A method for treating a poor geological section of an underground storage

Abstract

This invention provides a method for treating unfavorable geological sections in underground gas storage facilities. The treatment structure includes replacement concrete placed 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 facility. 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 side edges are connected to the surrounding rock on both sides of the replacement concrete. The length of the upper base is... L 3 is less than the length of the lower base. L 1. The processing structure of the present invention can prevent the weak structural layer from causing safety problems to the gas storage facility due to its low strength and easy deformation.

Description

Technical Field

[0001] This invention relates to the field of compressed air energy storage technology, specifically to a method for treating unfavorable geological sections of underground storage facilities. Background Technology

[0002] Compressed air energy storage is a technology that uses compressed air as a medium to store energy and generate electricity. Currently, underground caverns such as salt caverns and artificially excavated chambers are commonly used as gas storage containers. Among them, rock-lined caverns can be constructed in widely distributed hard rock strata, allowing for more flexible site selection and making them suitable for large-scale promotion.

[0003] Due to the uncertainty of geological conditions and limitations imposed by factors such as the scope of the engineering site, the level of geological exploration, and the scale of the project, gas storage caverns often inevitably traverse or intersect with weak structural layers such as interlayers and faults. Because these weak structural layers have low strength and are easily deformed, they pose a significant threat to the stability of the surrounding rock and the safety of the sealing structure. Furthermore, the exposed thickness of these weak structural layers varies in different sections of the cavern, and the degree of impact on the structural stability of the cavern varies depending on the thickness of the weak structural layers. Therefore, appropriate structural treatment and design for weak structural layers of varying thicknesses are crucial to ensuring the safe and stable operation of the gas storage facility during its operational period.

[0004] In summary, there is an urgent need for a method to treat the unfavorable geological sections of underground storage facilities in order to solve the problems existing in the current technology. Summary of the Invention

[0005] The purpose of this invention is to provide a method for treating underground storage tunnels with unfavorable geological conditions. This method aims to address the problem that weak structural layers, due to their low strength and susceptibility to deformation, pose a significant threat to the stability of the surrounding rock and the safety of the sealing structure. The specific technical solution is as follows: A method for treating a section of underground gas storage with unfavorable geological conditions, the gas storage facility comprising a sealing steel plate, backfill concrete, and surrounding rock, wherein the backfill concrete is disposed between the sealing steel plate and the surrounding rock, and the treatment structure includes replacement concrete disposed between the weak structural layer and the backfill concrete; the replacement concrete has an isosceles trapezoidal cross-section in the radial direction of the gas storage facility, the upper base of the isosceles trapezoid is connected to the weak structural layer, its lower base is connected to the backfill concrete, and its two sides are respectively connected to the surrounding rock on both sides of the replacement concrete, wherein the length of the upper base is... L 3 is less than the length of the lower base. L 1; The design method for the processing structure includes determining the most economical thickness of the sealing steel plate, and the specific steps are as follows: A1. Determine the diameter and safety level of the gas storage facility, and at the same time determine the proposed dimensions of the processing structure; A2. Determine the structural stability safety factor for the replacement concrete based on the diameter and safety level of the gas storage facility. Simultaneously, the thrust force on the replacement concrete is calculated. ; A3. Calculate the most economical thickness of the sealing steel plate. ; (12) in, The internal pressure of the gas storage facility; The resistance limit of the sealing steel plate; The radius of the sealing steel plate; L 1 represents the length of the bottom edge of the replacement concrete section in the radial direction of the gas storage tank.

[0006] Preferably, the length of the upper bottom edge L 3. The maximum thickness of the weak structural layer is equal to that of the upper bottom edge, and the two ends of the upper bottom edge are respectively connected to the surrounding rock on both sides of the weak structural layer.

[0007] Preferably, the distance between the upper bottom edge and the lower bottom edge L 2 and the length of the upper bottom edge L The following conditions must be met between 3: ,in N It is 1.5-2.0.

[0008] Preferably, the angle between the waist of the isosceles trapezoid and the horizontal plane is . θ The range is 30°-60°.

