Design method of unfavorable geological section treatment structure of underground storage cavern

Abstract

The invention provides a design method for an unfavorable geological section treatment structure of an underground storage. The design method comprises the steps that S1, the structure size of the gas storage and the set size of the treatment structure are determined; s2, the thrust Fd borne by the replacement concrete, the thrust Fu generated by the internal pressure of the gas storage borne by the replacement concrete and the additionally-improved bearing capacity Fv of the reinforcing steel bar sets on the replacement concrete are calculated; s3, calculating a structural stability safety coefficient Ks of the processing structure according to Fd, Fu and Fv; and S4, comparing Ks with a specified structural stability safety coefficient K's, if Ks is greater than or equal to K's, ending verification, otherwise, adjusting the prepared size of the processing structure and / or the structural size of the gas storage, and then returning to S1. According to the invention, the safety problem of the gas storage caused by the characteristics of low strength, easy deformation and the like of the weak structural layer can be prevented.

Description

Technical Field

[0001] The invention relates to the technical field of compressed air energy storage, and in particular to a design method for a treatment structure of a poor geological section of an underground reservoir. Background Art

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

[0003] Due to the uncertainty of geological conditions and the limitations of many factors such as the scope of the project site, the level of geological survey, and the scale of the project, it is usually difficult for gas storage caverns to avoid crossing or intersecting weak structural layers such as weak interlayers and faults. Since the weak structural layers have low strength and are easy to deform, they pose a great threat to the stability of the cavern surrounding rock and the safety of the sealing structure. At the same time, the exposed thickness of the weak structural layers in different cave sections is not the same, and the degree of influence of weak structural layers of different thicknesses on the stability of the cavern structure is also different. Therefore, reasonable structural treatment and design for weak structural layers of different thicknesses is crucial to ensure the safety and stability of the gas storage during the operation period.

[0004] In summary, there is an urgent need for a design method for treating a structure of an underground reservoir with poor geological conditions to solve the problems existing in the prior art. Summary of the invention

[0005] The purpose of the present invention is to provide a design method for treating the bad geological section of an underground reservoir, aiming to solve the problem that the weak structural layer, due to its low strength and easy deformation, poses a great threat to the stability of the surrounding rock of the cavern and the safety of the sealing structure. The specific technical scheme is as follows:

[0006] A method for designing a treatment structure for a bad geological section of an underground reservoir, wherein the gas storage reservoir comprises a sealing steel plate, backfill concrete and surrounding rock, wherein the backfill concrete is arranged between the sealing steel plate and the surrounding rock, and the treatment structure comprises a replacement concrete arranged between a weak structural layer and the backfill concrete and a reinforcing steel bar group buried in the replacement concrete; the replacement concrete has an isosceles trapezoidal cross section in the radial direction of the gas storage reservoir, wherein the upper base of the isosceles trapezoid is connected to the weak structural layer, the lower base of the isosceles trapezoid is connected to the backfill concrete, and the two waists of the isosceles trapezoid are connected to the surrounding rock on both sides of the replacement concrete, and the length L3 of the upper base is less than the length L1 of the lower base:

[0007] The design method includes verifying whether the structural stability safety factor of the current treatment structure is qualified, and the specific steps are as follows:

[0008] S1. Determine the structural dimensions of the gas storage and the proposed dimensions of the processing structure;

[0009] S2. Calculate the resistance thrust force F on the replacement concrete d , the thrust force F generated by the internal pressure of the gas storage reservoir on the replacement concrete u and the additional bearing capacity F improved by the reinforcing steel bar group for the replacement concrete v ;

[0010] S3. According to F d , F u and F v calculate the structural stability safety factor K of the treatment structure s ;

[0011] S4. Compare the structural stability safety factor K s with the specified structural stability safety factor K′ s . If K s ≥K′ s then end the verification. Otherwise, adjust the proposed dimensions of the treatment structure and / or the structural dimensions of the gas storage reservoir and then return to step S1.

[0012] Preferably, the reinforcing steel bar group includes a plurality of arch rib assemblies arranged at intervals along the height direction of the isosceles trapezoid; each arch rib assembly includes a steel bar arch rib and stirrups, and the plurality of steel bar arch ribs are arranged at intervals along the longitudinal direction of the gas storage reservoir, and the steel bar arch ribs arranged at intervals longitudinally are connected in series by stirrups.

