A method for filling and grouting compensation of a top pilot hole of an underground energy storage cavern

Abstract

The application discloses a kind of underground energy storage cave roof guide hole filling and compensation grouting compaction methods, the compaction method includes: guide hole is divided into multiple pouring sections;Grouting pipe is pre-embedded at the top of each pouring section, and closed formwork is installed outside;Closed formwork is provided with pumping port and exhaust hole;Initial filling, self-compacting micro-expansion concrete is pumped to the inside of pouring section;Transition filling, when self-compacting micro-expansion concrete is filled to the preset state, gradually retract pump pipe;Pumping is carried out during retraction to fill the gap formed by pump pipe withdrawal;Final filling, continuous pumping after pump pipe is withdrawn to pumping port;Compensation grouting: at least twice compensation grouting is carried out on the top of pouring section through grouting pipe, the flow rate of second grouting is less than that of first grouting, and the duration of second grouting is greater than that of first grouting.The compaction method can realize active compaction forming of top guide hole backfill structure, improve the integrity and compactness of underground energy storage cave top backfill structure.

Description

Technical Field

[0001] This invention relates to the field of underground energy storage engineering technology, specifically to a method for filling and compensating for grouting the top guide tunnel of an underground energy storage cavern. Background Technology

[0002] In recent years, underground energy storage projects such as cavern hydrogen storage, underground compressed air energy storage, and underground gas storage facilities have gradually developed. Compared with ordinary traffic tunnels and conventional underground caverns, underground energy storage caverns have higher requirements for structural integrity, backfill compaction, long-term service stability, and operational safety. The top pilot tunnel, arch cavity, or enclosed space at the top of the cavern is a special part of the construction of underground energy storage caverns, and the quality of its backfill directly affects the stress transmission of the cavern top structure and its overall working performance.

[0003] When carrying out backfilling work on the top guide tunnel of underground energy storage cavern, the guide tunnel usually has a certain longitudinal length and has the characteristics of small space, closed top, difficulty in observing the internal condition after the formwork is installed, and difficulty in entering conventional vibration equipment. The concrete flows a long distance in the closed space, which can easily lead to insufficient filling at the far end of the guide tunnel, the highest point of the top, and local irregular areas due to increased flow resistance, insufficient pump pressure transmission, or local stagnation, resulting in cavities, voids, or non-dense areas.

[0004] Currently, grouting with formwork at the arch of secondary lining is used in existing tunnel engineering to address the issue of voids in the arch of the secondary lining. However, this technology mainly addresses local voids between the secondary lining and the initial support, focusing on repairing defects or grouting reinforcement after the initial formwork is completed. In contrast, the backfilling of the top pilot tunnel of an underground energy storage cavern involves a closed pilot tunnel space with a certain longitudinal length, requiring longitudinal concrete flow, top lifting and filling, and subsequent shrinkage compensation during the construction and forming stage. Existing methods such as post-grouting at the arch or single-point pumping at the formwork opening cannot directly solve problems such as insufficient filling of the deep part of the pilot tunnel, residual ducts after pump pipe withdrawal, residual voids at the top, and early shrinkage compensation.

[0005] Therefore, existing backfilling and compaction methods have problems such as insufficient filling at the far end of the pilot tunnel, residual voids at the top, and inability to compensate for early shrinkage, which cannot meet the engineering requirements of high integrity and high compaction for the top backfilling of underground energy storage caverns. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose a method for filling and compensating for grouting the top guide tunnel of an underground energy storage cavern, thereby solving the technical problem of insufficient integrity and compactness of the top guide tunnel backfill structure in the prior art.

[0007] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution: This invention provides a method for filling and compensating for grouting the top tunnel of an underground energy storage cavern. The method includes: dividing the tunnel into multiple pouring sections along the extension direction of the underground energy storage cavern; pre-embedding grouting pipes at the top of each pouring section and installing a closed template on the outside of the pouring section; opening pump inlets and vent holes in the closed template, with the inner end of the grouting pipe extending into the pouring section and the outer end exiting the closed template; during initial filling, extending a pump pipe through the pump inlet into the pouring section to pump self-compacting micro-expansion concrete into the pouring section and then... The process involves filling from the inside out; transitional filling, where the pump pipe is gradually withdrawn when the self-compacting micro-expansion concrete has reached the preset state; during the withdrawal process, self-compacting micro-expansion concrete is pumped to fill the gaps formed by the withdrawal of the pump pipe; final filling, where the pump pipe is withdrawn to the pumping port and pumping continues, relying on pump pressure to lift and fill the top space of the pouring section; and compensation grouting, where at least two compensation grouting operations are performed on the top of the pouring section through the grouting pipe, with the second grouting flow rate being lower than the first grouting flow rate and the second grouting duration being longer than the first grouting duration.

