A structure for treating poor geological sections of an underground high-pressure gas storage reservoir and its design method

Abstract

The present invention provides a treatment structure for poor geological sections of an underground high-pressure gas storage reservoir and a design method thereof. The treatment structure comprises replacement concrete disposed between a weak structural layer and backfill concrete. The replacement concrete has an isosceles trapezoidal cross-section in the radial direction of the gas storage reservoir. The upper base of the isosceles trapezoid is connected to the weak structural layer, the lower base is connected to the backfill concrete, and the two lower sides are connected to the surrounding rock on either side of the replacement concrete. The length L3 of the upper base is less than the length L1 of the lower base. The treatment structure of the present invention can prevent the weak structural layer from causing safety problems in the gas storage reservoir due to its low strength and easy deformation.

Description

Technical Field

[0001] The present invention relates to the technical field of compressed air energy storage, and in particular to a structure for processing poor geological sections of an underground high-pressure gas storage reservoir and a design method thereof. Background Art

[0002] Compressed air energy storage (CAES) uses compressed air as a medium to store energy and generate electricity. Currently, underground chambers such as salt caverns and artificially excavated caverns are commonly used as storage vessels. Rock-lined caverns, among others, can be constructed in widely distributed hard rock formations, offering greater flexibility in site selection and paving the way for large-scale deployment.

[0003] Due to the uncertainty of geological conditions and limitations imposed by factors such as the project site, geological survey level, and project scale, gas storage caverns inevitably intersect or intersect weak structural layers, such as interlayers and faults. Due to their low strength and susceptibility to deformation, these weak structural layers pose a significant threat to the stability of the cavern's surrounding rock and the safety of its sealing structure. Furthermore, the exposed thickness of these weak structural layers varies across different sections of the cavern, and the impact of these layers on cavern structural stability varies. Therefore, appropriate structural treatment and design for these weak structural layers of varying thickness is crucial to ensuring the safety and stability of the gas storage facility during its operation.

[0004] In summary, there is an urgent need for a structure for processing poor geological sections of underground high-pressure gas storage and a design method thereof to solve the problems existing in the prior art. Summary of the Invention

[0005] The present invention aims to provide a structure for treating adverse geological sections of underground high-pressure gas storage facilities, aiming to solve the problem that weak structural layers, due to their low strength and easy deformation, pose a significant threat to the stability of the surrounding rock and the safety of the sealing structure of the cavern. The specific technical solution is as follows:

[0006] A treatment structure for poor geological sections of an underground high-pressure gas storage reservoir, the gas storage reservoir comprising a sealing steel plate, backfill concrete and surrounding rock, wherein the backfill concrete is arranged between the sealing steel plate and the surrounding rock, and the treatment structure comprises replacement concrete arranged between a weak structural layer and the backfill concrete; the cross-section of the replacement concrete in the radial direction of the gas storage reservoir is an isosceles trapezoid, the upper base of the isosceles trapezoid is arranged in contact with the weak structural layer, the lower base is arranged in contact with the backfill concrete, and the two waists are respectively arranged in contact with the surrounding rock on both sides of the replacement concrete, and the length L3 of the upper base is less than the length L1 of the lower base.

[0007] Preferably, in the above technical solution, the length L3 of the upper bottom edge is equal to the maximum thickness of the weak structural layer, and the two end points of the upper bottom edge are respectively connected to the surrounding rocks on both sides of the weak structural layer.

[0008] Preferably, in the above technical solution, the distance L2 between the upper base and the lower base and the length L3 of the upper base satisfy: L2=N·L3, wherein N is 1.5-2.0.

[0009] Preferably, in the above technical solution, the angle θ between the waist side of the isosceles trapezoid and the horizontal plane is 30°-60°.

[0010] The present invention also provides a design method for the treatment structure of the adverse geological section of the underground high-pressure gas storage reservoir, the design method including verifying whether the structural stability safety factor of the current treatment structure is qualified, and the specific steps are as follows:

[0011] S1. Determine the structural dimensions of the gas storage and the proposed dimensions of the processing structure;

[0012] S2. Calculate the thrust force F on the replacement concrete d and the thrust F generated by the internal pressure of the gas storage on the replacement concrete u ;

[0013] S3, according to F d and F u Calculate the structural stability safety factor K of the processed structure s ;

[0014] S4. The structural stability safety factor K s Compared with the specified structural stability safety factor K' s Compare, if K s ≥K′ s The verification is then ended; otherwise, the proposed size of the processing structure and / or the structural size of the gas storage are adjusted and the process returns to step S1.