[0013] Preferably, the steel bar arch rib is arched, its crown is located on the side close to the backfill concrete, and its springing is located on the side close to the weak structural layer; the steel bar arch rib is anchored in the surrounding rock through an anchoring section at the springing, and a plurality of stirrups are arranged at intervals along the circumferential direction of the steel bar arch rib.

[0014] Preferably, the length L3 of the upper base is equal to the maximum thickness of the weak structural layer, and the two endpoints of the upper base are respectively connected to the surrounding rock on both sides of the weak structural layer.

[0015] Preferably, the distance L2 between the upper base and the lower base and the length L3 of the upper base satisfy: L2 = N·L3, where N is 1.5 - 2.0.

[0016] Preferably, the included angle θ between the waist side of the isosceles trapezoid and the horizontal plane is 30° - 60°.

[0017] Preferably, calculate the resistance thrust force F on the replacement concrete according to formula (9) d :

[0018] F d = F s cosθ + F n sinθ (9),

[0019] Calculate the thrust force F generated by the replacement concrete due to the internal pressure of the gas storage reservoir according to formula (10). u :

[0020]

[0021] Calculate the additional bearing capacity F of the replacement concrete enhanced by the reinforcing steel bar group according to formula (11). v :

[0022]

[0023] Among them, the waist side of the isosceles trapezoid represents the replacement surface where the replacement concrete is in contact with the surrounding rock, and F n is the normal pressure acting on the replacement surface of the replacement concrete, F s is the shear force acting on the replacement surface of the replacement concrete, θ is the angle between the replacement surface and the horizontal direction, p is the internal pressure of the gas storage reservoir, p2 is the internal pressure borne by the surrounding rock, σ R is the resistance limit value of the sealing steel plate, t is the thickness of the sealing steel plate, r is the radius of the sealing steel plate, L1 is the length of the lower bottom side of the cross-section of the replacement concrete in the radial direction of the gas storage reservoir, f c is the design value of the compressive strength of the steel bar arch rib, f t is the design value of the tensile strength of the steel bar arch rib. is the stability coefficient of the replacement concrete structure, A s is the sum of the cross-sectional areas of all the steel bar arch ribs on the replacement surface.

[0024] Preferably, calculate the normal pressure F acting on the replacement surface of the replacement concrete according to formula (6). n :

[0025]

[0026] Calculate the shear force F acting on the replacement surface of the replacement concrete according to formula (7). s :

[0027]

[0028] Among them, dl is the differential element; L2 is the distance between the upper bottom side and the lower bottom side of the cross-section of the replacement concrete in the radial direction of the gas storage reservoir; σ n represents the normal stress acting on the replacement surface; τ n represents the shear stress acting on the replacement surface; f R is the friction coefficient between the replacement concrete and the surrounding rock.

[0029] Preferably, calculate the normal stress σ acting on the replacement surface according to formula (4). n :

[0030]

[0031] Calculate the shear stress τ acting on the replacement surface according to formula (5) n :

[0032] τ n = σ n f R + C R (5),

[0033] wherein, σ x is the in-situ stress in the horizontal direction of the gas storage reservoir; σ y is the in-situ stress in the vertical direction of the gas storage reservoir; C R is the cohesion between the replacement concrete and the surrounding rock; π is the ratio of the circumference of a circle to its diameter.

[0034] Preferably, calculate the structural stability safety factor K of the current treatment structure according to formula (12) s :

[0035]

[0036] Applying the technical solution of the present invention has the following beneficial effects:

[0037] The replacement concrete of the present invention has an isosceles trapezoidal cross-section in the radial direction of the gas storage reservoir. The lower base is the long side, which has a large contact area with the backfill concrete, reducing the pressure on the replacement concrete and preventing the replacement concrete from being damaged. At the same time, by connecting with the surrounding rock through the two waist sides, the internal pressure on the replacement concrete can be evenly distributed to the surrounding rock on both sides, reducing the stress on the weak structural layer and preventing the weak structural layer from causing safety problems to the gas storage reservoir due to its low strength and easy deformation.

[0038] The present invention buries a reinforcing steel bar group in the replacement concrete, which can well improve the stress form of the replacement concrete structure, transfer more of the pressure borne by the middle part of the replacement concrete structure to the surrounding rock on both sides, and at the same time increase the shear resistance of the replacement surface, improving the bearing capacity and structural safety reserve of the replacement concrete structure.

