A method for optimizing design of compressed air energy storage cavern in shallow hard rock

Abstract

The present application relates to a kind of shallow hard rock compressed air energy storage chamber optimization design method, comprising the following steps: according to the maximum air internal pressure of the chamber to be built obtained by preliminary determination of use demand;Determine the initial depth of chamber;Get the earth stress of chamber periphery, determine the strike of chamber;Calculate the zero stress axis ratio and the best axis ratio of chamber;Check whether the air internal pressure of chamber is lower than the maximum value that the surrounding rock of chamber at initial depth can bear;Check whether the surrounding rock pressure of chamber at initial depth under the best axis ratio is greater than the preset threshold, to determine the depth of chamber;Determine the cross-sectional area of chamber, calculate vertical half axis and transverse half axis length according to zero stress axis ratio or best axis ratio, determine the shape of chamber, to determine shallow chamber.Compared with prior art, the present application has the advantages that the chamber can meet the requirements of stability and sealing, and economic considerations.

Description

Technical Field

[0001] This invention relates to a method for designing the cross-sectional shape of energy storage chambers, and more particularly to an optimized design method for shallow-buried hard rock compressed air energy storage chambers. Background Technology

[0002] Energy storage is a key technology driving the shift from fossil fuels to renewable energy, offering unique advantages in improving power quality, addressing peak load demands, and promoting clean energy development. Compressed air energy storage is a grid-compatible method capable of large-scale energy storage. Besides above-ground high-pressure tanks and underground salt karst caverns, artificially excavated hard rock chambers have seen numerous international trials in recent years. Utilizing artificially excavated underground chambers for gas storage significantly reduces dependence on regional geological conditions and offers numerous advantages such as high reliability, flexible layout, and negligible environmental impact, making it the most likely form of large-scale energy storage for widespread adoption.

[0003] Gas storage chambers require high stability and airtightness, but are also subject to the combined effects of surrounding rock pressure caused by external geostress and high internal gas pressure, making them prone to damage and rupture, which can further lead to instability. While some pilot studies and demonstration projects have been conducted both domestically and internationally regarding the design of gas storage chambers, no commercially viable power plant utilizing artificial rock chambers for gas storage has yet been successfully put into operation. my country has also conducted some preliminary explorations in the construction of artificial gas storage chambers, but it is still in its early stages. There are currently no relevant standards or demonstration projects to provide clear guidance and basis for the design and construction of gas storage chambers. Key aspects such as the chamber's shape, burial depth, gas pressure, and sealing methods are still under discussion. Currently, commonly discussed gas storage chamber shapes include circular tunnels, straight-walled tunnels, inclined-walled tunnels, and large tank-type chambers. However, all of these suffer from the problem of tensile stress concentration and plastic zones in the surrounding rock, making it impossible to avoid cracking of the surrounding rock walls under the combined effects of surrounding rock pressure and high internal gas pressure. Therefore, achieving a balance between stability, airtightness, and economic efficiency remains challenging. Summary of the Invention

[0004] The purpose of this invention is to provide an optimized design method for shallow-buried hard rock compressed air energy storage chambers that satisfies stability, sealing performance, and economic efficiency.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] An optimized design method for shallow-buried hard rock compressed air energy storage chambers includes the following steps:

[0007] The maximum internal air pressure of the proposed chamber is initially determined based on usage requirements;

[0008] The initial burial depth of the chamber is determined based on the maximum internal air pressure.

[0009] Obtain the geostress around the chamber to determine the orientation of the chamber;

[0010] Based on the ground stress around the chamber and the maximum internal air pressure, calculate the zero-stress axial ratio and the optimal axial ratio of the chamber.

[0011] An initial check is performed based on whether the air pressure inside the chamber is lower than the maximum value that the surrounding rock of the chamber can withstand at the initial burial depth. If so, no operation is performed; if not, the burial depth is adjusted and increased according to the check results.

