An underground gas storage tunnel

Abstract

The application discloses an underground gas storage tunnel, belongs to the technical field of underground pressure gas storage, and is mainly used for storing high-pressure gas and generating power by using the high-pressure gas. The application aims to provide an underground gas storage tunnel, which comprises a gas storage unit and a vertical shaft. The gas storage unit comprises horizontal sections and bending parts. The horizontal sections are multiple and are arranged at intervals. Adjacent horizontal sections are connected in a head-to-tail mode through the bending parts to form a serpentine structure. One end of the vertical shaft is connected to the ground, and the other end is connected to the gas storage unit. The inner wall of the gas storage unit comprises, from outside to inside, a rock-soil body, a lining and a sealing layer. The multiple horizontal sections are connected through the bending parts to form a serpentine structure of the gas storage unit. The range of exploration required before construction is small, and the gas storage tunnel is less restricted by factors such as site and geology. The input and output of gas can be completed by using one vertical shaft, power conversion is realized, and the cost of construction of multiple vertical shafts is saved.

Description

Technical Field

[0001] This invention relates to the field of underground pressure gas storage (CAES), specifically to an underground gas storage tunnel. Background Technology

[0002] Compressed air energy storage (CAES) is a technology for large-scale storage of electrical energy. Its working principle is as follows: when the energy supply exceeds the basic electricity demand, the surplus electricity from the power grid is used to compress air under high pressure, or the air is compressed under high pressure using energy that is not easy to store, such as waste wind power and waste solar power generated by renewable energy sources. The compressed high-pressure air is then stored in an air storage device. When there is a demand for electricity, the compressed high-pressure air is released to drive a turbine to generate electricity.

[0003] The gas storage equipment can be either surface steel tanks or underground gas storage facilities. Compared with surface steel tanks, underground gas storage facilities have a larger storage capacity, greater mobility, and a wider peak-shaving range. Although they are more expensive, they are durable and have a high safety factor, so underground gas storage facilities are often used as gas storage equipment.

[0004] Underground gas storage facilities mainly fall into four categories: abandoned mine shafts, underground aquifers, salt caves, and artificial caves. However, because underground gas storage facilities involve high-pressure and variable-pressure storage, with storage pressures ranging from 5MPa to 30MPa, the requirements for the pressure-bearing capacity, airtightness, and safety of the storage structure are high. The number of usable gas storage facilities of the first three types (abandoned mine shafts, underground aquifers, and salt caves) that meet these requirements is limited. For example, the invention "Underground Gas Storage Facility and its Site Selection and Renovation Method" with application number 202111142705.3 utilizes natural... The characteristics of the layer enable gas sealing, which has high requirements for site selection. When the characteristics of the natural strata cannot be used for gas sealing, sealing materials or steel plates are usually used for sealing, such as the gas sealing method mentioned in the invention "Independently Operable Intersection-Free Compressed Gas Energy Storage Underground High-Pressure Gas Storage System and Method" with application number 202211535611.7. In order to ensure the gas storage capacity, its shape will be adjusted according to geological conditions to ensure the capacity. Therefore, the irregular shape of the gas storage is not convenient for laying sealing materials or steel plates.

[0005] Underground gas storage tunnels, as a type of man-made cave gas storage facility, are often chosen when it is impossible to build gas storage facilities using abandoned mines, underground aquifers, or rock salt caves due to their convenient site selection and construction. To ensure the smooth flow of gas storage, long, straight tunnels are often used. However, long, straight tunnels have the following problems: ① They occupy a long and narrow area and have many limitations in their layout; ② They require extensive geological exploration and a large amount of work; ③ The geological conditions through which the tunnel passes are complex and variable; ④ There are many types of support structures and they are complex. Summary of the Invention

[0006] This invention provides an underground gas storage tunnel that facilitates the installation of a sealing layer. The folded tunnel design concentrates the land area, ensures gas storage capacity, reduces the scope of pre-construction exploration, is less constrained by site and geological factors, and saves construction costs.

[0007] The present invention discloses an underground gas storage tunnel, including a vertical shaft and a gas storage unit. The gas storage unit includes horizontal sections and bending sections. There are multiple horizontal sections and they are spaced apart in the same horizontal plane. Every two adjacent horizontal sections are connected end to end through the bending section to form a serpentine structure.

[0008] One end of the vertical shaft extends above the ground, and the other end is vertically connected to the gas storage unit.

