Lining structure design method for preset joint of compressed air energy storage underground cavern

Abstract

The invention discloses a method for designing a lining structure of a preset joint of a compressed air energy storage underground cavern, which comprises the following steps of: if an evaluation result shows that the compressed air energy storage underground cavern is suitable for building the compressed air energy storage underground cavern, initially designing a lining structure according to a whole-ring lining without a preset joint; calculating the maximum crack width of the preliminarily designed lining structure, judging whether the maximum crack width meets the crack limiting requirement, if the maximum crack width meets the crack limiting requirement, taking the preliminarily designed lining structure as the final design, if the maximum crack width does not meet the crack limiting requirement, optimizing the burial depth, the inner diameter and the inner pressure of the cavern, and if the maximum crack width does not meet the requirement after optimization, taking the preliminarily designed lining structure as the final design; if yes, the maximum crack width of the lining structure of the preset joint and the maximum opening displacement of the joint are calculated and judged, and the lining structure design of the preset joint is completed. According to the design method, the application range of the compressed air energy storage underground cavern is widened, the designed flexible sealing compressed air energy storage underground cavern with the preset joint is lower in cost, has more economic benefits, is easier to construct and has more feasibility, and the effect of more obviously controlling the maximum crack width is achieved.

Description

Technical Field

[0001] The invention relates to the field of underground energy storage, and in particular to a lining structure design method for a compressed air energy storage underground cavern with preset joints. Background Art

[0002] The sealing layers of compressed gas energy storage underground caverns are mainly of two types: flexible sealing layers (polymer material sealing layers) and steel lining sealing layers. Compared with steel lining sealing layers, flexible sealing layers have the advantages of large deformability, convenient and fast construction, and low cost, and are a more ideal type of sealing layer. Under the action of high internal air pressure, compressed gas energy storage underground caverns may face lining cracking, resulting in failure of the flexible sealing layer. Therefore, flexible sealed compressed gas energy storage underground caverns have strict restrictions on the maximum crack width of the lining. In order to prevent the corrosion of reinforced concrete, the hydraulic concrete structure design code stipulates that the maximum crack width limit of reinforced concrete structures that have been underground for a long time is 0.3mm. This is difficult to achieve under the conditions of high internal pressure and medium surrounding rock quality grade. When the elastic modulus of the surrounding rock is low, the surrounding rock deformation is large, resulting in wider cracks in the lining. This means that the full-ring lining structure of the compressed gas energy storage underground cavern designed with limited cracking is usually suitable for conditions with good surrounding rock quality or low gas storage pressure, while the lining design of the compressed gas energy storage underground cavern with high internal pressure under conditions of medium surrounding rock quality faces major challenges.

[0003] In order to adapt to the larger deformation of the surrounding rock and reduce the degree of cracking of the lining, a block reinforced concrete lining can be used. There is a joint between the two adjacent reinforced concrete linings, which allows the radial displacement of the lining to be released through the joint to avoid wider cracks in the lining. Xu et al. (2024) proposed a block lining design method suitable for compressed gas energy storage underground caverns. The analytical solution method considering the elastic deformation of the lining is adopted, and the cracking of the lining cannot be considered. Qiu et al. (2024) proposed a block lining design method for hydrogen storage underground caverns. Compared with the whole ring lining, the flexible caulking material disperses the hoop stress, making the stress level and damage of the block lining lower. Jiang Zhongming et al. (2021) invented a concrete joint adaptive rebound boosting sealing device for underground gas storage caverns, which solves the problems of insufficient long-term sealing efficiency of the lining joint sealing treatment structure and slow installation and replacement. At present, the application research of block lining in compressed gas energy storage underground caverns is still in its infancy, and there is no unified understanding of the design method of flexible sealed compressed gas energy storage underground cavern lining structure.

[0004] In view of the imperfection of the current compressed gas energy storage underground cavern lining structure design method, the applicability of the existing compressed gas energy storage underground cavern block lining structure design method under different surrounding rock conditions is still unclear, and a design method specifically for solving the problem of cracking of the flexible sealed compressed gas energy storage underground cavern lining has not yet been formed. The present invention proposes a compressed gas energy storage underground cavern lining structure design method with preset joints. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a lining structure design method with preset joints for a compressed air energy storage underground cavern in view of the shortcomings of the prior art. The design method broadens the application scope of the compressed air energy storage underground cavern. The designed flexible sealing compressed air energy storage underground cavern with preset joints has lower cost and is more economical. It is easier to construct and more feasible, and achieves a more obvious effect of controlling the maximum crack width of the lining structure.