[0039] The design method of the present invention can verify whether the structural stability safety factor of the current treatment structure is qualified, timely discover the deficiencies in the design, and help the designers timely adjust the relevant structural dimensions. At the same time, by conducting the verification of the structural stability safety factor, it can help the designers understand the key factors affecting the structural stability safety factor and provide a direction for adjusting the structural stability safety factor.

[0040] In addition to the purposes, features and advantages described above, the present invention has other purposes, features and advantages. The present invention will be further described in detail below with reference to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings, which form a part of this application, are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0042] Figure 1 It is a schematic cross-sectional view of the gas storage reservoir after being processed by the processing structure of the present invention;

[0043] Figure 2 is Figure 1 A partial structural schematic diagram after hiding the reinforcing bar group at location A in

[0044] Figure 3 is Figure 1 A top view of the reinforcing bar group at location A in

[0045] Figure 4 is Figure 3 A side view of the reinforcing bar group in

[0046] Figure 5 It is a flowchart for verifying the structural stability safety factor of the current processing structure;

[0047] Figure 6 It is a flowchart for determining the most economical thickness of the sealing steel plate;

[0048] Figure 7 It is a construction flowchart of the processing structure;

[0049] Among them, 1 - soft structural layer; 2 - surrounding rock; 3 - replacement concrete; 4 - replacement surface; 5 - steel bar arch rib; 6 - stirrup; 7 - anchorage section; 8 - sealing steel plate; 9 - backfill concrete; 10 - gas storage reservoir. Detailed implementation manners

[0050] For the convenience of understanding the present invention, the present invention will be described more comprehensively below, and preferred embodiments of the present invention are given. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure content of the present invention more thorough and comprehensive.

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

[0052] Embodiment 1:

[0053] The existing underground high-pressure gas storage 10 generally adopts a combined load-bearing structure composed of a sealed steel plate 8, backfilled concrete 9, and surrounding rock 2. The backfilled concrete 9 is arranged between the sealed steel plate 8 and the surrounding rock 2. The function of the sealed steel plate 8 is to prevent high-pressure gas leakage and bear part of the internal pressure. The backfilled concrete 9 is a force-transferring structure, which is responsible for evenly conducting the pressure to the surrounding rock 2, and the internal pressure it bears can be ignored as a safety reserve. The surrounding rock 2 bears most of the pressure loads inside the gas storage 10.

[0054] Due to the uncertainty of geological conditions and being restricted by many factors such as the scope of the engineering site, the level of geological exploration, and the engineering scale, the gas storage 10 usually inevitably crosses or intersects with a weak structural layer 1 (i.e., a bad geological section, such as a weak interlayer, a fault, etc.). The weak structural layer 1 has problems such as low strength and easy deformation, which pose a great threat to the stability of the surrounding rock of the gas storage 10 and the safety of the sealing structure. In response to this, this embodiment provides a treatment structure for the bad geological section of the underground storage (the underground storage is the underground high-pressure gas storage), as Figures 1 - 4 shown, the treatment structure includes replacement concrete 3 arranged between the weak structural layer 1 and the backfilled concrete 9 and a reinforcing steel bar group buried inside the replacement concrete 3. The cross-section of the replacement concrete 3 in the radial direction of the gas storage 10 is an isosceles trapezoid. The upper base of the isosceles trapezoid is connected to the weak structural layer 1, its lower base is connected to the backfilled concrete 9, and its two waist sides are respectively connected to the surrounding rock 2 on both sides of the replacement concrete 3. The length L3 of the upper base is less than the length L1 of the lower base.

[0055] In this embodiment, the cross-section of the replacement concrete in the radial direction of the gas storage is an isosceles trapezoid, and the lower base is the long side, which has a large contact area with the backfilled concrete 9, reducing the pressure on the replacement concrete and preventing the replacement concrete from being damaged. At the same time, by connecting the two waist sides to the surrounding rock, the internal pressure on the replacement concrete can be evenly distributed to the surrounding rock on both sides, reducing the stress on the weak structural layer and preventing the weak structural layer from causing safety problems to the gas storage due to its low strength and easy deformation. Among them, when constructing the replacement concrete 3, first groove excavation is carried out at the position of the weak structural layer 1 and the cross-section of the groove excavation is measured. After meeting the design requirements, the base surface is cleaned. After the groove excavation is completed, the replacement concrete 3 is poured and constructed at the groove excavation position.

