Double-layer sealing structure for underground gas storage, design method and construction method

Abstract

The present application relates to the technical field of underground gas storage, and discloses a double-layer sealing structure for underground gas storage, a design method and a construction method thereof. In the double-layer sealing structure, a complete closed shell is formed by on-site roll bending and continuous welding of a high-elastic steel plate, and together with a sliding layer, forms an overall sealing system without joints and weak links. Compared with the traditional block lining or the scheme of setting expansion joints, the leakage hidden danger caused by stress concentration or material aging at the joints or joints is completely avoided, and the long-term gas-tight reliability of the gas storage under the repeated action of high internal pressure is improved. At the same time, the sliding layer is made of flexible material, which can effectively absorb the displacement and cracking deformation of the surrounding rock caused by pressure change, and uniformly transmit the deformation to the high-elastic steel sealing layer, so that the sealing structure can be transformed from passive adaptation to active adaptation, avoiding stress concentration and crack propagation caused by deformation incoordination of the traditional rigid lining, thereby preventing the sealing layer from being torn or pierced.

Description

Technical Field

[0001] This invention relates to the field of underground gas storage technology, specifically to a double-layer sealing structure, design method, and construction method for underground gas storage. Background Technology

[0002] Compressed air energy storage (CAES) is a crucial long-term energy storage technology supporting new power systems. Underground artificial gas storage facilities, due to their flexible site selection and controllable volume, have become key gas storage infrastructures. During operation, these facilities must withstand high internal pressures of 10 MPa and above, and endure cyclical temperature and pressure loads from repeated inflation and deflation. Under these conditions, the surrounding rock and support structure are prone to significant deformation and cracking. If the sealing structure cannot adapt to the deformation of the surrounding rock and maintain reliable airtightness, high-pressure gas leakage will occur, directly affecting the safe and stable operation of the gas storage facility. Therefore, in addition to supporting the surrounding rock and transmitting internal pressure, the lining and sealing layer of the gas storage facility must be able to deform in coordination with the surrounding rock to ensure long-term airtightness and structural safety.

[0003] In related technologies, underground gas storage facilities often use integral rigid concrete lining combined with an inner sealing layer, or segmented lining with flexible expansion joints, or steel plate lining added to the inner wall of the concrete as a sealing layer, or sliding interfaces or flexible waterstops introduced between lining segments by setting sliding layers or movable expansion joints to alleviate tensile stress in the concrete.

[0004] However, the above solutions all rely on rigid or semi-rigid materials to construct the sealing layer and on structural joints or sliding interfaces to cope with deformation, which is essentially a passive adaptive approach. This makes it difficult for the sealing structure to balance deformation adaptability with overall airtightness. For example, if rigid materials are used to achieve integrity, these materials are prone to cracking due to inconsistent deformation; if stress is released through joints or sliding, numerous seams and weak points are introduced, weakening the overall structural integrity and creating potential leakage hazards. Summary of the Invention

[0005] This invention provides a double-layer sealing structure, design method, and construction method for underground gas storage facilities, in order to solve the problem that traditional underground gas storage solutions cannot simultaneously achieve both deformation adaptability and overall airtightness.

[0006] In a first aspect, the present invention provides a double-layer sealing structure for underground gas storage facilities, disposed on the inner surface of the surrounding rock of the gas storage cavern, comprising a slip layer and a high-elastic steel sealing layer. The slip layer is a flexible material layer tightly attached to the inner surface of the surrounding rock, used to absorb and buffer deformation of the surrounding rock; the high-elastic steel sealing layer is a continuous closed shell made of a highly elastic metal material, attached to the inner surface of the slip layer, used to elastically deform with the deformation of the slip layer, and to provide an airtight seal. The stiffness of the slip layer is lower than that of the surrounding rock and the high-elastic steel sealing layer.

[0007] Beneficial Effects: By using high-elastic steel plates for on-site rolling and continuous welding to form a complete closed shell, together with the slip layer, a seamless and weak-point-free overall sealing system is created. Compared to traditional segmented lining or expansion joint solutions, this completely avoids leakage risks caused by stress concentration or material aging at joints and seams, improving the long-term airtight reliability of the gas storage facility under repeated high internal pressure. Simultaneously, the slip layer, made of flexible material, effectively absorbs displacement and cracking deformation of the surrounding rock caused by pressure changes and evenly transfers the deformation to the high-elastic steel sealing layer. This allows the sealing structure to shift from passive to active adaptation, avoiding stress concentration and crack propagation caused by inconsistent deformation in traditional rigid linings, thus preventing the sealing layer from being torn or punctured. Furthermore, the use of a formwork-free, continuous construction process eliminates the complex procedures of traditional segmented formwork erection, joint alignment, and assembly, reducing human error and the difficulty of interface treatment.