[0008] In some embodiments, the length L1 of the pouring section satisfies: L1≤6m; during the initial filling, the length L2 of the pump pipe extending into the pouring section satisfies: 0.5≤L2 / L1≤1.

[0009] In some embodiments, the length L1 of the pouring section satisfies: 3m≤L1≤5m; during the initial filling, the length L2 of the pump pipe extending into the pouring section satisfies: 2m≤L2≤4m.

[0010] In some embodiments, an observation port is provided near the top of the closed template; when the self-compacting micro-expansion concrete is filled to the preset state, the pump pipe is gradually withdrawn; the preset state satisfies at least one of the following conditions: the top surface of the self-compacting micro-expansion concrete is 20cm-50cm away from the top surface of the guide hole; self-compacting micro-expansion concrete appears at the observation port; the pumping pressure rises and stabilizes; the grouting pipe, observation port or vent hole shows reduced venting or grout return.

[0011] In some embodiments, pumping self-compacting micro-expansion concrete during the retraction process to fill the voids formed by the withdrawal of the pump pipe includes: the retraction process employs continuous pumping or intermittent pumping to fill the voids formed by the withdrawal of the pump pipe.

[0012] In some embodiments, at least two grouting pipes are pre-embedded in each casting section. The two grouting pipes are a first grouting pipe and a second grouting pipe. The inner ends of the first grouting pipe and the second grouting pipe are located at the two ends of the extension direction inside the casting section, respectively.

[0013] In some embodiments, performing at least two compensatory grouting operations on the top of the cast section through a grouting pipe includes: a first compensatory grouting operation, in which cement slurry is filled into the cast section through a first grouting pipe to fill the residual voids at the top after the self-compacting micro-expansion concrete is poured; and a second compensatory grouting operation, in which one or more of ultrafine cement slurry, micro-expansion cement slurry, and shrinkage-compensating cement-based slurry are filled into the cast section through a second grouting pipe to compensate for the tiny voids formed by concrete bleeding, settlement, or shrinkage.

[0014] In some embodiments, there are multiple vent holes, which are respectively located at the top and end corners of the closed template.

[0015] In some embodiments, the self-compacting micro-expansion concrete contains one or more of the following: water-reducing agent, expansion agent, and mineral admixture.

[0016] In some embodiments, after the compensation grouting is completed, the compaction method further includes: sealing the pipe and quality inspection, wherein the quality inspection includes one or more of the following: visual inspection, impact testing, core drilling testing, radar scanning, and ultrasonic testing.

[0017] Compared with existing technologies, this invention provides a method for filling and compensating grouting the top guide tunnel of an underground energy storage cavern. This method uses self-compacting micro-expansion concrete to backfill the top guide tunnel, and combines segmented construction to shorten the concrete flow distance. It relies on pump pressure and the material's self-flowability to fill the enclosed space. It adopts a three-stage filling process of initial, transition, and final pump pressure lifting to solve the problem of insufficient filling of the arch by single-point pumping. Grouting pipes and vent holes are pre-embedded at the top of each pouring section. After molding, compensating grouting can be carried out directly. Venting and grouting can be observed through the vent holes to avoid secondary drilling and disturbing the structure. The construction is set up with two levels of differentiated compensating grouting. The first filling is for large-sized residual cavities, and the second low-pressure grouting is to make up for the micro-cracks formed by bleeding, settlement, and shrinkage. Multiple processes work together to improve the overall compactness of the backfill structure and meet the high-standard use requirements of underground energy storage caverns. Attached Figure Description

[0018] Figure 1 This is a schematic flowchart of a method for filling and compensating for grouting the top tunnel of an underground energy storage cavern, provided in an embodiment of the present invention. Figure 2 This is a schematic flowchart of another method for filling and compensating for grouting the top tunnel of an underground energy storage cavern provided in an embodiment of the present invention; Figure 3 This is a cross-sectional view of the overall layout of the segmented pump-pressurized filling of the top guide tunnel of the underground energy storage cavern provided in this embodiment of the invention. Figure 1 ; Figure 4 This is a cross-sectional view of the overall layout of the segmented pump-pressurized filling of the top guide tunnel of the underground energy storage cavern provided in this embodiment of the invention. Figure 2 ; Figure 5 This is a cross-sectional view of the pump pipe retraction and pump pressure jacking filling of the top guide tunnel of the underground energy storage cavern provided in this embodiment of the invention; Figure 6 This embodiment of the invention provides a cross-sectional view of the double-grouting pipe compensation grouting process in the top guide tunnel of an underground energy storage cavern. Figure 1 ; Figure 7 This embodiment of the invention provides a cross-sectional view of the double-grouting pipe compensation grouting process in the top guide tunnel of an underground energy storage cavern. Figure 2 .