[0006] The technical solution adopted by the present invention to solve the above technical problems is: a design method for a lining structure with preset joints in a compressed air energy storage underground cavern, wherein the lining structure of the compressed air energy storage underground cavern comprises a primary lining, a sliding layer, a secondary lining and a flexible sealing layer arranged in sequence from outside to inside along the cavern wall of the underground cavern, wherein the secondary lining is composed of a reinforced concrete lining, and the design method comprises the following steps:

[0007] 1) Obtain the mechanical parameters of the surrounding rock through site investigation and testing to assess whether it is suitable for building an underground cavern for compressed gas energy storage;

[0008] 2) If the evaluation result shows that it is suitable to construct an underground cavern for compressed gas energy storage, then according to the properties of the surrounding rock, the burial depth, inner diameter and internal pressure of the cavern shall be preliminarily designed according to the full ring lining without preset joints, and the preliminary designed lining structure shall be obtained;

[0009] 3) Calculate the maximum crack width w of the lining structure in the preliminary design max , and judge whether the crack limit requirement is met, that is, w max Is it less than 0.3mm? If w max <0.3mm, the crack limit requirement is met, and the preliminary designed lining structure is used as the final design, and the lining structure design is completed; if w max ≥0.3mm, optimize the burial depth, inner diameter and internal pressure of the cavern. If the crack limit requirements are still not met after optimization, proceed to step 4) to design the lining structure with preset joints;

[0010] 4) Calculate the maximum crack width w of the lining structure with preset joints max and the maximum opening displacement of the joint D max , and judge w max Is it less than 0.3mm and D max Is it less than the allowed value? If w maxNot less than 0.3mm and / or D max If the value is not less than the allowable value, the depth, inner diameter and internal pressure of the cavern are further optimized until w max Less than 0.3mm and D max If it is less than the allowable value, the lining structure design of the preset joints of the compressed air energy storage underground cavern is completed.

[0011] Furthermore, the maximum crack width w max The calculation method is as follows:

[0012]

[0013] in:

[0014]

[0015] In the formula, w max The unit of σ is mm; s is the tensile steel bar stress, in N / mm 2 ; E s is the elastic modulus of the steel bar, in N / mm 2 ψ is the coefficient of non-uniform strain of the longitudinal tensile reinforcement between cracks; l f is the average crack spacing, in mm; f tk It is the standard value of concrete axial tensile strength, in N / mm 2 ρ s is the reinforcement ratio of the tensile reinforcement; α 1 and α 2 is the calculation coefficient, α 1 =0.16,α 2 =0.60; ν is a coefficient related to the surface shape of the tensile reinforcement; d is the diameter of the tensile reinforcement, in mm.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] (1) Compared with the whole ring lining without preset joints, the lining structure with preset joints designed by the method of the present invention can be used to build a compressed air energy storage underground cavern in medium-quality surrounding rock, which broadens the application scope of the compressed air energy storage underground cavern;

[0018] (2) Compared with steel-lined sealed compressed air energy storage underground caverns, the flexible sealed compressed air energy storage underground caverns with preset joints designed by the method of the present invention have lower costs, more economic benefits, are easier to construct, and are more feasible;

[0019] (3) Compared with the lining structure without sliding layer, the method of the present invention takes into account the sliding layer between the primary lining and the secondary lining, which can fully release the radial displacement of the secondary lining, making the lining annular stress lower, thereby achieving a more obvious effect of controlling the maximum crack width of the lining structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic cross-sectional view of a lining structure with preset joints before gas storage is shown as an example;

[0021] Figure 2 A schematic cross-sectional view of a lining structure with preset joints when storing gas to the maximum gas pressure is shown as an example;

[0022] Figure 3 The nonlinear constitutive curve of the tangential spring when the nonlinear spring is used to simulate the bond-slip behavior of the sliding layer based on Abaqus;

[0023] Figure 4 It is a schematic diagram of using a linear spring in the normal direction of the interface of the joint to simulate the tension and compression behavior of the upper plate and the lower plate of the secondary lining;

[0024] Figure 5 A flow chart of the design method of the present invention. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below in combination with the working principle of the lining structure with a preset joint, the force analysis of the sliding layer and the preset joint, and the embodiments of the drawings.

