A composite lining structure for long-term and efficient hydrogen storage in underground rock caves and its preparation method

Abstract

The present invention belongs to the technical field of underground gas storage, and specifically relates to a long-term and efficient hydrogen storage composite lining structure for underground rock caverns and a preparation method thereof. The long-term and efficient hydrogen storage composite lining structure for underground rock caverns disclosed by the present invention includes surrounding rock and its internal composite structure. The surrounding rock reinforcement layer is formed by pre-grouting with pressure inside the surrounding rock, which can resist the tensile stress transmitted to the surrounding rock by the internal gas pressure and enhance the air tightness; the inner side of the surrounding rock reinforcement layer is a permeable layer, which can discharge groundwater to prevent hydrostatic pressure from causing extrusion deformation and damage to the concrete bearing layer during construction and causing instability of the sealed steel lining; the reinforced concrete bearing layer is arranged on the inner side of the permeable layer and the outer side of the sliding layer, and micro self-healing capsules that can repair cracks and enhance sealing are evenly added during the injection molding process; the drag-reducing sliding layer is between the steel lining and the bearing layer, which inhibits the shear damage of the sealing steel lining to the bearing layer under high internal pressure; the steel lining sealing layer is arranged on the inner side of the sliding layer to bear part of the gas load and seal the gas.

Description

Technical Field

[0001] The present invention belongs to the technical field of underground gas storage, and in particular relates to a long-term and efficient hydrogen storage composite lining structure for an underground rock cave and a preparation method thereof. Background Art

[0002] Large-scale hydrogen storage in underground space is a key technology to overcome the regional and non-sustainable supply of clean energy such as wind, light, and water. The density of hydrogen is extremely low. Under standard conditions, its density is only one ten-thousandth of that of water. Under conditions of limited storage space, high-pressure compressed hydrogen is required to meet the requirements. Hydrogen storage caverns face the risk of instability under high internal pressure. The atomic radius of hydrogen is very small and can pass through most micropores. Under high temperature and high pressure, hydrogen can even pass through conventional sealing barriers, which makes it easy for hydrogen to leak through tiny gaps or holes during storage. Therefore, in order to cope with the problems of surrounding rock instability and sealing failure control faced by hydrogen storage, it is necessary to provide an underground hydrogen storage composite structure to achieve long-term and stable storage of hydrogen.

[0003] The basic concept of the Skallen gas storage chamber in Sweden is that the high-pressure load is entirely borne by the high-strength surrounding rock, and the backfill concrete only serves to transfer the load, which places extremely high demands on the geological conditions of the site. If the bearing capacity of the gas storage composite structure can be fully mobilized, the requirements for the strength of the surrounding rock can be greatly reduced, and even the underground space of abandoned mines can be used. The traditional underground gas storage structure uses a steel lining as a sealing layer, and a reinforced concrete bearing layer is set on the outside of the sealing layer. However, in actual applications, the slippage of the steel lining under the high internal pressure of the gas storage will cause shear damage to the concrete. In addition, the internal air pressure is transmitted to the concrete through the steel lining, which is very easy to crack the concrete.

[0004] Therefore, how to reduce the shear damage of the steel lining to the concrete lining has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0005] In view of this, the first object of the present invention is to provide a long-term and efficient hydrogen storage composite lining structure for an underground rock cave in order to address the problems existing in the prior art.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A long-term and efficient hydrogen storage composite lining structure for an underground rock cave, comprising, from outside to inside, surrounding rock, a surrounding rock reinforcement layer, a permeable layer, a bearing layer, a sliding layer and a sealing layer, wherein the surrounding rock reinforcement layer is formed by applying pressure pre-grouting to the surrounding rock, and the surrounding rock reinforcement layer is a closed space;

[0008] The thickness of the permeable layer is 10-20 mm, a drainage pipe is arranged inside, and the drainage pipe is fixed by spraying concrete;

[0009] The bearing layer is a self-compacting reinforced concrete bearing layer with a thickness of 500-800 mm, in which sodium fluorosilicate curing agent and micro self-healing capsules are evenly distributed;

[0010] The thickness of the sliding layer is 5-10 mm, and it consists of a low-friction polymer modified asphalt layer in the middle and geotextiles on both sides, and one side of the geotextile is arranged on the outside of the sealing layer, and the other side of the geotextile is arranged on the inside of the bearing layer;

[0011] The sealing layer has a thickness of 5-15 mm and is composed of a steel lining in the middle and epoxy resin anti-rust paint on both sides, and high-pressure hydrogen is stored inside the sealing layer.

