Consider the most unfavorable underground repository pressure structure and its quantitative design method

Abstract

The application discloses a pressure-bearing structure of an underground storage considering a most unfavorable working condition and a quantitative design method thereof, and is suitable for the technical field of underground engineering and comprises the following steps: S1, finding out mechanical boundary conditions of a multilayer structure, determining conditions of the underground storage and corresponding operation parameters; S2, obtaining the most unfavorable working condition of the underground storage based on the mechanical boundary conditions of the multilayer structure; S3, calculating relevant parameters of the pressure-bearing structure of the underground storage under the most unfavorable working condition according to a three-way stress balance equation and taking the parameters obtained in step S1 as input. The quantitative design method of each layer structure of the high internal pressure underground storage is proposed by setting a pressure-bearing mode of the pressure-bearing structure under the most unfavorable working condition and comprehensively considering classical theories; the pressure-bearing structure is considered from multiple conditions and multiple aspects, the underground storage is reduced to be restricted by hard conditions, and thus the stability and safety of the underground storage can be effectively improved.

Description

Technical Field

[0001] This invention relates to the field of underground engineering technology, specifically to the pressure-bearing structure of underground storage facilities considering the most unfavorable working conditions and its quantitative design method. Background Technology

[0002] The underground storage facility determines the energy storage capacity and peak-shaving capability, making it a crucial component of energy reserves. Underground storage facilities typically consist of multiple layers, including hard surrounding rock, support layers, and sealing layers. The hard surrounding rock, under pressure, generates elastic deformation to resist internal high pressure. However, during construction and injection / extraction, the surrounding rock undergoes differential deformation under cyclic alternating loads, leading to radial peeling and circumferential misalignment at the contact interfaces of the multi-layered structure. This directly impacts the long-term stability and sealing of the underground storage facility.

[0003] Pressure differential conditions are a crucial factor in the design of underground energy storage caverns. Reasonable pressure differential conditions must be considered during the design and construction of underground energy storage caverns. It is essential to ensure that the pressure within the cavern is neither too high nor too low, to prevent excessive pressure on the surrounding rock that could lead to leakage of the stored medium. Therefore, high-internal-pressure underground storage caverns that utilize the small-strain elastic resistance of the surrounding rock can be adopted to address the controllable and coordinated deformation problem of multi-layered structures under the combined effects of surrounding rock stress and internal pressure.

[0004] Chinese patent publication number CN116446950A discloses an adaptive deformation sealing structure for an artificial rock cavern gas storage facility. This structure boasts advantages such as strong deformation adaptability, low stress in the flexible sealing layer, and no cracking under normal operating pressure conditions, making it particularly suitable for the construction of high-deformation, high-pressure underground storage facilities in soft rock strata. However, this invention does not consider the differential deformation of multi-layered structures under the combined effects of surrounding rock stress and internal pressure in the most unfavorable working conditions, nor does it propose a specific quantitative design method for each layer of the gas storage facility. Summary of the Invention

[0005] The purpose of this invention is to address the problem that existing underground storage facilities are heavily constrained by rigid conditions due to the lack of a pressure-bearing mode for the pressure-bearing structure under the most unfavorable working conditions. This invention proposes a pressure-bearing structure for underground storage facilities that considers the most unfavorable working conditions and its quantitative design method. It utilizes the elastic resistance generated by controllable small strain in the surrounding rock to resist internal high pressure, while simultaneously setting the pressure-bearing mode of the structure under the most unfavorable working conditions. Furthermore, it proposes a quantitative design method for the structure of each layer of a high-internal-pressure underground storage facility, comprehensively considering multiple conditions and aspects of the pressure-bearing structure to avoid structural instability caused by incoordination deformation at the interfaces of multiple material layers during operation. This reduces the constraints of rigid conditions on underground storage facilities, thereby effectively improving their stability and safety.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by this invention is: a quantitative design method for the pressure-bearing structure of underground storage tanks considering the most unfavorable working conditions, comprising the following steps:

[0007] S1. Determine the mechanical boundary conditions of the multi-layered structure and the underground storage conditions and corresponding operating parameters;

[0008] S2. Based on the mechanical boundary conditions of the multi-layered structure, obtain the most unfavorable working condition of the underground storage tank;

[0009] S3. Based on the triaxial stress balance equation, using the parameters obtained in step S1 as input, calculate the relevant parameters of the underground storage pressure structure under the most unfavorable working condition.

[0010] This solution addresses the problem of existing underground storage facilities being heavily constrained by rigid conditions due to the lack of a design consideration for the pressure-bearing structure under the most unfavorable operating conditions. It proposes a design method for an underground storage pressure-bearing structure considering the most unfavorable operating conditions and its quantitative design. By identifying the mechanical boundary conditions of the multi-layered structure, the underground storage conditions and corresponding operating parameters are determined. Based on these conditions, the first and second most unfavorable operating conditions are obtained. Using the triaxial stress balance equation and the underground storage conditions and corresponding operating parameters as input, the relevant parameters of the underground storage pressure-bearing structure under the most unfavorable operating conditions are calculated. This paper presents a simplified method for simulating and calculating the relevant parameters of the pressure-bearing structure of an underground storage facility under the most unfavorable working conditions. It realizes the pressure-bearing mode of the underground storage facility considering the most unfavorable working conditions. When the internal pressure is greater than the external pressure, the surrounding rock, segment support layer, and flexible sealing layer expand radially, and the surrounding rock bears the internal and external pressure difference. When the internal pressure is less than the external pressure, the surrounding rock, segment support layer, and flexible sealing layer contract radially, and the support layer bears the internal and external pressure difference. Furthermore, it proposes a quantitative design method for each layer of the high internal pressure underground storage facility by integrating classical theories, thereby minimizing the constraints of rigid conditions on the underground storage facility to the greatest extent possible, effectively improving the stability and safety of the underground storage facility.

