A kind of three-way stress under pressure storage cavern fills-storage-puts gas whole process glass steel sealing performance mesoscale test equipment and method

Abstract

The application belongs to the technical field of energy storage, and particularly relates to a kind of three-way stress under pressure storage cavern charge-storage-gas whole process glass steel sealing performance mesoscale test equipment and method.The test equipment includes glass steel sealing cavity sample, three-way prestress applying device, air pressure pressurizing device, flow control device, monitoring device, can simulate real three-way ground stress environment, carry out high air pressure pressure storage cavern charge-storage-gas whole process test.Monitoring device through intelligent pressure gauge, resistance strain gauge, data acquisition instrument, real-time monitoring sample strain, pressure drop and analyzing data, finally obtain glass steel cavity sealing performance, overall sample stress deformation law.The application effectively solves the technical problems that the existing technology test scene restoration degree is low, and air pressure parameter cannot match actual working condition, can obtain glass steel cavity overall sealing performance and butt joint core area stress deformation characteristics, provides reliable test support for glass steel sealing structure engineering design.

Description

Technical Field

[0001] This invention belongs to the field of energy storage technology, specifically relating to a mesoscale testing equipment and method for the full-process fiberglass sealing performance of a pressurized storage cavern under triaxial stress during the filling-storage-venting process. Background Technology

[0002] Compressed air energy storage is one of the most promising large-scale, long-term physical energy storage technologies. Underground gas storage facilities are its core components, and their sealing performance directly determines the system's operational efficiency and safety. Traditional underground gas storage facilities mostly use steel plate sealing technology, which has disadvantages such as easy cracking and leakage of welds, severe electrochemical corrosion, and high total life cycle costs. Fiberglass, with its advantages of low permeability, strong corrosion resistance, and high specific strength, has become an ideal solution to replace steel plate sealing.

[0003] In practical engineering, the sealing structure of gas storage chambers inevitably has a large number of component connection points. The sealing performance and stress-deformation characteristics of these connection points directly determine the reliability of the entire gas storage system. Currently, there is a lack of experimental methods that can simulate the actual structural form of FRP gas storage chambers, making it impossible to verify the sealing performance of the overall sealed space formed after connection. Furthermore, a system that matches engineering sites, can reproduce the deep-earth triaxial stress environment, and can conduct full-process testing of filling, storage, and venting has not been established. As a result, existing research cannot support the engineering application of FRP sealing technology. Summary of the Invention

[0004] To address existing shortcomings, this invention proposes a mesoscale testing equipment and method for the full-process FRP (fiberglass reinforced plastic) sealing performance of pressurized storage caverns under triaxial stress. By fabricating a FRP butt-wound sealing cavity consistent with engineering connection methods, an integral "FRP-lining-surrounding rock" specimen is constructed. Combined with a triaxially independent and controllable prestressing loading device and a high-pressure inflation / deflation control system, this enables the full-process testing of FRP sealing performance under deep-earth conditions, providing precise experimental support for the engineering design of FRP sealing structures.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows.

[0006] The testing equipment of this invention includes a sample with a fiberglass sealed cavity, a triaxial prestressing device, a pneumatic pressurization device, a flow control device, and a monitoring device. The core structure of each part is as follows:

[0007] (1) Sample containing FRP sealed cavity: From the inside out, the sample consists of FRP sealed cavity, lining layer, and surrounding rock similar material layer, which is the main body of the test. The FRP sealed cavity is formed by coaxially connecting two symmetrical FRP components with straight pipe sections and hemispherical end cap sections. At the joint, the seepage-proof inner lining layer, structural reinforcement layer and outer protective layer are cured from the inside out to form a joint winding reinforcement area, which restores the actual FRP sealing connection form of the project. The lining layer uses the same lining material as the actual project, and the mechanical parameters of the surrounding rock similar material layer match the actual surrounding rock parameters.