[0026] 1. Working principle of lining structure with preset joints

[0027] The reinforced concrete lining of the whole ring will crack under high internal pressure conditions, which may cause the bearing performance of the lining structure to fail. The radial displacement of the lining (secondary lining) can be released by pre-setting the joints, and the high air pressure in the cave can be transferred to the surrounding rock, so that the bearing capacity of the surrounding rock can be fully utilized.

[0028] An example of a lining structure with a preset joint is as follows Figure 1 and Figure 2 The lining structure includes a primary lining 1, a sliding layer 2, a secondary lining 3 and a flexible sealing layer 4 arranged in sequence from outside to inside along the wall of the underground cavern, wherein the secondary lining 3 is composed of a reinforced concrete lining ( Figure 1 and Figure 28 is concrete, 9 is steel bar), there are two joints 5 between two adjacent reinforced concrete linings, the inner side of the joints 5 is covered with arc-shaped steel pads 6, the steel pads 6 are pressed by carbon steel grooves 7, and the steel pads 6 are arranged between the secondary lining 3 and the flexible sealing layer 4 to prevent the flexible sealing layer 4 from sinking into the joints 5 under high pressure; the sliding layer 2 arranged between the primary lining 1 and the secondary lining 3 is used to ensure that the joints 5 can be opened smoothly under internal pressure and disperse the hoop stress of the lining. The working principle of the lining structure with preset joints is as follows:

[0029] (a) Before the cavern gas is stored, the joints are closed. Figure 1 shown.

[0030] (b) When the cavern is inflated, the internal pressure of the cavern increases, and sliding occurs between the secondary lining and the primary lining, causing the joint to gradually open, releasing the radial displacement of the lining, dispersing the hoop stress of the lining, and fully transferring the internal pressure to the surrounding rock. If there is no sliding layer, a large shear stress will be generated between the secondary lining and the primary lining to balance the internal pressure of the secondary lining, and the hoop stress of the lining cannot be dispersed. The joint cannot open, resulting in the inability to release the radial displacement of the lining.

[0031] (c) When the pressure in the cave reaches the maximum, the opening displacement of the joint reaches the maximum value D max , at this time, the radial displacement of the lining is released to the maximum, such as Figure 2 shown.

[0032] 2. Sliding layer

[0033] In order to ensure that the preset joints can open smoothly and disperse the hoop stress of the lining, it is necessary to set a sliding layer on the contact interface between the primary lining and the secondary lining. For the sliding layer between the primary lining and the secondary lining, if the two contacting objects have rough surfaces, the bonding effect between the contact surfaces will produce friction shear stress. If the friction shear stress reaches a critical value (critical shear stress), the object will slip. It is assumed that in the bonding area, the shear force and yield stress of the sliding layer are equal. In the slip zone, it conforms to the Coulomb friction law. For the Coulomb friction model, the friction force is proportional to the normal pressure. When the friction force of the contact interface is less than the critical shear stress, the interface is bonded, otherwise, the interface slips relatively. The sliding layer control equation is:

[0034]

[0035] In formula (4), τ is the shear stress of the contact surface; u is the friction coefficient; τ crit is the critical shear force before slip; σ is the normal pressure.

[0036] Based on Abaqus, nonlinear springs are used to simulate the adhesion-slip behavior of the sliding layer. The nonlinear constitutive curve of the tangential spring is as follows: Figure 3As shown in Figure 2, the constitutive relation of the spring is defined by the force-displacement relation, so the shear stress in equation (4) needs to be converted into tangential force. crit is the critical tangential force corresponding to the critical shear stress:

[0037] F crit =τ crit A=u·R in / R out ·p·A (5)

[0038] In formula (5), A is the area of ​​the sliding layer, R in and R out are the inner radius and outer radius of the second lining respectively. The air pressure p is transmitted from the inner side to the outer side of the second lining. Due to the diffusion effect, the positive pressure on the sliding layer is R in / R out ·p.