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

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

[0058] Since the cross-section of the replacement concrete 3 in the radial direction of the gas storage reservoir 10 is an isosceles trapezoid, the relationship among L1, L2, and L3 satisfies:

[0059] L1 = 2L2tanθ + L3 (1),

[0060] See Figure 3 and Figure 4 , the reinforcing steel bar group includes a plurality of arch rib assemblies arranged at intervals along the height direction of the isosceles trapezoid; each arch rib assembly includes a steel bar arch rib 5 and stirrups 6. A plurality of steel bar arch ribs 5 are arranged at intervals along the longitudinal direction of the gas storage reservoir 10, and the plurality of longitudinally spaced steel bar arch ribs 5 are connected in series by stirrups 6 ( Figure 4 the stirrups 6 are not shown in

[0061] Further, the steel bar arch rib 5 is arched, its crown is located on the side close to the backfill concrete 9, and its arch feet are located on the side close to the weak structural layer 1. The steel bar arch rib 5 is anchored in the surrounding rock 2 through an anchoring section 7 at the arch feet, and a plurality of stirrups 6 are arranged at intervals along the circumferential direction of the steel bar arch rib 5. The reinforcing steel bar group can transfer more of the pressure borne by the middle part of the replacement concrete 3 structure to the surrounding rocks on both sides, and at the same time increase the shear resistance of the replacement surface.

[0062] Preferably, to ensure that the structural strength of the replacement concrete 3 itself meets the stress requirements, in this embodiment, the strength grade of the replacement concrete is taken to be not less than C30.

[0063] To ensure the safety of the treatment structure in this embodiment and the economy of the gas storage reservoir design, this embodiment also provides a design method for the above treatment structure. The design method is to verify whether the structural stability safety factor of the current treatment structure is qualified and provides detailed treatment steps for guiding the rapid determination of the most economical thickness of the sealing steel plate:

[0064] See Figure 5 , the steps for verifying whether the structural stability safety factor of the current treatment structure is qualified are specifically as follows:

[0065] S1. Determine the structural dimensions of the gas storage reservoir and the proposed dimensions of the treatment structure;

[0066] Specifically, the proposed dimensions of the treatment structure include the proposed structural dimensions of the replacement concrete and the proposed structural dimensions of the reinforcement steel bar group. The proposed dimensions of the treatment structure are determined according to the dimensions of the weak structural layer. Since the cross-section of the replacement concrete in the radial direction of the gas storage reservoir is an isosceles trapezoid, the structural dimensions of the replacement concrete should meet the requirements of formula (1).

[0067] S2. Calculate the resistance thrust F d received by the replacement concrete, the thrust F u generated by the internal pressure in the gas storage reservoir on the replacement concrete, and the additional bearing capacity F v provided by the reinforcement steel bar group to the replacement concrete;

[0068] See Figure 2 . The internal pressure sharing in the gas storage reservoir satisfies formula (2):

[0069] p = p1 + p2 (2), where the internal pressure p1 borne by the sealing steel plate can be expressed as:

[0070]

[0071] where: p is the internal pressure in the gas storage reservoir; p1 is the internal pressure borne by the sealing steel plate (this part of the internal pressure is offset by the deformation of the sealing steel plate); p2 is the internal pressure borne by the surrounding rock; σ R is the resistance limit value of the sealing steel plate, in MPa; t is the thickness of the sealing steel plate, in m; r is the radius of the sealing steel plate, in m.

[0072] The normal stress and shear stress on the replacement surface under the ultimate state are:

[0073]

[0074] τ n = σ n f R + C R (5),

[0075] where, σ x is the horizontal in-situ stress of the gas storage reservoir, in MPa; σ y is the vertical in-situ stress of the gas storage reservoir, in MPa; θ is the angle between the replacement surface and the horizontal direction, in degrees; f R is the friction coefficient between the replacement concrete and the surrounding rock; C R is the cohesion between the replacement concrete and the surrounding rock, in MPa; σ n represents the normal stress acting on the replacement surface; τ nDenote the shear stress acting on the replacement surface; π is the ratio of the circumference of a circle to its diameter.

[0076] Obtain the normal pressure F acting on the replacement surface n and the shear force F s as:

[0077]

[0078] wherein, dl is the differential element; L2 is the distance between the upper base and the lower base of the replacement concrete (i.e., the height of the isosceles trapezoid), with the unit of m.