[0012] It is worth noting that the present invention arranges a low-friction modified asphalt sliding layer between the sealing steel lining and the concrete to inhibit shear damage of the concrete; and replaces the traditional cement lining with self-healing reinforced concrete, which can not only delay the appearance of cracks through the action of the steel bars, but also extend the service life of the structure by setting a crack repair agent inside the reinforced concrete. In addition, as the structure closest to the sealing steel lining, its sealing must be guaranteed in case of gas leakage. In addition, the present invention arranges a permeable layer on the outside of the reinforced concrete bearing layer to prevent the extrusion deformation caused by the hydrostatic pressure during construction from damaging the unformed reinforced concrete and causing the sealing steel lining to become unstable.

[0013] In addition, when gas storage rock caves are excavated, fracture zones will inevitably be formed, and grouting is usually used to reinforce the rock mass to enhance the stability of the gas storage cavern. The present invention injects a certain pressure of anti-permeability modified slurry into the surrounding rock to form a surrounding rock reinforcement layer, which can not only increase the diffusion range of the slurry, but also use the cementation effect of the slurry to enhance the strength of the surrounding rock to resist the partial load of high-pressure hydrogen transferred to the surrounding rock; and can also use the anti-permeability ability of the modified slurry to enhance the sealing of the surrounding rock, forming another sealing barrier for underground hydrogen storage.

[0014] Therefore, the present invention promotes the optimization of the stress performance of the rock cave composite structure and the surrounding rock from the construction to the operation stage, and ensures the long-term stability and sealing of the underground rock cave hydrogen storage.

[0015] Furthermore, the pressure pre-grouting of the surrounding rock reinforcement layer includes ultra-fine bentonite.

[0016] Furthermore, the drainage pipe is a PE pipe and is fixed using permeable shotcrete.

[0017] Furthermore, the micro self-healing capsule is a composite component micro capsule of sodium silicate and expanded silicate cement.

[0018] Furthermore, a low-friction polymer having a friction coefficient between 0.04 and 0.2 is added to the material of the low-friction polymer modified asphalt layer.

[0019] Furthermore, the low friction polymer includes polytetrafluoroethylene or polyoxymethylene.

[0020] In particular, considering that the technical solution of using a larger friction coefficient modifier in the prior art will increase the shear force transmitted from the sealing layer to the bearing layer, so that the sliding layer cannot fully play its role, and using low-friction polymer modified asphalt as the sliding layer between the sealing layer and the bearing layer can effectively reduce the shear force transmitted from the sealing layer to the bearing layer to inhibit the shear damage of the bearing layer, the present invention uses low-friction polymer modified asphalt. Therefore, any technical solution that uses asphalt modified sliding layer modified by adding drag-reducing polymer without creative work is within the protection scope of the present invention.

[0021] The second object of the present invention is to provide a method for preparing the underground rock cave long-term and efficient hydrogen storage composite lining structure as described above.

[0022] A method for preparing a long-term and efficient hydrogen storage composite lining structure for an underground rock cave, the construction steps comprising:

[0023] S1. Excavate underground space in the surrounding rock according to actual needs;

[0024] S2. Drill holes inside the surrounding rock face to perform advanced pressure pre-grouting treatment to form a surrounding rock reinforcement layer within a certain range;

[0025] S3. Install a fixed drainage pipe on the inner surface of the surrounding rock, spray 10-20 mm concrete to fix the drainage pipe and level the surface of the surrounding rock to form a permeable layer;

[0026] S4. Lay a 500-800 mm reinforced concrete bearing layer on the inner side of the shotcrete, and evenly add sodium fluorosilicate curing agent and micro self-healing capsules during injection molding;

[0027] S5, placing the solidified low-friction polymer modified asphalt layer between two layers of geotextiles to form a sliding layer;

[0028] S6. The steel lining of the sealing layer is welded and formed;

[0029] S7. After laying the sliding layer on the outside of the sealing layer, push the sealing layer and the sliding layer together into the inside of the concrete bearing layer;

[0030] S8. Introduce high-pressure hydrogen into the sealing layer for storage.