[0008] (2) Triaxial prestressing application device: It consists of loosely bonded prestressed steel strands, a hydraulic tensioning machine, and an anchor assembly. The loosely bonded prestressed steel strands are arranged independently along the three orthogonal directions of the specimen, and are equipped with anti-corrosion grease and sheaths, so no additional corrugated pipes are required; the hydraulic tensioning machine applies the pre-set prestress using the post-tensioning method, and the anchor assembly is used to fix the steel strands and maintain a stable triaxial stress state.

[0009] (3) Air pressure pressurization device: It consists of an air compressor and a gas booster pump. It is connected to the fiberglass sealed cavity through an air injection pipe to provide a high-pressure air source that matches the actual working conditions for the test.

[0010] (4) Flow control device: It consists of a gas flow meter, an electric valve and a control box. The control box is electrically connected to the flow meter and the valve. It is used to set and control the charging and discharging rates to achieve controllable operation of the entire process.

[0011] (5) Monitoring device: It consists of a data acquisition instrument, resistance strain gauges, and intelligent pressure gauges. The strain gauges are installed on the straight pipe section, hemispherical end cap, butt-wound reinforcement area, and lining surface of the FRP sealed cavity. The intelligent pressure gauge is installed in the gas path. The monitoring device can collect and analyze the strain and gas pressure parameters in real time during the test.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] (1) The fiberglass sealed cavity is made in accordance with the actual engineering structure, which can truly simulate the fiberglass sealed gas storage chamber after construction is completed, and solves the problem that existing research only focuses on the fiberglass material itself and cannot evaluate the overall sealing performance of the sealed space.

[0014] (2) It can accurately reproduce the three-dimensional geostress environment in deep earth. Combined with the overall structure of "fiberglass-lining-surrounding rock", it can truly restore the collaborative stress state of the project and greatly improve the engineering applicability of the test data;

[0015] (3) It can realize the full process test of charging-storage-discharging matching the actual working conditions, and simultaneously obtain the overall sealing performance of the FRP sealed cavity and the stress deformation characteristics of the docking core area, providing accurate data support for the design and construction of deep underground compressed air energy storage FRP sealed caverns. Attached Figure Description

[0016] Figure 1 is a schematic diagram of the connection of a mesoscale test equipment and method for the full process of filling, storing and releasing gas in a pressurized storage cavern under triaxial stress.

[0017] Figure 2 is a schematic diagram of the fiberglass sealed cavity;

[0018] Figure 3 is a schematic diagram of the casting lining mold;

[0019] Figure 4. Schematic diagram of a perforated template for casting similar materials to the surrounding rock;

[0020] Figure 5 is a schematic cross-sectional view of the sample containing a fiberglass sealed cavity;

[0021] Figure 6 is a schematic diagram of a device for simulating a triaxial geostress environment using prestressed steel strands;

[0022] Figure 7 is a schematic diagram of the tensioning end and fixed end nodes of the prestressed steel strand.

[0023] Figure 8 is a flowchart of a mesoscale test method for the sealing performance of fiberglass reinforced plastic (FRP) in a pressurized storage cavern under triaxial stress throughout the filling, storage, and venting process.

[0024] In the figure: 11 FRP sealed cavity, 12 left FRP pipe specimen, 13 right FRP pipe specimen, 14 FRP pipe specimen joint, 15 inner lining impermeable layer and structural layer, 16 air injection pipe, 17 high-strength concrete layer; 21 axial strain gauge, 22 circumferential strain gauge, 23 data acquisition instrument, 24 smart pressure gauge; 31 air compressor, 32 booster pump; 41 mold used for pouring high-strength concrete, 42 reserved hole (reserved for air injection pipe).

[0025] In the figure: 1. Sample with FRP sealed cavity; 2. Triaxial prestressing device; 3. Air pressure device; 4. Flow control device; 5. Monitoring device; L1, L2, L3, L4. Valves; D1. Electric valve; 101. Mold used for pouring lining layer; 102. Reserved hole (for air injection pipe); 103. Opening template for pouring surrounding rock similar material.