[0079] Substitute formula (5) into formula (7) to obtain:

[0080]

[0081] Obtain the resistance thrust F received by the replacement concrete d as:

[0082] F d = F s cosθ + F n sinθ (9),

[0083] The thrust F generated by the internal pressure of the gas storage in the replacement concrete (the internal pressure here is the internal pressure p2 borne by the surrounding rock) u is:

[0084]

[0085] The additional bearing capacity F of the replacement concrete improved by the reinforcing steel bar group v is:

[0086]

[0087] wherein, f c is the design value of the compressive strength of the steel arch rib; f t is the design value of the tensile strength of the steel arch rib; is the stability coefficient of the replacement concrete structure; A s is the sum of the cross-sectional areas of all the steel arch ribs on the replacement surface.

[0088] S3. Calculate the structural stability safety factor K of the processing structure s ;

[0089] After obtaining the resistance thrust F received by the replacement concrete d , the thrust F generated by the internal pressure of the gas storage received by the replacement concrete u and the additional bearing capacity F of the replacement concrete improved by the reinforcing steel bar group v , the structural stability safety factor K of the current processing structure can be calculated according to formula (12)s :

[0090]

[0091] S4. Compare the structural stability safety factor K s with the specified structural stability safety factor K′ s . If K s ≥K′ s , end the verification; otherwise, after adjusting the proposed dimensions of the treatment structure and / or the structural dimensions of the gas storage reservoir, return to step S1.

[0092] Specifically, according to the safety level of the gas storage reservoir and the hole diameter D, look up the table to obtain the specified structural stability safety factor K′ under the current structural dimensions of the gas storage reservoir s ; in this embodiment, a value table of the structural stability safety factor K′ under different safety levels of the gas storage reservoir and different specifications of the hole diameter D is provided s , as shown in Table 1:

[0093] Table 1: Structural stability safety factor K′ of the replacement concrete s Value table

[0094]

[0095] When K s ≥K′ s , it indicates that the structural stability safety factor of the treatment structure under the current proposed dimensions is qualified. If K s <K′ s , it indicates that the structural stability safety factor of the treatment structure under the current proposed dimensions is unqualified, and it is necessary to adjust the proposed dimensions of the treatment structure and / or the structural dimensions of the gas storage reservoir (here, the structural dimensions of the gas storage reservoir refer to the thickness dimension of the sealing steel plate. When the structural dimensions of the gas storage reservoir are not determined, the structural stability safety factor can be adjusted by adjusting the structural dimensions of the gas storage reservoir) to ensure the safety of the gas storage reservoir. Through steps S1 - S4, it is possible to verify whether the current structural dimensions of the gas storage reservoir and the current proposed structural dimensions of the treatment structure meet the safety requirements, helping designers to adjust the relevant structural dimensions in a timely manner.

[0096] Furthermore, referring to Figure 6 , the specific steps to quickly determine the most economical thickness of the sealing steel plate are as follows:

[0097] A1. Determine the hole diameter and safety level of the gas storage reservoir, and at the same time determine the proposed dimensions of the treatment structure;

[0098] Specifically, the hole diameter and safety level of the gas storage reservoir are confirmed according to the design requirements of the gas storage reservoir. The determination of the proposed dimensions of the treatment structure is the same as in step S1, so it will not be elaborated here.

[0099] A2. Determine the structural stability safety factor K′ specified for the replacement concrete according to the borehole diameter and safety level of the gas storage reservoir s , and meanwhile, calculate the resistance thrust force F exerted on the replacement concrete d and the additional bearing capacity F provided by the reinforcement steel bar group for the replacement concrete v ;

[0100] Specifically, look up the table (i.e., query Table 1) according to the borehole diameter and safety level of the gas storage reservoir to obtain the structural stability safety factor K′ specified for the replacement concrete s , then calculate the resistance thrust force F exerted on the replacement concrete according to formula (9) d , and calculate the additional bearing capacity F provided by the reinforcement steel bar group for the replacement concrete according to formula (11) v .

[0101] A3. Calculate the most economical thickness t′ of the sealing steel plate;

[0102]

[0103] where p is the internal pressure of the gas storage reservoir; σ R is the resistance limit value of the sealing steel plate; r is the radius of the sealing steel plate; L1 is the length of the lower bottom edge of the cross-section of the replacement concrete in the radial direction of the gas storage reservoir.