[0031] It is worth noting that in the advance pressure pre-grouting process in step S2, the pre-grouting is designed according to the information obtained from the advance detection hole of 25-35 m (whether a water reservoir is encountered, whether the joints contain mud, etc.), and the excavation surface can be advanced by 30-50 m, and injected into the surrounding rock through the grouting pipe at a pressure of 2-3 MPa.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) The sliding layer between the sealing layer and the bearing layer is composed of two layers of geotextiles with a modified asphalt layer sandwiched between them to inhibit the shear damage of the bearing layer caused by the sliding of the steel liner under high internal pressure. The two layers of geotextiles can effectively prevent asphalt from squeezing into the cracks of the concrete, thereby increasing the deformation space of the steel liner, and further causing cracks in the steel liner itself and the weld, resulting in further gas leakage.

[0034] (2) A self-healing reinforced concrete bearing layer is set between the permeable layer and the sliding layer. The appearance of cracks can be delayed by the action of the steel bars. An appropriate amount of micro self-healing capsules containing bonding and expansion components are evenly added during the concrete injection molding process. Not only can the bonding components be used to repair cracks, but the expansion components can also be used to block pores and become a sealing barrier to prevent gas leakage.

[0035] (3) Drilling holes into the inner part of the surrounding rock face for pressure pre-grouting to form a surrounding rock reinforcement layer. Adding an appropriate amount of ultrafine bentonite into the slurry can not only utilize the slurry cementing components to enhance the surrounding rock strength to resist the partial load of high-pressure hydrogen transferred to the surrounding rock; it can also produce a water absorption and expansion effect in the surrounding rock through the ultrafine bentonite in the slurry, thereby blocking the leakage channel (pore space) in the surrounding rock and significantly improving the air tightness of the surrounding rock reinforcement layer, which comprehensively plays the role of reinforcing the surrounding rock and forming another sealing barrier.

[0036] (4) Drainage pipes are installed on the inner surface of the surrounding rock and fixed with permeable shotcrete to form a permeable layer. The shotcrete enhances the hydraulic connection with the groundwater in the surrounding rock and can dredge most of the groundwater in the surrounding rock to the surrounding of the lining through the drainage pipes, thus avoiding the hydrostatic pressure from squeezing and damaging the concrete bearing layer during construction and causing the instability of the sealed steel lining.

[0037] (5) Shotcrete leveling treatment is carried out on the internal surface of the surrounding rock to fill the cracks and pores on the surface of the surrounding rock, and to play the role of draining water and protecting the drainage pipe.

[0038] Therefore, the present invention optimizes the stress performance of the hydrogen storage chamber during the operation stage through the synergistic effect of steel lining, modified asphalt sliding layer, self-healing reinforced concrete and surrounding rock reinforcement; and forms a permeable layer by spraying concrete leveling treatment on the inner surface of the surrounding rock to avoid hydrostatic pressure from squeezing and damaging the concrete bearing layer during construction and causing instability of the sealed steel lining. The present invention optimizes the stress performance of the gas storage chamber from the construction period to the operation period by taking into account technical issues such as surrounding rock instability and sealing failure, and cooperates with various technical means to ensure the long-term stability and sealing of underground rock cave hydrogen storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0040] Figure 1 It is a schematic diagram of the underground rock cave long-term efficient hydrogen storage composite lining structure of the present invention.

[0041] Figure 2 It is a partial cross-sectional view of the underground rock cave long-term efficient hydrogen storage composite lining structure of the present invention.

[0042] Figure 3 For the present invention Figure 1 A partial enlarged view of point A in the middle.

[0043] Figure 4 It is a schematic diagram of the structure of the micro self-healing capsule of the present invention.

[0044] Figure 5 It is a schematic diagram of the water conducting channel and drainage of surrounding rock fractures according to the present invention.

[0045] Figure 6 It is a schematic diagram of the partial structure of the PE drainage pipe of the present invention.

[0046] Figure 7 This is the shear stress-displacement curve of the steel lining / lining after adding 5.0% polytetrafluoroethylene modified asphalt sliding layer in Comparative Example 1 of the present invention.

[0047] Figure 8 This is the shear stress-displacement curve of the steel lining / lining after adding a pure asphalt sliding layer in Comparative Example 1 of the present invention.

[0048] Fig. 9 This is the shear stress-displacement curve of the steel lining / lining without adding a sliding layer in Comparative Example 1 of the present invention.

[0049] Fig.10 This is a photo of the steel lining / lining after adding a slip layer in Comparative Example 1 of the present invention.