[0019] Explanation of reference numerals in the attached figures: 100. Compacting methods; 200. Energy storage cavern; 210. Main cavern; 220. Guide tunnel; 230. Pouring section; 240. Grouting pipe; 250. Pump pipe; 260. Enclosed formwork; 261. Vent hole; 270. Concrete pump; 280. Grouting equipment. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] Currently, underground energy storage projects such as cavern hydrogen storage, underground compressed air energy storage, and underground gas storage facilities are gradually developing. Compared with ordinary traffic tunnels and conventional underground caverns, underground energy storage caverns have higher requirements for structural integrity, backfill compaction, long-term service stability, and operational safety. Existing backfill compaction methods have problems such as insufficient filling at the far end of the pilot tunnel, residual voids at the top, and inability to compensate for early shrinkage, which cannot meet the engineering requirements of high integrity and high compaction of the top backfill of underground energy storage caverns.

[0022] To address the technical problem of insufficient integrity and compactness of the top guide tunnel backfill structure, this invention provides a method for filling and compensating for grouting the top guide tunnel of an underground energy storage cavern. This compaction method enables active compaction and shaping of the top guide tunnel backfill structure, thereby improving the integrity and compactness of the top backfill structure of the underground energy storage cavern.

[0023] It should be noted that the compaction method provided by this invention is applicable to, but not limited to, backfilling construction scenarios of top guide tunnels in underground energy storage projects such as rock cave hydrogen storage caverns, underground compressed air energy storage caverns, and underground gas storage caverns. For ease of explanation, this invention only uses the application of the compaction method to the backfilling construction scenario of the guide tunnel of a rock cave hydrogen storage cavern as an example. The principle of the compaction method applied to the backfilling construction scenario of the top guide tunnel of other underground energy storage projects is essentially the same as that applied to the backfilling construction scenario of the guide tunnel of a rock cave hydrogen storage cavern, and will not be elaborated here.

[0024] This invention provides a method 100 for filling and compensating grouting the top guide tunnel of an underground energy storage cavern, such as... Figure 1 As shown, the compaction method 100 includes: Step S110: Divide the pilot tunnel into multiple pouring sections along the extension direction of the underground energy storage cavern.

[0025] Specifically, in step S110, based on the longitudinal length (length in the direction of the underground energy storage cavern's extension), cross-sectional dimensions, top space shape, bearing capacity of the closed formwork, and the flowability of the self-compacting micro-expansion concrete, the top guide tunnel is divided longitudinally into several pouring sections. The length of each pouring section is determined based on the effective flow distance of the self-compacting micro-expansion concrete, ensuring that the length of a single pouring section matches the flowability of the backfill concrete.

[0026] For example, the length L1 of the pouring section satisfies: L1≤6m; the length L1 of the pouring section can specifically be 3m, 4m, 5m, 6m, or any value between any two adjacent values ​​mentioned above. By controlling the pouring length of a single section, the flow path of the self-compacting micro-expansion concrete in the closed guide tunnel at the top of the underground energy storage cavern is shortened, allowing the concrete to smoothly diffuse to the ends of the pouring section, the highest point at the top, and local irregular areas under the combined action of its own fluidity and pump pressure, reducing the risk of insufficient filling at the far end, residual voids at the top, and non-compactness caused by excessive flow distance.

[0027] In this step S110, based on the field spread, pumping status and filling effect of the test pouring section of the self-compacting micro-expansion concrete, the length of the pouring section, the pump pipe extension distance and the pumping pressure control parameters are checked to ensure that the length of the pouring section is adapted to the field flowability of the concrete.

[0028] Step S120: Pre-embed grouting pipes at the top of each pouring section and install closed templates on the outside of the pouring section; the closed templates have pumping ports and venting holes, the inner end of the grouting pipes extends into the pouring section, and the outer end protrudes through the closed templates.

[0029] Specifically, in step S120, grouting pipes are pre-embedded at the top of each pouring section, a closed template is installed on the outside of each pouring section, and a concrete pumping port and an exhaust port are set on the closed template; the exhaust port can also serve as an observation port, or an observation port can be set separately.

[0030] The number of grouting pipes can be single or multiple, and they can be arranged at both ends of the top of the casting section, at the highest point of the top, at the far end, or in areas prone to voids. The inner end of the grouting pipe extends into the backfill area at the top of the casting section, and the outer end protrudes out of the closed template with a reserved operating end, which will be used as a compensation grouting channel later.

[0031] For example, at least two grouting pipes are pre-embedded in each casting section. The two grouting pipes are divided into a first grouting pipe and a second grouting pipe. The inner ends of the first grouting pipe and the second grouting pipe are located at the two ends of the extension direction of the casting section, respectively.