[0104] According to steps A1 - A3, after confirming the proposed dimensions of the treatment structure, the most economical thickness of the sealing steel plate in the gas storage reservoir can be quickly confirmed, guiding the selection of the thickness of the sealing steel plate, and achieving the effect of saving project investment.

[0105] See Figure 7 , in this embodiment, the brief construction steps of the treatment structure for the poor geological section of the underground high-pressure gas storage reservoir are as follows:

[0106] B1. Design the thickness of the sealing steel plate and the structural dimensions of the replacement concrete according to the weak structural layer, and determine the final design scheme after verification;

[0107] B2. Groove and excavate the position of the weak structural layer according to the design scheme, measure the excavation section, and carry out base surface cleaning after meeting the design requirements;

[0108] B3. Bury embedded parts such as the reinforcement steel bar group, sensors, and grouting pipes;

[0109] B4. Erect the formwork and pour the replacement concrete;

[0110] B5. Remove the formwork after the strength of the replacement concrete meets the requirements, and carry out backfill grouting;

[0111] B6. After passing the quality inspection, carry out the pouring of the replacement soil for the next section.

[0112] Example 2:

[0113] The net cross-sectional diameter of a compressed air energy storage chamber is 10 m. The gas storage reservoir requires a safety level of Class I, the designed maximum operating pressure is 10 MPa, the sealing steel plate uses Q490R steel, the designed thickness of the steel plate is 20 mm, and the measured in-situ stress of the chamber is σ x = 9 MPa, σ y = 7 MPa. There is a soft interlayer with a maximum exposed thickness of 1.5 m at the waist of some sections of the chamber; C30 replacement concrete is designed to be used, and the structural dimensions are L1 = 4.10 m, L2 = 2.25 m, L3 = 1.50 m, θ = 30°, f R is taken as 0.8, and C R is taken as 0.8 MPa; three layers of arch rib components are arranged in the replacement concrete structure, and HRBF400 steel bars are used, and the layout spacing is 200 mm; the calculated stability safety factor K s of the replacement concrete structure is 1.18, which is greater than 1.10 in Table 1, meeting the structural stability requirements.

[0114] Example 3:

[0115] The net cross-sectional diameter of a compressed air energy storage chamber is 12 m, the designed maximum operating pressure is 11 MPa, the safety level of the gas storage reservoir is Class I, the sealing steel plate uses Q490R steel, and the measured in-situ stress of the chamber is σ x = 9 MPa, σ y = 7 MPa. There is a soft interlayer with a maximum exposed thickness of 1.5 m at the waist of some sections of the chamber. C30 replacement concrete is designed to be used, and the structural dimensions of the replacement concrete are L1 = 4.10 m, L2 = 2.25 m, L3 = 1.50 m, θ = 30°; f R is taken as 0.8, and C R is taken as 0.8 MPa. Three layers of arch rib components are arranged in the replacement concrete structure, and HRBF400 steel bars are used, and the layout spacing is 200 mm; on the premise of meeting the requirement that the structural stability safety factor is not less than 1.10, the most economical thickness t′ of the sealing steel plate is calculated to be 35 mm.

[0116] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for designing a treatment structure for a poor geological section of an underground reservoir, wherein the gas storage reservoir (10) comprises a sealing steel plate (8), backfill concrete (9) and surrounding rock (2), wherein the backfill concrete (9) is arranged between the sealing steel plate (8) and the surrounding rock (2), and the treatment structure comprises replacement concrete (3) arranged between a weak structural layer (1) and the backfill concrete (9) and a reinforcing steel bar group buried in the replacement concrete (3); the cross section of the replacement concrete (3) in the radial direction of the gas storage reservoir (10) is an isosceles trapezoid, the upper base of the isosceles trapezoid is connected to the weak structural layer (1), the lower base is connected to the backfill concrete (9), and the two waists are respectively connected to the surrounding rock (2) on both sides of the replacement concrete (3), the length L3 of the upper base is less than the length L1 of the lower base, and the characteristics are: The design method includes verifying whether the structural stability safety factor of the current treatment structure is qualified, and the specific steps are as follows: S1. Determine the structural dimensions of the gas storage and the proposed dimensions of the processing structure; S2. Calculate the thrust force F on the replacement concrete d , the thrust F generated by the internal pressure of the gas storage tank on the replacement concrete u And the additional bearing capacity F of the replacement concrete is increased by the reinforcement group v ; S3. According to F d 、F u and F v Calculate the structural stability safety factor K of the processed structure s ; S4. The structural stability safety factor K s Compared with the specified structural stability safety factor K′ s For comparison, if K s ≥K′ s The verification is then ended, otherwise the proposed size of the processing structure and / or the structural size of the gas storage reservoir is adjusted and the process returns to step S1.