[0050] Fig.11 This is a photograph of the damage of the steel lining / lining after no asphalt sliding layer was added in Comparative Example 1 of the present invention.

[0051] Fig.12 This is a photo of asphalt extruding into lining cracks in Comparative Example 1 of the present invention.

[0052] Among them, 1-surrounding rock, 2-surrounding rock reinforcement layer, 3-permeable layer, 4-bearing layer, 5-sliding layer, 6-sealing layer, 7-drainage pipe, 8-sprayed concrete, 9-low friction polymer modified asphalt layer, 10-geotextile, 11-steel lining, 12-micro self-healing capsule, 13-steel mesh, 14-capsule wall, 15-capsule core, 16-surrounding rock cracks. DETAILED DESCRIPTION

[0053] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] The word "embodiment" used here as an "exemplary" does not necessarily mean that any embodiment described is superior to or better than other embodiments. Unless otherwise specified, the performance index tests in the embodiments of this application are performed using conventional test methods in the art. It should be understood that the terms described in this application are only used to describe specific implementation methods and are not used to limit the content disclosed in this application.

[0055] Unless otherwise specified, the technical and scientific terms used in this document have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs; other experimental methods and technical means not specifically specified in this application refer to experimental methods and technical means commonly used by ordinary technicians in this field.

[0056] In order to better illustrate the content of the present application, numerous specific details are provided in the specific examples below. It should be understood by those skilled in the art that the present application can also be implemented without certain specific details. In the embodiments, some methods, means, instruments, equipment, etc. well known to those skilled in the art are not described in detail in order to highlight the main purpose of the present application.

[0057] In the description of the present invention, it is necessary to understand that the orientations or positional relationships indicated by the terms "inside" and "outside" etc. are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0058] Under the premise of no conflict, the technical features disclosed in the embodiments of the present application can be combined arbitrarily, and the resulting technical solutions belong to the contents disclosed in the embodiments of the present application.

[0059] The present invention discloses a long-term and efficient hydrogen storage composite lining structure for underground rock caverns and a preparation method thereof, and belongs to the field of underground gas storage technology. The long-term and efficient hydrogen storage composite lining structure for underground rock caverns disclosed by the present invention comprises surrounding rock and its internal composite structure. The surrounding rock reinforcement layer is formed by pre-grouting of the surrounding rock internal pressure, which can resist the tensile stress transmitted to the surrounding rock by the internal gas pressure and enhance the air tightness; the inner side of the surrounding rock reinforcement layer is a permeable layer, which can discharge groundwater to prevent the hydrostatic pressure from causing extrusion deformation and damage to the concrete bearing layer during construction and causing the sealed steel lining to become instable; the reinforced concrete bearing layer is arranged on the inner side of the permeable layer and the outer side of the sliding layer, and micro self-healing capsules that can repair cracks and enhance sealing are evenly added during the injection molding process; the drag-reducing sliding layer is between the steel lining and the bearing layer, which inhibits the shear damage of the sealing steel lining to the bearing layer under high internal pressure; the steel lining sealing layer is arranged on the inner side of the sliding layer to bear part of the gas load and seal the gas. The present invention utilizes steel lining, sliding layer, reinforced concrete, permeable layer and surrounding rock reinforcement to optimize the stress performance of the hydrogen storage chamber during the construction and operation stages; utilizes the steel lining as a sealing barrier, utilizes the self-healing capsule expansion components of the bearing layer and the expansion components of the surrounding rock reinforcement to form another sealing barrier in the bearing layer and the surrounding rock, thereby ensuring the long-term stability of hydrogen storage in the underground rock cavern.

[0060] In order to better understand the present invention, the present invention is further specifically described below through the following examples, but it should not be understood as a limitation of the present invention. Some non-essential improvements and adjustments made by technicians in this field based on the above invention content are also considered to fall within the protection scope of the present invention.

[0061] Example 1

[0062] refer to Figure 1-Figure 6 The present invention discloses a long-term and efficient hydrogen storage composite lining structure for an underground rock cave, comprising a surrounding rock 1 and a composite structure opened in the surrounding rock 1; a surrounding rock reinforcement layer 2, which is arranged inside the surrounding rock 1, and the surrounding rock reinforcement layer 2 is formed by pressure pre-grouting to the face of the surrounding rock 1, and the surrounding rock reinforcement layer 2 is a closed space; a water-permeable layer 3 is provided with a drainage pipe 7 on the inner side of the surrounding rock reinforcement layer 2, and the surface is formed by spraying concrete 8; the inside of the water-permeable layer 3 is a self-healing reinforced concrete bearing layer, which is arranged on the outer side of the sliding layer 5 and the inner side of the water-permeable layer 3, and an appropriate amount of sodium fluorosilicate curing agent and micro self-healing capsules 12 are evenly added during the injection molding process.