[0032] One or more vents can be installed, connected to the top space of the pouring section, and arranged at the highest point of the top of the pouring section or in areas with poor venting. They are used to discharge residual air at the top during the concrete pumping and filling and compensation grouting stages, and also serve as a channel for observing grout return.

[0033] For example, there are multiple vent holes, which are respectively located at the top and end corners of the closed template. The end corners are dead corners or areas where venting is not smooth.

[0034] For example, the vent hole can also be equipped with an vent pipe, with one end of the vent pipe located at the vent hole position and the other end located in the area of ​​poor venting within the casting section.

[0035] Step S130, initial filling: the pump pipe is extended into the pouring section through the pumping port to pump self-compacting micro-expansion concrete into the pouring section and fill it from the inside out.

[0036] Specifically, step S130 belongs to the initial stage of concrete pouring. A rigid pump pipe or steel pump pipe is inserted into the pouring section through the concrete pumping port, so that the discharge end of the pump pipe is located in a predetermined position inside the pouring section. After the concrete pumping equipment is started, the self-compacting micro-expansion concrete enters the pouring section from the discharge end (inner end) of the pump pipe, and flows from the inside of the pouring section towards the ends, top and the pumping port of the closed formwork to fill the concrete.

[0037] For example, the length L2 of the pump pipe extending into the pouring section satisfies: 0.5≤L2 / L1≤1. By limiting the ratio of the pump pipe extension length to the pouring section length to between 0.5 and 1, the self-compacting micro-expansion concrete diffuses from the inside of the guide hole to the outside, rather than being fed from a single point at the pump outlet, which greatly reduces the risk of internal air blockage and improves the uniformity of filling within the section.

[0038] For example, the length L2 of the pump pipe extending into the pouring section satisfies: 2m ≤ L2 ≤ 4m. The length L2 of the pouring section can specifically be 2m, 3m, 4m, or any value between any two adjacent values ​​mentioned above.

[0039] It should be noted that self-compacting micro-expansion concrete has good fluidity, workability, filling properties and shrinkage compensation performance. It can fill the closed space of the top guide tunnel of the underground energy storage cavern by its own fluidity, pumping pressure and micro-expansion effect without strong vibration or with little vibration.

[0040] For example, self-compacting micro-expansion concrete is mixed with one or more of water-reducing agents, expansion agents, and mineral admixtures to meet the requirements for pumping filling, jacking compaction, and shrinkage compensation of the closed space of the top guide tunnel of the underground energy storage cavern.

[0041] In this step S130, by directly delivering the self-compacting micro-expansion concrete into the pouring section, the distance the self-compacting micro-expansion concrete travels from the pumping port to the interior is reduced, allowing the self-compacting micro-expansion concrete to complete diffusion and filling within a shorter path, thereby improving the filling effect inside the top guide tunnel and the top high point area of ​​the underground energy storage cavern.

[0042] Step S140, transition filling: when the self-compacting micro-expansion concrete is filled to the preset state, the pump pipe is gradually withdrawn; during the withdrawal process, self-compacting micro-expansion concrete is pumped to fill the gaps formed by the withdrawal of the pump pipe.

[0043] Specifically, step S140 belongs to the concrete transition filling stage. As the self-compacting micro-expansion concrete is continuously pumped, it is gradually withdrawn from the pump pipe when it reaches the predetermined state.

[0044] For example, an observation port is provided near the top of the closed template; the pump pipe can be gradually withdrawn when one or more of the following preset conditions are met. The preset conditions include: the top surface of the self-compacting micro-expansion concrete is 20cm-50cm away from the top surface of the guide hole; self-compacting micro-expansion concrete appears at the observation port; the pumping pressure rises and then tends to stabilize; the venting of the grouting pipe, the observation port, or the vent hole shows reduced venting or grout return.

[0045] For example, the retraction process employs continuous or intermittent pumping to fill the gaps created by the removal of the pump tube, thereby preventing the formation of new channels, segregation zones, or localized voids due to the removal of the pump tube.

[0046] Step S150, final filling: after the pump pipe is moved back to the pumping port, pumping continues, relying on pump pressure to lift and fill the top space of the pouring section.

[0047] Specifically, step S150 belongs to the final stage of concrete filling. After the pump pipe is withdrawn to the vicinity of the concrete pumping port, self-compacting micro-expansion concrete continues to be pumped into the pouring section through the concrete pumping port. At this time, under the combined action of pump pressure and its own fluidity, the self-compacting micro-expansion concrete rises and diffuses towards the top of the underground energy storage cavern, the arch area, the end area, and local irregular spaces, and compacts and fills the closed space at the top.

