:

[0021] The acceptance standard for seepage volume is as follows: By establishing The curve predicts when the equivalent crack width reaches its maximum, thus guiding the timing of grouting.

[0022] Compared with the prior art, the beneficial effects of the present invention are: (1) This invention successfully upgrades the traditional experience-dependent sealing plug seepage control measures into a quantifiable and predictable scientific guidance system, which couples the hydration heat field of concrete, the viscoelastic strain field considering creep relaxation, and the seepage field based on the cubic law of fluid mechanics. It can accurately predict the generation process of microcracks and the dynamic leakage volume through the temperature change of concrete. (2) By constructing a prediction curve of the change of the grouting value over time, the construction personnel can accurately determine the node where the equivalent width of the crack reaches its maximum, thereby capturing the best grouting time. This not only avoids the waste of resources and leakage risk caused by grouting too early or too late, but also provides reliable data support for temperature control and seepage control treatment throughout the entire process of sealing plug construction, ultimately ensuring the quality of engineering construction and guaranteeing the overall controllability of the construction period and investment. Attached Figure Description

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0024] Figure 1 This is a flowchart illustrating the method for predicting the leakage of water from the sealing plug of a water-sealed cavern according to the present invention. Detailed Implementation

[0025] The present invention will be further described below through specific embodiments, but this is not a limitation of the present invention. Those skilled in the art can make various modifications or improvements based on the basic idea of ​​the present invention, but as long as they do not depart from the basic idea of ​​the present invention, they are all within the protection scope of the present invention.

[0026] This invention provides a method for predicting the leakage of water-sealed cavern sealing plugs, aiming to solve the leakage problem caused by micro-cracks induced by the constraint of hard rock masses during the cooling and contraction process of underground water-sealed cavern sealing plugs. This method upgrades traditional empirical seepage control measures into a quantifiable and predictable guiding system by coupling the hydration heat field of concrete, the viscoelastic strain field considering creep relaxation, and the seepage field based on the cubic law through a mathematical model. This provides a scientific basis for temperature control and seepage control treatment during sealing plug construction.

[0027] See Figure 1 One embodiment provided by the present invention is as follows: Calculation of the spatiotemporal temperature distribution of the concrete sealing plug: Since the cooling period after the concrete sealing plug is constructed is a critical window for structural safety, and the temperature rise due to concrete hydration heat and the subsequent cooling and shrinkage have a non-linear relationship, this step uses finite element analysis software (such as ANSYS) to establish a model. Simulation is performed based on the heat conduction equation:

[0028] Where ρ, c, and λ are the density, specific heat capacity, and thermal conductivity of concrete, respectively. The key parameter input into the model is the cumulative release of heat of hydration. According to the formula Calculation, where The final total calorific value is determined by the type of cement. The heating rate coefficient is determined by the activity of cement. The software simulates and outputs the temperature-time curve of the entire hydration heat process of concrete, and calculates the effective temperature drop difference ΔT(t) at any time t. This effective temperature drop difference is expressed by the formula... Obtain, among which This refers to the highest core temperature of the concrete at its peak. The real-time temperature is t at any time after the peak is reached.

[0029] After acquiring the temperature field data, real-time stress and tensile strength are calculated. Given the significant viscoelastic characteristics of concrete in its early stages, a stress relaxation coefficient correction is needed for the actual tensile stress. First, the instantaneous elastic modulus of the concrete is calculated. ,in The elastic modulus of concrete after 28 days of standard curing. This is the growth factor of the elastic modulus; thus, the real-time tensile strength is derived. Simultaneously, the net shrinkage strain of the concrete is calculated. The strain is given by the formula It was determined that the linear expansion coefficient was taken into account. Temperature difference contraction and autogenous contraction terms And the compensation item generated by the expanding agent Among them, the self-contraction term It is a shrinkage value-time curve obtained by measuring the volume deformation of concrete from initial setting onwards using the bellows method or a non-contact displacement gauge under constant temperature and humidity conditions, and includes a compensation term. This involves artificially inducing the concrete to expand outwards through interventions such as adding expansion agents to counteract the shrinkage tendency. Based on this, the real-time tensile stress strength of the concrete due to cooling shrinkage at any given time t is calculated. ,in This is the real-time effective elastic modulus (usually taken as 0.6 times $E(t)$). This is the rock mass constraint coefficient, which reflects the elastic constraint of the surrounding hard rock mass on the shrinkage of concrete.

[0030] The crack width was determined and calculated. The real-time tensile stress calculated for each time period was then used. Compare with the real-time tensile strength f(t). At a certain moment... When the value is greater than f(t), it is determined that the interface between the sealing plug and the rock mass or the weak point has been pulled apart, and an opening crack has begun to form. The real-time equivalent crack width at this moment is... Through formula The calculation shows that L is the constraint length. This determination mechanism can pinpoint the specific time point at which cracks occur, providing an early warning for taking insulation measures during construction to reduce the temperature difference ΔT.