[0012] Based on the optimal axial ratio, the burial depth is re-verified according to whether the surrounding rock pressure of the chamber at the initial burial depth is greater than the preset threshold. If so, the burial depth is adjusted and reduced according to the verification result and the burial depth is finally determined. If not, no operation is performed.

[0013] The cross-sectional area of ​​the chamber is determined, and the lengths of the vertical and horizontal half-axis are calculated based on the zero-stress axis ratio or the optimal axis ratio to determine the external shape of the chamber, thereby determining the shallow-buried chamber.

[0014] Furthermore, the geostress around the chamber includes the vertical stress at a predetermined burial depth, the maximum horizontal principal stress, and the minimum horizontal principal stress.

[0015] Furthermore, the maximum horizontal principal stress is selected as the orientation of the chamber.

[0016] Furthermore, the formula for calculating the optimal shaft ratio of the chamber is as follows:

[0017]

[0018] In the formula, m1 is the optimal axial ratio; p0 is the horizontal stress around the chamber, p0 = S v S v The vertical stress around the chamber; p a S is the maximum air pressure inside the chamber; λ is the pressure measurement coefficient, calculated using the formula λ = S h / S v For shallow-buried chambers, λ>1 is usually present; S h It is the minimum horizontal principal stress around the perimeter of the chamber.

[0019] Furthermore, the tangential stress of the tunnel wall is used to check whether the air pressure inside the chamber is lower than the maximum value that the surrounding rock of the chamber can withstand at the initial burial depth. The formula for calculating the tangential stress of the tunnel wall is:

[0020]

[0021] In the formula, σ θ Let m1 be the tangential stress of the tunnel wall, m1 be the optimal axial ratio, and p0 be the horizontal stress around the tunnel perimeter, p0 = Sv S v p represents the vertical stress around the chamber. a λ represents the maximum air pressure inside the chamber; λ is the pressure measurement coefficient.

[0022] Furthermore, the specific steps for the initial inspection include:

[0023] Determine if the tangential stress at each point on the tunnel wall is greater than 0. If it is, do not perform any operation. If not, increase the burial depth until all stresses are greater than 0.

[0024] Furthermore, the specific steps for re-verification include:

[0025] Determine whether the tangential stress at each point on the tunnel wall is greater than a preset threshold. If so, reduce the burial depth until it is close to 0 but still greater than 0. If not, do nothing.

[0026] Furthermore, the expression for calculating the lengths of the vertical and horizontal half-axis using the optimal axis ratio is as follows:

[0027]

[0028]

[0029] In the formula, s is the determined cross-sectional area; a is the transverse half-axis of the chamber; b is the vertical half-axis of the chamber; and m1 is the optimal axis ratio.

[0030] Furthermore, the expression for calculating the external shape of the tunnel using the optimal axis ratio is as follows:

[0031]

[0032] In the formula, s is the determined cross-sectional area; x is the abscissa of the chamber with the center of the circle as the origin; y is the ordinate of the chamber with the center of the circle as the origin; and m1 is the optimal axial ratio.

[0033] Furthermore, the chamber is an elliptical chamber.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) The present invention obtains the orientation of the chamber based on the ground stress, calculates the zero pressure axis ratio and the optimal axis ratio of the chamber, so that the surrounding rock does not exhibit tensile stress and plastic deformation, which can meet the requirements of chamber stability and sealing, and further determines the burial depth, thereby obtaining an optimized shallow burial chamber.

[0036] (2) The present invention adjusts the burial depth through multiple verification operations so that the chamber can have a shallower burial depth. Compared with deep burial projects, it can save construction and maintenance costs and has strong economic value.

[0037] (3) The construction of artificial gas storage chambers is still in its early stages. There are no relevant patents, standards and demonstration projects that can provide clear guidance and basis for the design and construction of gas storage chambers. The shape, burial depth and orientation of the chambers are still under discussion. The technical solution of this invention provides a calculation method for determining the shape, burial depth and orientation of the chambers, which fills the gap of lack of theoretical support for the design of the chamber shape.

[0038] (4) The zero stress axis ratio of the present invention can theoretically make the tangential stress of the surrounding rock of the tunnel wall approximately uniformly distributed compressive stress. At this time, the tunnel reaches the optimal stress state and has the best stability.