[0011] Preferably, the mechanical boundary conditions in S1 include the geological conditions of the surrounding rock and the corresponding mechanical parameters; the geological conditions of the surrounding rock include the rock mass type, surrounding rock grade and maximum principal stress of the surrounding rock in the proposed reservoir area; the corresponding mechanical parameters include minimum principal stress, elastic modulus, Poisson's ratio, cohesion and internal friction angle; the underground reservoir conditions and corresponding operating parameters include excavation diameter, maximum internal pressure and minimum internal pressure during operation.

[0012] In this scheme, by identifying the mechanical boundary conditions of the multi-layer structure, determining the underground storage conditions and corresponding operating parameters, the performance of the underground storage can be analyzed more accurately, its design can be further optimized, and the operating efficiency and stability of the underground storage can be improved. Appropriate operating parameters can improve the flexibility of the energy storage, enabling it to better cope with changes in energy demand and achieve rapid response. At the same time, accurate condition setting and parameter selection can ensure that the energy storage facility can operate stably at critical moments, improving the reliability and stability of energy.

[0013] Preferably, the most unfavorable operating condition described in S2 includes a first most unfavorable operating condition and a second most unfavorable operating condition;

[0014] During the operation of the underground storage facility, the elastic deformation of the surrounding rock in the direction of the minimum principal stress is the largest under the first most unfavorable working condition, and σ min -σ ci ≤σ≤σ max -σ ci ;

[0015] During the period when the underground storage is not in operation, the stress in the segment support layer is the greatest in the direction of the maximum principal stress of the surrounding rock under the second most unfavorable working condition, and σ = σ cm ;

[0016] In the formula, σ ci σ is the minimum principal stress of the surrounding rock. cm The maximum principal stress of the surrounding rock is σ. max σ represents the maximum internal pressure during the operation of the underground cavern. min σ represents the minimum internal pressure during the operation of the underground cavern, and σ is the vector sum of the surrounding rock stress and the internal pressure, which is negative radially outward and positive radially inward.

[0017] In this scheme, by considering the first and second most unfavorable working conditions, the pressure-bearing mode of the underground storage structure is realized from the perspective of the most unfavorable working conditions. When the internal pressure is greater than the external pressure, the surrounding rock, the segment support layer, and the flexible sealing layer expand radially, and the surrounding rock bears the internal and external pressure difference. When the internal pressure is less than the external pressure, the surrounding rock, the segment support layer, and the flexible sealing layer contract radially, and the support layer bears the internal and external pressure difference. Thus, the constraints of hard conditions on the underground storage are minimized to the greatest extent, which can effectively improve the stability and safety of the underground storage.

[0018] As a preferred embodiment, the relevant parameters of the underground storage pressure-bearing structure mentioned in S3 include the relevant parameters of the surrounding rock elastic deformation layer, the thickness of the segment support layer, and the material performance indicators of the segment arc length, socket length, and flexible sealing layer.

[0019] In this plan, determining the relevant parameters of the pressure-bearing structure of the underground storage facility ensures its stability and prevents structural deformation or damage caused by excessive or insufficient pressure. Secondly, a reasonable pressure-bearing structure design guarantees the safety of the underground storage facility under normal operation and extreme conditions, effectively preventing safety accidents such as leaks and explosions. At the same time, optimizing the pressure-bearing structure parameters can improve the energy efficiency of the underground storage facility, enabling more efficient storage and release of energy and improving energy utilization efficiency. Finally, a reasonable pressure-bearing structure design can reduce construction and operating costs and improve economic benefits while ensuring safety and stability.

[0020] As a preferred embodiment, the triaxial stress balance equation described in S3 is expressed as follows:

[0021] When R=R1: σ r =0;

[0022] When R = R2: σ r =σ;

[0023] In the formula, R1 is the outer radius of the elastic deformation layer of the surrounding rock, R2 is the inner radius of the elastic deformation layer of the surrounding rock, and σ r For radial stress, σ θ For circumferential stress, Let be the axial stress, and i be R1 / R2.

[0024] In this scheme, the relevant parameters of the pressure-bearing structure of the underground storage facility are calculated under the most unfavorable working conditions using the triaxial stress balance equation. This enables accurate calculation of the pressure state of the underground storage facility under various working conditions, including the most unfavorable condition, which helps to more accurately assess the load-bearing capacity and safety of the structure. Based on the calculation results of the triaxial stress balance equation, the pressure-bearing structure of the underground storage facility can be optimized to make it more economical and reasonable while meeting safety requirements. Through accurate stress calculation, resources can be allocated more rationally, and the rates of energy storage and release can be arranged more reasonably to improve energy utilization efficiency.

[0025] Preferably, the relevant parameters of the surrounding rock elastic deformation layer include radial deformation, circumferential deformation, and elastic deformation layer thickness.

[0026] In this scheme, by accurately calculating parameters such as the radial deformation, circumferential deformation, and thickness of the elastic deformation layer of the surrounding rock, the accuracy of the data calculation model can be improved. This allows for a more accurate assessment of the bearing capacity, stability, and potential risks of the underground storage pressure structure, providing an important basis for subsequent engineering design and safety assessment, thereby enhancing the safety of the field in which this method is applied.

[0027] Preferably, the radial deformation ΔR, circumferential deformation Δθ, and elastic deformation layer thickness s are calculated under the first most unfavorable working condition, and the calculation formulas are expressed as follows:

[0028]

[0029] In the formula, ΔR is the radial deformation, k is the surrounding rock resistance coefficient, and E r Let μ be the elastic modulus of the surrounding rock. r The Poisson's ratio of the surrounding rock;

[0030] The formulas for calculating the circumferential deformation Δθ and the elastic deformation layer thickness s are expressed as follows:

[0031] Δθ=2π(R2+ΔR)-2πR2=2πΔR

[0032]

[0033] s = R1 - R2 = (i-1)R2;

[0034] In the formula, s is the thickness of the elastic deformation layer, and Δθ is the circumferential deformation of the inner wall of the elastic deformation layer.

[0035] in

[0036] In this scheme, radial deformation, circumferential deformation, and elastic deformation layer thickness are accurately calculated using formulas, simplifying the calculation process and improving calculation efficiency. The formulas for calculating radial deformation, circumferential deformation, and elastic deformation layer thickness more accurately reflect the actual situation, improving the precision of the calculation results. This enhances the accuracy of the data calculation model, enabling a more accurate assessment of the bearing capacity, stability, and potential risks of underground storage pressure structures. It provides crucial information for subsequent engineering design and safety assessments, thereby improving the safety of the field in which this method is applied.

