Method for determining critical rock mass deformation modulus and maximum gas storage pressure of shallow-buried underground gas storage cavern

Abstract

The application discloses a method for determining critical rock mass deformation modulus and maximum gas storage pressure of a shallow-buried underground gas storage cavern. Starting from the basic design concept of "all internal pressure load is borne by surrounding rock, steel lining only serves as airtight structure, and concrete plays a role of load transmission and deformation distribution" of the shallow-buried underground gas storage cavern, combining with the theory of elastic mechanics and circular tunnel surrounding rock resistance, a functional relationship between the limit gas storage pressure and rock mass deformation modulus is established, the concept and calculation formula of the minimum critical rock mass deformation modulus required by the surrounding rock when the shallow-buried underground gas storage cavern satisfies the maximum operating internal pressure P max , and the determination method of the maximum allowable gas storage pressure of the shallow-buried underground gas storage cavern is given. The application can scientifically and quantitatively judge the engineering geological suitability and gas storage internal pressure potential of various shallow-buried underground gas storage caverns.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of underground gas storage, in particular to a method for determining the critical rock mass deformation modulus and maximum gas storage pressure of a shallow-buried underground gas storage cavern. BACKGROUND

[0002] The shallow-buried underground gas storage cavern (LRC) storage concept is one of the latest underground cavern storage technologies, and has had more than 20 years of successful operation experience. The shallow-buried underground gas storage cavern is essentially a regular rock cave built by using traditional underground engineering excavation methods, and then lined with artificial and airtight barrier materials. The burial depth of such a gas storage cavern is generally 100-200 m, and the normal gas storage internal pressure can reach 10-30 MPa, and can be operated at high frequency. The inner wall of the shallow-buried underground gas storage cavern is lined with a concrete lining and an innermost fully closed thin steel lining plate, and the main design concept is that the steel lining maintains the airtightness of the storage, the surrounding rock bears the high internal pressure load, and the concrete uniformly transmits the gas pressure to the rock mass. In order to ensure the stability of the cavern, the cross section of the cavern is generally circular, including circular adit, circular shaft, dome barrel type cavern and other forms.

[0003] The construction cost of the shallow-buried underground gas storage cavern may be higher than that of the salt cave or natural reservoir, but it makes the site selection more flexible, and can be located at a relatively shallow depth, and is more easily accessible to energy supply and demand areas (wind and solar power generation, natural gas supply, etc.), reducing the intermediate loss of energy. From the current development situation, the shallow-buried underground gas storage cavern storage concept can be used as an efficient natural gas and all other gas storage, which can effectively store pressurized gases such as hydrogen and air (compressed air energy storage, CAES). This storage concept is also particularly suitable for gas storage technology for future energy systems.

[0004] Even so, using shallow underground gas storage cavern for high pressure underground gas storage is still a new technology, and there is currently no mature design practice experience, and no design and construction specifications and technical standards for shallow underground gas storage caverns to follow. At this stage, design units mostly refer to the design experience of high water head pumped storage or large hydropower projects as the main reference, lacking a deep understanding of the bearing mechanism and technology of sealed underground space under high gas storage pressure. In addition, due to the complex geological structure of China, it is also impossible to copy the relatively mature experience of similar projects in Europe and the United States; and shallow underground gas storage caverns have obvious differences from relatively mature salt cavern gas storage, and the relevant experience is not applicable. Therefore, with the rapid development of shallow underground gas storage technology, how to determine the limit operation gas pressure of the underground gas storage scientifically and effectively from the design concept and bearing characteristics of the shallow underground gas storage cavern has become a difficult problem that needs to be solved at present. Researching the maximum operating pressure of the gas storage is an important prerequisite for effectively utilizing the capacity of the gas storage and ensuring the safe operation of the gas storage. SUMMARY

[0005] The present application aims at the problem that the geological criterion for site selection of shallow underground gas storage cavern is not clear and the limit operation pressure of gas storage cavern is difficult to calculate quantitatively quickly, and proposes a method for determining the critical rock mass deformation modulus and the maximum gas storage pressure of shallow underground gas storage cavern, thereby providing a scientific basis for engineering site selection and gas storage potential analysis of shallow underground gas storage cavern.