[0048] It should be noted that during the pump-pressure jacking filling process, the pumping pressure, pumping speed, and deformation of the closed formwork should be controlled to prevent bulging, grout leakage, segregation, or local instability of the closed formwork. When continuous and stable grout return occurs at the observation port, vent, or grouting pipe, and the pumping pressure reaches a stable state, it is determined that the top space of the pouring section is basically filled, pumping is stopped, and the concrete pumping port is sealed.

[0049] Step S160, Compensation grouting, at least two compensation groutings are performed on the top of the cast section through the grouting pipe. The flow rate of the second grouting is less than that of the first grouting, and the duration of the second grouting is greater than that of the first grouting.

[0050] Specifically, step S160 belongs to the compensation grouting stage, including steps S161 and S162, such as... Figure 2 As shown.

[0051] Step S161, first compensation grouting.

[0052] Specifically, after the self-compacted micro-expansion concrete is poured and reaches a preliminary stable state, the first compensation grouting is performed on the top area of ​​the poured section through pre-embedded grouting pipes. The first compensation grouting is mainly used to fill large gaps, local voids, or dead corners that may remain at the top after pouring, or that are difficult to completely cover by pump pressure.

[0053] For example, the grouting material for the first injection may be cement grout, micro-expansion cement grout, shrinkage-compensating cement-based grout, or other grouts suitable for backfilling and reinforcing underground energy storage caverns.

[0054] For example, the first compensation grouting can be performed using one grouting pipe, with the other grouting pipe assisting in grouting or serving as a grout return observation channel. The vent hole is used to expel residual air at the top and observe the grout return situation. When stable grout return occurs in an adjacent grouting pipe or vent hole, and the grouting pressure reaches a set stable state, the first compensation grouting is stopped.

[0055] Step S162, second compensation grouting.

[0056] Specifically, after the first grouting is completed and a predetermined interval has elapsed (e.g., 2 hours, 4 hours, depending on the actual situation), a second grouting is performed via a pre-embedded grouting pipe. The second grouting is primarily used to compensate for bleeding, settlement, early shrinkage, and the tiny voids created by the grout's setting and shrinkage after the first grouting in the self-compacting micro-expansion concrete. The second grouting can be performed at low pressure, slowly, and with a stable pressure to improve the filling effect of the grout on these fine voids. The second grouting should be stopped when one or more of the following occurs: grouting pressure stabilizes, grout volume significantly decreases, grout returns from adjacent grouting pipes, grout returns from vent holes, or grout returns from observation ports.

[0057] For example, the secondary grouting material may be one or more of ultrafine cement grout, micro-expansion cement grout, and shrinkage-compensating cement-based grout.

[0058] In some embodiments, the inner ends of the first grouting pipe and the second grouting pipe are located at opposite ends of the extension direction within the casting section. The initial compensation grouting injects cement grout into the cavity via the first grouting pipe to fill the larger residual voids remaining at the top after the self-compacting micro-expansion concrete is poured. The secondary compensation grouting injects ultrafine cement grout through the second grouting pipe to fill the micro-cracks caused by concrete bleeding, settlement, and subsequent shrinkage. The grout from the initial injection flows from the far end of the casting section towards the closed formwork side, while the grout from the secondary injection flows in the opposite direction from the closed formwork side towards the far end of the casting section. This bidirectional filling further enhances the overall compactness of the backfill.

[0059] In some embodiments, such as Figure 2 As shown, after the compensation grouting is completed, the compaction method 100 also includes: Step S170: Sealing and quality inspection. Quality inspection includes one or more of the following: visual inspection, impact testing, core drilling testing, radar scanning, and ultrasonic testing.

[0060] Specifically, in step S170, after all compensation grouting operations are completed, the exposed grouting pipes are sequentially cut off and sealed, and anti-corrosion protection treatment is carried out. Combining process parameters such as grouting pressure, total grouting volume, and grout return status at the borehole opening, and simultaneously supplementing with methods such as visual inspection after the removal of the closed template, impact testing, core sampling, radar scanning, and ultrasonic detection, the compaction quality of the backfill body in the top guide tunnel is comprehensively verified.

[0061] To better understand this invention, the following example uses the backfilling construction of the top guide tunnel in a rock cave hydrogen storage project, combined with... Figures 3 to 7 A detailed explanation of the entire construction process is provided below: Figure 3 and Figure 4 This diagram illustrates the overall layout of the segmented pump-pressurized filling of the top pilot tunnel of the 200-meter underground energy storage cavern. Figure 3 and Figure 4 The diagram shows the arrangement of the top guide tunnel 220, main chamber 210, closed formwork 260, several pouring sections 230, pouring section segment length L1, concrete pump inlet, steel pump pipe 250, and pre-embedded grouting pipe 240. It also shows the initial stage of pouring, where the steel pump pipe 250 extends into the pouring section 230, and the self-compacting micro-expansion concrete is filled into the backfill area of ​​the top guide tunnel 220 by the concrete pump 270. The diagram shows the state of the self-compacting micro-expansion concrete flowing and filling from the inside towards the end, top, and pump inlet of the closed formwork.