[0008] In one alternative embodiment, the slip layer is a coating or roll layer that continuously covers the surface of the surrounding rock.

[0009] Beneficial effects: The slip layer, applied continuously to the surrounding rock surface in the form of a coating or roll, eliminates the weak areas of joints and overlaps that may occur with traditional segmented laying or splicing. It not only uniformly transmits deformation but also prevents localized stress concentration, ensuring the slip layer performs the same shear buffering and displacement absorption functions across its entire size range. This fundamentally avoids localized deterioration of airtightness caused by interface discontinuities. Furthermore, both coatings and rolls offer excellent process adaptability, particularly suitable for complex tunnel shapes such as irregular cross-sections, bends, and transition zones. The construction process eliminates the need for complex formwork and positioning fixtures, simplifying procedures, shortening construction time, and reducing manual operation difficulty, facilitating large-scale, standardized construction in large underground projects. In addition, it effectively seals micro-cracks on the surrounding rock surface, reducing potential pathways for gas diffusion along the interface between the surrounding rock and the slip layer, further enhancing the overall impermeability of the sealing system.

[0010] In one alternative embodiment, the material of the slip layer is one of modified bitumen-based elastomer, EPDM rubber, self-adhesive polymer, and high-ductility concrete.

[0011] Beneficial Effects: By selecting one of the following materials for the slip layer—modified asphalt-based elastomer, EPDM rubber, self-adhesive polymer, or high-ductility concrete—a material with low elastic modulus, high ductility, and high toughness can maintain good material integrity even under large deformation. For example, modified asphalt-based elastomers and EPDM rubber exhibit significant flexibility and resilience; self-adhesive polymers combine flexibility and interface following properties; and ECC concrete possesses high ductility, exhibiting the characteristic of multi-crack formation under tension while maintaining overall integrity. This allows the slip layer to more effectively absorb and disperse surrounding rock deformation, preventing stress concentration in the high-elasticity steel sealing layer, thereby significantly improving the structure's deformation coordination under repeated loading. Furthermore, it provides flexible options for different engineering conditions and construction equipment, thus reducing dependence on complex construction environments.

[0012] In one optional embodiment, the thickness of the slip layer is 5 mm to 20 mm.

[0013] Beneficial effects: Setting the thickness of the slip layer to 5mm to 20mm ensures that the slip layer can effectively absorb the displacement disturbance induced by the surrounding rock cracks and disperse stress transmission. It also achieves a good balance between material usage and engineering costs, avoiding the situation where the thickness is too thin, which would prevent it from fully exerting its role in dispersing stress and buffering deformation. It also avoids the situation where the slip layer is too thick, which would increase material costs and affect the overall mechanical properties of the structure.

[0014] In one alternative embodiment, the high-elasticity steel sealing layer is formed by connecting multiple arc-shaped steel plates through circumferential and axial butt welds.

[0015] Beneficial effects: By connecting multiple arc-shaped steel plates into a complete shell through circumferential and longitudinal butt welds, a continuous sealed interface without bolts or lap joints is formed. Compared with traditional segmented lining that relies on bolt connections or lap welding, butt welds can achieve equal strength connections between the base materials, avoiding stress concentration and potential leakage points caused by loose connectors and lap joints, and improving the structural integrity and airtightness of the sealing layer under high pressure and cyclic loads.

[0016] In one alternative embodiment, a low-modulus, micro-expansion backfill material is filled between the high-elasticity steel sealing layer and the slip layer.

[0017] Beneficial effects: By filling the space between the high-elasticity steel sealing layer and the slip layer with low-modulus, micro-expansion backfill material, which has good flexibility and compressibility, it can adapt to the relative micro-deformation of the slip layer and the steel plate during the stress process, and always maintain close contact between the layers. At the same time, it can also avoid the local bending stress concentration caused by uneven back support of the steel plate under high pressure gas, and ensure that the internal pressure is evenly transmitted to the slip layer and the surrounding rock through the filling layer. This makes the double-layer structure truly form an overall synergistic stress-bearing working system, significantly improving the overall load-bearing stability of the structure.

[0018] In one alternative implementation, the low-modulus, micro-expansion backfill material is a polyurethane elastomer or a micro-expansion polymer slurry.

[0019] Beneficial effects: By using polyurethane elastomer or micro-expansion polymer slurry as a low-modulus, micro-expansion backfill material, which has low modulus and micro-expansion characteristics, it can be used as a cushion layer to optimize the stress uniformity transfer process and deformation between the high-elastic steel layer and the slip layer. It can also be more tightly integrated with the high-elastic steel sealing layer and the slip layer, thereby effectively suppressing interlayer micro-movement or voids that may occur under pressure fluctuations, and improving the stability and airtightness of the entire sealing system under dynamic loads.