[0009] The horizontal section and the inner wall of the bend are, from the outside to the inside, the soil body, the lining and the sealing layer.

[0010] Furthermore, multiple gas storage units are arranged along the vertical direction of the shaft, and the multiple gas storage units are connected into a whole through the shaft. A vertical clearance S1 is provided between every two layers of gas storage units. The vertical clearance S1 should satisfy: S1≥m1H; where: m1 is the ratio of S1 to H, m1=2 for Class I surrounding rock, m1=2.5 for Class II surrounding rock, m1=3 for Class III surrounding rock, and m1=4 for Class IV surrounding rock; H is the tunnel height.

[0011] In a preferred embodiment, the vertical shaft includes vertical shaft I and vertical shaft II, with multiple odd-numbered gas storage units connected through vertical shaft I and multiple even-numbered gas storage units connected through vertical shaft II.

[0012] As a preferred approach, the vertical clearance S1 is determined based on the tunnel surrounding rock grade, gas storage pressure, original formation pressure, and finite element and numerical calculation analysis, so that the rock mass plastic zone between adjacent gas storage units is not connected.

[0013] Furthermore, the spacing S should satisfy:

[0014]

[0015] Where: m is the ratio of S to B, m = 2 for Class I surrounding rock, m = 2.5 for Class II surrounding rock, m = 3 for Class III surrounding rock, and m = 4 for Class IV surrounding rock; Pu is the overall tunnel uplift failure limit value, F is the safety factor, generally not less than 2.0, γ is the average unit weight of the soil and rock above the calculation surface, H is the tunnel burial depth, n is the number of horizontal sections in the gas storage unit of this layer, S is the distance between adjacent horizontal sections, B is the tunnel width, k = ν / (1-ν) is the lateral pressure coefficient, ν is the Poisson's ratio of the rock mass, φ is the internal friction angle of the rock mass, P max p is the maximum gas storage pressure inside the gas storage tunnel. maxThe tunnel as a whole experiences upward lifting force.

[0016] Furthermore, the bent portion is semi-circular, and the diameter of the semi-circle is consistent with the spacing S.

[0017] Furthermore, the vertical shaft is located at the midpoint of the central horizontal section of the gas storage unit.

[0018] Furthermore, the cross-sectional shape of the horizontal segment and the bent portion is elliptical, circular, or horseshoe-shaped.

[0019] Furthermore, the sealing layer is made of composite steel-plastic composite board or polymer resin board.

[0020] As a preferred embodiment, the polymer resin board is modified ultra-high molecular weight polyethylene, heat-resistant polyethylene, or polybutene.

[0021] The beneficial effects of this invention are as follows: By setting up an underground gas storage tunnel, it is convenient to select a site for construction. Since the cross-section of the underground gas storage tunnel is uniform and has a regular arc surface, it is convenient to lay a sealing layer. At the same time, the setting of bending section connects multiple spaced horizontal sections to form a serpentine gas storage unit, so that gas input and output can be completed with only one vertical shaft, realizing power conversion and saving the cost of constructing multiple vertical shafts. In addition, since the underground gas storage tunnel is a serpentine structure, compared with a long straight gas storage tunnel of the same gas storage capacity, its land occupation is concentrated, the area required for pre-construction exploration is smaller, and it is less constrained by site and geological factors. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the single-layer underground gas storage tunnel structure of the present invention;

[0023] Figure 2 This is a schematic diagram of the structure of a gas storage unit according to the present invention;

[0024] Figure 3 for Figure 1 The front view;

[0025] Figure 4 This is a schematic diagram of the multi-layer underground gas storage tunnel structure of the present invention;

[0026] Figure 5 A schematic diagram of the structure of a vertical shaft for a multi-layer underground gas storage tunnel according to the present invention;

[0027] Figure 6 This is a schematic diagram of the structure of the multi-layer underground gas storage tunnel of the present invention, which includes two vertical shafts.

[0028] Figure 7 This is a schematic diagram of the first cross-section of the underground gas storage tunnel of the present invention;

[0029] Figure 8This is a schematic diagram of a second cross-section of the underground gas storage tunnel of the present invention;

[0030] Figure 9 This is a schematic diagram of the third cross-section of the underground gas storage tunnel of the present invention.