[0062] Figure 5 Cross-sectional view of the pump pipe retraction and pump pressure jacking filling of the top guide tunnel of the 200-meter underground energy storage cavern. Figure 5 As shown in the diagram, after the steel pump pipe 250 gradually withdraws to the vicinity of the closed template 260, the self-compacting micro-expansion concrete, under the combined action of pump pressure and its own fluidity, is lifted and filled into the top space, end area and irregular cavity of the top guide hole 220, thereby achieving the compaction and filling of the closed space of the top guide hole 220.

[0063] Figure 6 and Figure 7 This diagram illustrates the double-grouting pipe compensation grouting process used in the top guide tunnel of a 200mm underground energy storage cavern. Figure 6 and Figure 7 The diagram shows that at least two grouting pipes 240 and one vent hole 261 are installed at the top of each pouring section 230. Grouting is performed in stages to compensate for the backfilling area of ​​the top guide hole 220 through grouting equipment 280, so as to fill the residual voids and shrinkage micro voids at the top and improve the compactness and integrity of the backfilling structure of the top guide hole 220.

[0064] During the backfilling construction of the top guide tunnel in a cavern hydrogen storage project, the top guide tunnel is located above the main cavern, in a confined space with a high degree of enclosure at the top, making it difficult to observe the internal concrete filling status after the installation of the enclosed formwork. Because cavern hydrogen storage facilities have high requirements for structural integrity, density, and long-term service safety, conventional formwork-pumped pouring can easily lead to issues such as insufficient compaction at the top, voids at the far end, and localized voids. To improve the backfilling quality of the top guide tunnel, the method for filling and compensating for grouting the top guide tunnel of an underground energy storage cavern, as provided in this invention, is adopted.

[0065] Pre-construction preparation: Observe the spread, pumping continuity, filling status and grout return of the self-compacting micro-expansion concrete through on-site trial pouring or grouting, and check the single-section pouring length, pump pipe extension distance and pumping pressure control parameters accordingly.

[0066] Step S310: Based on the length and cross-sectional dimensions of the top guide tunnel, the flow properties of the self-compacting micro-expansion concrete, and the load-bearing capacity of the formwork, the top guide tunnel is divided longitudinally into several pouring sections. For example, the length of each pouring section is controlled at 5m, so that the pouring distance of a single section matches the effective flow distance of the concrete, ensuring that the concrete completes diffusion, lifting, and filling within a shorter flow path.

[0067] Step S320: Before constructing each pouring section, install the outer closed formwork. The formwork is equipped with a concrete pump inlet, observation port, and necessary venting holes. Two grouting pipes are pre-embedded at the top of the pouring section, along with one venting hole. The inner ends of the two grouting pipes extend into the backfill area of ​​the top guide hole, while the outer ends protrude through the closed formwork and are temporarily sealed. The venting hole is connected to the top space of the pouring section. The two grouting pipes are respectively positioned at both ends of the top of the pouring section or in areas prone to voids for later compensation grouting. The venting hole is positioned at the highest point of the top of the pouring section for observing venting, backflow, and determining the compaction status during concrete pumping and compensation grouting.

[0068] In step S330, during the initial stage of concrete pouring, a steel pump pipe is inserted approximately 3 meters into the pouring section from the concrete pump outlet, ensuring the pump outlet is located inside the pouring section. After starting the concrete pump, self-compacting, micro-expansion concrete begins to fill the pouring section from within, gradually flowing and spreading towards the ends, top, and the pump outlet of the closed formwork. This method avoids all concrete flowing a long distance inward from the pump outlet of the closed formwork, reducing the risk of insufficient filling in the deeper parts of the guide tunnel.

[0069] In step S340, when the height of the self-compacting micro-expansion concrete filling is close to the top surface of the top guide tunnel, the construction personnel gradually withdraw the steel pump pipe. During the withdrawal process, pumping is maintained continuously or intermittently to ensure that the space originally occupied by the pump pipe is promptly filled by concrete. After the pump pipe is withdrawn to the vicinity of the concrete pumping port, the self-compacting micro-expansion concrete continues to be pumped through the concrete pumping port, causing the concrete to rise towards the top space under the combined action of pump pressure and its own fluidity, thus compacting and filling the top high points, end dead corners, and local irregular spaces.