[0037] Preferably, the calculation of the thickness of the segment support layer, the segment arc length, and the socket length under the second most unfavorable working condition includes: the thickness satisfying the critical failure condition.

[0038]

[0039]

[0040]

[0041] In the formula, h is the thickness of the arc-shaped segment, M is the bending moment, R3 is the outer radius of the segment support layer, and k is σ. min / σ max , σ t denoted as , where I is the tensile strength of the segment support layer, I is the moment of inertia of the rectangular section, and b is the axial length of the arc-shaped segment;

[0042] Calculate the thickness of the segment support layer, segment arc length, and socket length based on the maximum value of ΔR in the first most unfavorable working condition:

[0043]

[0044]

[0045] In the formula, l is the arc length of the segment, l0 is the length of the circumferential socket, n is the number of segments, and f is the joint allowance coefficient.

[0046] In this scheme, by accurately calculating the thickness of the segment support layer, as well as the arc length and socket length of the segment, under the first and second most unfavorable working conditions, accurate segment support layer parameters can be achieved, providing sufficient support and protection, effectively preventing structural deformation, cracking, or collapse, and ensuring the safety of the underground storage facility. It can also ensure the stability of the underground storage facility under various pressures and stresses, helping to avoid structural instability or damage caused by the thickness of the elastic deformation layer of the support.

[0047] As a preferred option, based on the condition of maximum radial deformation in the first most unfavorable working condition, the material performance indicators of the flexible sealing layer should meet the following formula:

[0048]

[0049] R4 = R3 - h;

[0050] In the formula, E f σt is the elastic modulus of the flexible sealing layer, σt is the allowable tensile strength of the flexible sealing layer, and R4 is the outer radius of the flexible sealing layer.

[0051] In this scheme, the material performance indicators of the flexible sealing layer are calculated based on the working condition with the maximum radial deformation in the first most unfavorable working condition. This helps to improve the accuracy of the data calculation model and can more accurately assess the sealing capacity, stability, and potential risks of the flexible sealing layer's material performance indicators. This provides an important basis for the subsequent engineering design and safety assessment of the scheme, thereby improving the safety of the field in which this method is applied.

[0052] Preferably, the pressure-bearing structure includes, from the outside to the inside, surrounding rock 1, segment support layer 3, flexible sealing layer 5, and cavern 6; the surrounding rock includes a surrounding rock stabilizing layer 1-1 and a surrounding rock elastic deformation layer 1-2, and the internal pressure load is balanced by the resistance generated by the elastic deformation of the surrounding rock; the segment support layer 3 includes several arc-shaped segments 3-1, with sockets 3-2 and interfaces 3-3 provided at both ends of the arc-shaped segments; an elastic sealing gasket 3-4 is provided at the socket 3-2, and a caulking gasket 3-5 is provided at the interface 3-3 to ensure coordinated deformation at the interface with the surrounding rock and the sealing layer; the elastic modulus of the flexible sealing layer 5 is lower than that of the surrounding rock 1, and it is used for sealing; the cavern 6 is used to store energy medium, and the axis of the cavern 6 is perpendicular to the direction of the maximum principal stress of the surrounding rock 1.

[0053] In this scheme, the pressure-bearing structure, from the outside to the inside, includes surrounding rock 1, segment support layer 3, flexible sealing layer 5, and cavern 6. The surrounding rock includes a surrounding rock stabilizing layer 1-1 and a surrounding rock elastic deformation layer 1-2, and the internal pressure load is balanced by the resistance generated by the elastic deformation of the surrounding rock. The segment support layer 3 includes several arc-shaped segments 3-1, with sockets 3-2 and interfaces 3-3 at both ends of the arc-shaped segments. Elastic sealing gaskets 3-4 are installed at the sockets 3-2, and caulking gaskets 3-5 are installed at the interfaces 3-3 to ensure coordinated deformation at the interface with the surrounding rock and the sealing layer. The elastic modulus of the flexible sealing layer 5 is lower than that of the surrounding rock 1 and is used for sealing. The cavern 6 of the pressure-bearing structure is used to store energy media, and the axis of the cavern 6 is perpendicular to the direction of the maximum principal stress of the surrounding rock 1.

[0054] The substantial effects of this invention are as follows:

[0055] 1. By setting the pressure-bearing structure under the most unfavorable working conditions, and by integrating classical theories, a quantitative design method for the structure of each layer of a high-pressure underground storage facility is proposed. By comprehensively considering the pressure-bearing structure under multiple conditions and aspects, the constraints of rigid conditions on the underground storage facility are reduced, thereby effectively improving the stability and safety of the underground storage facility.

[0056] 2. By considering the first and second most unfavorable working conditions, a pressure-bearing mode for the underground storage structure is realized, taking into account the most unfavorable working conditions. When the internal pressure is greater than the external pressure, the surrounding rock, the segment support layer, and the flexible sealing layer expand radially, and the surrounding rock bears the internal and external pressure difference. When the internal pressure is less than the external pressure, the surrounding rock, the segment support layer, and the flexible sealing layer contract radially, and the support layer bears the internal and external pressure difference. This approach maximizes the reduction of the constraints imposed on the underground storage by rigid conditions, effectively improving the stability and safety of the underground storage.

[0057] 3. By determining the relevant parameters of the pressure-bearing structure of underground storage facilities, the stability of the facilities can be ensured, avoiding structural deformation or damage caused by excessive or insufficient pressure. Secondly, a reasonable pressure-bearing structure design can guarantee the safety of underground storage facilities under normal operation and extreme conditions, effectively preventing safety accidents such as leaks and explosions. At the same time, optimizing the pressure-bearing structure parameters can improve the energy efficiency of underground storage facilities, enabling more efficient storage and release of energy and improving energy utilization efficiency. Finally, a reasonable pressure-bearing structure design can reduce construction and operating costs and improve economic benefits while ensuring safety and stability. Attached Figure Description

[0058] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings. The drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0059] Figure 1 The flowchart illustrates the quantitative design method for the pressure-bearing structure of an underground storage facility, taking into account the most unfavorable working conditions, as described in this invention.