[0063] A sliding layer 5 is provided between the sealing layer 6 and the self-healing reinforced concrete bearing layer to inhibit shear damage to the bearing layer 4 caused by the sliding of the steel lining 11 under the action of high internal pressure; a self-healing reinforced concrete bearing layer is provided between the permeable layer 3 and the sliding layer 5, which can delay the appearance of cracks through the action of the steel bars, and an appropriate amount of micro self-healing capsules 12 containing bonding and expansion components are evenly added during the concrete injection molding process, which can not only use the bonding components to repair cracks, but also use the expansion components to block pores to form a sealing barrier to prevent gas leakage; a surrounding rock reinforcement layer 2 is formed by drilling holes inside the tunnel face of the surrounding rock 1 for pressure pre-grouting, and an appropriate amount of ultrafine bentonite is added to the slurry, which can not only use The cementing components of the slurry enhance the strength of the surrounding rock to resist the partial load of high-pressure hydrogen transferred to the surrounding rock. It can also produce a water absorption and expansion effect in the surrounding rock through the ultrafine bentonite in the slurry, block the leakage channel (pore space) in the surrounding rock, and significantly improve the air tightness of the surrounding rock reinforcement layer; a drainage pipe 7 is installed on the inner surface of the surrounding rock 1, so that most of the groundwater in the surrounding rock 1 can be dredged to the surrounding of the rock cave through the drainage pipe 7, avoiding the hydrostatic pressure from causing squeezing deformation and damage to the concrete bearing layer during construction and causing the sealing steel lining to become unstable; the inner surface of the surrounding rock 1 is leveled with sprayed concrete 8 to fill the cracks and pores on the surface of the surrounding rock 1, and play a role in draining water and protecting the drainage pipe 7.

[0064] In Example 1 of the present invention, the rock cave is located 400-500 meters underground, with a pressure of 15-30 MPa, which meets the storage requirements of hydrogen.

[0065] To further optimize the solution, the hydrogen storage rock cave sealing layer and the high internal pressure hydrogen stored in the sealed structure can bear the tensile stress load transmitted to the steel lining by the high internal pressure of the hydrogen storage. The inside and outside of the steel lining 11 are painted with epoxy resin anti-rust paint to isolate the steel lining 11 from rust caused by moisture inside and outside the steel lining, thereby preventing the tensile strength of the steel lining 11 from decreasing.

[0066] Further optimizing the scheme, adopting TIG welding method to weld the steel lining 11 can achieve high-quality welding and effectively improve the strength of the welded joint.

[0067] A further optimized solution is that the sliding layer 5 includes a modified asphalt layer and two layers of geotextiles, one layer of geotextile is arranged on the outside of the sealing layer 6, and the other layer of geotextile is arranged on the inside of the self-healing reinforced concrete bearing layer. The modified asphalt layer is located between the two geotextiles. The function of the modified asphalt layer is to suppress the shear damage of the bearing layer to the steel lining sliding under the action of high internal pressure. The function of the geotextile 10 is to prevent the asphalt from being pressed into the concrete after the concrete cracks, and to prevent the steel lining 11 from being squeezed into the crack after the concrete cracks to produce local deformation, thereby causing the weld to crack (it has the function of protecting the weld from cracking).

[0068] To further optimize the plan, modified asphalt is used for the asphalt layer. An appropriate amount of low-friction polymer materials such as polytetrafluoroethylene is added to the asphalt in a high-temperature melt state. The asphalt is mixed with low-friction polymer materials such as polytetrafluoroethylene to reduce the friction coefficient of the modified asphalt sliding layer to about 0.07. The modified asphalt is solidified into a solid and placed between two layers of geotextiles and evenly wrapped around the outside of the sealing layer.

[0069] To further optimize the solution, the bearing layer 4 uses self-healing reinforced concrete and arranges a steel mesh 13. After pouring the concrete, the concrete and the steel bars are bonded, and the overall crack resistance is good and the rigidity is large. After being loaded, the cracks are delayed in appearing, and the stress change caused by loading or unloading during the use stage is relatively small, so the fatigue strength can be improved.