[0006] To solve the above technical problems, the present application realizes the technical scheme as follows:

[0007] S1, for a target gas storage cavern with a circular cross section, the radial unit resistance P max , P rock and P steel provided by the surrounding rock and the steel lining under the maximum gas storage pressure P max are calculated respectively;

[0008] S2, based on the internal and external pressure balance of the target gas storage cavern, a calculation formula of the steel lining and the surrounding rock combined bearing is established, and the calculation expression of the maximum gas storage pressure P max of the target gas storage cavern is obtained;

[0009] S3, the minimum critical rock mass deformation modulus E m-critical required for the target gas storage cavern to be completely borne by the surrounding rock is derived;

[0010] S4, the correlation between the maximum gas storage pressure and the rock mass deformation modulus is established, and the engineering economy or site suitability is evaluated quickly and effectively accordingly.

[0011] Further, in S1, the surrounding rock mass is regarded as a uniform, continuous and isotropic perfect elastic body, and for a circular tunnel, the surrounding rock elastic resistance coefficient can be estimated according to the elastic theory as follows:

[0012]

[0013] k is the elastic resistance coefficient of surrounding rock, MPa / m; E m is the deformation modulus of rock mass, MPa; μ is the Poisson's ratio of rock mass; r is the radius of tunnel, m. In which, it should also be ensured that the surrounding rock is large enough, and the cover thickness of the tunnel should be ensured that H≥6r.

[0014] Under the action of gas storage internal pressure P, the radial strain of steel lining is the same as the hoop strain, which is In which E is the elastic modulus of steel material in plane strain problem, E s E is the elastic modulus of steel material, MPa; γ s is the Poisson's ratio of steel material; σ θ is the hoop normal stress of steel lining, MPa.

[0015] Affected by the setting of sliding layer, construction gap, temperature gap and other factors, a certain gap between surrounding rock and structure needs to be considered, and the total cumulative gap value is recorded as δ. Then the radial deformation of the tunnel surrounding rock is

[0016] According to the resistance theory of circular tunnel surrounding rock, under the action of internal pressure, the radial unit resistance provided by the surrounding rock is:

[0017]

[0018] According to the thin-walled circular management theory, under the action of internal pressure, the radial unit resistance provided by the steel lining is:

[0019]

[0020] In which, t is the structural thickness of steel lining.

[0021] Further, in the step S2, according to the internal and external pressure balance of the target gas storage cavern, the maximum gas storage pressure expression of the target gas storage cavern is:

[0022]

[0023] Above, P rock and P steel respectively represent the load shared by the surrounding rock and the steel lining respectively under the condition of resisting the gas internal pressure P max ;

[0024] Because the elastic modulus of plain concrete lining is generally higher than that of rock mass, and its tensile strength is low, under the action of higher internal pressure, the concrete is easy to crack and lose its bearing capacity, so the radial resistance P concretewhich mainly plays a role in transferring the internal load, and the corresponding P concrete ≈0.

[0025] Since the circumferential normal stress σ θ of the steel lining does not exceed the allowable stress [σ] of the steel material, i.e. σ θ ≤ [σ];

[0026] Finally, the maximum gas storage pressure is obtained as:

[0027]

[0028] Further, in step S3, according to the design principle of the shallow-buried underground gas storage cavern, the thickness of the steel lining only needs to meet the construction requirements, but it also theoretically bears part of the internal pressure load. After excluding the 2mm corrosion allowance, the construction thickness of the steel lining can generally be taken as t = 0.0025r. Then the radial unit resistance provided by the steel lining is Overall, the magnitude of P steel is very small for the high internal pressure of 5-30MPa of the gas storage cavern, and the safety margin of the steel lining structure is considered.

[0029] In step S3, let the thickness of the steel lining t = 0, and take the circumferential normal stress σ θ of the steel lining as the allowable stress [σ] of the steel material, i.e. σ θ = [σ], then the critical rock deformation modulus E m-critical of the gas storage tunnel completely borne by the surrounding rock under the action of the maximum gas storage pressure P max is derived.