[0060] Figure 2 This is a schematic diagram of the pressure-bearing structure of an underground storage facility considering the most unfavorable working conditions for the present invention.

[0061] Figure 3 This is a schematic diagram of the segment support layer structure of the underground storage pressure-bearing structure considering the most unfavorable working conditions for the present invention.

[0062] The attached diagram lists the components represented by each number as follows:

[0063] 1. Surrounding rock; 3. Segment support layer; 5. Flexible sealing layer; 6. Cavern; 1-1. Surrounding rock stabilization layer; 1-2. Surrounding rock elastic deformation layer; 3-1. Curved segment; 3-2. Socket; 3-3. Interface; 3-4. Elastic sealing gasket; 3-5. Joint caulking gasket. Detailed Implementation

[0064] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only one preferred embodiment of this invention and are only used to explain this invention. They do not limit the scope of protection of this invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0065] Example 1: As Figure 1 As shown, the quantitative design method for the pressure-bearing structure of an underground storage facility considering the most unfavorable working conditions includes the following steps:

[0066] S1. Investigate the mechanical boundary conditions of the multi-layered structure and determine the underground storage conditions and corresponding operating parameters.

[0067] Specifically, the mechanical boundary conditions in S1 include the geological conditions of the surrounding rock and the corresponding mechanical parameters; the geological conditions of the surrounding rock include the rock mass type, surrounding rock grade and maximum principal stress of the surrounding rock in the proposed reservoir area; the corresponding mechanical parameters include minimum principal stress, elastic modulus, Poisson's ratio, cohesion and internal friction angle; the underground reservoir conditions and corresponding operating parameters include excavation diameter, maximum internal pressure and minimum internal pressure during operation.

[0068] In this embodiment, by identifying the mechanical boundary conditions of the multi-layer structure, the underground storage conditions and corresponding operating parameters can be determined, allowing for a more accurate analysis of the underground storage's performance, further optimization of its design, and improvement of its operational efficiency and stability. Appropriate operating parameters can enhance the flexibility of the energy storage facility, enabling it to better cope with changes in energy demand and achieve rapid response. At the same time, accurate condition settings and parameter selection can ensure that the energy storage facility can operate stably at critical moments, improving the reliability and stability of energy.

[0069] Understandably, mechanical boundary conditions are an important consideration, primarily involving external forces and constraints acting on underground structures. Accurate analysis of mechanical boundary conditions is crucial for ensuring the safety and stability of underground reservoirs; boundary conditions may include ground pressure, lateral displacement, horizontal displacement, and groundwater pressure. These factors need to be considered when calculating the thickness of the segment support layer, as they directly affect the stress state and stability of the structure.

[0070] S2. Based on the mechanical boundary conditions of the multi-layer structure, obtain the most unfavorable working condition of the underground storage tank.

[0071] Specifically, the most unfavorable operating conditions in S2 include the first most unfavorable operating condition and the second most unfavorable operating condition.

[0072] During the operation of the underground storage facility, the elastic deformation of the surrounding rock in the direction of the minimum principal stress is the largest under the first most unfavorable working condition, and σ min -σ ci ≤σ≤σ max -σ ci ;

[0073] During the period when the underground storage is not in operation, the stress in the segment support layer is the greatest in the direction of the maximum principal stress of the surrounding rock under the second most unfavorable working condition, and σ = σ cm ;

[0074] In the formula, σ ci σ is the minimum principal stress of the surrounding rock. cm The maximum principal stress of the surrounding rock is σ. maxσ represents the maximum internal pressure during the operation of the underground cavern. min σ represents the minimum internal pressure during the operation of the underground cavern, and σ is the vector sum of the surrounding rock stress and the internal pressure, which is negative radially outward and positive radially inward.

[0075] In this embodiment, by considering the first and second most unfavorable working conditions, the pressure-bearing mode of the underground storage structure is realized from the perspective of the most unfavorable working conditions. When the internal pressure is greater than the external pressure, the surrounding rock, the segment support layer, and the flexible sealing layer expand radially, and the surrounding rock bears the internal and external pressure difference. When the internal pressure is less than the external pressure, the surrounding rock, the segment support layer, and the flexible sealing layer contract radially, and the support layer bears the internal and external pressure difference. Thus, the constraints of the underground storage on the rigid conditions are reduced to the greatest extent, which can effectively improve the stability and safety of the underground storage.

[0076] It is understandable that the most unfavorable operating condition refers to adverse conditions or events that may occur during the construction and operation of underground storage facilities. These conditions may severely impact the safety, stability, and economic efficiency of the underground storage facilities. The most unfavorable operating condition may include uncontrollable factors such as geological disasters, extreme weather, and equipment failures, as well as other natural and human factors that may damage the operation of the underground storage facilities. Simultaneously, human factors may also affect the safety and stability of the underground storage facilities. During the construction and operation of underground storage facilities, a thorough risk assessment and preventative measures should be developed for the most unfavorable operating conditions. In this embodiment, the first and second most unfavorable operating conditions consider the pressure-bearing structure of the underground storage facility from these two perspectives to ensure the safe and stable operation of the underground storage facility.

[0077] S3. Based on the triaxial stress balance equation, using the parameters obtained in step S1 as input, calculate the relevant parameters of the underground storage pressure structure under the most unfavorable working condition.

[0078] Specifically, the relevant parameters of the pressure-bearing structure of the underground storage in S3 include the relevant parameters of the elastic deformation layer of the surrounding rock, the thickness of the segment support layer, and the material performance indicators of the segment arc length, socket length, and flexible sealing layer.