[0039] (5) Existing schemes for artificial gas storage chambers, such as inclined wall type, straight wall type and tank type, cannot avoid the occurrence of tensile stress areas in the surrounding rock of the chamber wall. The occurrence of tensile stress causes the surrounding rock to crack under tension and form a plastic zone, which is not conducive to the stability and sealing of the gas storage chamber. However, the technical solution of the present invention can effectively avoid the occurrence of tensile stress and plastic zone in the confining pressure by obtaining the cross-sectional shape of the chamber wall through zero stress axis ratio and optimal axis ratio.

[0040] (6) By taking into account the air pressure inside the chamber, this invention ensures that the surrounding rock does not experience tensile stress and also avoids tensile cracking, thus ensuring the integrity of the surrounding rock. For gas storage chambers with extremely strict requirements for air tightness, this invention also contributes to the air tightness of the chamber to a certain extent.

[0041] (7) By taking the maximum horizontal principal stress as the optimal orientation of the chamber, the present invention can optimize the stress performance of the chamber, thereby improving the stability and safety of the chamber. Attached Figure Description

[0042] Figure 1 This is a flowchart of the method of the present invention;

[0043] Figure 2 This is a schematic diagram of the load effect on the cross-section of the shallowly buried elliptical gas storage chamber of the present invention;

[0044] Figure 3 This is a schematic diagram of the tangential stress distribution in the shallow-buried hard rock gas storage chamber designed according to the minimum critical value of zero stress axis ratio in this invention;

[0045] Figure 4 This is a schematic diagram of the tangential stress distribution in the shallow-buried hard rock gas storage chamber designed according to the maximum critical value of zero stress axis ratio in this invention;

[0046] Figure 5 This is a schematic diagram of the tangential stress distribution in the shallow-buried hard rock gas storage chamber designed according to the optimal stress axis ratio of this invention.

[0047] In the diagram: 1 represents the boundary of the chamber. Detailed Implementation

[0048] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0049] This embodiment provides an optimized design method for a shallow-buried hard rock compressed air energy storage chamber, such as... Figure 1 As shown, this method determines the optimal axial ratio of a shallow-buried compressed air energy storage chamber in hard rock based on the required internal air pressure, the required chamber cross-sectional area, and the geostress conditions of the engineering site. Based on this, the chamber cross-sectional shape is designed to ensure that the surrounding rock of the chamber does not have a tensile stress zone and achieves the optimal state of approximately equal distribution of compressive stress.

[0050] like Figure 2-5 As shown, the external shape of the chamber in this embodiment is elliptical. The ratio of the longitudinal semi-axis to the transverse semi-axis of the ellipse is determined based on the maximum air pressure and the ground stress of the site. The surrounding rock of the entire chamber does not exhibit tensile stress, and even achieves a stress distribution state where the compressive stress is approximately uniform. The specific design method of the entire chamber includes the following steps:

[0051] S1. Determine the maximum internal air pressure of the proposed chamber based on usage requirements.

[0052] Based on the geotechnical engineering investigation report, a preliminary site selection for the chamber is carried out. The preliminary site selection must meet the requirement that there is a hard, thick or dense rock mass with intact rock mass, undeveloped joints, and good integrity within an appropriate burial depth below the surface.

[0053] The maximum internal air pressure that the gas storage chamber must withstand is determined based on the planned installed capacity of the chamber. This pressure is generally within ten MPa, but in a few cases it can reach more than ten MPa.

[0054] S2. The burial depth of the chamber is initially determined based on the maximum internal air pressure.

[0055] Based on the maximum internal air pressure determined in step S1, the burial depth of the chamber is initially determined. Generally, the burial depth of a chamber with a maximum internal air pressure of less than 10 MPa does not exceed 200 m.

[0056] S3. Obtain the geostress and maximum horizontal principal stress around the chamber to determine the orientation of the chamber.