[0030]

[0031] In the above formula, E m-critical is the critical rock deformation modulus, MPa; P max is the maximum internal pressure of the gas storage cavern, MPa; μ is the Poisson's ratio of the surrounding rock; [σ] is the allowable stress of the steel material, MPa; E s is the elastic modulus of the steel material, MPa; γ s is the Poisson's ratio of the steel material; δ is the cumulative gap value between the surrounding rock of the tunnel and the structure, m; r is the radius of the lining of the tunnel, m.

[0032] Further, in step S4, the correlation calculation expression of the maximum gas storage pressure P max required by the target gas storage cavern and the critical rock deformation modulus E m-critical of the target gas storage cavern is: And for various typical steel lining material properties, the "feasibility criterion" zoning map of shallow-buried underground gas storage engineering construction is drawn.

[0033] Further, in the S4, the correlation calculation expression of the maximum gas storage pressure P max of the target gas storage cavern and the rock mass deformation modulus E m of the target gas storage cavern is: And for various typical steel lining material properties, a recommended maximum gas storage pressure table under different rock mass conditions is drawn.

[0034] The beneficial effects of the present application mainly include: scientific and quantitative calculation of the critical rock mass deformation modulus and the maximum gas storage pressure of the shallow underground gas storage cavern. The theoretical calculation method proposed by the present application has good adaptability when applied to multiple shallow gas storage cavern practical engineering cases. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 A typical cross section of the shallow underground gas storage cavern to which the present application is applicable is shown.

[0036] Figure 2 The critical rock mass deformation modulus and the engineering feasibility zoning map of the shallow underground gas storage cavern proposed by the present application include three types of different steel lining materials such as Q345R low alloy steel, 600MPa grade and 800MPa grade high strength steel, and the allowable stress values of the corresponding steel lining materials are 232MPa, 304MPa and 388MPa respectively.

[0037] Figure 3 The actual engineering case application situation of the engineering feasibility zoning map proposed by the present application is shown. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the present application clearer and more apparent, the present application will be further described in detail below with reference to the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0039] A determination method of the critical rock mass deformation modulus and the maximum gas storage pressure of a shallow underground gas storage cavern is applicable to the case where the cross section of the shallow underground gas storage cavern is circular, including circular adit, circular shaft, dome barrel type cavern and other forms. The specific steps are as follows:

[0040] S1, for the shallow underground gas storage cavern with a circular cross section as shown in Figure 1 , according to the theory of elasticity and rock resistance, and combining with the structural characteristics of the shallow underground gas storage cavern, the radial unit resistance P max and P rock provided by the surrounding rock and the steel lining under the action of the maximum gas storage pressure P steel are calculated respectively.

[0041] S2, based on the internal and external pressure balance of the target gas storage cavern, the calculation formula of the steel lining and surrounding rock combined load bearing is established, and the maximum gas storage pressure P is obtained max ;

[0042] S3, based on the design concept of shallow buried underground gas storage cavern relying on "surrounding rock bearing, concrete lining force transmission, steel lining only plays the role of gas tightness", the minimum critical rock mass deformation modulus E m-critical required for the surrounding rock to bear the gas storage tunnel is derived;

[0043] S4, according to the above formula, the correlation between the maximum gas storage pressure and the rock mass deformation modulus is established, and the engineering economy or site suitability is evaluated quickly and effectively.

[0044] In step S1, the radial unit resistance provided by the surrounding rock is: The radial unit resistance provided by the steel lining is:

[0045] In the above formula, k is the elastic resistance coefficient of the surrounding rock, MPa / m; s' is the radial deformation of the tunnel surrounding rock, m; E m is the rock mass deformation modulus, MPa; μ is the rock mass Poisson's ratio, r is the tunnel radius, m; E s2 is the elastic modulus of steel material for plane strain problem, MPa; σ θ is the hoop stress of steel lining, MPa; δ is the cumulative gap value between surrounding rock and structure, m; E s is the elastic modulus of steel material, MPa; t is the structural thickness of steel lining.