[0031] Attached reference numerals: 1-Horizontal section; 2-Bend; 3-Vertical shaft; 31-Vertical shaft I; 32-Vertical shaft II; 4-Ground plane; 5-Surface soil and rock; 6-Soil and rock body; 7-Liner; 8-Sealing layer. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0033] An underground gas storage tunnel includes a vertical shaft 3 and a gas storage unit. The gas storage unit includes a horizontal section 1 and a bending section 2. There are multiple horizontal sections 1, which are spaced apart in the same horizontal plane. Every two adjacent horizontal sections 1 are connected end to end by the bending section 2 to form a serpentine structure.

[0034] One end of the vertical shaft 3 extends to the ground, and the other end is vertically connected to the gas storage unit.

[0035] The inner walls of the horizontal section 1 and the bending section 2, from the outside to the inside, consist of the soil and rock body 6, the lining 7, and the sealing layer 8.

[0036] The aforementioned underground gas storage tunnel is a sealed tunnel. External gas is connected to the underground gas storage tunnel via a vertical shaft 3, and compressed gas is stored through multiple horizontal sections 1 and bends 2. To avoid excessively long horizontal sections 1 requiring extensive geological surveys, multiple horizontal sections 1 are spaced apart on the same horizontal plane. Each pair of adjacent horizontal sections 1 is connected end-to-end by the bends 2 to form a serpentine gas storage unit. The vertical shaft 3 connects to the gas storage unit, allowing one vertical shaft 3 to meet the gas input and output needs of multiple horizontal sections 1 and bends 2. Simultaneously, to effectively avoid stress concentration and excessive gas residue at bends, the plane of the bends 2 is arc-shaped. To ensure underground... To ensure the impermeability of the gas storage tunnel and prevent groundwater from seeping into it, the lining 7 can be lined with impermeable concrete or grouting material, or with admixtures to improve its impermeability. To ensure the airtightness of the underground gas storage tunnel, a sealing layer 8 is installed outside the tunnel lining. The sealing layer 8 can be made of welded steel plate, steel-plastic composite plate, or polymer resin plate. In addition to ensuring the airtightness of the tunnel, the sealing layer 8 can also serve as temporary support during construction to prevent local rockfalls and ensure construction safety. When in use, in addition to preventing gas leakage, it can also become an integral part of the rock mass, jointly bearing the internal gas pressure and preventing severe deformation and instability of the surrounding rock of the tunnel.

[0037] The aforementioned underground gas storage tunnel relies solely on shaft 3 for gas input and output. The top of shaft 3 is connected to both an inlet pipe and an outlet pipe. The air pressure inside the inlet pipe is higher than that inside the sealed tunnel, while the air pressure inside the outlet pipe is lower than that inside the sealed tunnel. When filling with gas, the inlet pipe valve is opened while the outlet pipe valve is closed; when releasing gas, the outlet pipe valve is opened while the inlet pipe valve is closed.

[0038] In addition to being used in compressed air energy storage, this underground gas storage tunnel can also be used to store natural gas when necessary. When used in compressed air energy storage, the gas (air) in the tunnel does not need to be completely discharged. It can be used to generate electricity and store energy by utilizing pressure differences (such as 6-10 MPa, the pressure variation range inside the tunnel). When used to store natural gas and other media, like other types of underground gas storage facilities, the presence of residual gas in the storage facility is allowed.

[0039] To expand gas storage capacity without extending the geological exploration area of ​​the gas storage tunnel, and to concentrate the land area of ​​the gas storage tunnel for convenient gas storage, multiple gas storage units are arranged vertically along the shaft 3. These multiple gas storage units are connected into a whole through the shaft 3, with a vertical clearance S2 between every two layers of gas storage units. Multiple gas storage units are arranged downwards along the vertical direction of the shaft 3 and connected to form a whole. Gas is input and output through the shaft 3, and the gas pressure is controlled within a specified range. To facilitate subsequent use and avoid the excavation of each gas storage unit affecting adjacent gas storage units, a vertical clearance S1 is provided between every two layers of the gas storage units. The vertical clearance S1 should satisfy: S1≥m1H, where m1 is the ratio of S1 to H. For Class I surrounding rock, m1=2; for Class II surrounding rock, m1=2.5; for Class III surrounding rock, m1=3; and for Class IV surrounding rock, m1=4. H is the tunnel height. This is to meet the minimum value of the vertical clearance S1 and reduce the mutual influence between adjacent gas storage units during construction.