[0009] Preferably, the thrust force on the replacement concrete is calculated according to formula (9). : (9), in, To replace the normal pressure on the replacement surface of the concrete. This refers to the shear force acting on the replacement surface of the replaced concrete. θ The angle between the displacement surface and the horizontal direction.

[0010] Preferably, the shear force on the replacement surface of the replacement concrete is calculated according to formula (7). : (7), in, dl It is a differential unit; L 2 represents the distance between the top and bottom edges of the replacement concrete; This represents the shear stress acting on the replacement surface; This is to replace the friction coefficient between the concrete and the surrounding rock.

[0011] Preferably, the shear stress acting on the replacement surface is calculated according to formula (5). : (5), in, To replace the friction coefficient between the concrete and the surrounding rock; To replace the cohesion between the concrete and the surrounding rock; This represents the normal stress acting on the replacement surface.

[0012] Preferably, the normal pressure on the replacement surface of the replacement concrete is calculated according to formula (6). : (6).

[0013] Preferably, the normal stress acting on the replacement surface is calculated according to formula (4). : (4), in, The horizontal stress in the gas storage facility; The vertical stress in the gas storage facility; π Pi is the mathematical constant of a circle.

[0014] The application of the technical solution of the present invention has the following beneficial effects: The replacement concrete of this invention has an isosceles trapezoidal cross-section in the radial direction of the gas storage facility. The bottom side is the long side, which has a large contact area with the backfill concrete, reducing the pressure on the replacement concrete and preventing damage to it. At the same time, by connecting with the surrounding rock through the two waist sides, 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 facility due to its low strength and easy deformation.

[0015] The design method of this invention can help designers quickly determine the most economical thickness of the sealing steel plate, and minimize the thickness of the sealing steel plate to save on engineering investment while ensuring the structural stability of the gas storage facility in the weak structural section.

[0016] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the cross-section of the gas storage tank after the structure is processed using the present invention; Figure 2 yes Figure 1 A schematic diagram of the local structure at point A in the middle; Figure 3 This is a flowchart for verifying the structural stability and safety factor of the current processing structure; Figure 4 This is a flowchart for determining the most economical thickness of the sealing steel plate; Figure 5 It is a construction flowchart for handling the structure; 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 Implementation

[0018] To facilitate understanding of the present invention, a more complete description is provided below, along with preferred embodiments. 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 thorough and complete understanding of the disclosure of the present invention.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0020] Example 1: Existing underground high-pressure gas storage facilities 7 are generally constructed using a combined load-bearing structure consisting of a sealing steel plate 5, backfill concrete 6, and surrounding rock 2. The backfill concrete 6 is placed between the sealing steel plate 5 and the surrounding rock 2. The sealing steel plate 5 serves to prevent high-pressure gas leakage and bear part of the internal pressure. The backfill concrete 6 is a force-transmitting structure, responsible for uniformly transmitting pressure to the surrounding rock 2. The internal pressure it bears is negligible and serves as a safety reserve. The surrounding rock 2 bears the majority of the pressure load inside the gas storage facility 7.

[0021] Due to uncertainties in geological conditions and limitations imposed by factors such as the project site scope, geological exploration level, and project scale, gas storage 7 often inevitably traverses or intersects with weak structural layers 1 (i.e., unfavorable geological sections, such as weak interlayers, faults, etc.). Weak structural layers 1 suffer from low strength and easy deformation, posing a significant threat to the stability of the surrounding rock and the safety of the sealing structure of gas storage 7. Therefore, this embodiment provides a structure for treating unfavorable geological sections in underground high-pressure gas storage, such as... Figures 1-2As shown, the treatment structure includes replacement concrete 3 disposed between the weak structural layer 1 and the backfill concrete 6; the replacement concrete 3 has an isosceles trapezoidal cross-section in the radial direction of the gas storage tank 7, with its upper base connected to the weak structural layer 1, its lower base connected to the backfill concrete 6, and its two sides connected to the surrounding rock 2 on both sides of the replacement concrete 3. The length of the upper base is... L 3 is less than the length of the lower base. L 1.