[0020] Secondly, the present invention also provides a design method for a double-layer sealing structure for an underground gas storage facility, used to design the double-layer sealing structure for an underground gas storage facility provided in the first aspect. The design method includes the following steps: S1: Obtaining the design parameters of the gas storage facility, including at least the maximum internal gas storage pressure. Elastic modulus of surrounding rock Poisson's ratio of surrounding rock Equivalent tensile strength of surrounding rock S2: Calculate the minimum elastic limit strain required for the high-elasticity steel sealing layer based on the design parameters. S3: Based on the minimum elastic limit strain Determine the yield strength of the steel used in the high-elasticity steel sealing layer. S4: Based on the design parameters and the determined steel properties, design the thickness of the slip layer. With elastic modulus This ensures that the deformation coordination conditions between the slip layer and the high-elasticity steel sealing layer are met.

[0021] Beneficial effects: Since the design method for the double-layer sealing structure used in underground gas storage is also used to design the double-layer sealing structure for underground gas storage, it has the same effect as the double-layer sealing structure used in underground gas storage, and will not be elaborated here.

[0022] Thirdly, the present invention also provides a construction method for a double-layer sealing structure for an underground gas storage facility, used for constructing the double-layer sealing structure for an underground gas storage facility provided in the first aspect, comprising the following steps: S5: constructing a continuous slip layer on the surface of the surrounding rock of the gas storage cavern; S6: on the inner side of the slip layer, forming a closed shell attached to the slip layer by welding multiple high-elasticity metal plates together, serving as a high-elasticity steel sealing layer.

[0023] Beneficial effects: Since the construction method of the double-layer sealing structure used for underground gas storage is applied to the double-layer sealing structure of underground gas storage, it has the same effect as the double-layer sealing structure used for underground gas storage, and will not be elaborated here.

[0024] In an optional embodiment, after step S6, step S7 is further included: injecting a low-modulus, micro-expansion backfill material into the gap between the high-elastic steel sealing layer and the sliding layer to form a continuous and uniform support.

[0025] Beneficial effects: Since there will inevitably be some microscopic gaps or areas of incomplete fit between the high-elastic steel sealing layer and the sliding layer, by actively filling the gap between the high-elastic steel sealing layer and the sliding layer with low-modulus, micro-expansion backfill material, the material will expand moderately during the curing process, actively compensating for the deformation caused by the chemical shrinkage and moisture evaporation shrinkage of the material itself, thereby eliminating these initial gaps. This allows the back of the steel plate to obtain full-circumference, continuous and uniform solid support, ensuring that when the gas storage tank is subjected to high internal pressure, the pressure can be uniformly and continuously transmitted to the sliding layer and the surrounding rock through the filling layer. This avoids the risk of bending stress concentration and instability caused by local suspension or inadequate support of the steel plate, and transforms the double-layer structure from a contact fit to a combined form, making the mechanical force transmission path more reliable. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings used in the description of the specific embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0027] Figure 1 An annular cross-sectional view of a double-layer sealed structure for an underground gas storage facility provided in an embodiment of the present invention; Figure 2 A construction schematic diagram of a double-layer sealed structure for an underground gas storage facility provided in an embodiment of the present invention; Figure 3 A construction flowchart for a double-layer sealed structure for an underground gas storage facility, provided in an embodiment of the present invention.

[0028] Explanation of reference numerals in the attached figures: 1. Slip layer; 2. High-elastic steel sealing layer; 3. Circumferential drainage blind pipe; 4. Longitudinal drainage blind pipe. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Compressed air energy storage (CAES) is a crucial long-term energy storage technology supporting new power systems. Underground artificial gas storage facilities, due to their flexible site selection and controllable volume, have become key gas storage infrastructures. During operation, these facilities must withstand high internal pressures of 10 MPa and above, and endure cyclical temperature and pressure loads from repeated inflation and deflation. Under these conditions, the surrounding rock and support structure are prone to significant deformation and cracking. If the sealing structure cannot adapt to the deformation of the surrounding rock and maintain reliable airtightness, high-pressure gas leakage will occur, directly affecting the safe and stable operation of the gas storage facility. Therefore, in addition to supporting the surrounding rock and transmitting internal pressure, the lining and sealing layer of the gas storage facility must be able to deform in coordination with the surrounding rock to ensure long-term airtightness and structural safety.