[0070] Moreover, the bearing layer 4 is a self-healing reinforced concrete bearing layer, which adopts self-compacting concrete. It can pass through dense steel bars and fill and form in complex templates without vibration and segregation only by its own weight. It has uniform self-compacting forming performance and excellent mechanical properties and durability after hardening. It can effectively avoid concrete cracking, improve the crack resistance and durability of the structure, and the structure has high rigidity and small total deformation, which helps to improve the overall stability of the structure.

[0071] The scheme is further optimized, in which the micro self-healing capsules 12 are evenly sprinkled in the poured self-compacting concrete, and in the process of mixing the self-compacting concrete, sodium fluorosilicate with a dosage of about 15% is added as a curing agent for the self-healing capsules.

[0072] The trigger mechanism of the micro self-healing capsule 12 adopted in the present invention is physical triggering. Once cracks appear in the concrete bearing layer, the capsule wall of the self-healing capsule will be induced to rupture, exposing the self-healing material inside the capsule core 15; the capsule wall 14 is made of ethyl cellulose, which has good bonding, film-forming and filling effects, has relatively stable chemical properties, and can better ensure the sealing of the capsule wall. The capsule core 15 is made of a composite component of sodium silicate and expanded silicate cement. Sodium silicate is used as a binder and has good compatibility with cement-based materials. Since the permeable layer 3 only discharges most of the water in the surrounding rock to prevent the hydrostatic pressure from damaging the structure, some water is filled in the pores of the concrete bearing layer. Once the concrete bearing layer cracks, sodium silicate reacts with calcium hydroxide in the concrete in a water environment to form calcium silicate, and further reacts in a calcium fluorosilicate environment to form silicon hydroxide with gel properties to repair the cracks in the form of adhesion. Expanded silicate cement is an expansive component. When it comes into contact with water, it undergoes a hydration reaction to form calcium aluminate, which will cause the volume of the cement stone to expand, further effectively filling the cracks and enhancing the air tightness. The micro self-healing capsule 12 can play a dual role in repairing cracks and enhancing air tightness.

[0073] The micro self-healing capsule 12 is prepared by an extrusion spray method. Sodium silicate, expanded silicate cement, water, a thickener, and an emulsifier are mixed into a wet material in proportion, and then formed into small spheres by extrusion and rotation. The spheres are then coated with a coating solution containing ethyl cellulose and dried to form capsules.

[0074] Further optimization scheme, the permeable layer 3 is set outside the self-healing steel bar bearing layer, and the drainage pipe 7 is placed inside the permeable layer 3 and fixed by spraying permeable concrete. In addition, the natural cracks in the surrounding rock are used as water-conducting channels, and the drainage pipe 7 is installed on the inner surface of the surrounding rock. Most of the groundwater in the surrounding rock 1 can be dredged to the surrounding of the rock cave through the drainage pipe 7, avoiding the hydrostatic pressure from causing compression deformation and damage to the concrete bearing layer during construction and causing the sealing steel lining to become unstable ( Figure 5-Figure 6 ).

[0075] To further optimize the scheme, face advance pressure pre-grouting is used in surrounding rock reinforcement layer 2, and an appropriate amount of ultrafine bentonite is added to the slurry. After being injected into the rock formation, the bentonite absorbs the water in the rock pores, causing the bentonite crystal layer spacing to increase and then expand to block the leakage channel (pore space) in the surrounding rock, which can effectively prevent the passage of gas, thereby further improving its air tightness. The prepared slurry is injected into the surrounding rock through the grouting pipe at a pressure of 2-3 MPa using a pressure grouting pump. After the grouting liquid is solidified, the surrounding rock has high strength and stiffness, which improves the integrity and tensile properties of the surrounding rock, enhances the bearing capacity of the surrounding rock reinforcement body itself, and the slurry binds the rock to resist the tensile stress load transmitted to the surrounding rock by high-pressure hydrogen; in addition, through pressure grouting, the gaps and holes between the linings can be accurately blocked, effectively preventing groundwater leakage and erosion.