[0015] The preferred technical solution is to calculate the thrust force F on the replacement concrete according to formula (9): d :

[0016] F d =F s cosθ+F n sinθ (9),

[0017] According to formula (10), the thrust F generated by the internal pressure of the gas storage reservoir on the replacement concrete is calculated as u :

[0018]

[0019] Among them, F n is the normal pressure on the replacement surface of the replacement concrete, F s is the shear force on the replacement surface of the replacement concrete, θ is the angle between the replacement surface and the horizontal direction, p is the internal pressure of the gas storage, p2 is the internal pressure borne by the surrounding rock, σR is the resistance limit of the sealing steel plate, t is the thickness of the sealing steel plate, r is the radius of the sealing steel plate, and L1 is the length of the lower base of the replacement concrete in the radial direction of the gas storage reservoir.

[0020] In the above technical solution, the positive pressure F on the replacement surface of the replacement concrete is calculated according to formula (6): n :

[0021]

[0022] According to formula (7), the shear force F on the replacement surface of the replacement concrete is calculated as s :

[0023]

[0024] Where, dl is the differential unit; L2 is the distance between the upper and lower bases of the replacement concrete; σ n represents the normal stress acting on the displacement surface; τ n represents the shear stress acting on the displacement surface; θ is the angle between the displacement surface and the horizontal direction; f R is the friction coefficient between replacement concrete and surrounding rock.

[0025] The preferred technical solution above is to calculate the normal stress σ acting on the displacement surface according to formula (4): n :

[0026]

[0027] The shear stress τ acting on the displacement surface is calculated according to formula (5): n :

[0028] τ n =σ n f R +C R (5),

[0029] Among them, σ x is the horizontal ground stress of the gas storage reservoir; σ y is the vertical ground stress of the gas storage reservoir; θ is the angle between the displacement surface and the horizontal direction; f R is the friction coefficient between replacement concrete and surrounding rock; C R is the cohesion between replacement concrete and surrounding rock; π is the pi.

[0030] The preferred technical solution is to calculate the structural stability safety factor K of the current processing structure according to formula (11): s :

[0031]

[0032] The present invention also provides another design method for a structure for treating a poor geological section of an underground high-pressure gas storage reservoir. The design method includes determining the most economical thickness of a sealing steel plate. The specific steps are as follows:

[0033] A1. Determine the gas storage cavity diameter and safety level, and the proposed dimensions of the treatment structure;

[0034] A2. Determine the structural stability safety factor K′ specified for replacement concrete based on the hole diameter and safety level of the gas storage reservoir. s At the same time, calculate the thrust force F on the replacement concrete d ;

[0035] A3. Calculate the most economical thickness t' of the sealing steel plate;

[0036]

[0037] Where p is the internal pressure of the gas storage; σ R is the resistance limit of the sealing steel plate; r is the radius of the sealing steel plate; L1 is the length of the lower base of the replacement concrete in the radial direction of the gas storage reservoir.

[0038] The application of the technical solution of the present invention has the following beneficial effects:

[0039] The cross-section of the replacement concrete in the radial direction of the gas storage reservoir is an isosceles trapezoid, and the lower base is the long side, which has a larger contact area with the backfill concrete, reducing the pressure on the replacement concrete and preventing the replacement concrete from being damaged; at the same time, through the two waist sides connected to the surrounding rock, the internal pressure on the replacement concrete can be evenly distributed to the surrounding rocks on both sides, reducing the stress on the weak structural layer, and preventing the weak structural layer from causing safety problems to the gas storage reservoir due to its low strength and easy deformation.

[0040] The design method of the present invention can verify whether the structural stability safety factor of the current processing structure is qualified, promptly discover design deficiencies, and help designers adjust relevant structural dimensions in a timely manner; at the same time, by performing structural stability safety factor verification, it can help designers understand the key factors affecting the structural stability safety factor and provide direction for adjusting the structural stability safety factor.

[0041] The design method of the present invention can help designers quickly determine the most economical thickness of the sealing steel plate, while ensuring the structural stability of the gas storage reservoir in the weak structural layer, and at the same time minimize the thickness of the sealing steel plate to save engineering investment.