[0046] In step S2, according to the internal and external pressure balance of the target gas storage cavern, the maximum gas storage pressure expression of the target gas storage cavern is:

[0047] Wherein, P rock and P steel respectively represent the load shared by the surrounding rock and the steel lining respectively under the condition that the gas storage internal pressure P max ; The plain concrete lining is easy to crack under the action of high internal pressure, and the bearing capacity is lost, so the radial resistance P concrete shared by the lining is not considered, and the main role of the lining is to transfer the internal load, and the corresponding P concrete ≈0;

[0048] Since the hoop stress σ θ of the steel lining does not exceed the allowable stress [σ] of the steel material, σ θ ≤[σ];

[0049] Finally, the maximum gas storage pressure is: Wherein, γ sPoisson's ratio of steel material.

[0050] In the step S3, according to the design principle of the shallow-buried underground gas storage cavern, the thickness of the steel lining only needs to meet the construction requirement, and although it theoretically bears part of the internal pressure load, it is very small for the high internal pressure of 5-30 MPa of the gas storage cavern, and the safety margin of the steel lining structure is considered; the thickness of the steel lining t=0, and the circumferential normal stress of the steel lining is taken as θ The allowable stress [sigma] of steel material, that is, sigma θ =[sigma], and the critical rock deformation modulus E max of the target gas storage cavern completely borne by the surrounding rock under the action of the maximum gas storage pressure P m-critical The calculation formula is:

[0051] In the above formula, E m-critical is the critical rock deformation modulus, MPa; P max is the maximum internal pressure of the gas storage cavern, MPa; mu is the Poisson's ratio of the surrounding rock; [sigma] is the allowable stress of steel material, MPa; E s is the elastic modulus of steel material, MPa; gamma s is the Poisson's ratio of steel material; delta is the cumulative gap value between the surrounding rock of the tunnel and the structure, m; and r is the radius behind the lining of the tunnel, m.

[0052] In the step S4, the correlation calculation expression of the maximum gas storage pressure P max required by the target gas storage cavern and the critical rock deformation modulus E m-critcal of the target gas storage cavern is: And the "feasibility criterion" zoning map of the shallow-buried underground gas storage engineering construction is drawn for a plurality of typical steel lining material properties.

[0053] In the step S4, the correlation calculation expression of the maximum gas storage pressure P max required by the target gas storage cavern and the rock deformation modulus E m of the target gas storage cavern is: And the recommended maximum gas storage pressure table under different rock mass conditions is drawn for a plurality of typical steel lining material properties.

[0054] The designer can directly refer to the relevant map and table, and according to the rock deformation modulus E m of the proposed site and the maximum gas storage pressure P max required by the proposed gas storage engineering, quickly and effectively evaluate the engineering economy or site suitability.

[0055] The method of the present application and its application will be specifically described below by using examples and in combination with the drawings.

[0056] Example 1:

[0057] For any circular cross-section shallow-buried underground gas storage cavern, the critical rock mass deformation modulus E max under the action of the maximum gas storage pressure P m-critical The calculation formula is:

[0058]

[0059] In the formula, E m-critical mainly related to the internal pressure load P in the gas storage and is proportional to the internal pressure load P; is negatively related to the allowable stress [σ] of the steel material; in addition, is also related to the cumulative gap value δ of the tunnel, and the greater the gap, the higher the critical rock mass modulus obtained by calculation. According to experience, δ can generally be taken as 0-0.0005r, so the relationship between the critical rock mass modulus and the size r of the tunnel is also small.