[0057] Based on the engineering geological parameters of the chamber obtained from the geotechnical engineering investigation, the engineering geological parameters of the chamber are the in-situ stress at the predetermined burial depth, including the maximum horizontal principal stress and the minimum horizontal principal stress S at the predetermined burial depth. h and vertical stress S v .like Figure 2 The diagram shows the stress distribution of a shallowly buried elliptical gas storage chamber. The chamber is elliptical, with lengths a and b of its horizontal and vertical semi-axis, respectively. The axial ratio is m = b / a, and the lateral pressure coefficient is λ = S.h / S v λ>1. The direction of the maximum horizontal principal stress is selected as the orientation of the chamber, meaning the axial direction of the chamber is consistent with the direction of the maximum horizontal principal stress. The selection of the chamber orientation is a crucial issue in the design and construction of chambers. The maximum horizontal principal stress is the largest horizontal stress component in the chamber and is one of the important factors affecting the stability and safety of the chamber. Therefore, selecting the maximum horizontal principal stress as the chamber orientation can optimize the stress performance of the chamber, thereby improving its stability and safety.

[0058] S4. Calculate the zero-stress axial ratio and the optimal axial ratio of the chamber based on the ground stress around the chamber and the maximum internal air pressure.

[0059] First, the pressure measurement coefficient is calculated based on the vertical stress and minimum horizontal principal stress at the predetermined burial depth obtained from the geotechnical engineering investigation. The formula is as follows:

[0060] λ=S h / S v

[0061] In the formula, λ is the pressure measurement coefficient, which is usually greater than 1 for shallow buried chambers; S v S is the vertical stress around the perimeter of the chamber. h It is the minimum horizontal principal stress around the perimeter of the chamber.

[0062] The formula for calculating the range of zero-stress axial ratio is:

[0063]

[0064] In the formula, m2 is the zero-stress axis ratio; p0 is the horizontal stress around the chamber, p0 = S v ;p a λ represents the maximum air pressure inside the chamber; λ is the pressure measurement coefficient.

[0065] Within the given m² range, no tensile stress occurs around the chamber, but determining when the stress distribution is most uniform remains a question worth exploring further. Stress analysis of the elliptical perimeter reveals that a strictly uniform stress distribution does not exist across the entire chamber wall. Therefore, an equal stress axis ratio, as seen in unpressurized tunnels, does not exist. However, finding a m² value that minimizes stress differences across the chamber wall—approaching an equal stress distribution—would be desirable. Based on the stress distribution characteristics of elliptical chambers, such as... Figure 3The diagrams shown are: a schematic diagram of tangential stress distribution in a shallow-buried hard rock gas storage chamber designed based on the minimum critical value of zero-stress axial ratio, and a schematic diagram of tangential stress distribution in a shallow-buried hard rock gas storage chamber designed based on the maximum critical value of zero-stress axial ratio, as shown in Figure 4. Here, 1 represents the inner boundary of the chamber. A simple method is that when the difference in compressive stress between the two stress extreme points (one maximum and one minimum) at the arch crown (or arch bottom) and arch waist is minimized, the stress distribution is closest to a circle. The corresponding m1 is the optimal axial ratio to be found, calculated using the following formula:

[0066]

[0067] In the formula, m1 is the optimal axial ratio; p0 is the horizontal stress around the chamber, p0 = S v ;p a λ represents the maximum air pressure inside the chamber; λ is the pressure measurement coefficient.

[0068] At this point, the schematic diagram of the tangential stress distribution of the shallow-buried hard rock gas storage chamber with the optimal stress axis ratio design is as follows: Figure 5 As shown.

[0069] S5. Perform an initial check based on whether the air pressure inside the chamber is lower than the maximum value that the surrounding rock of the chamber can withstand at the initial burial depth. If yes, no operation is performed; if no, the burial depth is adjusted and increased based on the check results.