[0042] In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0044] Figure 1 is a schematic cross-sectional view of a gas storage reservoir after adopting the processing structure of the present invention;

[0045] Figure 2 yes Figure 1 Schematic diagram of the local structure at A in the middle;

[0046] Figure 3 It is a flow chart for verifying the structural stability safety factor of the current processing structure;

[0047] Figure 4 It is a flow chart for determining the most economical thickness of the sealing steel plate;

[0048] Figure 5 It is a construction flow chart for processing structures;

[0049] Among them, 1-weak structural layer; 2-surrounding rock; 3-replacement concrete; 4-replacement surface; 5-sealing steel plate; 6-backfill concrete; 7-gas storage. DETAILED DESCRIPTION

[0050] To facilitate understanding of the present invention, the present invention will be described more fully below, along with preferred embodiments thereof. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of the present invention.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0052] Example 1:

[0053] The existing underground high-pressure gas storage reservoir 7 is generally a joint load-bearing structure composed of a sealing steel plate 5, backfill concrete 6, and surrounding rock 2; the backfill concrete 6 is arranged between the sealing steel plate 5 and the surrounding rock 2. The function of the sealing steel plate 5 is to prevent the leakage of high-pressure gas and to bear part of the internal pressure; the backfill concrete 6 is a force transmission structure, which is responsible for evenly transmitting the pressure to the surrounding rock 2. The internal pressure it bears can be ignored and serves as a safety reserve; the surrounding rock 2 bears most of the pressure load inside the gas storage reservoir 7.

[0054] Due to the uncertainty of geological conditions and the limitations of many factors such as the scope of the project site, the level of geological survey, and the scale of the project, it is usually inevitable that the gas storage reservoir 7 will pass through or intersect with the weak structural layer 1 (i.e., unfavorable geological sections, such as weak interlayers, faults, etc.). The weak structural layer 1 has problems such as low strength and easy deformation, which poses a great threat to the stability of the surrounding rock and the safety of the sealing structure of the gas storage reservoir 7. In this regard, this embodiment provides a structure for processing unfavorable geological sections of underground high-pressure gas storage reservoirs, such as Figure 1-Figure 2 As shown, the treatment structure includes replacement concrete 3 arranged between the weak structural layer 1 and the backfill concrete 6; the cross-section of the replacement concrete 3 in the radial direction of the gas storage reservoir 7 is an isosceles trapezoid, the upper base of the isosceles trapezoid is connected to the weak structural layer 1, the lower base is connected to the backfill concrete 6, and the two waists are respectively connected to the surrounding rocks 2 on both sides of the replacement concrete 3, and the length L3 of the upper base is less than the length L1 of the lower base.

[0055] In this embodiment, the cross-section of the replacement concrete in the radial direction of the gas storage reservoir is an isosceles trapezoid, with the lower base being the longer side, creating a larger contact area with the backfill concrete 6. This reduces the pressure on the replacement concrete and prevents damage to the replacement concrete. Furthermore, by connecting the two waists with the surrounding rock, the internal pressure on the replacement concrete can be evenly distributed to the surrounding rock on both sides, reducing the stress on the weak structural layer and preventing the weak structural layer from causing safety problems to the gas storage reservoir due to its low strength and easy deformation. During the construction of the replacement concrete 3, a groove is first excavated at the location of the weak structural layer 1 and the groove excavation section is measured. When the groove excavation meets the design requirements, the base surface is cleaned. After the groove excavation is completed, the replacement concrete 3 is poured at the groove excavation location.

[0056] Furthermore, the length L3 of the upper bottom edge is equal to the maximum thickness of the weak structural layer 1, as shown in FIG. Figure 2 As shown, the two end points of the upper base are respectively connected to the surrounding rocks 2 on both sides of the weak structural layer 1; the height L2 of the isosceles trapezoid (i.e., the distance between the upper base and the lower base) and the length L3 of the upper base satisfy: L2 = N·L3, where N is 1.5-2.0, to ensure the structural strength of the replacement concrete 3.

[0057] The waist of the isosceles trapezoid represents the replacement surface 4 where the replacement concrete 3 meets the surrounding rock 2. The angle between the waist of the isosceles trapezoid and the horizontal plane is θ. Although increasing the angle θ can increase the positive pressure F on the replacement surface 4 to a certain extent, n and shear force F s However, considering the construction difficulty of on-site groove excavation and replacement concrete pouring, as well as the structural strength and stress characteristics of the replacement concrete itself, the angle θ between the waist side of the isosceles trapezoid and the horizontal plane is set to 30°-60° in this embodiment.