[0060] In general, the surrounding rock of a shallow-buried underground gas storage cavern is of Class II-III, the Poisson's ratio of the surrounding rock is 0.2-0.3, and generally 0.28 can be taken; the comprehensive deformation modulus of the rock mass after relaxation and yielding of the surrounding rock generally decreases, but grouting and reinforcement treatment are generally carried out during the excavation stage of the underground gas storage cavern, and the increase of the confining pressure under the action of the internal pressure of the gas also alleviates the adverse decrease of the deformation modulus, so it can be considered that the deformation modulus of the surrounding rock basically remains constant within the normal operation range of the gas storage; the elastic modulus of the steel material is taken as 206GPa, and the Poisson's ratio is taken as 0.3. The critical rock mass deformation modulus formula of the surrounding rock proposed in the application can be converted to:

[0061]

[0062] Further, the allowable stress [σ] of the steel lining is determined. The material performance of the steel lining is a key element for the design of a shallow-buried underground gas storage cavern, the steel lining needs to resist the long-term adverse effects of high-frequency internal pressure cyclic load of the gas, temperature fluctuation cyclic load, chemical corrosion, etc., and maintain the air tightness, stability and durability of the structure, and the stress and strain in the whole life cycle of the steel lining need to be strictly controlled. The strain control level of the steel lining of the built projects is investigated, and combined with the engineering environment, operation life and disaster risk characteristics of the shallow-buried underground gas storage cavern, the steel lining of such a gas storage cavern is designed according to the elastic state, and the strain of the steel material is generally controlled within 1-2 ‰.

[0063] Of course, the allowable stress or design strength of the steel lining should also be reasonably selected based on the actual operating conditions of the project. For different types of underground gas storage projects, if the number of cycles within the full life cycle is relatively high, the gas storage pressure is relatively high, or the geological conditions are abnormal, a higher structural safety factor should be considered. For example, natural gas storage facilities are seasonally cycled and generally operate hundreds of times throughout their full life cycle, while compressed air energy storage caverns are daily cycled and can exceed 40,000 cycles throughout their life cycle, placing higher requirements on the fatigue resistance of the steel lining.

[0064] Considering that there are no direct regulations to follow, the value of the allowable stress [σ] of the steel lining of shallow buried gas storage caverns can refer to the "Design Specification for Penstocks of Hydropower Stations" (NB / T 35056-2015), the "Design Specification for Penstocks of Water Conservancy and Hydropower Projects" (SL / T281-2020), as well as relevant domestic and foreign standards for pressure vessels and conventional pressure piping. The basic requirements for the allowable stress of the steel lining are as follows: If the yield strength of the steel material σ is used, the allowable stress of the steel lining is as follows: s As a reference, allowable stress [σ] = σ s / n, where the safety factor n is 1.5; the tensile strength of steel σ b As a benchmark, the allowable stress steel [σ] = σ b / n, where the safety factor n is 2.0; and the allowable stress [σ] of the steel lining is the smaller of the two values. These safety factors are generally consistent with those in the latest hydraulic tunnel penstock design specifications. See Table 1 for details. The inner lining steel plates are made of Q345R low-alloy steel, 600MPa-grade high-strength steel, or 800MPa-grade high-strength steel, with corresponding allowable stresses [σ] of 232, 304, and 388MPa, respectively.

[0065] Table 1: Mechanical properties and allowable stress of typical steels

[0066]

[0067] Furthermore, for the above different steel lining materials, the range of values ​​of the critical rock deformation modulus of the surrounding rock of the shallow underground gas storage cavern can be further clarified. Among them, for the case where the steel lining material is Q345R, 500MPa grade steel, the critical rock deformation modulus of the surrounding rock is:

[0068]

[0069] Among them, when the steel lining material is 07Mn-MoVR, 600MPa grade high strength steel, the critical rock deformation modulus of the surrounding rock is:

[0070]

[0071] Wherein, in the case of steel lining material Q690CF, 800MPa high-strength steel, the critical rock mass deformation modulus of surrounding rock:

[0072]

[0073] According to the above three relationships, the maximum gas storage pressure P max Next, the critical rock mass deformation modulus of the surrounding rock of the underground gas storage cavern is calculated. Further, the "feasibility criterion" zoning map of the shallow-buried underground gas storage cavern construction can be drawn to quickly determine whether the proposed site is suitable for the construction of a shallow-buried underground gas storage cavern, as shown in Figure 3