[0079] In this embodiment, determining the relevant parameters of the pressure-bearing structure of the underground storage facility ensures its stability and prevents structural deformation or damage caused by excessive or insufficient pressure. Secondly, a reasonable pressure-bearing structure design guarantees the safety of the underground storage facility under normal operation and extreme conditions, effectively preventing safety accidents such as leaks and explosions. At the same time, optimizing the pressure-bearing structure parameters can improve the energy efficiency of the underground storage facility, enabling more efficient storage and release of energy and improving energy utilization efficiency. Finally, a reasonable pressure-bearing structure design can reduce construction and operating costs and improve economic benefits while ensuring safety and stability.

[0080] Specifically, the triaxial stress balance equation described in S3 is expressed as follows:

[0081] When R=R1: σ r =0;

[0082] When R = R2: σ r =σ;

[0083] In the formula, R1 is the outer radius of the elastic deformation layer of the surrounding rock, R2 is the inner radius of the elastic deformation layer of the surrounding rock, and σ r For radial stress, σ θ For circumferential stress, Let be the axial stress, and i be R1 / R2.

[0084] In this embodiment, the relevant parameters of the pressure-bearing structure of the underground storage facility are calculated under the most unfavorable working conditions using the triaxial stress balance equation. This enables accurate calculation of the pressure state of the underground storage facility under various working conditions, including the most unfavorable conditions, which helps to more accurately assess the load-bearing capacity and safety of the structure. Based on the calculation results of the triaxial stress balance equation, the pressure-bearing structure of the underground storage facility can be optimized to make it more economical and reasonable while meeting safety requirements. Through accurate stress calculation, resources can be allocated more rationally, and the rates of energy storage and release can be arranged more reasonably to improve energy utilization efficiency.

[0085] Specifically, the relevant parameters of the surrounding rock elastic deformation layer include radial deformation, circumferential deformation, and elastic deformation layer thickness.

[0086] In this embodiment, by accurately calculating parameters such as the radial deformation, circumferential deformation, and thickness of the elastic deformation layer of the surrounding rock, the accuracy of the data calculation model can be improved. This allows for a more accurate assessment of the bearing capacity, stability, and potential risks of the underground storage pressure structure, providing an important basis for subsequent engineering design and safety assessment, thereby enhancing the safety of the field in which this method is applied.

[0087] Specifically, the radial deformation ΔR, circumferential deformation Δθ, and elastic deformation layer thickness s are calculated under the first most unfavorable working condition, and the calculation formulas are expressed as follows:

[0088]

[0089] In the formula, ΔR is the radial deformation, k is the surrounding rock resistance coefficient, and E r Let μ be the elastic modulus of the surrounding rock. r Let σ be the Poisson's ratio of the surrounding rock. In the above formula, since σ min -σ ci ≤σ≤σ max -σ c ΔR varies within a certain range with the internal pressure during operation.

[0090] Furthermore, based on the stress balance equation, the maximum stress in the elastic deformation layer is the circumferential stress of the inner wall. According to Hooke's law, the strain balance equation is established, and the formulas for calculating the circumferential deformation Δθ and the elastic deformation layer thickness s are expressed as follows:

[0091] Δθ=2π(R2+ΔR)-2πR2=2πΔR

[0092]

[0093] s = R1 - R2 = (i-1)R2;

[0094] In the formula, s is the thickness of the elastic deformation layer, and Δθ is the circumferential deformation of the inner wall of the elastic deformation layer; where

[0095] In this embodiment, the radial deformation, circumferential deformation, and elastic deformation layer thickness are accurately calculated using formulas, simplifying the calculation process and improving calculation efficiency. The formulas for calculating radial deformation, circumferential deformation, and elastic deformation layer thickness more accurately reflect the actual situation, improving the precision of the calculation results. This enhances the accuracy of the data calculation model, enabling a more accurate assessment of the bearing capacity, stability, and potential risks of the underground storage pressure structure. This provides crucial information for subsequent engineering design and safety assessment, thereby improving the safety of the field in which this method is applied.

[0096] Understandably, once the site is determined, the elastic model Er and Poisson's ratio μr of the surrounding rock are also determined. At this point, the radial deformation ΔR is positively correlated with the stress vector σ and the tunnel diameter R2. That is, the greater the gas storage pressure or the larger the tunnel diameter, the greater the deformation of the surrounding rock, which is more detrimental to the stability of the gas storage facility. At the same time, the greater the difference between σmin and σmax, the greater the cyclic variation of the radial deformation of the surrounding rock, and the more likely it is to cause fatigue damage to the rock mass. Therefore, rock strata with a high elastic modulus should be used during the site selection stage of underground caverns, and the internal pressure, gas storage pressure difference, and tunnel diameter should be reduced during the design stage. However, considering the economic benefits during the operation stage, there are optimal values ​​for the internal pressure, storage pressure difference, and tunnel diameter. Furthermore, the elastic deformation layer thickness of the surrounding rock is only related to Poisson's ratio. That is, under different internal pressure conditions, the elastic deformation range of the surrounding rock is the same, only the magnitude of the deformation differs. However, there is a limit to the elastic deformation. According to the triaxial stress balance equation, the circumferential stress is the maximum stress. When the circumferential stress exceeds the tensile strength of the surrounding rock, the surrounding rock undergoes plastic tensile failure. Therefore, the circumferential tensile strength of the surrounding rock should be selected as the critical failure condition for the operational internal pressure of underground caverns. Through specific formula analysis, the bearing capacity, stability, and potential risks of the pressure-bearing structure of underground storage can be more accurately assessed, providing an important basis for subsequent engineering design and safety assessment, thereby improving the safety of the field in which this method is applied.

[0097] Specifically, based on the second most unfavorable working condition, the direction of the maximum principal stress in the surrounding rock is the location of the maximum stress in the segment support layer, and the direction of the minimum principal stress in the surrounding rock is the location of the maximum bending moment in the segment support layer. The segment support layer is most prone to tensile cracking failure at the location of the maximum bending moment, and its thickness should meet the critical failure conditions: when the maximum principal stress is in the horizontal direction and the minimum principal stress is in the vertical direction, the segment support layer is most prone to tensile cracking at the top and bottom; when the maximum principal stress is in the vertical direction and the minimum principal stress is in the horizontal direction, the segment support layer is most prone to tensile cracking on both sides.

