Design method of lining structure of preset joint of compressed air energy storage underground cavern

Abstract

The application discloses a kind of lining structure design methods of pre-set joint of compressed air energy storage underground cavern, comprising the following steps: if the evaluation result is suitable to build compressed air energy storage underground cavern, first according to the whole ring lining without pre-set joint, preliminary design lining structure;The maximum crack width of the lining structure of preliminary design is calculated, and whether it meets the requirement of crack limiting is judged, if it meets the requirement, then the lining structure of preliminary design is used as final design, if it does not meet the requirement, then the depth of cavern, inner diameter and internal pressure are optimized, if it still does not meet the requirement after optimization, then the maximum crack width of the lining structure of pre-set joint and the maximum opening displacement of joint are calculated and judged, and the lining structure design of pre-set joint is completed.The design method widens the application range of compressed air energy storage underground cavern, the cost of designed pre-set joint flexible sealing compressed air energy storage underground cavern is lower, more economic benefit, and more easily construction, more implementable, achieve more obvious effect of controlling maximum crack width.

Description

Technical Field

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

[0002] The sealing layers of compressed air 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 quick construction, and low cost, making them a more ideal type of sealing layer. Under the action of high internal air pressure, compressed air energy storage underground caverns may face lining cracking, resulting in failure of the flexible sealing layer due to cracking. Therefore, flexible sealed compressed air 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 are underground for a long time is 0.3mm. This is difficult to achieve under conditions of high internal pressure and medium surrounding rock quality. When the elastic modulus of the surrounding rock is low, the surrounding rock deformation is large, causing wider cracks in the lining. This means that the full-ring lining structure of compressed gas energy storage underground caverns designed with limited cracking is usually suitable for conditions with good surrounding rock quality or low gas storage pressure. However, the lining design of compressed gas energy storage underground caverns 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-type 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 wide cracks in the lining. Xu et al. (2024) proposed a block-type lining design method suitable for compressed gas energy storage underground caverns. The analytical solution method that considers the elastic deformation of the lining is adopted, and the cracking of the lining cannot be considered. Qiu et al. (2024) proposed a block-type lining design method for hydrogen storage underground caverns. Compared with the whole ring lining, the flexible filling material disperses the hoop stress, making the stress level and damage of the block-type lining lower. Jiang Zhongming et al. (2021) invented a concrete joint adaptive rebound pressurization 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 research on the application 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] Given the current imperfections in compressed gas energy storage cavern lining structure design methods, the applicability of existing block-type compressed gas energy storage cavern lining structure design methods under different surrounding rock conditions is unclear, and a design method specifically addressing the cracking problem of flexible sealed compressed gas energy storage cavern linings has not yet been developed. This present invention proposes a lining structure design method for compressed gas energy storage caverns with pre-set 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 compressed air energy storage underground caverns in response to the shortcomings of the existing technology. This design method broadens the scope of application of compressed air energy storage underground caverns. The designed flexible sealed compressed air energy storage underground caverns with preset joints have lower cost, are more economical, easier to construct, and are more feasible, achieving 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 for a compressed air energy storage underground cavern, wherein the lining structure of the compressed air energy storage underground cavern includes a primary lining, a sliding layer, a secondary lining, and a flexible sealing layer sequentially arranged along the cavern wall from the outside to the inside, wherein the secondary lining is composed of reinforced concrete lining. 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 the construction of a compressed gas energy storage underground cavern;

[0008] 2) If the assessment result indicates that the underground cavern is suitable for compressed gas energy storage, then based on the properties of the surrounding rock, the cavern's burial depth, inner diameter, and internal pressure are preliminarily designed according to the full-ring lining without pre-set joints, resulting in a preliminary design of the lining structure.

[0009] 3) Calculate the maximum crack width w of the preliminary designed lining structure max , and judge whether the crack limit requirements are 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 cavern's burial depth, inner diameter, and internal pressure. If the crack limit requirements are still not met after optimization, proceed to step 4) to design a 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] Where w max The unit of σ is mm; s is the stress of the tensile reinforcement, 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; α1 and α2 are calculation coefficients, α1 = 0.16, α2 = 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 full-ring lining without preset joints, the lining structure with preset joints designed by the method of the present invention can be used to build compressed air energy storage underground caverns in medium-quality surrounding rocks, which broadens the scope of application of compressed air energy storage underground caverns;

[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 are lower in cost, more economical, easier to construct, and 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 circumferential 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 gas is stored to the maximum pressure is shown as an example;

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

[0023] Figure 4 Schematic diagram of using linear springs in the normal direction of the joint interface to simulate the tension and compression behavior of the upper and lower plates of the secondary lining;

[0024] Figure 5 Flowchart of the design method of the present invention. DETAILED DESCRIPTION

[0025] The present invention will be described in further detail below in conjunction with the working principle of the lining structure with preset joints, the force analysis of the sliding layer and the preset joints, and the accompanying drawings.

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

[0027] The reinforced concrete lining of a whole ring can crack under high internal pressure, potentially leading to failure of the lining structure's bearing capacity. Pre-set joints can release radial displacement of the lining (secondary lining), transferring the high pressure inside the tunnel to the surrounding rock, fully utilizing the rock's bearing capacity.