[0074] Figure 2 The recommended area and the uneconomic area are divided according to the actual rock mass deformation modulus of the project, which is greater than or equal to the calculated critical rock mass deformation modulus of the surrounding rock, and the actual rock mass deformation modulus of the project is less than the calculated critical rock mass deformation modulus of the surrounding rock. The recommended area is further divided into two areas according to the different cumulative gap values that may exist in the construction and operation of the actual project, Figure 2 The two zoning lines in each figure correspond to two extreme cases of comprehensive gap δ taking 0 or 0.0005r. Specifically, the recommended area 1 has excellent site suitability, is safe and economical under the bearing of internal pressure of surrounding rock, the recommended area 2 has good ~ good site suitability, needs in-depth study, and weighs safety and economy, and the uneconomic area has general ~ poor site suitability, combined bearing of surrounding rock and steel lining, low structural safety performance, and is uneconomic. Among them, considering the economy of the project, the steel lining material Q345R (500MPa grade) is recommended as the first choice of design scheme.

[0075] Figure 2 The engineering "feasibility criterion" zoning of the steel lining material Q345R, 600MPa high-strength steel, and 800MPa high-strength steel is given according to the critical rock mass deformation modulus of the surrounding rock, corresponding to Figure 3 (a), Figure 3 (b), Figure 3 (c). Among them, considering the economy of the project, the first type of steel lining material Q345R (500MPa grade) is generally selected as the first choice of design scheme.

[0076] Further, Table 2 lists the main design and operation indicators of the currently built shallow-buried underground gas storage cavern cases at home and abroad. By putting the design gas storage pressure and rock mass deformation modulus of these actual engineering cases into Figure 3 (a), it can be found that the theoretical calculation method proposed in the present application has good adaptability when applied to the above multiple shallow-buried gas storage cavern actual engineering cases, and the specific details are shown in​Figure 3 .

[0077] Table 2: Typical actual engineering cases of shallow-buried underground gas storage caverns

[0078]

[0079] Example 2:

[0080] For any circular cross-section shallow-buried underground gas storage cavern, the circumferential normal stress σ θ of the steel lining does not exceed the allowable stress [σ] of the steel material, i.e. σ θ ≤ [σ], then the maximum gas storage pressure is:

[0081]

[0082] In the formula, the Poisson's ratio of the surrounding rock is uniformly taken as 0.28; the cumulative gap value δ of the tunnel can generally be taken as 0-0.0005r; the elastic modulus of the steel material is taken as 206 GPa, and the Poisson's ratio is taken as 0.3. The thickness of the steel lining can be taken as 0, as a safety margin of the structure. Then the maximum gas storage pressure calculation formula of the shallow-buried underground gas storage cavern proposed by the present application can be converted to:

[0083]

[0084] Further, for the above different steel lining materials, the maximum gas storage pressure range of the shallow-buried underground gas storage cavern under different surrounding rock conditions can be further clarified. Among them, for the case that the steel lining material is Q345R, the maximum gas storage pressure of the cavern is:

[0085]

[0086] Among them, for the case that the steel lining material is 07Mn-MoVR, 600 MPa high-strength steel, the maximum gas storage pressure of the cavern is:

[0087]

[0088] Among them, for the case that the steel lining material is Q690CF, 800 MPa high-strength steel, the maximum gas storage pressure of the cavern is:

[0089]

[0090] Further, according to the above three relationship formulas, the maximum gas storage pressure of the underground gas storage cavern under different steel lining materials and different rock mass conditions can be calculated respectively. Combined with the rock mass BQ classification and the recommended rock mass deformation modulus index in the “Engineering Rock Mass Classification Standard” GB 50218 of China, Table 3 gives the recommended range of the maximum gas storage pressure under different rock mass conditions (I-V class surrounding rock), which can be used as a preliminary basis for judging the gas storage potential of the shallow-buried underground gas storage cavern.