[0070] To verify whether the chamber in step S4 meets the requirements for safety and economy, the following two aspects need to be verified sequentially:

[0071] The first aspect of the verification is as follows: (i) First, verify whether the air pressure inside the optimal axial ratio chamber obtained in step S4 at the predetermined burial depth is lower than the maximum value that the surrounding rock of the chamber can withstand. It is necessary to verify the tangential stress distribution of the tunnel wall under this condition. This value may be either approximately uniformly distributed compressive stress or approximately uniformly distributed tensile stress around the circumference of the chamber. The formula for calculating the tangential stress of the tunnel wall is:

[0072]

[0073] In the formula, σ θ Let m1 be the tangential stress of the tunnel wall, m1 be the optimal axial ratio, and p0 be the horizontal stress around the tunnel perimeter, p0 = S v S v p represents the vertical stress around the chamber. a λ represents the maximum air pressure inside the chamber; λ is the pressure measurement coefficient.

[0074] For example, at various points σ around the chamber θ If all values ​​are greater than 0, it indicates that the compressive stress is approximately evenly distributed, meaning that the air pressure inside the chamber is lower than the maximum value that the surrounding rock of the chamber at the predetermined burial depth can withstand, which meets the requirements.

[0075] Otherwise, slightly increase the burial depth and recheck using this method until it meets the requirements.

[0076] S6. Based on the optimal axial ratio, re-verify whether the pressure of the surrounding rock of the chamber at the burial depth after the initial verification is much greater than 0. If so, adjust and reduce the burial depth according to the verification result and finally determine the burial depth. If not, do not perform any operation.

[0077] The second aspect of the verification is as follows: (ii) If the burial depth meets the requirements of (i), it indicates that the lower limit of the burial depth is met, which can ensure the stability of the chamber. To further meet the economic requirements, under the condition of meeting stability, the shallower the burial depth of the chamber, the more economical it is. It is also necessary to verify whether there is room for increasing the burial depth.

[0078] Calculate σ using the formula for calculating the tangential stress of the tunnel wall in (i). θ For example, to determine σ θ Is the value greater than a preset threshold, which is much greater than 0? If it is only slightly greater than 0, it means the burial depth is close to the upper limit and can not be adjusted further. If it is greater than 0, it means there is a large room for adjustment, and the burial depth can be reduced slightly. Repeat the verification according to (i) and (ii) until σ is reached. θ It is close to 0, but still greater than 0.

[0079] S7. Determine the cross-sectional area of ​​the chamber, and calculate the size of the minor axis and major axis according to the zero stress axis ratio or optimal axis ratio of the ellipse, determine the external shape of the chamber, and thus determine the shallow buried chamber.

[0080] The cross-sectional area is determined based on usage requirements and construction feasibility. In practical applications, the minor and major axes can be calculated using the zero-stress axial ratio or the optimal axial ratio to determine the external shape of the tunnel.

[0081] In this embodiment, the calculation is performed based on the optimal axis ratio. First, based on the determined cross-sectional area, the lengths of the vertical and horizontal semi-axis of the ellipse are calculated to determine the expression for the shape of the elliptical tunnel.

[0082] The formulas for calculating the lengths of the vertical and horizontal semi-axes of an ellipse are as follows:

[0083]

[0084]

[0085] In the formula, s is the determined cross-sectional area; a is the transverse half-axis of the elliptical chamber; b is the transverse half-axis of the elliptical chamber; and m1 is the optimal axis ratio.

[0086] Based on the calculated values ​​of a and b, and according to the standard expression for an ellipse, the expression for the exterior shape of the elliptical cave with its center at the origin is as follows:

[0087]

[0088] In the formula, s is the determined cross-sectional area; x is the abscissa of the elliptical chamber with the center of the circle as the origin; y is the ordinate of the elliptical chamber with the center of the circle as the origin; and m1 is the optimal axial ratio.