[0076] A long-term and efficient hydrogen storage composite lining structure and method for underground rock caves, the construction steps comprising:

[0077] S1. Excavate rock cave space in the surrounding rock as required;

[0078] S2. Drill holes in the tunnel face inside the surrounding rock 1 to perform pre-grouting treatment under advanced pressure, forming a surrounding rock reinforcement layer 2 within a certain range; the pre-grouting is designed based on the information obtained from the 25-35 m advance detection hole (whether a water storage layer is encountered, whether the joints contain mud, etc.), and can be 30-50 m ahead of the excavation face, and injected into the surrounding rock 1 through the grouting pipe at a pressure of 2-3 MPa;

[0079] S3. After installing and fixing the drainage pipe 7 on the inner surface of the surrounding rock 1, spray 10-20 mm concrete to fill the cracks on the surface of the surrounding rock, prevent the fragments from falling off and loosening, and fill the opened cracks with slurry at high spraying speed and pressure to improve the strength and integrity of the rock mass;

[0080] S4, laying a 500-800 mm self-healing reinforced concrete bearing layer outside the sliding layer 5, designing a specific mold according to the requirements, arranging the steel mesh 13, pouring the sodium fluoride silicate self-compacting concrete, and evenly adding the sodium silicate and expanded silicate cement micro self-healing capsules 12 during the pouring process, and injection molding to form the bearing layer 4;

[0081] S5. Apply epoxy resin anti-rust paint on the inside and outside of the 5-15 mm steel lining 11, weld the steel lining 11 on the inside of the slip layer 5 by TIG method, grind the weld thickness flat, and improve the strength of the weld;

[0082] S6. When the asphalt is heated and pre-melted and before it reaches boiling, add the modified low-friction polymer to the asphalt material, so that the mixture is infiltrated and cross-linked in a liquid state. First, lay a layer of geotextile, then evenly lay a solid asphalt layer of about 5-10 mm. After cooling and solidification, finally lay another layer of geotextile and wrap it tightly.

[0083] S7, laying the slip layer 5 on the outside of the sealing layer 6;

[0084] S8, pushing the sealing layer 6 and the sliding layer 5 together into the concrete bearing layer;

[0085] S9, introducing high internal pressure hydrogen into the sealing layer 6 for storage.

[0086] In order to further demonstrate the beneficial effects of the present invention and to better understand the present invention, the following comparative examples are used to further illustrate the technical features of the underground rock cave long-term efficient hydrogen storage composite lining structure and its preparation method disclosed in the present invention, but they should not be understood as limitations of the present invention. The parameters and process flow adjustments made by those skilled in the art according to the above invention content or the applications made according to the above properties are also considered to fall within the protection scope of the present invention.

[0087] Comparative Example 1

[0088] The asphalt was first heated and pre-melted and before boiling, 5.0% polytetrafluoroethylene-modified low-friction polymer was added to the asphalt material, so that the mixture was infiltrated and cross-linked in a liquid state, and then cooled and solidified. In order to compare the effect of unmodified asphalt, pure asphalt sliding layer material was also processed and produced. In order to further observe the destructive effect of steel lining and concrete lining without adding asphalt sliding layer, shear tests without adding sliding layer were also carried out. The shear test was carried out under constant vertical stress, and the shear stress and shear displacement were recorded in real time.

[0089] The shear test fully proved that the modified asphalt sliding layer inhibited the shear damage of the steel lining to the concrete lining. Compared with the reliability of the non-modified asphalt sliding layer, the sliding shear displacement of the steel lining and the concrete lining under the constant vertical stress of 10 MPa reached 3.8 mm, corresponding to a shear force of 0.89 MPa and a friction coefficient of about 0.07 ( Figure 7 and Fig.10 The shear suppression effect of the pure asphalt sliding layer is poor, and a 2 mm sliding displacement is generated between the steel lining and the concrete lining, the shear force is as high as 3.9 MPa, and the friction coefficient is 0.39 ( Figure 8 ). The shear test without adding a slip layer found that under the vertical load of 5 MPa, only 0.6 mm sliding displacement between the steel lining and the concrete lining caused shear failure of the concrete lining ( Fig.11 ), corresponding to 5 MPa vertical stress and 3 MPa shear force, the friction coefficient can reach 0.6 ( Fig. 9 ). In addition, in the further shear test of polymer modified asphalt sliding layer, the constant vertical stress was increased to 15 MPa, and it was found that once the concrete was sheared and cracked, the modified asphalt layer would squeeze into the cracks ( Fig.12 ), which also indirectly proves the necessity of setting geotextiles on both sides of the modified asphalt layer. If only conventional modified asphalt rolls are used without taking measures to prevent asphalt from squeezing in (i.e., setting two layers of geotextiles), the deformation space of the steel lining will inevitably increase, which will lead to cracks in the steel lining itself and the welds, causing further gas leakage.