[0026] Among them: 11 FRP sealed cavity, 12 FRP pipe left specimen, 13 FRP pipe right specimen, 14 FRP pipe specimen joint, 15 inner lining impermeable layer and structural layer, 16 gas injection pipe, 17 lining layer, 18 surrounding rock similar material layer.

[0027] 21 Slow-bonding prestressed steel strand, 22 Hydraulic tensioning machine, 23 Fixed end extrusion anchor, 24 Anchor plate, 25 Anchor bottom spiral stirrup, 26 Tensioning end wedge anchor.

[0028] 31 Air compressor, 32 Gas booster pump;

[0029] 41 Gas flow meter; 42 Control box;

[0030] 51 Axial measuring point of resistance strain gauge, 52 Circumferential measuring point of resistance strain gauge, 53 Data acquisition instrument, 54 Intelligent pressure gauge. Detailed Implementation

[0031] The specific implementation and operation methods of a mesoscale testing equipment and method for the full-process filling-storage-venting of a pressure reservoir under triaxial stress are as follows:

[0032] (1) Based on the dimensions of the fiberglass sealed cavity designed for the experiment, two symmetrical fiberglass pipe specimens 12 and 13, which are integrally formed with straight pipe sections and hemispherical end caps, were prefabricated. The two components were coaxially connected by butt-wound. At the joint 14 of the fiberglass pipe specimen, an impermeable inner lining, a structural reinforcement layer and an outer protective layer were formed sequentially from the inside to the outside. After curing, an impermeable inner lining layer and a structural layer 15 and a complete fiberglass sealed cavity 11 were formed. The butt-wound structure can simulate the connection process of fiberglass components in actual engineering. Holes were drilled at appropriate positions in the fiberglass sealed cavity 11, and the gas injection pipe 16 was connected to the fiberglass sealed cavity 11 by bolts. Axial measuring points 51 and circumferential measuring points 52 of resistance strain gauges were arranged on the surface of the straight pipe section, hemispherical end cap and butt-wound reinforcement area of ​​the fiberglass sealed cavity 11 to realize the deformation monitoring of the surface of the fiberglass sealed cavity during the subsequent test.

[0033] (2) Drill holes at appropriate positions in the mold 101 used for pouring the lining layer (which should correspond to the position of the air injection pipe 16 of the fiberglass sealing cavity) to reserve positions for the air injection pipe. Place the fiberglass sealing cavity 11 into the mold 101 used for pouring the lining layer and pour concrete to form the lining layer 17. After the lining layer is poured, wait for it to solidify, demold, and cure. Arrange axial measuring points 51 and circumferential measuring points 52 of resistance strain gauges on the surface of the lining layer 17 to monitor the deformation of the lining layer surface during subsequent tests.

[0034] (3) Based on the target triaxial stress values, calculate the number of prestressed steel strands 21 required in each direction, their spacing, and the tension force per strand. Design the formwork 103 for casting similar materials around the surrounding rock, ensuring that the opening positions on each side of the formwork are consistent with the design coordinates. Prepare components such as anchor plates 24, spiral stirrups under the anchor 25, fixed-end compression anchors 23, and tension-end wedge anchors 26.

[0035] (4) At the fixed end of the specimen, install the fixed end extrusion anchor 23 at the end of the loosely bonded prestressed steel strand 21. Pass the loosely bonded prestressed steel strand 21 with the fixed end extrusion anchor 23 through the corresponding hole of the perforated template 103 for the surrounding rock, and use the template for end positioning. Tie a steel grid inside the template to provide auxiliary support and positioning for the middle section of the loosely bonded prestressed steel strand 21, forming a preliminary spatial skeleton. At the tensioning end of the specimen, install the anchor plate 24 tightly against the inside of the template, and tie the anchor spiral stirrup 25 behind it. Pass the other end of the loosely bonded prestressed steel strand 21 through the area of ​​the anchor plate 24 and the anchor spiral stirrup 25, in preparation for subsequent tensioning.

[0036] (5) Place the specimen with the lining layer poured into the center of the template frame and fix it. Lead out the wires of the resistance strain gauge and connect them to the data acquisition instrument 53 to complete the debugging of the monitoring system. Pour the surrounding rock similar material into the template. After pouring, perform standard curing until the design strength is reached to form the surrounding rock similar material layer 18.