[0089] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for optimizing the design of a shallow-buried hard rock compressed air energy storage chamber, characterized in that, Includes the following steps: The maximum internal air pressure of the proposed chamber is initially determined based on usage requirements; The initial burial depth of the chamber is determined based on the maximum internal air pressure. Obtain the geostress around the chamber to determine the orientation of the chamber; Based on the ground stress around the chamber and the maximum internal air pressure, calculate the zero-stress axial ratio and the optimal axial ratio of the chamber. An initial check is performed based on whether the air pressure inside the chamber is lower than the maximum value that the surrounding rock of the chamber can withstand at the initial burial depth. If so, no operation is performed; if not, the burial depth is adjusted and increased according to the check results. Based on the optimal axial ratio, the burial depth is re-verified according to whether the surrounding rock pressure of the chamber at the initial burial depth is greater than the preset threshold. If so, the burial depth is adjusted and reduced according to the verification result and the burial depth is finally determined. If not, no operation is performed. The cross-sectional area of ​​the chamber is determined, and the lengths of the vertical and horizontal half-axis are calculated based on the zero-stress axis ratio or the optimal axis ratio to determine the external shape of the chamber, thereby determining the shallow-buried chamber.

2. The optimized design method for a shallow-buried hard rock compressed air energy storage chamber according to claim 1, characterized in that, The geostress around the chamber includes the vertical stress at the predetermined burial depth, the maximum horizontal principal stress, and the minimum horizontal principal stress.

3. The optimized design method for a shallow-buried hard rock compressed air energy storage chamber according to claim 2, characterized in that, The maximum horizontal principal stress is selected as the orientation of the chamber.

4. The optimized design method for a shallow-buried hard rock compressed air energy storage chamber according to claim 2, characterized in that, The formula for calculating the optimal shaft ratio of the chamber is as follows: In the formula, m 1 is the optimal shaft ratio; p 0 Horizontal stress around the chamber, p 0 =S v , S v This refers to the vertical stress around the chamber; p a This represents the maximum air pressure inside the chamber. λ The pressure measurement coefficient is calculated using the following formula: ; S h It is the minimum horizontal principal stress around the perimeter of the chamber.

5. The optimized design method for a shallow-buried hard rock compressed air energy storage chamber according to claim 1, characterized in that, The tangential stress of the tunnel wall is used to check whether the air pressure inside the chamber is lower than the maximum value that the surrounding rock of the chamber can withstand at the initial burial depth. The formula for calculating the tangential stress of the tunnel wall is as follows: In the formula, σ θ The tangential stress in the tunnel wall. m 1 is the optimal shaft ratio. p 0 The horizontal stress around the chamber. p 0 =S v , S v The vertical stress around the chamber. p a This represents the maximum air pressure inside the chamber. λ This is the pressure measurement coefficient.

6. The optimized design method for a shallow-buried hard rock compressed air energy storage chamber according to claim 5, characterized in that, The specific steps for the initial inspection include: Determine if the tangential stress at each point on the tunnel wall is greater than 0. If it is, do not perform any operation. If not, increase the burial depth until all stresses are greater than 0.

7. The optimized design method for a shallow-buried hard rock compressed air energy storage chamber according to claim 5, characterized in that, The specific steps for re-verification include: Determine whether the tangential stress at each point on the tunnel wall is greater than a preset threshold. If so, reduce the burial depth until it is close to 0 and still greater than 0. If not, do not perform any operation.

8. The optimized design method for a shallow-buried hard rock compressed air energy storage chamber according to claim 1, characterized in that, The expression for calculating the lengths of the vertical and horizontal half-axis using the optimal axis ratio is as follows: In the formula, s For a given cross-sectional area; a This is the transverse half-axis of the chamber; b This is the vertical half-axis of the chamber; m 1 is the optimal shaft ratio.

9. The optimized design method for a shallow-buried hard rock compressed air energy storage chamber according to claim 8, characterized in that, The expression for calculating the external shape of the tunnel using the optimal axial ratio is as follows: In the formula, s For a given cross-sectional area; x Let x be the x-coordinate of the chamber with the center of the circle as the origin; y The vertical coordinate of the chamber is given by the center of the circle as the origin. m 1 is the optimal shaft ratio.

10. The optimized design method for a shallow-buried hard rock compressed air energy storage chamber according to claim 1, characterized in that, The chamber is an elliptical chamber.

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