[0031] In related technologies, underground gas storage facilities often employ integral rigid concrete lining combined with an internal sealing layer, or segmented lining with flexible expansion joints. Relying on formwork for segmented construction inevitably creates construction joints or gaps, forming weak points in the structure. Under long-term high internal pressure operation, the concrete lining is prone to cracking along the circumferential direction. These cracks can cause corresponding cracks in the sealing layer, leading to tearing, puncture, or partial voiding of the sealing layer, ultimately causing gas storage facility leakage and failure. Alternatively, a steel plate lining can be added to the inner wall of the concrete as a sealing layer. While this provides higher pressure resistance, the steel plate's elasticity makes it difficult to deform in tandem with the concrete lining. When the lining cracks, the steel plate lining may experience stress concentration failure. Furthermore, laying thick steel plate linings in large-section caverns is complex, requiring segmented processing and welding, resulting in long cycles and high costs, which is not conducive to large-scale engineering applications. Alternatively, a sliding interface or flexible waterstop can be introduced between lining sections by setting a sliding layer or movable expansion joint to release the tensile stress of the concrete. However, such solutions require the combination of many components, have many interfaces and splices, and the overall sealing and durability are still difficult to guarantee.

[0032] In summary, all the above solutions rely on rigid or semi-rigid materials to construct the sealing layer and address deformation through structural joints or sliding interfaces, essentially remaining passive adaptive solutions. This makes it difficult for the sealing structure to balance deformation adaptability with overall airtightness. For example, if rigid materials are used to achieve integrity, these materials are prone to cracking due to inconsistent deformation; if stress is released through joints or sliding, numerous seams and weak points are introduced, weakening the overall structural integrity and creating potential leakage hazards.

[0033] To address this issue, this application proposes a double-layered sealed structure and construction method for underground gas storage facilities. By incorporating a flexible slip layer to disperse stress concentration caused by surrounding rock cracking, and by using a highly elastic sealing material to accommodate the deformation of the slip layer, airtightness is ensured. This solves the problem of traditional underground gas storage solutions struggling to balance deformation adaptability with overall airtightness.

[0034] The following is combined Figures 1 to 3 The following describes embodiments of the present invention.

[0035] According to an embodiment of the present invention, in one aspect, the provided double-layer sealing structure for an underground gas storage facility is disposed on the inner surface of the surrounding rock of the gas storage cavern, such as... Figure 1 As shown, it includes a sliding layer 1 and a high-elastic steel sealing layer 2.

[0036] Specifically, the slip layer 1 is a flexible material layer that is closely attached to the inner surface of the surrounding rock. Its stiffness is lower than that of the surrounding rock and the high-elastic steel sealing layer 2. It is used to absorb and buffer the deformation of the surrounding rock. The high-elastic steel sealing layer 2 is a continuous closed shell made of high-elastic metal material. It is attached to the inner surface of the slip layer 1 and directly contacts the gas inside the gas storage tank. It is used to undergo elastic deformation with the deformation of the slip layer 1 and to provide gas sealing.

[0037] This design, through on-site rolling and continuous welding of high-elastic steel plates to form a complete closed shell, together with the sliding layer 1, constitutes a seamless and weak-point-free overall sealing system. Compared with the traditional segmented lining or expansion joint scheme, it completely avoids the leakage risks caused by stress concentration or material aging at joints and seams, and improves the long-term airtight reliability of the gas storage facility under repeated high internal pressure.

[0038] Meanwhile, the slip layer 1 is made of flexible material, which effectively absorbs the displacement and cracking deformation of the surrounding rock caused by pressure changes, and uniformly transmits the deformation to the high-elastic steel sealing layer 2, so that the sealing structure can transform from passive adaptation to active adaptation, avoiding stress concentration and crack expansion caused by deformation incoordination in traditional rigid lining, thereby preventing the sealing layer from being torn or punctured.

[0039] In addition, the use of a template-free, continuous construction process eliminates the complex procedures of traditional block formwork erection, jointing, and assembly, reducing human error and the difficulty of interface treatment.

[0040] It can be noted that the slip layer 1 is a coating or roll layer that continuously covers the surface of the surrounding rock.

[0041] With this configuration, the slip layer 1 is continuously applied to the surface of the surrounding rock in the form of a coating or roll material. This eliminates the weak areas of joints and overlaps that may occur with traditional segmented laying or splicing. It can not only transmit deformation evenly, but also prevent local stress concentration. This ensures that the slip layer 1 plays the same shear buffering and displacement absorption function across the entire size range, and avoids local deterioration of airtightness caused by interface discontinuity from the root.

[0042] At the same time, both the coating and the roll layer have good process adaptability, and are especially suitable for complex tunnel shapes such as irregular cross sections, bends and transition zones. The construction process does not require complicated templates and positioning tools, which can simplify the process, shorten the construction period and reduce the difficulty of manual operation, which is conducive to achieving large-scale and standardized construction in large underground projects.

[0043] In addition, it can effectively seal micro-cracks on the surface of the surrounding rock, reduce the potential path of gas diffusion along the interface between the surrounding rock and the slip layer 1, and further improve the overall seepage prevention performance of the sealing system.

[0044] It can be noted that the material of slip layer 1 is one of modified asphalt-based elastomer, ethylene propylene diene monomer (EPDM) rubber, self-adhesive polymer, and high ductility concrete (ECC).