[0058] Since the cross section of the replacement concrete 3 in the radial direction of the gas storage reservoir 7 is an isosceles trapezoid, the relationship between L1, L2, and L3 satisfies:

[0059] L1=2L2tanθ+L3 (1),

[0060] Preferably, in order to ensure that the structural strength of the replacement concrete 3 itself meets the stress requirements, the strength grade of the replacement concrete in this embodiment is not less than C30.

[0061] In order to ensure the safety of the processing structure in this embodiment and the economy of the gas storage design, this embodiment also provides a design method for the above-mentioned processing structure, which provides detailed processing steps for verifying whether the structural stability safety factor of the current processing structure is qualified and for guiding the rapid determination of the most economical thickness of the sealing steel plate.

[0062] See also Figure 3 , the steps to verify whether the structural stability safety factor of the current processing structure is qualified are as follows:

[0063] S1. Determine the structural dimensions of the gas storage and the proposed dimensions of the processing structure;

[0064] Specifically, the proposed dimensions of the treatment structure include the proposed structural dimensions of the replacement concrete. The proposed dimensions of the treatment structure are determined based on the dimensions of the weak structural layer. Since the cross-section of the replacement concrete in the treatment structure in the radial direction of the gas storage reservoir is an isosceles trapezoid, the structural dimensions of the replacement concrete should meet the requirements of formula (1).

[0065] S2. Calculate the thrust force F on the replacement concrete d and the thrust F generated by the internal pressure of the gas storage on the replacement concrete u ;

[0066] See also Figure 2 , the internal pressure sharing of the gas storage reservoir satisfies formula (2):

[0067] p=p1+p2 (2), where the internal pressure p1 borne by the sealing steel plate can be expressed as:

[0068]

[0069] Where: p is the internal pressure of the gas storage reservoir; p1 is the internal pressure borne by the sealing steel plate (this part of the internal pressure is offset by the deformation of the sealing steel plate); p2 is the internal pressure borne by the surrounding rock; σ R is the resistance limit of the sealing steel plate, in MPa; t is the thickness of the sealing steel plate, in m; r is the radius of the sealing steel plate, in m.

[0070] The normal stress and shear stress on the displacement surface in the limit state are:

[0071]

[0072] τ n =σ n f R +C R (5),

[0073] Among them, σ x is the horizontal ground stress of the gas storage reservoir, in MPa; σ y is the vertical ground stress of the gas storage reservoir, in MPa; θ is the angle between the displacement surface and the horizontal direction, in degrees; f R is the friction coefficient between replacement concrete and surrounding rock; C R is the cohesion between replacement concrete and surrounding rock, in MPa; σ n represents the normal stress acting on the displacement surface; τ n represents the shear stress acting on the displacement surface; π is the circumference of a circle.

[0074] Get the positive pressure F on the displacement surface n and shear force F s for:

[0075]

[0076] Where dl is the differential unit; L2 is the distance between the upper and lower bases of the replacement concrete (i.e., the height of the isosceles trapezoid), in meters.

[0077] Substituting formula (5) into formula (7) yields:

[0078]

[0079] Calculate the thrust force F on the replacement concrete d for:

[0080] F d =F s cosθ+F n sinθ (9),

[0081] The thrust F generated by the internal pressure of the gas storage (the internal pressure here is the internal pressure p2 borne by the surrounding rock) on the replacement concrete u for:

[0082]

[0083] Wherein, L1 is the length of the lower base of the replacement concrete in the radial section of the gas storage reservoir.

[0084] S3. Calculate the structural stability safety factor K of the structure s ;

[0085] The thrust force F on the replacement concrete is obtained. d and the thrust F generated by the internal pressure of the gas storage on the replacement concrete u After that, the structural stability safety factor K of the current processing structure can be calculated according to formula (11): s :

[0086]

[0087] S4. The structural stability safety factor K s Compared with the specified structural stability safety factor K' s Compare, if K s ≥K′ s The verification is then ended; otherwise, the proposed size of the processing structure and / or the structural size of the gas storage are adjusted and the process returns to step S1.