[0091] Table 3: Recommended range of maximum gas storage pressure for different rock mass conditions (based on BQ classification)

[0092]

[0093] The above description is only the preferred embodiment of the present application, and does not limit the present application in any form. Any simple modification or equivalent change of the above embodiment according to the technical essence of the present application falls within the protection scope of the present application.

Claims

1. A method for determining the critical rock deformation modulus and maximum gas storage pressure of a shallow underground gas storage cavern, the method comprising the following steps: S1. For the target gas storage cavern with circular cross section, calculate the maximum gas storage pressure P max Under the action of the radial unit resistance P provided by the surrounding rock and steel lining rock and P steel ; S2. Based on the internal and external pressure balance of the target gas storage cavern, a calculation formula for the combined bearing of the steel lining and surrounding rock is established to obtain the maximum gas storage pressure P of the target gas storage cavern. max The calculation expression of S3. Derivation of the minimum critical rock deformation modulus E required for the target gas storage cavern to be fully supported by the surrounding rock m-critical Calculation formula; S4. Establish the correlation between the maximum gas storage pressure and the rock mass deformation modulus, and use this to quickly and effectively evaluate the project economy or site suitability; In step S1, the radial unit resistance provided by the surrounding rock is: Radial unit resistance provided by steel lining: In the above formulas, k is the elastic resistance coefficient of the surrounding rock, MPa / m; s' is the radial deformation of the tunnel surrounding rock, m; E m is the rock mass deformation modulus, MPa; μ is the rock mass Poisson's ratio, r is the tunnel radius, m; E s2 is the elastic modulus of steel for plane strain problems, MPa; σ θ is the hoop normal stress of the steel lining, MPa; δ is the cumulative gap value between the surrounding rock and the structure, m; E s is the elastic modulus of steel, MPa; t is the structural thickness of the steel lining; In step S2, according to the internal and external pressure balance of the target gas storage cavern, the maximum gas storage pressure of the target gas storage cavern is expressed as: Among them, P rock and P steel They represent the combined resistance of surrounding rock and steel lining to the internal pressure of gas storage P max Under the action of high internal pressure, the plain concrete lining is very easy to crack under tension and lose its bearing capacity, so the radial resistance P shared by the lining is not considered. concrete , which mainly plays the role of transferring internal load, the corresponding P conctete ≈0; Due to the hoop normal stress σ θ Do not exceed the allowable stress of steel [σ], σ θ ≤[σ]; Finally, the maximum gas storage pressure is obtained as: Among them, γ s is the Poisson’s ratio of steel; In step S3, according to the design principle of shallow underground gas storage caverns, the thickness of the steel lining is set only to meet the structural requirements. Although it theoretically bears part of the internal pressure load, it is very small for the high internal pressure of 5-30 MPa in the gas storage caverns and is considered as a safety margin of the steel lining structure; let the steel lining thickness t = 0, and take the hoop normal stress σ of the steel lining as θ is the allowable stress of steel [σ], that is, σ θ =[σ], then it can be deduced that at the maximum gas storage pressure P max Under the action of the critical rock deformation modulus E when the target gas storage cavern is completely supported by the surrounding rock m-critical Calculation formula: In the above formula, E m-critical is the critical rock deformation modulus, MPa; P max is the maximum internal pressure of the gas storage cavern, MPa; μ is the Poisson's ratio of the surrounding rock; [σ] is the allowable stress of the steel, MPa; E s is the elastic modulus of steel, MPa; γ s is the Poisson's ratio of steel; δ is the cumulative gap value between the tunnel surrounding rock and the structure, m; r is the lining radius of the tunnel, m; In said S4, the maximum gas storage pressure P required by the target gas storage cavern is max and the critical rock deformation modulus E of the target gas storage cavern m-critical The correlation calculation expression is: Based on the properties of various typical steel lining materials, a "feasibility criterion" zoning map for shallow underground gas storage project construction was drawn; In said S4, the maximum gas storage pressure P required by the target gas storage cavern is max and the rock deformation modulus E of the target gas storage cavern m The correlation calculation expression is: Based on the properties of various typical steel lining materials, a table of recommended maximum gas storage pressures under different rock mass conditions is drawn.

Images