[0039] According to Jon (2003), in underground caverns with high internal pressure, asphalt can be used as a sliding layer. The shear stiffness of asphalt in the bonding stage is K t =40MPa / m. According to the research of Damasceno et al. (2023), the sliding friction coefficient u between concrete and asphalt can be taken as 0.35. Assuming that the static friction coefficient is equal to the dynamic friction coefficient, the critical bonding displacement S before sliding can be obtained crit for:

[0040]

[0041] Thus, the tangential spring stiffness k of the sliding layer bonding section is obtained adhe :

[0042]

[0043] For the slip segment, when the tangential force of the sliding layer exceeds the critical tangential force and no longer changes, the sliding layer slips and the tangential stiffness k of the slip segment is slip =0N / m.

[0044] 3. Preset Seams

[0045] The lining on the upper side of the joint is called the secondary lining upper plate, and the lining on the lower side of the joint is called the secondary lining lower plate. At the interface of the joint, a linear spring is used in the normal direction to simulate the tension and compression behavior of the secondary lining upper plate and lower plate, such as Figure 4 As shown. Abaqus software is used for simulation, and the compression stress is defined as negative and the tensile stress is defined as positive. The width of the preset joint is set to 0 mm. For linear springs (see Figure 4 ), the spring stiffness k when stretched (the part where the displacement is greater than 0) t 0N / m, which means the joint can open freely; the spring stiffness k during compressionc Approaching infinity (1×10 13 N / m), which means that the linings at the joints cannot corrode each other.

[0046] Based on the working principle of the lining structure with preset joints, the force analysis of the sliding layer and the preset joints, we propose a lining structure design method for preset joints of a compressed air energy storage underground cavern of the present invention, and its flow chart is as follows: Figure 5 The design method includes the following steps:

[0047] 1) Obtain the mechanical parameters of the surrounding rock through site investigation and testing to assess whether it is suitable for building an underground cavern for compressed gas energy storage;

[0048] 2) If the evaluation result shows that it is suitable to construct an underground cavern for compressed gas energy storage, then according to the properties of the surrounding rock, the burial depth, inner diameter and internal pressure of the cavern shall be preliminarily designed according to the full ring lining without preset joints, and the preliminary designed lining structure shall be obtained;

[0049] 3) Calculate the maximum crack width w of the lining structure in the preliminary design max , and judge whether the crack limit requirement is met, that is, w max Is it less than 0.3mm? If w max <0.3mm, the crack limit requirement is met, and the preliminary designed lining structure is used as the final design, and the lining structure design is completed; if w max ≥0.3mm, optimize the burial depth, inner diameter and internal pressure of the cavern. If the crack limit requirements are still not met after optimization, proceed to step 4) to design the lining structure with preset joints;

[0050] 4) Calculate the maximum crack width w of the lining structure with preset joints max and the maximum opening displacement of the joint D max , and judge w max Is it less than 0.3mm and D max Is it less than the allowed value? If w max Not less than 0.3mm and / or D max If the value is not less than the allowable value, the depth, inner diameter and internal pressure of the cavern are further optimized until w max Less than 0.3mm and D max If it is less than the allowable value, the lining structure design of the preset joints of the compressed gas energy storage underground cavern is completed;

[0051] Among them, the maximum crack width w max The calculation method is as follows:

[0052]

[0053] in:

[0054]

[0055] In the formula, w max The unit of σ is mm; s is the tensile steel bar stress, in N / mm 2 , which can be obtained through numerical simulation or theoretical calculation; E s is the elastic modulus of the steel bar, in N / mm 2 ψ is the coefficient of non-uniform strain of the longitudinal tensile reinforcement between cracks; l f is the average crack spacing, in mm; f tk It is the standard value of concrete axial tensile strength, in N / mm 2 ρ s is the reinforcement ratio of the tensile reinforcement; α 1 and α 2 is the calculation coefficient, α 1 =0.16,α 2 =0.60; ν is a coefficient related to the surface shape of the tensile reinforcement; d is the diameter of the tensile reinforcement, in mm.