[0070] In step S350, during the pumping and jacking process at the closed formwork pumping port, control the pumping speed and pumping pressure, and observe the deformation of the closed formwork, the discharge of grout from the vent holes, the return of grout from the injection pipes, and the state of the concrete at the observation port. When continuous and stable return of grout occurs in the injection pipes or vent holes, and the pumping pressure tends to stabilize, it is determined that the top space of the pouring section is basically filled, pumping is stopped, and the concrete pumping port is sealed.

[0071] Step S360: After the concrete pouring is completed and reaches a preliminary stable state, the first compensation grouting is performed. The first compensation grouting uses cement-based micro-expansion grout. The grout is injected into the top area through one of the pre-embedded grouting pipes. The other grouting pipe serves as an auxiliary grouting or grout return observation channel. The vent hole is used to expel residual air from the top and observe the grout return situation. When stable grout return occurs in an adjacent grouting pipe or vent hole, and the grouting pressure reaches a stable state, the first grouting is stopped.

[0072] Step S370: After the first compensation grouting is completed and a certain time interval has elapsed, the second compensation grouting is performed. The second compensation grouting adopts a low-pressure, slow injection method, continuing to inject compensation shrinkage cement-based grout into the top area through pre-embedded grouting pipes to compensate for the tiny voids formed by early bleeding, settlement, and shrinkage of the concrete. The second grouting is stopped when the grouting volume decreases significantly, the grouting pressure stabilizes, grout returns from adjacent grouting pipes, or grout returns again from the vent holes.

[0073] Step S380: After the compensation grouting is completed, the exposed grouting pipes are sealed and cut off. After the closed formwork is removed, the appearance quality of the poured section, the grouting records, and the compaction effect are inspected. If necessary, the compaction degree of the top guide tunnel backfill can be verified by tapping inspection, core drilling, or non-destructive testing.

[0074] In this embodiment, the method for filling and compensating for the compaction of the top guide tunnel of the underground energy storage cavern has the following beneficial effects: 1. Applicable to high-density backfilling requirements for underground energy storage caverns. This invention addresses the backfilling of the top guide tunnel in underground energy storage projects such as rock cave hydrogen storage facilities and underground compressed air energy storage caverns. It can meet the stringent control requirements of these projects on the integrity, density, durability, and long-term service safety of the backfill structure.

[0075] 2. Achieve active and dense backfilling of the top guide tunnel structure, avoiding the need for post-construction defect repair. This invention differs from the traditional process of passively reinforcing voided areas by grouting after concrete has been formed. Instead, it uses an integrated construction system that combines raw material selection, segment length control, pump pipe insertion and retraction, arch pump pressure lifting, and multi-level compensation grouting to actively fill the top closed cavity with concrete during the casting and forming stage, thereby improving the overall compactness of the backfill structure from the source.

[0076] 3. The material properties and construction techniques are highly compatible. This invention uses self-compacting micro-expansion concrete as the backfill material for the top guide hole, and controls the flow of the concrete in short segments to match the length of the pouring section. The concrete can fully diffuse and fill the enclosed space under the combined action of pump pressure and its own fluidity, while utilizing its micro-expansion properties to compensate for early shrinkage, thus improving the compactness and integrity of the top backfill structure.

[0077] 4. Improve the filling effect inside the sealed guide tunnel and at the highest point of the top. This invention adopts a combination of "initial filling by extending the pump pipe, transitional filling by withdrawing the pump pipe, and compaction filling by pumping pressure at the pumping port". First, the concrete is sent into the guide tunnel, and then the concrete is filled to the top high point, irregular space and end area by pumping pressure at the pumping port. This overcomes the problem that conventional single-point pumping at the formwork port is difficult to fill the closed space at the top.

[0078] 5. Reduce subsequent drilling operations and minimize disturbance to existing structures. This invention pre-embeds grouting pipes and sets vent holes at the top of each pouring section. Later, compensation grouting can be carried out directly through the grouting pipes, and the vent holes can be used to vent air and observe the grout return situation. This eliminates the need for extensive drilling after the concrete has been formed, reducing disturbance and damage to the already formed structure.

[0079] 6. Staged grouting can specifically eliminate different types of voids and improve the reinforcement effect. This invention employs at least two differentiated compensation grouting processes. The first grouting mainly treats the initial residual voids, while the second grouting mainly compensates for the tiny voids caused by bleeding, settlement, and shrinkage. Compared with a single grouting process, the backfilling and reinforcement effect is better.

[0080] 7. Highly versatile construction method and low equipment investment cost. The entire process of this invention does not require customized large-scale machinery. It can be completed by relying on general-purpose concrete pumping equipment, steel conveying pipelines, conventional sealing systems and ordinary grouting equipment. It can be widely used in backfilling projects of the closed space at the top of various energy storage caverns, such as hydrogen storage in caverns, compressed air energy storage, and underground gas storage.