[0045] This design, by selecting one of the following materials for the slip layer 1: modified asphalt-based elastomer, EPDM rubber, self-adhesive polymer, and high-ductility concrete, provides low elastic modulus, high ductility, and high toughness, enabling it to maintain good material integrity even under large deformation.

[0046] For example, modified bitumen-based elastomers and EPDM rubber exhibit significant flexibility and resilience; self-adhesive polymers combine flexibility and interface following properties; and ECC concrete possesses high ductility, exhibiting the characteristic of multi-crack formation under tension while maintaining overall integrity. This allows the slip layer 1 to more effectively absorb and disperse surrounding rock deformation, preventing stress concentration in the high-elasticity steel sealing layer 2, thereby significantly improving the structure's deformation coordination under repeated loading.

[0047] In addition, it provides flexible options for different engineering conditions and construction equipment, thereby reducing dependence on complex construction environments.

[0048] It can be noted that the construction method of slip layer 1 is hot melt spraying, wet application or spraying.

[0049] It can be noted that the thickness of slip layer 1 is 5mm to 20mm.

[0050] With this setting, the thickness of the slip layer 1 is set to 5mm to 20mm. This thickness range can ensure that the slip layer 1 can effectively absorb the displacement disturbance induced by the surrounding rock cracks and disperse stress transmission. It can also achieve a good balance between material usage and engineering cost, avoiding the problem that the thickness is too thin and cannot give full play to its role in dispersing stress and buffering deformation. It also avoids the slip layer 1 being too thick, which would increase material cost and affect the overall mechanical performance of the structure.

[0051] It can be explained that the high-elastic steel sealing layer 2 is composed of multiple arc-shaped steel plates connected by circumferential and axial butt welds.

[0052] This design connects multiple curved steel plates into a complete shell through circumferential and longitudinal butt welds, forming a continuous sealed interface without bolts or lap joints. Compared with traditional segmented lining that relies on bolt connections or lap welding, butt welds can achieve equal strength connections between the base materials, avoiding stress concentration and potential leakage points caused by loose connectors and lap joints, and improving the structural integrity and airtightness of the sealing layer under high pressure and cyclic loads.

[0053] It can be noted that the high-elastic steel sealing layer 2 is preferably made of high-elastic steel plate lining.

[0054] Among them, the yield strength of the high elasticity metal material used in the high elasticity steel sealing layer 2 satisfies the following relationship (1):

[0055] In the formula, The elastic modulus of high-elasticity steel materials The required elastic limit strain is determined based on the surrounding rock parameters and the internal pressure of the gas storage tank. in, The following relation (2) must be satisfied: .

[0056] In the formula, This represents the maximum strain value calculated from the cracking of the surrounding rock of the gas storage facility. Poisson's ratio of the surrounding rock This represents the highest pressure inside the gas storage facility. It is the equivalent tensile strength of the surrounding rock (the difference between the tensile strength of the surrounding rock and the ground stress). This represents the elastic modulus of the surrounding rock of the gas storage facility.

[0057] This design provides a theoretical basis for the design and material selection of the high-elasticity steel sealing layer 2, allowing designers to consider the internal pressure of the gas storage tank and the yield strength of the high-elasticity steel material. With surrounding rock physical parameters ( , , By linking these factors together, the material strength requirements calculated using this formula can guarantee that even under the most unfavorable working conditions (when the surrounding rock cracks and reaches maximum strain), the required strength can be achieved. Under the combined action of the deformation of the slip layer 1 and the deformation of the slip layer 2, the total strain borne by the steel sealing layer is still less than its elastic limit strain. This ensures that the steel liner remains within its elastic deformation range throughout its service life, without yielding or plastic failure.

[0058] At the same time, by forming a quantitative and refined material selection design, it is possible to optimize material costs and improve the economic efficiency of the solution while ensuring safety.

[0059] Furthermore, considering the surrounding rock as the main load-bearing structure to control overall deformation, the slip layer 1 is regarded as a linearly compressible layer (thickness). Modulus Compression under internal pressure The following relation (3) must be satisfied:

[0060] Additional circumferential strain contributed to the steel liner The following relation (4) must be satisfied:

[0061] Among them, the total circumferential strain of the steel lining indicates that the steel lining must move with the surrounding rock displacement; the more "compressible" the slip layer 1 is, the greater the total strain of the steel lining.

[0062] Therefore, the elastic limit strain of the selected steel is... It needs to be greater than the strain of the surrounding rock plus the additional circumferential strain contributed by the slip layer 1.

[0063] Furthermore, the elastic limit strain of steel The following relation (5) must be satisfied:

[0064] In the formula, The elastic limit strain of the selected steel.

[0065] Therefore, by combining equations (1), (4) and (5), we can obtain the following relationship between the thickness of slip layer 1 and the elastic modulus (6):

[0066] It can be noted that a low-modulus, micro-expansion backfill material is filled between the high-elastic steel sealing layer 2 and the sliding layer 1.