[0088] Specifically, according to the safety level and hole diameter D of the gas storage, the structural stability safety factor K′ specified under the current structural size of the gas storage is obtained by looking up the table. s This embodiment provides different safety levels of gas storage and different hole diameter D specifications for structural stability safety factor K' s The value table of , see Table 1:

[0089] Table 1: Stability safety factor K′ of replacement concrete structure s Value Table

[0090]

[0091] When K s ≥K′ s This indicates that the structural stability safety factor of the treatment structure is qualified under the current proposed size. If K s <K′ s This indicates that the structural stability safety factor of the treatment structure under the current proposed dimensions is unsatisfactory, and the proposed dimensions of the treatment structure and / or the structural dimensions of the gas storage reservoir need to be adjusted (the structural dimensions of the gas storage reservoir refer to the thickness of the sealing steel plate. When the structural dimensions of the gas storage reservoir are not determined, the structural stability safety factor can be adjusted by adjusting the structural dimensions) to ensure the safety of the gas storage reservoir. Steps S1-S4 verify whether the current structural dimensions of the gas storage reservoir and the proposed structural dimensions of the treatment structure meet safety requirements, helping designers to adjust the relevant structural dimensions in a timely manner.

[0092] For further information, see Figure 4 The specific steps to guide the quick determination of the most economical thickness of the sealing steel plate are as follows:

[0093] A1. Determine the diameter and safety level of the gas storage reservoir, and determine the proposed dimensions of the treatment structure;

[0094] Specifically, the hole diameter and safety level of the gas storage reservoir are confirmed according to the design requirements of the gas storage reservoir, and the proposed size of the processing structure is determined to be the same as that in step S1, so it will not be described in detail.

[0095] A2. Determine the structural stability safety factor K′ specified for replacement concrete based on the hole diameter and safety level of the gas storage reservoir. s At the same time, calculate the thrust force F on the replacement concrete d ;

[0096] Specifically, according to the hole diameter and safety level of the gas storage, the structural stability safety factor K′ specified for the replacement concrete is obtained by looking up the table (i.e., looking up Table 1). s Then, the thrust force F exerted on the replacement concrete is calculated according to formula (9): d .

[0097] A3. Calculate the most economical thickness t' of the sealing steel plate;

[0098]

[0099] Where p is the internal pressure of the gas storage; σ R is the resistance limit of the sealing steel plate; r is the radius of the sealing steel plate; L1 is the length of the lower base of the replacement concrete in the radial direction of the gas storage reservoir.

[0100] According to steps A1-A3, after confirming the proposed size of the processing structure, the most economical thickness of the sealing steel plate in the gas storage reservoir can be quickly determined, guiding the thickness selection of the sealing steel plate, thereby saving project investment.

[0101] See also Figure 5 The brief construction steps of the treatment structure for the poor geological section of the underground high-pressure gas storage in this embodiment are as follows:

[0102] B1. Design the thickness of the sealing steel plate and the structural dimensions of the replacement concrete based on the weak structural layer, and determine the final design after verification;

[0103] B2. Carve grooves and excavate the weak structural layer according to the design plan, measure the excavation section, and clean the base surface after it meets the design requirements;

[0104] B3. Install embedded parts such as sensors and grouting pipes;

[0105] B4. Set up formwork and pour replacement concrete;

[0106] B5. After the strength of the replaced concrete meets the requirements, the formwork is removed and backfill grouting is carried out;

[0107] B6. After passing the quality inspection, pour the replacement soil of the next section.

[0108] Example 2:

[0109] The net cross-sectional diameter of a compressed air energy storage cavern is 8m, the designed maximum operating pressure is 8MPa, the safety level of the gas storage is level 1, the sealing steel plate is made of Q490R steel, and the designed thickness of the steel plate is 30mm; the measured ground stress σ x =9MPa,σ y =7MPa; a weak interlayer with a maximum thickness of 0.8m is exposed at the waist of some sections of the cave.

[0110] The design uses C30 replacement concrete, and the structural dimensions of the replacement concrete are L1 = 4.0m; L2 = 1.6m; L3 = 0.8m; θ = 45°; f R Take the value 0.8, C R The value is 0.8MPa. The structural stability safety factor of the replacement concrete is calculated to be K s =1.12, which is greater than the specified 1.10. The replacement concrete structure in this embodiment meets the requirement.

[0111] Example 3:

[0112] The net cross-sectional diameter of a compressed air energy storage cavern is 8m, the designed maximum operating pressure is 8MPa, the safety level of the gas storage is level 1, the sealing steel plate is made of Q490R steel, and the measured ground stress σ x =9MPa,σ y =7MPa, and a weak interlayer with a maximum thickness of 1.0m is exposed at the waist of some sections of the cave.