[0031] A seepage prediction model based on the cubic law of fluid dynamics is established. The model assumes a head difference. The seepage path length is 1m. The total length of the crack is set to be approximately equal to the thickness of the sealing plug, taking the worst-case scenario into account. Let be the perimeter of the sealing plug's cross-section. The dynamic seam width calculated above... Substitute into the formula In the formula, the seepage rate Q through the crack per second under a water head of 1m is calculated. It is the acceleration due to gravity. The density of water, The dynamic viscosity of water is given. Finally, the calculation results are converted into engineering acceptance indicators to guide construction. The seepage volume Q is converted into a capacitance value. and establish The curve shows how the water leakage from the sealing plug changes over time. The calculation results are then compared with the acceptance criteria for water leakage from the sealing plug (e.g., ...). Compare the predicted values ​​with the actual values. If the predicted values ​​exceed the limits, it indicates that temperature control measures need to be adjusted. Simultaneously, through... The curve can accurately predict the seam width. To reach the maximum moment, thereby capturing the best grouting time, and avoiding poor results from grouting too early or leakage risks from grouting too late.

[0032] Taking the XAL underground water-sealed cavern project as an example, the project includes three construction tunnel sealing plugs and eight process shaft sealing plugs. Using the method described in this embodiment, technicians successfully predicted in advance the crack formation process and seepage evolution of the sealing plugs during the hydration heat cooling process, and accordingly formulated targeted temperature control schemes and grouting plans. This not only ensured that the sealing plugs met the requirements for low permeability performance and guaranteed the "water seal" function of the cavern, but also effectively controlled the construction period and investment, verifying the engineering practicality and beneficial effects of this method.

[0033] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for predicting the leakage of water from a water-sealed cavern sealing plug, characterized in that, Includes the following steps: Step S1: Calculate the spatiotemporal temperature distribution of the concrete sealing plug during the early hydration heat release process and the later cooling process, and obtain the effective temperature drop difference ΔT(t) at any time t. Step S2: Introduce the stress relaxation coefficient and calculate the net shrinkage strain generated by the concrete during the later cooling process based on the effective temperature drop difference ΔT(t). Thus, the real-time tensile stress at any time t can be obtained. And the real-time tensile strength f(t); Step S3, compare the real-time tensile stress And the real-time tensile strength f(t); like If the value is greater than f(t), then it is determined that an opening crack has occurred between the concrete sealing plug and the rock mass, and the equivalent crack width at this moment is calculated. ; Step S4: Based on the cubic law of fluid dynamics, establish a seepage prediction calculation model, and calculate the equivalent crack width. Substitute the data into the model to calculate the amount of water seepage Q through the crack between the concrete seal and the rock mass; Step S5: Convert the calculated seepage volume Q into a capacitance value. And establish a time curve The seepage control performance of the sealing plug was evaluated by comparing it with the seepage volume acceptance standard, and the evaluation results were obtained.

2. The method for estimating the leakage of water from the sealing plug of a water-sealed cavern according to claim 1, characterized in that, In step S1, the formula for calculating the effective temperature drop difference ΔT(t) is: in, This represents the highest core temperature of the concrete at its peak. Let t be the real-time temperature of the concrete at any time t after it has reached its peak temperature.

3. The method for estimating the leakage of water from the sealing plug of a water-sealed cavern according to claim 1, characterized in that, The spatiotemporal temperature distribution was simulated using finite element analysis software, which coupled the heat conduction equation and the heat release equation of concrete. The heat conduction equation is as follows: Where ρ, c, and λ are the density, specific heat capacity, and thermal conductivity of concrete, respectively. The rate of change of temperature over time. For thermal conduction gradient; This represents the cumulative heat of hydration release. The equation for the release of heat of hydration is: in, For the final total heat output, This is the heating rate coefficient.

4. The method for estimating the leakage of water from the sealing plug of a water-sealed cavern according to claim 1, characterized in that, The net shrinkage strain in step S2 The calculation formula is: in, is the linear expansion coefficient of concrete. It is a self-contracting term. As compensation; Real-time tensile stress in step S2 The calculation formula is: in, Let be the real-time effective elastic modulus of concrete at time t. This represents the constraint coefficient of the rock mass.

5. The method for estimating the leakage of water from the sealing plug of a water-sealed cavern according to claim 4, characterized in that, The formula for calculating the real-time tensile strength f(t) in step S2 is as follows: Where E(t) is the instantaneous elastic modulus, The elastic modulus of concrete after 28 days of standard curing. It is the growth factor of the elastic modulus. The tensile strength (MPa) of concrete after 28 days of standard curing.

6. The method for estimating the leakage of water from the sealing plug of a water-sealed cavern according to claim 1, characterized in that, The equivalent crack width in step S3 The calculation formula is: in, Where L is the constraint coefficient of the rock mass, and L is the constraint length. This represents net shrinkage strain.

7. The method for estimating the leakage of water from the sealing plug of a water-sealed cavern according to claim 1, characterized in that, The formula for calculating the seepage volume Q in step S4 is as follows: in, The rate of water seepage per second through the crack between the sealing plug and the surrounding rock mass, assuming a water head of 1m. It is the acceleration due to gravity. The density of water, The dynamic viscosity of water, Due to head difference, This is the seepage path length. This represents the total length of the crack.

8. The method for estimating the leakage of water from the sealing plug of a water-sealed cavern according to claim 7, characterized in that, In step S5, the value of Lv Rong The calculation formula is: The acceptance standard for seepage volume is as follows: By establishing The curve predicts when the equivalent crack width reaches its maximum, thus guiding the timing of grouting.

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