[0090] Therefore, the present invention adopts an asphalt sliding layer to effectively reduce the shear force (drag reduction), and combined with the layout of the geotextile on the inner and outer sides, it can effectively inhibit the shear damage of the steel lining sliding on the bearing layer under the action of high internal pressure, and effectively prevent asphalt from squeezing into the concrete cracks to increase the deformation space of the steel lining, thereby avoiding cracking of the steel lining itself and the weld, causing further gas leakage hazards.

[0091] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A long-term and efficient hydrogen storage composite lining structure for underground rock caverns, characterized in that: From the outside to the inside, it includes surrounding rock (1), surrounding rock reinforcement layer (2), permeable layer (3), bearing layer (4), sliding layer (5) and sealing layer (6), wherein: The surrounding rock reinforcement layer (2) is formed by applying pressure pre-grouting to the surrounding rock (1), and the surrounding rock reinforcement layer (2) is a closed space; The permeable layer (3) has a thickness of 10-20 mm, a drainage pipe (7) is arranged inside, and the drainage pipe (7) is fixed by spraying concrete (8); The bearing layer (4) is a self-healing reinforced concrete bearing layer with a thickness of 500-800 mm, and sodium fluorosilicate curing agent and micro self-healing capsules (12) are evenly distributed inside; The sliding layer (5) has a thickness of 5-10 mm and is composed of a low-friction polymer modified asphalt layer (9) in the middle and geotextiles (10) on both sides, wherein the geotextile (10) on one side is arranged on the outside of the sealing layer (6) and the geotextile (10) on the other side is arranged on the inside of the bearing layer (4); The sealing layer (6) has a thickness of 5-15 mm and is composed of a steel lining (11) in the middle and epoxy resin anti-rust paint on both sides, and high-pressure hydrogen is stored inside the sealing layer (6).

2. The underground rock cave long-term efficient hydrogen storage composite lining structure according to claim 1 is characterized in that: The pressure pre-grouting of the surrounding rock reinforcement layer (2) includes ultra-fine bentonite.

3. The underground rock cave long-term efficient hydrogen storage composite lining structure according to claim 1, characterized in that: The drainage pipe (7) is a PE pipe and is fixed using permeable sprayed concrete.

4. The underground rock cave long-term efficient hydrogen storage composite lining structure according to claim 1, characterized in that: The micro self-healing capsule (12) is a composite micro capsule of sodium silicate and expanded silicate cement.

5. The underground rock cave long-term efficient hydrogen storage composite lining structure according to claim 1, characterized in that: A low-friction polymer having a friction coefficient between 0.04 and 0.2 is added to the material of the low-friction polymer modified asphalt layer (9).

6. The underground rock cave long-term efficient hydrogen storage composite lining structure according to claim 5, characterized in that: The low friction polymer includes polytetrafluoroethylene or polyoxymethylene.

7. The method for preparing a long-term and efficient hydrogen storage composite lining structure for an underground rock cave as claimed in claim 1, characterized in that: The construction steps include: S1. Excavating underground space in the surrounding rock (1) according to actual needs; S2, drilling holes inside the tunnel face of the surrounding rock (1) to perform advanced pressure pre-grouting treatment to form a surrounding rock reinforcement layer (2) within a certain range; S3, installing a fixed drainage pipe (7) on the inner surface of the surrounding rock (1), spraying 10-20 mm concrete to fix the drainage pipe (7) and leveling the surface of the surrounding rock (1) to form a permeable layer (3); S4, laying a 500-800 mm reinforced concrete bearing layer on the inner side of the shotcrete (8), and evenly adding sodium fluorosilicate curing agent and micro self-healing capsules (12) during injection molding; S5, placing the solidified low-friction polymer modified asphalt layer (9) between two layers of geotextile (10) to form a sliding layer (5); S6, welding and forming of the steel lining of the sealing layer (6); S7, after laying the sliding layer (5) on the outside of the sealing layer (6), push the sealing layer (6) and the sliding layer (5) together into the inside of the bearing layer (4); S8. High-pressure hydrogen is introduced into the sealing layer (6) for storage.

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