[0040] To achieve simultaneous gas storage and power generation at multiple locations, the vertical shaft 3 includes vertical shaft I 31 and vertical shaft II 32. Multiple odd-numbered layers of the gas storage units are connected through vertical shaft I 31, and multiple even-numbered layers of the gas storage units are connected through vertical shaft II 32. Multiple vertical shafts 3 are used to ensure that compressed gas from multiple locations is stored in the underground gas storage tunnel or that a portion of the gas in the underground gas storage tunnel is used for power generation. Simultaneously, by setting up vertical shafts I 31 and II 32, the gas storage units are divided into two independent gas storage sections: odd-numbered layers and even-numbered layers. Figure 6As shown, there are four gas storage units from top to bottom. The first and third gas storage units are connected through vertical shaft I31, and the second and fourth gas storage units are connected through vertical shaft II32. When generating electricity using the odd-numbered gas storage units, the pressure inside the tunnel decreases as the high-pressure gas is released. If the gas pressure is insufficient in the later stages, the even-numbered gas storage units will be used to supplement the pressure to meet the power generation requirements. Secondly, when a section of the gas storage unit needs maintenance, it is not necessary to stop the operation of all gas storage units for maintenance. Only the odd-numbered or even-numbered gas storage section where the gas storage unit is located needs to be stopped for maintenance, which facilitates maintenance construction.

[0041] The spacing between tunnel layers varies depending on the type of surrounding rock. To prevent the plastic zones of adjacent gas storage units from becoming interconnected and to avoid mutual interference during excavation, which could lead to changes in the stability of the surrounding rock, the spacing S1 between two adjacent gas storage units should not be less than m times the tunnel height H, i.e., S1 ≥ mH, where m is the ratio of S1 to H. For Class I surrounding rock, m = 2; for Class II surrounding rock, m = 2.5; for Class III surrounding rock, m = 3; and for Class IV surrounding rock, m = 4. While meeting the minimum value, the specific value of the vertical net distance S1 can be determined based on the tunnel surrounding rock grade, gas storage pressure, original formation pressure, and finite element and numerical calculation analysis.

[0042] The finite element analysis calculation steps before the construction of the aforementioned underground gas storage tunnel are as follows: ① Determine the power station construction area, determine the volume of the underground gas storage tunnel based on the required compressed air volume, and build a three-dimensional geological model based on geological survey data. The model's scope extends outward from the outer edge of the tunnel by three times its diameter on the left, right, and lower sides, and extends to the ground surface on the upper side; ② Define various physical and mechanical properties of each layer of rock and soil (unit weight, elastic modulus, Poisson's ratio, cohesion, internal friction angle, tensile strength, etc.) and assign them to the corresponding rock and soil layers; ③ If there are weak structural surfaces in the rock strata, they should be modeled and simulated together. At the same time, the mechanical properties of the rock strata within the range of rock mass damage caused by construction should be reduced based on the actual construction method. Specifically, the reduction is based on the integrity of the rock mass within the damage range, such as C′=KvC, φ′=arctan(tan(Kvφ)), where Kv is the rock mass integrity coefficient, Kv=E′ / E=(V′ / V). 2E and E′ represent the elastic modulus of the undisturbed rock and the damaged rock mass, respectively; V and V′ represent the acoustic velocities of the undisturbed rock and the damaged rock mass, respectively, which can be tested by acoustic waves; C and C′ represent the cohesion of the undisturbed rock and the damaged rock mass, respectively; φ and φ′ represent the internal friction angles of the undisturbed rock and the damaged rock mass, respectively. ④ Simulate the tunnel opening during construction and perform construction stage verification calculations. ⑤ Incorporate the tunnel lining and panels into the model, apply gas storage pressure according to changes in gas storage pressure, and perform stress and deformation verification calculations during the operation stage. ⑥ Review the model calculation results, focusing on stress concentration and the development of the plastic zone in the rock mass. If the plastic zones of the upper and lower tunnels are connected, the vertical clearance between the tunnels should be increased, and the calculations should be repeated until the plastic zone connection is no longer observed.

[0043] The above modeling and analysis can be performed using software such as ANSYS, FLAC 3D, ABQS, and Midas GTS.