[0098] The maximum and minimum principal stresses of the surrounding rock were determined using both field measurement and theoretical methods. Field measurement methods included stress recovery, stress relief, strain recovery, strain relief, and hydraulic fracturing. The theoretical method used the unloading arch theory for calculation. When the burial depth / tunnel diameter was ≥20, the load was simplified to uniform load. When the burial depth / tunnel diameter was <20, the load was calculated based on the actual non-uniform load distribution.

[0099] The calculation of the thickness of the segment support layer, the arc length of the segment, and the socket length under the second most unfavorable working condition includes: the thickness meeting the critical failure condition.

[0100]

[0101]

[0102]

[0103] In the formula, h is the thickness of the arc-shaped segment, M is the bending moment, R3 is the outer radius of the segment support layer, and k is σ. min / σ max , σ t denoted as , where I is the tensile strength of the segment support layer, I is the moment of inertia of the rectangular section, and b is the axial length of the arc-shaped segment.

[0104] Calculate the thickness of the segment support layer, segment arc length, and socket length based on the maximum value of ΔR in the first most unfavorable working condition:

[0105]

[0106]

[0107] In the formula, l is the arc length of the segment, l0 is the length of the circumferential socket, n is the number of segments, and f is the joint allowance coefficient.

[0108] In this embodiment, by accurately calculating the thickness of the segment support layer, the arc length of the segment, and the length of the socket under the first and second most unfavorable working conditions, accurate segment support layer parameters can provide sufficient support and protection, effectively prevent structural deformation, cracking, or collapse, and ensure the safety of the underground storage facility. It can also ensure the stability of the underground storage facility under various pressures and stresses, and help avoid structural instability or damage caused by the thickness of the elastic deformation layer of the support.

[0109] It is understandable that the maximum value operating condition refers to the most unfavorable situation considered in the design and operation of the underground storage facility, which is the operating condition in which the relevant parameters of the underground storage facility reach their maximum values. For example, the first and second most unfavorable operating conditions in this embodiment, as well as the operating conditions in which parameters such as flow rate and pressure reach their maximum values ​​during the operation of the underground storage facility. These operating conditions are usually the most unfavorable situations considered in the design and operation of the underground storage facility, and require special attention and response.

[0110] Specifically, based on the condition of maximum radial deformation in the first most unfavorable working condition, the material performance indicators of the flexible sealing layer should meet the following formula:

[0111]

[0112] R4 = R3 - h;

[0113] In the formula, E f Let σt be the elastic modulus of the flexible sealing layer, [σt] be the allowable tensile strength of the flexible sealing layer, and R4 be the outer radius of the flexible sealing layer.

[0114] In this embodiment, the material performance indicators of the flexible sealing layer are calculated based on the working condition with the maximum radial deformation in the first most unfavorable working condition. This helps to improve the accuracy of the data calculation model and can more accurately assess the sealing capacity, stability, and potential risks of the flexible sealing layer's material performance indicators. This provides an important basis for the subsequent engineering design and safety assessment of the solution, thereby improving the safety of the field in which this method is applied.

[0115] Specifically, such as Figure 2 As shown, the pressure-bearing structure, from the outside to the inside, includes surrounding rock 1, segment support layer 3, flexible sealing layer 5, and cavern 6; the surrounding rock includes surrounding rock stabilization layer 1-1 and surrounding rock elastic deformation layer 1-2, and the internal pressure load is balanced by the resistance generated by the elastic deformation of the surrounding rock. Figure 3As shown, the segment support layer 3 includes several arc-shaped segments 3-1, with sockets 3-2 and interfaces 3-3 at both circumferential ends of the arc-shaped segments; elastic sealing gaskets 3-4 are provided at the sockets 3-2, and caulking gaskets 3-5 are provided at the interfaces 3-3 to ensure coordinated deformation at the contact interface with the surrounding rock and the sealing layer. The elastic modulus of the flexible sealing layer 5 is lower than that of the surrounding rock 1, and it is used for sealing; the cavern 6 is used to store energy medium, and the axis of the cavern 6 is perpendicular to the direction of the maximum principal stress of the surrounding rock 1.

[0116] In this embodiment, the pressure-bearing structure includes, from the outside to the inside, surrounding rock 1, segment support layer 3, flexible sealing layer 5, and cavern 6. The surrounding rock includes a surrounding rock stabilizing layer 1-1 and a surrounding rock elastic deformation layer 1-2, with the internal pressure load balanced by the resistance generated by the elastic deformation of the surrounding rock. The segment support layer 3 includes several arc-shaped segments 3-1, with sockets 3-2 and interfaces 3-3 at both circumferential ends of the arc-shaped segments. Elastic sealing gaskets 3-4 are provided at the sockets 3-2, and caulking gaskets 3-5 are provided at the interfaces 3-3 to ensure coordinated deformation at the contact interface with the surrounding rock and sealing layer. The segment support layer should simultaneously meet the requirements for structural waterproofing and joint waterproofing, with a segment impermeability grade ≥ P10. The elastic modulus of the flexible sealing layer 5 is lower than that of the surrounding rock 1 and is used for sealing. The cavern 6 of the pressure-bearing structure is used to store energy media, and the axis of the cavern 6 is perpendicular to the direction of the maximum principal stress of the surrounding rock 1.

[0117] This embodiment provides a detailed explanation (principle, etc.) of the effects, purpose, or a certain feature of the embodiment, and expands on the content.

[0118] Furthermore, taking the underground high-pressure gas storage facility of a compressed air energy storage power station as an example, this paper introduces a quantitative design method for the pressure-bearing structure of the underground storage facility considering the most unfavorable operating conditions.

[0119] Structural design steps for an underground high-pressure gas storage facility in a compressed air energy storage power station:

[0120] S1. As shown in Table 1, the mechanical boundary conditions of the multi-layered structure were determined, including the geological conditions of the surrounding rock and the corresponding mechanical parameters, and the gas storage conditions and corresponding operating parameters were determined. The geological conditions of the surrounding rock and the corresponding mechanical parameters include the rock mass type, rock grade, maximum and minimum principal stresses, elastic modulus, Poisson's ratio, cohesion, and internal friction angle of the proposed storage area. The gas storage conditions and corresponding operating parameters include the excavation diameter, and the maximum and minimum internal pressure during operation.