[0037] (6) Remove the lateral formwork. Install the tensioning end anchor 26 and hydraulic tensioning machine 22 at the tensioning end. Perform post-tensioning on the loosely bonded prestressed steel strands 21 in all directions according to the design tension force. During the tensioning process, the strain data is collected in real time by the data acquisition instrument 53 to monitor the strain response of the test specimen and verify the prestress transfer effect. After all loosely bonded prestressed steel strands 21 in all directions are tensioned and anchored, the system is in a stable triaxial stress state.

[0038] (7) After the above steps are completed, a medium-scale test of the sealing performance of the fiberglass sealing chamber during the entire process of filling, storing and venting can be carried out. During filling: open valves L1 and L3, run air compressor 31, drive gas booster pump 32 to output high-pressure gas, set the gas flow rate through gas flow meter 41 through control box 42, open electric valve D1 to control the gas injection flow rate, observe the gas pressure in fiberglass sealing cavity 11 through intelligent pressure gauge 54 until the design gas pressure is reached, close air compressor 31 and stop filling; close all valves and maintain pressure, observe the pressure drop change through intelligent pressure gauge 54 to obtain the sealing performance of fiberglass sealing cavity; During venting: open valves L2 and L4, set the gas flow rate through gas flow meter 41 through control box 42, open electric valve D1 to control the venting flow rate, observe the gas pressure in fiberglass sealing cavity 11 through intelligent pressure gauge 54 until the venting reaches the design minimum gas storage pressure, at which point the entire filling-storage-venting process is completed. Throughout the experiment, the strain data of the fiberglass sealed cavity surface and the lining layer surface can be stored and analyzed using the data acquisition instrument 53.

Claims

1. A mesoscale testing equipment and method for the sealing performance of a pressurized storage chamber under triaxial stress during the entire process of filling, storing and releasing gas, comprising a sample containing a FRP sealing cavity, a triaxial prestressing device, a gas pressure pressurization device, a flow control device and a monitoring device; The fiberglass-reinforced plastic (FRP) sealed cavity specimen serves as the main body of the test. The triaxial prestressing device acts on the FRP sealed cavity specimen to apply stresses of different directions and magnitudes to the entire specimen. The pneumatic pressurization device injects high-pressure gas into the FRP sealed cavity specimen through an injection pipe. The flow control device controls the flow rate of the injected and released gas. The monitoring device is arranged on the FRP sealed cavity specimen to monitor strain and pressure parameters in real time, enabling data storage and analysis.

2. The testing equipment according to claim 1, characterized in that, The fiberglass-reinforced plastic (FRP) sealed cavity specimen consists of, from the inside out, the FRP sealed cavity, the lining layer, and the surrounding rock similar material layer, which are connected to form an integral structure that shares the load and deforms synchronously. The FRP sealed cavity specimen is a medium-scale cubic specimen with sides of 1.5m × 1.5m × 2m; the lining layer is a concrete pouring layer; and the surrounding rock similar material layer is an artificially prepared rock mass simulation material, covering the outer wall of the lining layer, capable of bearing and uniformly transmitting triaxial prestress to simulate the stress characteristics of real rock mass.

3. The testing equipment according to claim 2, characterized in that, The fiberglass cavity is constructed by connecting two symmetrical fiberglass components, each consisting of a straight pipe section and a hemispherical end cap section. The straight pipe section is 0.7m long and 0.3m in diameter, and the hemispherical end cap is 0.3m in diameter. At the joint, a waterproof inner lining, a structural reinforcement layer, and an outer protective layer are sequentially formed from the inside out. The waterproof inner lining is a resin-impregnated fiberglass surface felt layer, which is rolled and degassed to form a continuous and dense waterproof structure. The structural reinforcement layer is formed by alternating layers of continuous fiberglass filaments and chopped strand mat. Fresh resin is applied before each layer is laid, and the width of each subsequent layer is greater than that of the previous layer, forming a gradual transition structure along the joint to both sides. The outer protective layer is a resin-impregnated outer surface felt layer.