[0067] This configuration, by filling the space between the high-elasticity steel sealing layer 2 and the sliding layer 1 with a low-modulus, micro-expansion backfill material, provides good flexibility and compressibility, enabling it to adapt to the relative micro-deformation of the sliding layer 1 and the steel plate during the stress process, and always maintain close contact between the layers.

[0068] At the same time, it can also avoid the local bending stress concentration caused by uneven support behind the steel plate under the action of high pressure gas, and ensure that the internal pressure is evenly transmitted to the slip layer 1 and the surrounding rock through the filling layer, so that the double-layer structure can truly form an overall synergistic force-bearing working system, significantly improving the overall load-bearing stability of the structure.

[0069] Preferably, the low-modulus, micro-expansion backfill material is a polyurethane elastomer or a micro-expansion polymer slurry.

[0070] This configuration, by using polyurethane elastomer or micro-expansion polymer slurry as a low-modulus, micro-expansion backfill material, possesses low-modulus and micro-expansion characteristics. It can serve as a soft padding layer to optimize the uniform stress transfer process and deformation during use between the high-elastic steel layer and the sliding layer 1. It can also be more tightly integrated with the high-elastic steel sealing layer 2 and the sliding layer 1, thereby effectively suppressing interlayer micro-movement or voids that may occur under pressure fluctuations, and improving the stability and airtightness of the entire sealing system under dynamic loads.

[0071] Furthermore, polyurethane elastomers contain urethane groups in their main chain, making them polymeric materials that combine the high elasticity of rubber with the strength of plastics. They are formed by the reaction of polyols (polyethers or polyesters, forming soft segments), polyisocyanates (such as MDI and TDI, forming hard segments), and chain extenders.

[0072] Similarly, micro-expansion polymer grout is a special grouting material made of cement, polymer and additives. The cementing material is silicate cement, the aggregate is refined quartz sand, and the additives are expansion agents (calcium sulfoaluminate, etc.), polymer emulsion / powder, water-reducing agent, water-retaining agent, etc.

[0073] In one embodiment, such as Figure 1 As shown, the double-sealed structure used for underground gas storage is also equipped with a circumferential drainage blind pipe 3 and a longitudinal drainage blind pipe 4.

[0074] The double-layer sealing structure for underground gas storage provided in the above embodiments achieves deformation coordination between the structure and the surrounding rock through a synergistic sealing mechanism of flexible buffering and elastic sealing. The slip layer 1 effectively disperses stress concentration caused by cracking of the surrounding rock, and the high-elasticity steel layer adapts to the uniform large deformation of the slip layer 1 with its elastic deformation capacity, thereby avoiding weld cracking and steel lining yielding. Compared with traditional rigid sealing structures, this invention exhibits higher airtightness stability and fatigue resistance under high-pressure conditions.

[0075] Secondly, the present invention also provides a design method for a double-layer sealing structure for an underground gas storage facility, used to design the double-layer sealing structure for an underground gas storage facility provided in the first aspect. The design method includes the following steps: S1: Obtaining the design parameters of the gas storage facility, including at least the maximum internal gas storage pressure. Elastic modulus of surrounding rock Poisson's ratio of surrounding rock Equivalent tensile strength of surrounding rock S2: Calculate the minimum elastic limit strain required for the high-elasticity steel sealing layer based on the design parameters. S3: Based on the minimum elastic limit strain Determine the yield strength of the steel used in the high-elasticity steel sealing layer. S4: Based on the design parameters and the determined steel properties, design the thickness of the slip layer. With elastic modulus This ensures that the deformation coordination conditions between the slip layer and the high-elasticity steel sealing layer are met.

[0076] Specifically: First, input the design parameters such as the maximum gas storage internal pressure, cavern radius, surrounding rock modulus, surrounding rock Poisson's ratio, and surrounding rock tensile strength; then calculate the maximum circumferential strain of the surrounding rock based on the above relationship (2). And further determine the steel selection by the maximum circumferential strain of the surrounding rock; then complete the setting of the thickness and material selection of the slip layer 1 according to the above relationship (6) to determine the upper limit of the thickness that the slip layer 1 can be set under different slip layer 1 material conditions; then, the steel lining thickness is selected according to the minimum thickness that can be controlled by the production and manufacturing conditions; finally, output the gas storage structure scheme and verification results to complete the structural design.

[0077] The following is based on a cavern depth of 150m, with surrounding rock consisting of hard sandstone, and a Poisson ratio for the surrounding rock. The maximum internal design pressure of the gas storage facility Equivalent tensile strength of surrounding rock Rock mass elastic modulus Provide a illustrative illustration.