[0056] Example: A compressed air energy storage cavern is designed as a full-ring lining structure without preset joints according to the existing method. The buried depth of the compressed air energy storage cavern is 146m, the inner diameter of the cavern (inner diameter for short) is 8m, and the internal pressure is 10MPa; the thickness of the primary lining (i.e., initial support) is 18cm, the secondary lining uses 50cm thick C30 concrete, and the thickness of the flexible sealing layer is 10mm; the rock mass elastic modulus is 6GPa, the cohesion is 1.5MPa, the internal friction angle is 45°, and the density is 2676kg / m 3 ; Threaded steel bars are used for tensile reinforcement, and the value of ν is 0.7. The method of the present invention is used to calculate the maximum crack width and the maximum opening displacement of the joint of the lining structure of the compressed air energy storage cavern, wherein the allowable value of the maximum opening position of the joint is set to 2 cm. Firstly, according to the reinforcement ratio of 1.0%, the maximum stress of the tensile steel bars of the entire ring lining is calculated to be 1030 MPa. According to formula (1), the maximum crack width is calculated to be 1.6 mm, which obviously does not meet the crack limit requirement. Therefore, the design method of the present invention is used to optimize the lining structure of the compressed air energy storage cavern, and two joints are preset on the second lining. Then, according to the threaded steel bar reinforcement ratio of 1.0%, the maximum stress of the tensile steel bars of the lining structure is calculated to be 198 MPa, and the maximum crack width is 0.15 mm, which meets the crack limit requirement. At the same time, the maximum opening displacement of the joint is 1.8 cm, which also meets the requirement of the maximum allowable value of 2 cm.

Claims

1. A method for designing a lining structure with preset joints for a compressed air energy storage underground cavern, wherein the lining structure of the compressed air energy storage underground cavern comprises a primary lining, a sliding layer, a secondary lining and a flexible sealing layer arranged in sequence from outside to inside along the cavern wall of the underground cavern, wherein the secondary lining is composed of reinforced concrete lining, and is characterized in that: The design method includes the following steps: 1) Obtain the mechanical parameters of the surrounding rock through site investigation and testing to assess whether it is suitable for building an underground cavern for compressed gas energy storage; 2) If the evaluation result shows that it is suitable to construct an underground cavern for compressed gas energy storage, then according to the properties of the surrounding rock, the burial depth, inner diameter and internal pressure of the cavern shall be preliminarily designed according to the full ring lining without preset joints, and the preliminary designed lining structure shall be obtained; 3) Calculate the maximum crack width w of the lining structure in the preliminary design max , and judge whether the crack limit requirement is met, that is, w max Is it less than 0.3mm? If w max <0.3mm, the crack limit requirement is met, and the preliminary designed lining structure is used as the final design, and the lining structure design is completed; if w max ≥0.3mm, optimize the burial depth, inner diameter and internal pressure of the cavern. If the crack limit requirements are still not met after optimization, proceed to step 4) to design the lining structure with preset joints; 4) Calculate the maximum crack width w of the lining structure with preset joints max and the maximum opening displacement of the joint D max , and judge w max Is it less than 0.3mm and D max Is it less than the allowed value? If w max Not less than 0.3mm and / or D max If the value is not less than the allowable value, the depth, inner diameter and internal pressure of the cavern are further optimized until w max Less than 0.3mm and D max If it is less than the allowable value, the lining structure design of the preset joints of the compressed air energy storage underground cavern is completed.

2. The method for designing a lining structure with preset joints for compressed air energy storage underground caverns according to claim 1 is characterized in that: The maximum crack width w max The calculation method is as follows: in: In the formula, w max The unit of σ is mm; s is the tensile steel bar stress, in N / mm 2 ; E s is the elastic modulus of the steel bar, in N / mm 2 ψ is the coefficient of non-uniform strain of the longitudinal tensile reinforcement between cracks; l f is the average crack spacing, in mm; f tk It is the standard value of concrete axial tensile strength, in N / mm 2 ρ s is the reinforcement ratio of the tensile steel bar; α1 and α2 are calculation coefficients, α1=0.16, α2=0.60; ν is a coefficient related to the surface shape of the tensile steel bar; d is the diameter of the tensile steel bar, in mm.

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