[0022] In this embodiment, the replacement concrete has an isosceles trapezoidal cross-section in the radial direction of the gas storage tank. The lower base is the longer side, providing a large contact area with the backfill concrete 6, reducing the pressure on the replacement concrete and preventing damage. Simultaneously, by connecting to the surrounding rock on both sides through the two waist edges, 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 safety issues caused by the low strength and easy deformation of the weak structural layer. During the construction of the replacement concrete 3, a groove is first excavated at the location of the weak structural layer 1, and the excavated section is measured. After meeting the design requirements, the base surface is cleaned. After the groove excavation is completed, the replacement concrete 3 is poured at the excavated location.

[0023] Furthermore, the length of the upper bottom edge L 3 has the same maximum thickness as the weak structural layer 1, such as Figure 2 As shown, the two endpoints of the upper base are respectively connected to the surrounding rock 2 on both sides of the weak structural layer 1; the height of the isosceles trapezoid... L 2 (i.e., the distance between the top and bottom edges) and the length of the top edge L The following conditions must be met between 3: ,in N The value is 1.5-2.0 to ensure the structural strength of the replacement concrete 3.

[0024] The side of the isosceles trapezoid represents the replacement surface 4 where the replacement concrete 3 meets the surrounding rock 2. The angle between the side of the isosceles trapezoid and the horizontal plane is... θ Although increasing the included angle θ It can increase the normal pressure on the replacement surface 4 to a certain extent. and shear force However, considering the construction difficulties of on-site grooving and excavation, and the pouring of replacement concrete, as well as the structural strength and stress characteristics of the replacement concrete itself, this embodiment takes the angle between the waist side of the isosceles trapezoid and the horizontal plane. θ The range is 30°-60°.

[0025] Since the replacement concrete 3 has an isosceles trapezoidal cross-section in the radial direction of the gas storage tank 7, therefore L1. L 2. L 3. The relationship between the three satisfies: (1), Preferably, to ensure that the structural strength of the replacement concrete 3 meets the stress requirements, in this embodiment, the strength grade of the replacement concrete is not less than C30.

[0026] To ensure the safety of the processing structure and the economy of the gas storage design in this embodiment, this embodiment also provides a design method for the above-mentioned processing structure. The design method 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.

[0027] See Figure 3 The specific steps for verifying whether the structural stability safety factor of the currently processed structure is qualified are as follows: S1. Determine the structural dimensions of the gas storage facility and the proposed dimensions of the processing structure; 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 radial direction of the gas storage tank is an isosceles trapezoid, the structural dimensions of the replacement concrete should meet the requirements of formula (1).

[0028] S2. Calculate the thrust force on the replacement concrete. The thrust generated by the internal pressure of the gas storage tank on the replacement concrete. ; See Figure 2 The pressure sharing within the gas storage facility satisfies formula (2): (2), The internal pressure borne by the sealing steel plate It can be represented as: (3), in: The internal pressure of the gas storage facility; The internal pressure borne by the sealing steel plate (this internal pressure is offset by the deformation of the sealing steel plate); The internal pressure borne by the surrounding rock; The resistance limit of the sealing steel plate is expressed in MPa. The thickness of the sealing steel plate is expressed in meters (m). The radius of the sealing steel plate is in meters (m).

[0029] The normal stress and shear stress on the replacement surface under the limit state are: (4), (5), in, The horizontal stress of the gas storage facility is expressed in units of... ; The vertical stress of the gas storage facility is expressed in units of . ; θ The angle between the displacement surface and the horizontal direction, in degrees; To replace the friction coefficient between the concrete and the surrounding rock; The unit is the cohesion between the replacement concrete and the surrounding rock. ; This represents the normal stress acting on the replacement surface; This represents the shear stress acting on the replacement surface; π Pi is the mathematical constant of a circle.

[0030] Obtain the normal pressure on the replacement surface and shear force for: (6), (7), in, dl It is a differential unit; L 2 represents the distance between the upper and lower bases of the replacement concrete (i.e., the height of the isosceles trapezoid), in meters.