[0113] The design uses C30 replacement concrete, and the structural dimensions of the replacement concrete are L1 = 5.0m; L2 = 2m; L3 = 1.0m; θ = 45°; f R Take the value 0.8, C R The value is 0.8MPa. Under the premise of ensuring that the structural stability safety factor is not less than 1.10, the most economical sealing steel plate thickness t′=27mm is calculated.

[0114] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A design method for a treatment structure of a poor geological section of an underground high-pressure gas storage reservoir, wherein the gas storage reservoir (7) comprises a sealing steel plate (5), backfill concrete (6) and surrounding rock (2), wherein the backfill concrete (6) is arranged between the sealing steel plate (5) and the surrounding rock (2), and the treatment structure comprises a replacement concrete (3) arranged between the weak structural layer (1) and the backfill concrete (6); the cross section of the replacement concrete (3) in the radial direction of the gas storage reservoir (7) is an isosceles trapezoid, the upper base of the isosceles trapezoid is connected to the weak structural layer (1), the lower base is connected to the backfill concrete (6), and the two waist sides are respectively connected to the surrounding rock (2) on both sides of the replacement concrete (3), and the length of the upper base is 1 / 4. L 3 is less than the length of the lower base L 1. It is characterized by: The design method includes verifying whether the structural stability safety factor of the current treatment structure is qualified, and the specific steps are as follows: S1. Determine the structural dimensions of the gas storage and the proposed dimensions of the processing structure; S2. Calculate the thrust resistance of the replacement concrete and the thrust exerted on the replacement concrete by the internal pressure of the gas storage tank ; S3. According to and Calculate the structural stability safety factor of the processed structure ; S4. Increase the structural stability safety factor and the specified structural stability safety factor Compare, if ≥ The verification is then ended, otherwise the proposed size of the processing structure and / or the structural size of the gas storage are adjusted and the process returns to step S1; According to formula (9), the thrust resistance of the replacement concrete is calculated as follows: : （9）， According to formula (10), the thrust generated by the internal pressure of the gas storage reservoir on the replacement concrete is calculated as follows: : （10）， in, is the normal pressure on the replacement surface of the replacement concrete, is the shear force on the replacement surface of the replacement concrete, θ is the angle between the displacement surface and the horizontal direction, is the internal pressure of the gas storage reservoir, is the internal pressure borne by the surrounding rock, is the resistance limit of the sealing steel plate, is the thickness of the sealing steel plate, is the radius of the sealing steel plate, L 1 is the length of the lower base of the replacement concrete in the radial direction of the gas storage reservoir.

2. The design method according to claim 1, characterized in that: The length of the upper base L 3 is equal to the maximum thickness of the weak structural layer (1), and the two end points of the upper bottom edge are respectively connected to the surrounding rocks (2) on both sides of the weak structural layer (1).

3. The design method according to claim 1, characterized in that: The distance between the upper bottom edge and the lower bottom edge L 2 and the length of the upper base L 3. Satisfy between: ,in N It is 1.5-2.

0.

4. The design method according to claim 1, characterized in that: The angle between the waist side of the isosceles trapezoid and the horizontal plane is θ 30°-60°.

5. The design method according to claim 1, characterized in that: According to formula (6), the normal pressure on the replacement surface of the replacement concrete is calculated as follows: : （6）， Calculate the shear force on the replacement surface of the replacement concrete according to formula (7): : （7）， in, dl is the differential unit; L 2 is the distance between the upper and lower bases of the replacement concrete; represents the normal stress acting on the displacement surface; represents the shear stress acting on the displacement surface; θ is the angle between the displacement surface and the horizontal direction; is the friction coefficient between replacement concrete and surrounding rock.

6. The design method according to claim 5, characterized in that: The normal stress acting on the displacement surface is calculated according to formula (4): : （4）， The shear stress acting on the displacement surface is calculated according to formula (5): : （5）， in, is the horizontal ground stress of the gas storage reservoir; is the vertical ground stress of the gas storage reservoir; θ is the angle between the displacement surface and the horizontal direction; is the friction coefficient between replacement concrete and surrounding rock; To replace the cohesion between concrete and surrounding rock; π is pi.

7. The design method according to claim 1, characterized in that: Calculate the structural stability safety factor of the current treatment structure according to formula (11): : （11）。

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