[0078] Based on the above design criteria, its elastic limit strain The following requirements should be met:

[0079] Since the elastic modulus of steel is generally 200 GPa, it can be calculated that:

[0080] As shown in the above calculations, to ensure that the steel lining maintains an elastic working state under the design internal pressure, its yield strength should not be less than 430 MPa. To ensure the reliability of material selection and long-term performance, this invention preferably uses Q690 grade low-alloy high-strength structural steel with a yield strength higher than 430 MPa. This steel has good weldability and toughness, and can meet the requirements of the steel lining's dynamic deformation and airtight stability.

[0081] Furthermore, according to equation (6), the relationship between the thickness of slip layer 1 and the elastic modulus must satisfy the following:

[0082] When the material modulus of slip layer 1 At that time, the upper limit of the thickness of slip layer 1 When the material modulus of slip layer 1 At that time, the upper limit of the thickness of slip layer 1 .

[0083] Thirdly, the present invention also provides a construction method for a double-layer sealing structure for an underground gas storage facility, used in the double-layer sealing structure for an underground gas storage facility provided in the first aspect, such as... Figure 2 and Figure 3 As shown, the process includes the following steps: S5: constructing a continuous slip layer 1 on the surface of the surrounding rock of the gas storage cavern; S6: on the inner side of the slip layer 1, welding multiple high-elasticity metal plates together to form a closed shell that covers the slip layer 1, serving as a high-elasticity steel sealing layer 2.

[0084] This setup is because the construction method for the double-layer sealing structure used in underground gas storage facilities is applied to the construction of the double-layer sealing structure for underground gas storage facilities, and has the same effect as the double-layer sealing structure used in underground gas storage facilities, so it will not be elaborated further here.

[0085] Meanwhile, this construction method abandons the traditional construction method of gas storage lining that relies on segmented formwork and assembly. Instead, it adopts a process of continuously constructing a sliding layer 1 on the surface of the surrounding rock and directly welding it to form a complete steel shell. This eliminates the structural weaknesses such as construction joints, splicing joints, and formwork joints that are inevitable in traditional methods. As a result, the final sealed structure becomes a seamless and uninterrupted continuous whole, solving the core problem of high-pressure gas leakage caused by stress concentration at joints, material aging, or construction defects, and improving the airtightness and safety level of the gas storage.

[0086] It can be explained that step S5 specifically includes: applying a hot melt spray polymer coating or wet-applying a prefabricated elastic roll material onto the leveling layer to form a sliding layer 1 with an average thickness of 5 to 20 mm.

[0087] During construction, it is essential to ensure that the sliding material is continuously covered with uniform thickness and free of defects and air bubbles, in order to guarantee its shear deformation performance and complete isolation effect.

[0088] It can be explained that step S6 specifically includes: transporting pre-cut high-elasticity steel plates into the tunnel, using on-site equipment to roll and bend them into arc-shaped plates that match the inner diameter of the tunnel, and welding the plates together. By butt welding multiple sections of steel plates in both the circumferential and axial directions, they are connected into a continuous closed double-layer steel shell, which is then hoisted and tightly attached to the inner wall of the sliding layer 1.

[0089] During the welding process, the quality of the weld should be strictly controlled, and if necessary, an additional layer of anti-corrosion and sealing coating can be sprayed on the outside of the weld to enhance airtightness.

[0090] It can be noted that after step S6, step S7 is also included: injecting low-modulus, micro-expansion backfill material into the gap between the high-elastic steel sealing layer 2 and the sliding layer 1 to form a continuous and uniform support.

[0091] With this configuration, since there will inevitably be some microscopic gaps or areas of incomplete fit between the high-elastic steel sealing layer 2 and the sliding layer 1, by actively filling the gap between the high-elastic steel sealing layer 2 and the sliding layer 1 with low-modulus, micro-expansion backfill material, the material will expand moderately during the curing process, actively compensating for the deformation caused by the chemical shrinkage and moisture evaporation shrinkage of the material itself, thereby eliminating these initial gaps. This allows the back of the steel plate to obtain full-circumferential, continuous and uniform solid support, ensuring that when the gas storage tank is subjected to high internal pressure, the pressure can be uniformly and continuously transmitted to the sliding layer 1 and the surrounding rock through the filling layer. This avoids the risk of bending stress concentration and instability caused by local suspension or inadequate support of the steel plate, and transforms the double-layer structure from a contact fit to a combined form, making the mechanical force transmission path more reliable.

[0092] It can be explained that step S7 specifically includes: after the steel plate is positioned and stabilized, filling it with low modulus, micro-expansion backfill material (such as polyurethane elastic filler or micro-expansion polymer slurry) by grouting or injection, so that a continuous and uniform support surface is formed behind the steel liner, so as to realize the coordinated force bearing of the steel liner and the sliding layer 1.