[0031] Substituting formula (5) into formula (7) yields: (8), Calculate the thrust force on the replacement concrete. for: (9), The internal pressure exerted on the replacement concrete by the gas storage tank (the internal pressure here is the internal pressure borne by the surrounding rock). The thrust generated for: (10) in, L 1 represents the length of the bottom edge of the replacement concrete section in the radial direction of the gas storage tank.

[0032] S3. Calculate the structural stability safety factor of the processed structure. ; To obtain the thrust force experienced by the replacement concrete. The thrust generated by the internal pressure of the gas storage tank on the replacement concrete. Then, the structural stability safety factor of the current structure can be calculated according to formula (11). : = (11), S4. Adjust the structural stability safety factor. With the specified structural stability safety factor Perform a comparison, if ≥ If the verification ends, then the process ends; otherwise, adjust the proposed dimensions of the processing structure and / or the structural dimensions of the gas storage tank and return to step S1.

[0033] Specifically, the structural stability safety factor for the current gas storage facility is obtained by referring to a table based on the safety level and tunnel diameter D. This embodiment provides structural stability safety factors for different gas storage facility safety levels and different tunnel diameters (D). The value table is shown in Table 1: Table 1: Stability Safety Factor of Replacement Concrete Structures Value table when ≥ This indicates that the structural stability safety factor of the structure under the current proposed dimensions is qualified. This indicates that the structural stability safety factor of the treatment structure under the current proposed dimensions is unqualified, and it is necessary to adjust the proposed dimensions of the treatment structure and / or the structural dimensions of the gas storage tank (here, the structural dimensions of the gas storage tank refer to the thickness of the sealing steel plate; when the structural dimensions of the gas storage tank are not determined, the structural stability safety factor can be adjusted by adjusting the structural dimensions of the gas storage tank) to ensure the safety of the gas storage tank. Steps S1-S4 can verify whether the current structural dimensions of the gas storage tank and the current proposed structural dimensions of the treatment structure meet the safety requirements, helping designers to adjust the relevant structural dimensions in a timely manner.

[0034] Further, see Figure 4 The specific steps for quickly determining the most economical thickness of the sealing steel plate are as follows: A1. Determine the diameter and safety level of the gas storage facility, and at the same time determine the proposed dimensions of the processing structure; Specifically, the diameter and safety level of the gas storage facility are confirmed according to the design requirements of the gas storage facility. The proposed dimensions of the treatment structure are the same as in step S1, so they will not be explained further.

[0035] A2. Determine the structural stability safety factor for the replacement concrete based on the diameter and safety level of the gas storage facility. Simultaneously, the thrust force on the replacement concrete is calculated. ; Specifically, the structural stability safety factor specified for the replacement concrete is obtained by referring to the table (i.e., Table 1) based on the diameter and safety level of the gas storage facility. Then, the thrust force on the replacement concrete is calculated according to formula (9). .

[0036] A3. Calculate the most economical thickness of the sealing steel plate. ; (12) in, The internal pressure of the gas storage facility; The resistance limit of the sealing steel plate; The radius of the sealing steel plate; L 1 represents the length of the bottom edge of the replacement concrete section in the radial direction of the gas storage tank.

[0037] By following steps A1-A3, after confirming the proposed dimensions of the treatment structure, the most economical thickness of the sealing steel plate in the gas storage facility can be quickly determined, guiding the selection of the sealing steel plate thickness and achieving the effect of saving project investment.

[0038] See Figure 5 The simplified construction steps for the treatment structure of the unfavorable geological section of the underground high-pressure gas storage facility in this embodiment are as follows: B1. Based on the thickness of the sealing steel plate and the structural dimensions of the replacement concrete, the final design scheme is determined after verification. B2. According to the design plan, grooves are excavated at the location of the weak structural layer, the excavation section is measured, and the base surface is cleaned after the design requirements are met. B3. Install embedded components such as sensors and grouting pipes; B4. Erect formwork and pour replacement concrete; B5. After the replacement concrete has reached the required strength, remove the formwork and proceed with backfilling and grouting. B6. After passing the quality inspection, the replacement soil for the next section will be poured.