[0044] After the analysis and calculations are completed and the corresponding tunnel dimensions are determined, tunnel construction and excavation will commence. First, mechanical excavation (shallow soil excavation) and drilling and blasting (rock strata) methods will be used sequentially for shaft excavation and support. Because the shaft needs to function as both a construction passage and an air intake / exhaust channel, its dimensions must accommodate gas input and output, as well as the entry and exit of various construction equipment during construction. After the shaft excavation and support are completed, horizontal connecting sections will be excavated from the shaft towards both ends. The excavation of these horizontal connecting sections can be carried out using conventional drill-and-blast methods, while the aforementioned bending sections will be constructed using controlled drill-and-blast methods. To minimize the impact of blasting damage on the bedrock bearing capacity, flexible, foldable panels are used at bends, facilitating installation while ensuring good sealing. To reduce the impact of construction on the surrounding rock of excavated or unexcavated gas storage sections within the same horizontal plane, the spacing between horizontal sections is set according to different rock types, generally with a horizontal spacing S not less than twice the tunnel width. For Class I-III surrounding rock, tunnels with spans of less than 10m without support can achieve basic self-stability during construction, and the integrated lining and panels formed after construction also provide support and reinforcement for soil and rock stability. Specifically, a three-dimensional geological model can be established to simulate the actual layout of the gas storage tunnel, analyze the construction and operation stages (gas pressure changes), and control stress and deformation indicators to meet specifications. Furthermore, the setting of the sealing layer 8 can be adjusted according to the actual construction steps. For example, if the lining is laid using high-pressure grouting, the panels should be laid first and then grouting; if it is reinforced concrete lining, the lining should be constructed first and then the sealing layer laid.

[0045] To avoid the two adjacent horizontal sections 1 being too close together, causing mutual interference during excavation and resulting in changes in the stability of the tunnel surrounding rock; and to meet the overall tunnel's resistance to uplift failure requirements, the spacing S should satisfy:

[0046]

[0047] Where: m is the ratio of S to B, m = 2 for Class I surrounding rock, m = 2.5 for Class II surrounding rock, m = 3 for Class III surrounding rock, and m = 4 for Class IV surrounding rock; Pu is the overall tunnel uplift failure limit value, F is the safety factor, generally not less than 2.0, γ is the average unit weight of the soil and rock above the calculation surface, H is the tunnel burial depth, n is the number of horizontal sections in the gas storage unit of this layer, S is the distance between adjacent horizontal sections, B is the tunnel width, k = ν / (1-ν) is the lateral pressure coefficient, ν is the Poisson's ratio of the rock mass, φ is the internal friction angle of the rock mass, P max p is the maximum gas storage pressure inside the gas storage tunnel. max The tunnel as a whole experiences upward lifting force.

[0048] To ensure that the plastic zones of the rock mass between adjacent horizontal segments 1 are not connected, and to avoid the two adjacent horizontal segments 1 being too close together and affecting each other during excavation, which would lead to changes in the stability of the tunnel surrounding rock, the distance S between two adjacent horizontal segments 1 should not be less than m times the tunnel width, i.e., S≥mB. To obtain a more accurate distance S between horizontal segments, finite element analysis can also be used. The specific numerical analysis process is basically the same as that for determining the vertical distance S1.

[0049] Furthermore, the horizontal clearance S and burial depth H of the tunnel must also meet the overall resistance to uplift failure requirements of the tunnel. For ease of analysis and calculation, based on construction experience and without considering the influence of groundwater buoyancy, the expression for the ultimate internal pressure within the tunnel is derived as follows:

[0050]

[0051] Right now

[0052] Where: Pu is the overall uplift failure limit value of the tunnel, F is the safety factor, generally not less than 2.0, γ is the average unit weight of the soil and rock above the calculation surface, H is the tunnel burial depth, n is the number of horizontal sections in the gas storage unit of this layer, S is the distance between adjacent horizontal sections, B is the tunnel width, k=ν / (1-ν) is the lateral pressure coefficient, ν is the Poisson's ratio of the rock mass, φ is the internal friction angle of the rock mass, P max p is the maximum gas storage pressure inside the gas storage tunnel. max The tunnel as a whole experiences upward lifting force.

[0053] To avoid stress concentration at the bends of the underground gas storage tunnel, the bend 2 is semi-circular, and the diameter of the semi-circle is the same as the spacing S.

[0054] To ensure uniform gas pressure throughout the underground gas storage tunnel, the vertical shaft 3 is located at the midpoint of the central horizontal section 1 of the gas storage unit; this allows gas to be evenly input into each horizontal section 1 and the bend 2, thus ensuring uniform gas pressure within the gas storage unit.