[0121] Table 1 Mechanical boundary conditions of the underground high-pressure gas storage tank of a compressed air energy storage power station

[0122]

[0123] S2. Based on the mechanical boundary conditions of the multi-layer structure, obtain the most unfavorable working condition of the underground storage tank.

[0124] The first most unfavorable working condition is during operation, when the elastic deformation of the surrounding rock in the direction of the minimum principal stress is the greatest, and 3MPa≤σ≤9MPa; the second most unfavorable working condition is during non-operation, when the stress of the segment support layer in the direction of the maximum principal stress of the surrounding rock is the greatest, and σ=2MPa. σ is the vector sum of the surrounding rock stress and internal pressure, negative radially outward and positive radially inward.

[0125] S3. Based on the triaxial (radial-circumferential-axial) stress balance equation, using the parameters obtained in step S1 as input, calculate the radial deformation, circumferential deformation, and elastic deformation layer thickness of the surrounding rock elastic deformation layer under the most unfavorable working condition, i.e., the maximum spatial range in which the surrounding rock balances the internal and external pressures solely through elastic resistance under the action of surrounding rock stress and internal pressure.

[0126] The triaxial (radial-circumferential-axial) stress balance equations for stress reduction effects are as follows:

[0127] When R=R1: σ r =0;

[0128] When R = R2: σ r =σ;

[0129] In the formula, R1 is the outer radius of the elastic deformation layer of the surrounding rock, R2 is the inner radius of the elastic deformation layer of the surrounding rock, σr is the radial stress, σθ is the circumferential stress, σφ is the axial stress, and i is R1 / R2.

[0130] Using the first most unfavorable working condition, i.e. 3MPa≤σ≤9MPa, calculate the radial deformation of the elastic deformation layer of the surrounding rock:

[0131]

[0132] 3*5(1+0.3) / 13*103≤ΔR≤9*5(1+0.3) / 13*103;

[0133] 0.15cm≤ΔR≤0.45cm;

[0134] In the formula, ΔR is the radial deformation, k is the surrounding rock resistance coefficient, Er is the elastic modulus of the surrounding rock, and μr is the Poisson's ratio of the surrounding rock. In the above formula, since 3MPa≤σ≤9MPa, ΔR varies with the gas storage pressure within the range of 0.15~0.45cm during operation.

[0135] Furthermore, based on the triaxial stress equilibrium equation, the maximum stress in the elastic deformation layer is the circumferential stress of the inner wall. Using Hooke's law, a strain equilibrium equation is established to calculate the thickness of the elastic deformation layer in the surrounding rock.

[0136] Δθ=2π(R2+ΔR)-2πR2=2πΔR

[0137]

[0138] s = R1 - R2 = (i-1)R2;

[0139] In the formula, s is the thickness of the elastic deformation layer, and Δθ is the circumferential deformation of the inner wall of the elastic deformation layer. The calculation yields:

[0140] 0.942cm≤Δθ≤2.826cm

[0141] s = 8.85m;

[0142] To avoid mutual disturbance between multiple parallel gas storage facilities, the outer walls of the elastic deformation layer of the surrounding rock of the two gas storage facilities should be spaced at least 2*8.85m apart.

[0143] The thickness of the segment support layer is calculated based on the second most unfavorable working condition to suppress radial shrinkage of the surrounding rock;

[0144] Assuming the maximum principal stress is vertical and the minimum principal stress is horizontal, the two sides of the segment support layer are where the maximum bending moment occurs, making them most susceptible to tensile cracking failure. Therefore, the thickness of the segment support layer should meet the critical failure condition.

[0145]

[0146]

[0147]

[0148] In the formula, h is the thickness of the arc-shaped segment, M is the bending moment, R3 is the outer wall radius of the segment support layer (equal to R2), k is σmin / σmax, σt is the tensile strength of the segment support layer, I is the moment of inertia of the rectangular section, and b is the axial length of the arc-shaped segment. From Table 1, σ, R3, and k can be obtained. Assuming the arc-shaped segment is cast with C40 reinforced concrete and has an axial length of 2m, the calculation parameters are shown in Table 2.

[0149] Table 2. Stress parameters of the segment support layer

[0150] σ R3 k σt b 2MPa 5m 0.5 150MPa 2m

[0151] The calculation yielded:

[0152] M = 62.5 * 10³ kN·m

[0153] h≥5*0.224=1.12m

[0154] Based on the maximum circumferential deformation of the inner wall of the elastic deformation layer obtained in step S3, the working condition with the maximum value of ΔR in the first most unfavorable working condition is adopted to calculate the arc length of the segment and the length of the circumferential socket to meet the circumferential coordinated deformation of the outer wall of the support layer and the inner wall of the surrounding rock.

[0155]

[0156]

[0157] In the formula, l is the arc length of the segment, l0 is the length of the circumferential socket, n is the number of segments (3≤n≤12), and f is the joint reservation coefficient (1.1≤f≤1.5).

[0158] Taking n = 8 and f = 1.2, we get:

[0159] l = 3.925m

[0160] l0 = 0.4239cm

[0161] Based on the condition of maximum radial deformation in the first most unfavorable working condition, the material performance indicators of the flexible sealing layer should meet the following formula:

[0162]

[0163] R4 = R3 - h;

[0164] In the formula, E f Let σt be the elastic modulus of the flexible sealing layer, [σt] be the allowable tensile strength of the flexible sealing layer, and R4 be the outer radius of the flexible sealing layer.

[0165] If E is adopted f Using rubber with a strength of 0.2 MPa and [σt] = 20 MPa as a flexible sealing layer, we obtain:

[0166] 20 > 0.2 * 0.45 * 10⁻² / (5 - 1.1²) = 0.0002

[0167] That is, rubber as a flexible sealing layer does not meet the strength requirements.

[0168] The above-described specific embodiments are preferred embodiments of the present invention and are not intended to limit the specific scope of the present invention. The scope of the present invention includes, but is not limited to, these specific embodiments. All equivalent changes made in accordance with the shape, structure, and method of the present invention are within the protection scope of the present invention.