[0093] In one embodiment, such as Figure 2 and Figure 3 As shown, before step S5, step S8 should also be included: using a TBM hard rock tunnel boring machine to excavate the tunnel and perform initial support to form a smooth tunnel surface, seal the surrounding rock fissures and pores, and provide a foundation for the construction process of subsequent layers.

[0094] In one embodiment, after construction is completed, the overall structure should also be tested for air tightness, such as by pressure testing, to ensure that there are no leaks before it can be put into use.

[0095] The construction method for the double-layer sealed structure of underground gas storage provided in the above embodiments eliminates the need for formwork during construction, simplifying the process, improving efficiency, and enhancing sealing integrity. Furthermore, the high-elasticity steel plates can be rolled and bent on-site, adapting to various tunnel diameters and complex curved surfaces, demonstrating excellent engineering adaptability. Simultaneously, the traditional formwork and modular assembly are eliminated, replaced by a streamlined construction process involving spraying a sliding layer 1, rolling and bending the steel plates, and continuous welding. This simplifies the process, ensures continuous welds, and prevents joint leakage. Upon completion, a fully sealed double-layer structure is formed, improving both construction efficiency and sealing integrity. Moreover, the continuous sealing structure and ease of maintenance make it suitable not only for underground gas storage facilities in compressed air energy storage power plants but also for underground space projects requiring high airtightness and adaptability, such as natural gas storage facilities and liquefied gas caverns, thus broadening its applicability.

[0096] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A double-layer sealing structure for underground gas storage, disposed on the inner surface of the surrounding rock of the gas storage cavern, characterized in that, include: The slip layer (1) is a flexible material layer that is closely attached to the inner surface of the surrounding rock and is used to absorb and buffer the deformation of the surrounding rock. The high-elastic steel sealing layer (2) is a continuous closed shell made of high-elastic metal material, which is attached to the inner surface of the sliding layer (1) to undergo elastic deformation with the deformation of the sliding layer (1) and to provide an airtight seal. Among them, the stiffness of the slip layer (1) is lower than that of the surrounding rock and the high-elasticity steel sealing layer (2).

2. The double-layer sealing structure for underground gas storage according to claim 1, characterized in that, The slip layer (1) is a coating or roll layer that is continuously covered on the surface of the surrounding rock.

3. The double-layer sealing structure for underground gas storage according to claim 2, characterized in that, The material of the slip layer (1) is one of modified asphalt-based elastomer, EPDM rubber, self-adhesive polymer and high ductility concrete.

4. The double-layer sealing structure for underground gas storage facilities according to any one of claims 1-3, characterized in that, The thickness of the slip layer (1) is 5mm to 20mm.

5. The double-layer sealing structure for underground gas storage facilities according to any one of claims 1-3, characterized in that, The high-elastic steel sealing layer (2) is formed by connecting multiple arc-shaped steel plates through circumferential and axial butt welds.

6. The double-layer sealing structure for underground gas storage facilities according to any one of claims 1-3, characterized in that, A low-modulus, micro-expansion backfill material is filled between the high-elasticity steel sealing layer (2) and the sliding layer (1).

7. The double-layer sealing structure for underground gas storage according to claim 6, characterized in that, Low-modulus, micro-expansion backfill materials use polyurethane elastomers or micro-expansion polymer slurries.

8. A design method for a double-layer sealing structure for an underground gas storage facility, used to design the double-layer sealing structure for an underground gas storage facility as described in any one of claims 1-7, characterized in that, The design methodology includes the following steps: S1: Obtain the design parameters of the gas storage facility, including at least the maximum internal pressure of the gas storage tank. Elastic modulus of surrounding rock Poisson's ratio of surrounding rock Equivalent tensile strength of surrounding rock ; S2: Calculate the minimum elastic limit strain required for the high-elasticity steel sealing layer based on the design parameters. ; S3: Based on the minimum elastic limit strain Determine the yield strength of the steel used in the high-elasticity steel sealing layer. ; S4: Based on the design parameters and the determined steel properties, design the thickness of the slip layer. With elastic modulus This ensures that the deformation coordination conditions between the slip layer and the high-elasticity steel sealing layer are met.

9. A construction method for a double-layer sealed structure for an underground gas storage facility, used for constructing the double-layer sealed structure for an underground gas storage facility as described in any one of claims 1-7, characterized in that, Includes the following steps: S5: A continuous slip layer is formed on the surface of the surrounding rock of the gas storage cavern (1). S6: On the inner side of the slip layer (1), multiple high-elasticity metal plates are welded together to form a closed shell that is attached to the slip layer (1) as a high-elasticity steel sealing layer (2).

10. The construction method for the double-layer sealed structure of an underground gas storage facility according to claim 9, characterized in that, Following step S6, the following is also included: Step S7: Inject low-modulus, micro-expansion backfill material into the gap between the high-elastic steel sealing layer (2) and the sliding layer (1) to form a continuous and uniform support.

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