[0028] An example of a lining structure with a preset joint is 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 reinforced concrete lining blocks ( Figure 1 and Figure 2 (In the figure, 8 is concrete and 9 is steel bar). Two adjacent reinforced concrete linings have two joints 5. The inner sides of these joints 5 are covered with curved steel pads 6, which are compressed by carbon steel channels 7. These pads 6 are positioned between the secondary lining 3 and the flexible sealing layer 4 to prevent the latter from sinking into the joints 5 under high pressure. The sliding layer 2, located between the primary lining 1 and the secondary lining 3, ensures that the joints 5 can open smoothly under internal pressure, dissipating the hoop stress of the lining. The operating principle of this pre-jointed lining structure is as follows:

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

[0030] (b) When the cavern is inflated, the internal pressure increases, causing sliding between the secondary and primary linings. This gradually opens the joints, releasing radial displacement of the lining, dissipating the hoop stress, and fully transferring the internal pressure to the surrounding rock. Without a sliding layer, a large shear stress would be generated between the secondary and primary linings to balance the internal pressure on the secondary lining. This would fail to disperse the hoop stress, preventing the joints from opening and releasing radial displacement.

[0031] (c) When the pressure inside the cave reaches its maximum, the opening displacement of the joint reaches its maximum value D max , at this time the radial displacement of the lining is released to the maximum, as shown in 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, a sliding layer needs to be set 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 generate 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 sticking-slip behavior of the sliding layer. The nonlinear constitutive curve of the tangential spring is as follows: Figure 3 As shown. 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 outare the inner radius and outer radius of the second lining respectively. The air pressure p is transferred 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 bond 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, as shown in the following example: Figure 4 As shown. Abaqus software is used for simulation, and the compression stress is defined as negative and the tension stress is defined as positive. The width of the preset joint is set to 0mm. For linear springs (see Figure 4 ), the spring stiffness k during stretching (the part where the displacement is greater than 0) t 0N / m means the joint can open freely; the spring stiffness k during compression c 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 design method for the lining structure with preset joints for compressed air energy storage underground caverns of the present invention, the flow chart of which 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 the construction of a compressed gas energy storage underground cavern;

[0048] 2) If the assessment result indicates that the underground cavern is suitable for compressed gas energy storage, then based on the properties of the surrounding rock, the cavern's burial depth, inner diameter, and internal pressure are preliminarily designed according to the full-ring lining without pre-set joints, resulting in a preliminary design of the lining structure.

[0049] 3) Calculate the maximum crack width w of the preliminary designed lining structure max , and judge whether the crack limit requirements are 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 cavern's burial depth, inner diameter, and internal pressure. If the crack limit requirements are still not met after optimization, proceed to step 4) to design a 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] Where w max The unit of σ is mm; s is the stress of the tensile reinforcement, 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 tkIt is the standard value of concrete axial tensile strength, in N / mm 2 ρ s is the reinforcement ratio of the tensile reinforcement; α1 and α2 are calculation coefficients, α1 = 0.16, α2 = 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 pre-set joints according to existing methods. The compressed air energy storage cavern has a buried depth of 146m, an inner diameter (inner diameter) of 8m, and an internal pressure of 10MPa. The primary lining (i.e., initial support) is 18cm thick, the secondary lining uses 50cm thick C30 concrete, and the flexible sealing layer is 10mm thick. The rock mass has an elastic modulus of 6GPa, a cohesion of 1.5MPa, an internal friction angle of 45°, and a density of 2676kg / m 3 ; The tensile reinforcement adopts threaded steel bars, 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 2cm. First, according to the reinforcement ratio of 1.0%, the maximum stress of the tensile reinforcement of the whole ring lining is calculated to be 1030MPa. According to formula (1), the maximum crack width is calculated to be 1.6mm, 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 reinforcement of the lining structure is calculated to be 198MPa, and the maximum crack width is 0.15mm, which meets the crack limit requirement. At the same time, the maximum opening displacement of the joint is 1.8cm, which also meets the requirement of the maximum allowable value of 2cm.

Claims

1. A method for designing a lining structure with preset joints for a compressed air energy storage underground cavern. 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 sequentially arranged along the cavern wall from the outside to the inside. The secondary lining is composed of reinforced concrete lining, and is characterized in that: The design approach 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 the construction of a compressed gas energy storage underground cavern; 2) If the assessment result indicates that the underground cavern is suitable for compressed gas energy storage, then based on the properties of the surrounding rock, a full-ring lining without pre-set joints is used to preliminarily design the cavern's burial depth, inner diameter, and internal pressure, resulting in a preliminary design of the lining structure. 3) Calculate the maximum crack width of the lining structure in the preliminary design w max , and judge whether the crack limit requirements are met, that is, w max Is it less than 0.3 mm? w max < 0.3 mm, 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 ≥ 0.3 mm, optimize the cavern's burial depth, inner diameter, and internal pressure. If the crack limit requirements are still not met after optimization, proceed to step 4) to design a lining structure with preset joints. 4) Calculate the maximum crack width of the lining structure with pre-set joints w max and the maximum opening displacement of the joint D max , and judge w max Is it less than 0.3 mm and D max Is it less than the allowed value? w max Not less than 0.3 mm and / or D max If the value is not less than the allowable value, the depth, inner diameter and internal pressure of the cavern will be further optimized until w max Less than 0.3 mm 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.

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