[0081] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for filling and compensating for grouting the top guide tunnel of an underground energy storage cavern, characterized in that, The compaction method includes: Along the extension direction of the underground energy storage cavern, the guide tunnel is divided into multiple pouring sections; Grouting pipes are pre-embedded at the top of each of the aforementioned pouring sections, and a closed template is installed on the outside of the pouring section; the closed template has a pumping port and an exhaust hole, the inner end of the grouting pipe extends into the interior of the pouring section, and the outer end protrudes out of the closed template; In the initial filling stage, the pump pipe is extended into the pouring section through the pumping port to pump self-compacting micro-expansion concrete into the pouring section and fill it from the inside out. During the transition filling process, when the self-compacting micro-expansion concrete is filled to the preset state, the pump pipe is gradually withdrawn; during the withdrawal process, the self-compacting micro-expansion concrete is pumped to fill the gaps formed by the withdrawal of the pump pipe. During the final filling stage, the pump pipe is retracted to the pumping port and pumping continues, relying on the pump pressure to lift and fill the top space of the pouring section. Compensation grouting involves performing at least two compensation grouting operations on the top of the cast section through the grouting pipe. The flow rate of the second grouting operation is lower than that of the first grouting operation, and the duration of the second grouting operation is longer than that of the first grouting operation.

2. The method for filling and compensating for grouting the top guide tunnel of an underground energy storage cavern according to claim 1, characterized in that, The length L1 of the pouring section satisfies: L1≤6m; during the initial filling, the length L2 of the pump pipe extending into the pouring section satisfies: 0.5≤L2 / L1≤1.

3. The method for filling and compensating for grouting the top guide tunnel of an underground energy storage cavern according to claim 2, characterized in that, The length L1 of the pouring section satisfies: 3m≤L1≤5m; during the initial filling, the length L2 of the pump pipe extending into the pouring section satisfies: 2m≤L2≤4m.

4. The method for filling and compensating for grouting the top guide tunnel of an underground energy storage cavern according to claim 1, characterized in that, The closed template has an observation port near the top. When the self-compacted micro-expansion concrete is filled to a preset state, the pump pipe is gradually withdrawn; the preset state satisfies at least one of the following conditions: The top surface of the self-compacting micro-expansion concrete is 20cm-50cm away from the top surface of the guide tunnel; The self-compacting micro-expansion concrete was observed at the observation port; The pumping pressure rises and then stabilizes; The grouting pipe, the observation port, or the vent hole experienced reduced venting or grout backflow.

5. The method for filling and compensating for grouting the top guide tunnel of an underground energy storage cavern according to claim 4, characterized in that, The pumping of the self-compacting micro-expansion concrete during the withdrawal process to fill the voids formed by the withdrawal of the pump pipe includes: The retraction process employs continuous or intermittent pumping to fill the gap created by the retraction of the pump pipe.

6. The method for filling and compensating for grouting the top guide tunnel of an underground energy storage cavern according to claim 1, characterized in that, At least two grouting pipes are pre-embedded in each of the casting sections. The two grouting pipes are a first grouting pipe and a second grouting pipe. The inner ends of the first grouting pipe and the inner ends of the second grouting pipe are located at the two ends of the extension direction inside the casting section, respectively.

7. The method for filling and compensating for grouting the top guide tunnel of an underground energy storage cavern according to claim 6, characterized in that, The process of performing at least two compensatory grouting operations on the top of the cast-in-place section through the grouting pipe includes: The first compensation grouting involves filling the pouring section with cement grout through the first grouting pipe to fill the residual voids at the top after the self-compacting micro-expansion concrete is poured. The second compensation grouting involves filling the cast section with one or more of the following: ultrafine cement grout, micro-expansion cement grout, and shrinkage-compensating cement-based grout, through the second grouting pipe, to compensate for the tiny voids formed by concrete bleeding, settlement, or shrinkage.

8. The method for filling and compensating for grouting the top guide tunnel of an underground energy storage cavern according to claim 1, characterized in that, The number of vent holes is multiple, and they are respectively located at the top and end corners of the closed template.

9. The method for filling and compensating for grouting the top guide tunnel of an underground energy storage cavern according to claim 1, characterized in that, The self-compacting micro-expansion concrete contains one or more of the following: water-reducing agent, expansion agent, and mineral admixture.

10. The method for filling and compensating for grouting the top guide tunnel of an underground energy storage cavern according to claim 1, characterized in that, After the compensation grouting is completed, the compaction method further includes: Sealing and quality inspection, wherein the quality inspection includes one or more of the following: visual inspection, impact testing, core drilling testing, radar scanning, and ultrasonic testing.

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