Claims

1. A quantitative design method for the pressure-bearing structure of an underground storage facility considering the most unfavorable working conditions, characterized by: S1. Determine the mechanical boundary conditions of the multi-layered structure and the underground storage conditions and corresponding operating parameters; The mechanical boundary conditions include the geological conditions of the surrounding rock and the corresponding mechanical parameters; The surrounding rock geological conditions include the rock mass type, surrounding rock grade, and maximum principal stress of the surrounding rock in the proposed reservoir area; The corresponding mechanical parameters include minimum principal stress, elastic modulus, Poisson's ratio, cohesion, and internal friction angle; The underground storage conditions and corresponding operating parameters include the excavation diameter, the maximum internal pressure during operation, and the minimum internal pressure. S2. Based on the mechanical boundary conditions of the multi-layered structure, obtain the most unfavorable working condition of the underground storage tank; The most unfavorable operating conditions include the first most unfavorable operating condition and the second most unfavorable operating condition; During the operation of the underground storage facility, the elastic deformation of the surrounding rock in the direction of the minimum principal stress is the largest under the first most unfavorable working condition, and σ min -σ ci ≤σ≤σ max -σ ci ; During the period when the underground storage is not in operation, the stress in the segment support layer is the greatest in the direction of the maximum principal stress in the surrounding rock under the second most unfavorable working condition, and σ = σ cm ; In the formula, σ ci σ is the minimum principal stress of the surrounding rock. cm The maximum principal stress of the surrounding rock is σ. max σ represents the maximum internal pressure during the operation of the underground cavern. min σ represents the minimum internal pressure during the operation of the underground cavern, and σ is the vector sum of the surrounding rock stress and the internal pressure. S3. Based on the triaxial stress balance equation, using the parameters obtained in step S1 as input, calculate the relevant parameters of the underground storage pressure structure under the most unfavorable working condition. The relevant parameters of the underground storage pressure-bearing structure include the relevant parameters of the surrounding rock elastic deformation layer, the thickness of the segment support layer, and the material performance indicators of the segment arc length, socket length, and flexible sealing layer. The triaxial stress balance equation is expressed as follows: ； In the formula, R1 is the outer radius of the elastic deformation layer of the surrounding rock, R2 is the inner radius of the elastic deformation layer of the surrounding rock, and σ r For radial stress, σ θ For circumferential stress, σ φ Let be the axial stress, and i be R1 / R2.

2. The quantitative design method for the pressure-bearing structure of underground storage facilities considering the most unfavorable working conditions as described in claim 1, characterized in that: The relevant parameters of the surrounding rock elastic deformation layer include radial deformation, circumferential deformation, and elastic deformation layer thickness.

3. The quantitative design method for the pressure-bearing structure of underground storage facilities considering the most unfavorable working conditions as described in claim 2, characterized in that: The radial deformation ΔR, circumferential deformation Δθ, and elastic deformation layer thickness s are calculated under the first most unfavorable working condition, and the calculation formulas are expressed as follows: ； In the formula, ΔR is the radial deformation, k is the surrounding rock resistance coefficient, and E r Let μ be the elastic modulus of the surrounding rock. r The Poisson's ratio of the surrounding rock; The formulas for calculating the circumferential deformation Δθ and the elastic deformation layer thickness s are expressed as follows: ； In the formula, s is the thickness of the elastic deformation layer, and Δθ is the circumferential deformation of the inner wall of the elastic deformation layer. in .

4. The quantitative design method for the pressure-bearing structure of underground storage facilities considering the most unfavorable working conditions as described in claim 3, characterized in that: The calculation of the thickness of the segment support layer, segment arc length, and socket length under the second most unfavorable working condition includes: The thickness satisfies the critical failure condition: ； In the formula, h is the thickness of the arc-shaped segment, M is the bending moment, R3 is the outer radius of the segment support layer, and k is σ. min / σ max , σ t denoted as , where I is the tensile strength of the segment support layer, I is the moment of inertia of the rectangular section, and b is the axial length of the arc-shaped segment; Calculate the thickness of the segment support layer, segment arc length, and socket length based on the condition of maximum radial deformation in the first most unfavorable working condition: ； In the formula, l For the arc length of the tunnel segment, l 0 represents the length of the circumferential socket, n represents the number of segments, and f represents the joint allowance coefficient.

5. The quantitative design method for the pressure-bearing structure of underground storage facilities considering the most unfavorable working conditions as described in claim 4, characterized in that: Based on the condition of maximum radial deformation in the first most unfavorable working condition, the material performance indicators of the flexible sealing layer should meet the following formula: ； In the formula, E f Let σt be the elastic modulus of the flexible sealing layer, [σt] be the allowable tensile strength of the flexible sealing layer, and R4 be the outer radius of the flexible sealing layer.

6. A pressure-bearing structure for underground storage considering the most unfavorable working conditions, applicable to the quantitative design method for pressure-bearing structures of underground storage considering the most unfavorable working conditions as described in any one of claims 1-5, characterized in that: The pressure-bearing structure, from the outside to the inside, includes surrounding rock (1), segment support layer (3), flexible sealing layer (5), and cavern (6). The surrounding rock includes a stable surrounding rock layer (1-1) and an elastic deformation surrounding rock layer (1-2), and the internal pressure load is balanced by the resistance generated by the elastic deformation of the surrounding rock. The segment support layer (3) includes several arc-shaped segments (3-1), and the circumferential ends of the arc-shaped segments are provided with sockets (3-2) and interfaces (3-3). An elastic sealing gasket (3-4) is provided at the socket (3-2), and a caulking gasket (3-5) is provided at the interface (3-3) to ensure coordinated deformation of the contact interface with the surrounding rock and the sealing layer; The elastic modulus of the flexible sealing layer (5) is lower than that of the surrounding rock (1), and it is used for sealing. The cavern (6) is used to store energy medium, and the axis of the cavern (6) is perpendicular to the direction of the maximum principal stress of the surrounding rock (1).

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