[0055] To facilitate the installation of the sealing layer 8, ensure the airtightness of the gas storage tunnel, and avoid and reduce stress concentration, the cross-sectional shape of the horizontal section 1 and the bending section 2 is elliptical, circular, or horseshoe-shaped.

[0056] As a preferred embodiment, the sealing layer uses a composite steel-plastic composite panel or a polymer resin panel. The polymer resin panel can be modified ultra-high molecular weight polyethylene (UHMW-PE), heat-resistant polyethylene (PE~RT II), or polybutene (PB). During the construction phase, the composite steel-plastic composite panel or polymer resin panel can serve as temporary support to prevent localized rockfalls and ensure construction safety. During operation, the polymer composite panel can prevent gas leakage and groundwater seepage, while forming a unified whole with the rock mass to jointly withstand the gas pressure inside the gas storage tunnel, reducing deformation of the gas storage tunnel caused by gas pressure.

[0057] To save costs while improving corrosion resistance, ensuring airtightness and pressure resistance, the polymer resin board can be modified ultra-high molecular weight polyethylene (UHMW-PE), heat-resistant polyethylene (PE~RT II), or polybutene (PB).

Claims

1. An underground gas storage tunnel, characterized in that: It includes a gas storage unit and a vertical shaft (3). The gas storage unit includes a horizontal section (1) and a bending section (2). There are multiple horizontal sections (1) and they are spaced apart in the same horizontal plane. Every two adjacent horizontal sections (1) are connected end to end through the bending section (2) to form a serpentine structure. One end of the vertical shaft (3) extends to the ground, and the other end is vertically connected to the gas storage unit; The inner walls of the horizontal section (1) and the bending section (2) are, from the outside to the inside, the soil body (6), the lining (7) and the sealing layer (8). Multiple gas storage units are arranged along the vertical direction of the shaft (3), and the multiple gas storage units are connected to form a whole through the shaft (3). A vertical clearance S1 is provided between every two layers of gas storage units. The vertical clearance S1 should meet the following requirements: ,in The ratio of S1 to H is used for Class I surrounding rock. =2, Class II surrounding rock =2.5, Class III surrounding rock =3, Class IV surrounding rock =4; H is the tunnel height; The vertical shaft (3) includes vertical shaft I (31) and vertical shaft II (32). The gas storage units in the odd-numbered layers are connected through vertical shaft I (31), and the gas storage units in the even-numbered layers are connected through vertical shaft II (32).

2. The underground gas storage tunnel as described in claim 1, characterized in that: The vertical clearance S1 is determined based on the tunnel surrounding rock grade, gas storage pressure, original formation pressure, and finite element numerical calculation and analysis, so that the rock mass plastic zone between adjacent gas storage units is not connected.

3. The underground gas storage tunnel as described in claim 1, characterized in that: The spacing S between any two adjacent horizontal segments (1) should satisfy: ； Where: m is the ratio of S to B, m=2 for Class I surrounding rock, m=2.5 for Class II surrounding rock, m=3 for Class III surrounding rock, and m=4 for Class IV surrounding rock; F is the safety factor, generally not less than 2.0; γ is the average unit weight of the soil and rock above the calculation surface; H is the tunnel burial depth; n is the number of horizontal sections in the gas storage unit of this layer; S is the distance between adjacent horizontal sections; B is the tunnel width; k=ν / (1-ν) is the lateral pressure coefficient; and ν is the Poisson's ratio of the rock mass. The friction angle within the rock mass. This represents the maximum gas storage pressure within the gas storage tunnel. c represents the cohesion of the rock mass.

4. The underground gas storage tunnel as described in claim 1, characterized in that: The bent portion (2) is semi-circular, and the diameter of the semi-circle is consistent with the spacing S.

5. An underground gas storage tunnel as described in claim 1, characterized in that: The vertical shaft (3) is located at the midpoint of the central horizontal section (1) of the gas storage unit.

6. The underground gas storage tunnel as described in claim 1, characterized in that: The cross-sectional shapes of the horizontal section (1) and the bent section (2) are elliptical, circular, or horseshoe-shaped.

7. The underground gas storage tunnel as described in claim 1, characterized in that: The sealing layer (8) is made of composite steel-plastic board or polymer resin board.

8. An underground gas storage tunnel as described in claim 7, characterized in that: The polymer resin board is made of modified ultra-high molecular weight polyethylene, heat-resistant polyethylene, or polybutene.

Images