[0039] Example 2: A compressed air energy storage cavern has a net cross-sectional diameter of 8m, a design maximum operating pressure of 8MPa, a safety level of Class I, and uses Q490R steel for sealing, with a design thickness of 30mm. The measured ground stress within the cavern is... , The waist of some sections of the cavern contains a weak interlayer with a maximum thickness of 0.8m.

[0040] The design uses C30 replacement concrete, and the structural dimensions of the replacement concrete are: 4.0m; 1.6m; 0.8m; 45°; The value is 0.8. The value is taken as 0.8 MPa. The calculated structural stability safety factor for the replacement concrete is: =1.12, which is greater than the specified 1.10. Therefore, the replacement concrete structure in this embodiment meets the requirements.

[0041] Example 3: A compressed air energy storage cavern has a net cross-sectional diameter of 8m, a design maximum operating pressure of 8MPa, a safety level of Class I, and Q490R steel for sealing. The measured ground stress within the cavern is... , In some sections of the cave, a weak interlayer with a maximum thickness of 1.0m is exposed at the waist.

[0042] The design uses C30 replacement concrete, and the structural dimensions of the replacement concrete are: 5.0m; 2m; 1.0m; 45°; The value is 0.8. The value is taken as 0.8 MPa. Under the premise that the structural stability safety factor is not less than 1.10, the most economical sealing steel plate thickness is calculated. 27mm.

[0043] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for treating a section of underground storage facility with unfavorable geological conditions, the gas storage facility (7) comprising a sealing steel plate (5), backfill concrete (6), and surrounding rock (2), wherein the backfill concrete (6) is disposed between the sealing steel plate (5) and the surrounding rock (2), characterized in that, The treatment structure includes replacement concrete (3) disposed between the weak structural layer (1) and the backfill concrete (6); the replacement concrete (3) has an isosceles trapezoidal cross section in the radial direction of the gas storage tank (7), the upper base of the isosceles trapezoid is connected to the weak structural layer (1), its lower base is connected to the backfill concrete (6), and its two sides are connected to the surrounding rock (2) on both sides of the replacement concrete (3), the length of the upper base is... L 3 is less than the length of the lower base. L 1; The design method for the processing structure includes determining the most economical thickness of the sealing steel plate, and the specific steps are as follows: A1. Determine the diameter and safety level of the gas storage facility, and at the same time determine the proposed dimensions of the processing structure; A2. Determine the structural stability safety factor for the replacement concrete based on the diameter and safety level of the gas storage facility. Simultaneously, the thrust force on the replacement concrete is calculated. ; A3. Calculate the most economical thickness of the sealing steel plate. ; （12）， in, The internal pressure of the gas storage facility; The resistance limit of the sealing steel plate; The radius of the sealing steel plate; L 1 represents the length of the bottom edge of the replacement concrete section in the radial direction of the gas storage tank; The thrust force on the replacement concrete is calculated according to formula (9). : （9）， in, To replace the normal pressure on the replacement surface of the concrete. This refers to the shear force acting on the replacement surface of the replaced concrete. θ The angle between the displacement surface and the horizontal direction.

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

3. The processing 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 bottom edge L The following conditions must be met between 3: ,in N It is 1.5-2.

0.

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

5. The processing method according to any one of claims 1-4, characterized in that, Calculate the shear force on the replacement surface of the replacement concrete according to formula (7). : （7）， in, dl It is a differential unit; L 2 represents the distance between the top and bottom edges of the replacement concrete; This represents the shear stress acting on the replacement surface; This is to replace the friction coefficient between the concrete and the surrounding rock.

6. The processing method according to claim 5, characterized in that, Calculate the shear stress acting on the replacement surface according to formula (5). : （5）， in, To replace the friction coefficient between the concrete and the surrounding rock; To replace the cohesion between the concrete and the surrounding rock; This represents the normal stress acting on the replacement surface.

7. The processing method according to claim 6, characterized in that, The normal pressure on the replacement surface of the replacement concrete is calculated according to formula (6). : （6）。 8. The processing method according to claim 7, characterized in that, The normal stress acting on the replacement surface is calculated according to formula (4). : （4）， in, The horizontal stress in the gas storage facility; The vertical stress in the gas storage facility; π Pi is the mathematical constant of a circle.

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