4. The testing equipment according to claim 1, characterized in that, The triaxial prestressing application device consists of a loosely bonded prestressed steel strand, a hydraulic tensioning machine, and an anchor assembly. The loosely bonded prestressed steel strand is arranged independently along the three orthogonal directions of the sample. The hydraulic tensioning machine applies the preset prestress through post-tensioning. The anchor assembly is used to lock the prestress to maintain a stable triaxial stress state.

5. The testing equipment according to claim 4, characterized in that, The anchorage assembly of the triaxial prestressing application device includes a fixed-end compression anchor, a tensioning-end wedge anchor, an anchor plate, and a spiral stirrup under the anchor. The fixed-end compression anchor is pre-embedded in the non-tensioning end of a similar material layer of the surrounding rock to provide reaction force support for tensioning. The anchor plate is used to bear the concentrated tension force and diffuse the stress. The spiral stirrup under the anchor is used to provide circumferential restraint to offset the splitting tensile stress. The tensioning-end wedge anchor is used to lock the prestress of the steel strand after tensioning. The loosely bonded prestressed steel strand comes with anti-corrosion grease and a protective sheath, eliminating the need for additional corrugated pipes. It is arranged independently in layers along the three orthogonal directions of the sample (up / down, left / right, and front / back) to achieve independent control of triaxial stress.

6. The testing equipment according to claim 1, characterized in that, The pneumatic pressurization device includes an air compressor and a gas booster pump connected in series, which inject high-pressure gas into the fiberglass sealed cavity through an injection pipe; the flow control device includes a gas flow meter, an electric regulating valve, and a control box; the control box is electrically connected to the gas flow meter and the electric regulating valve respectively, and is used to preset the flow threshold and adjust the valve opening according to the real-time feedback from the flow meter to achieve precise control of the inflation and deflation rate.

7. The testing equipment according to claim 1, characterized in that, The monitoring device includes a data acquisition instrument, a resistance strain gauge, and a smart pressure gauge. The resistance strain gauge is divided into axial measuring points and circumferential measuring points, which are correspondingly arranged on the straight pipe section, hemispherical end cap, butt-wound reinforcement area, and lining surface of the fiberglass sealed cavity. The smart pressure gauge is connected in series in the gas injection pipeline to collect real-time gas pressure data in the cavity.

8. The testing equipment according to any one of claims 1-7, wherein the operation method is as follows: (1) Prefabricate two symmetrical fiberglass components, and after joining them, form a joint winding reinforcement area at the joint to obtain a fiberglass sealed cavity and install strain monitoring elements on the surface of the cavity; pour the lining layer and cure it to the design strength, install strain monitoring elements on the surface of the lining layer, and complete the debugging of the monitoring system. (2) Based on the preset triaxial stress parameters, calculate the layout parameters and single tension of the prestressed steel strands in each direction, lay out the steel strands and anchor components, pour a similar material layer of surrounding rock and cure it to the design strength, tension the steel strands to the preset prestress through post-tensioning and lock them, and statically stabilize them to form a stable triaxial stress environment. (3) Start the pressurization device, control the inflation rate through the flow control device, and pressurize the fiberglass sealed cavity to the designed maximum gas storage pressure, then close the pressurization device and the gas circuit valve; (4) Close all valves in the charging and discharging circuit to enter the pressure holding stage. Collect the gas pressure data and sample strain data in the cavity throughout the process through the monitoring device. Calculate the leakage rate based on the gas pressure drop and evaluate the overall sealing performance of the fiberglass sealing cavity. (5) Control the venting rate by using a flow control device, open the venting circuit valve, and steadily reduce the gas pressure in the fiberglass sealed cavity to the minimum design gas storage pressure, then close the venting valve. (6) Process and analyze the strain and pressure data collected throughout the filling-storage-discharging process to obtain the overall sealing performance of the fiberglass sealed cavity and the stress deformation law of the sample.

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