2. The design method according to claim 1, characterized in that: The reinforcing steel bar group comprises a plurality of arch rib assemblies arranged at intervals along the height direction of the isosceles trapezoid; the arch rib assemblies comprise steel bar arch ribs (5) and stirrups (6); the plurality of steel bar arch ribs (5) are arranged at intervals along the longitudinal direction of the gas storage reservoir (10); and the plurality of steel bar arch ribs (5) arranged at intervals in the longitudinal direction are connected in series via stirrups (6).

3. The design method according to claim 2, characterized in that: The reinforced arch rib (5) is arch-shaped, with its arch top located on a side close to the backfill concrete (9) and its arch foot located on a side close to the weak structural layer (1); the reinforced arch rib (5) is anchored in the surrounding rock (2) at the arch foot through an anchoring section (7), and a plurality of stirrups (6) are provided at intervals along the circumferential direction of the reinforced arch rib (5).

4. The design method according to claim 2, characterized in that: The length L3 of the upper bottom edge is equal to the maximum thickness of the weak structural layer (1), and the two end points of the upper bottom edge are respectively connected to the surrounding rocks (2) on both sides of the weak structural layer (1).

5. The design method according to claim 2, characterized in that: The distance L2 between the upper base and the lower base and the length L3 of the upper base satisfy the following condition: L2=N·L3, wherein N is 1.5-2.

0.

6. The design method according to claim 2, characterized in that: The angle θ between the waist of the isosceles trapezoid and the horizontal plane is 30°-60°.

7. The design method according to any one of claims 2 to 6, characterized in that: According to formula (9), the thrust force F exerted on the replacement concrete is calculated: d : F d =F s cosθ+F n sinθ (9), According to formula (10), the thrust F generated by the internal pressure of the gas storage tank on the replacement concrete is calculated as u : According to formula (11), the additional bearing capacity F of the replacement concrete is calculated by strengthening the steel bar group. v : The waist of the isosceles trapezoid represents the replacement surface where the replacement concrete meets the surrounding rock. n is the normal pressure on the replacement surface of the replacement concrete, F s is the shear force on the displacement surface of the replacement concrete, θ is the angle between the displacement surface and the horizontal, p is the internal pressure of the gas storage, p2 is the internal pressure borne by the surrounding rock, σ R is the resistance limit of the sealing steel plate, t is the thickness of the sealing steel plate, r is the radius of the sealing steel plate, L1 is the length of the lower bottom side of the replacement concrete in the radial direction of the gas storage reservoir, and f c is the design value of the compressive strength of the reinforced arch rib, f t is the design value of tensile strength of reinforced arch rib, is the stability factor of the replacement concrete structure, A s It is the sum of the cross-sectional areas of all reinforced arch ribs on the replacement surface.

8. The design method according to claim 7, characterized in that: According to formula (6), the positive pressure F on the replacement surface of the replacement concrete is calculated as n : According to formula (7), the shear force F on the replacement surface of the replacement concrete is calculated as s : Where, dl is the differential unit; L2 is the distance between the upper and lower bases of the replacement concrete in the radial section of the gas storage reservoir; σ n represents the normal stress acting on the displacement surface; τ n represents the shear stress acting on the displacement surface; f R is the friction coefficient between replacement concrete and surrounding rock.

9. The design method according to claim 8, characterized in that: According to formula (4), the normal stress σ acting on the displacement surface is calculated as n : The shear stress τ acting on the displacement surface is calculated according to formula (5): n : t n =s n f R +C R (5), Among them, σ x is the horizontal geostress of the gas storage reservoir; y is the vertical ground stress of the gas storage; C R is the cohesion between replacement concrete and surrounding rock; π is the pi.

10. The design method according to claim 1, characterized in that: According to formula (12), the structural stability safety factor K of the current treatment structure is calculated s :

Images