An in-situ testing system for bearing capacity of surrounding rock of underground gas storage and a testing method thereof

Abstract

The present application relates to the field of underground gas storage engineering test equipment, and specifically discloses an in-situ test system for bearing capacity of surrounding rock of underground gas storage and a test method thereof; an in-situ test hole is drilled and extended to the in-situ test hole of the original rock stress area on the side wall of the existing underground chamber or roadway, a loading assembly filled with high-pressure compressible gas and radially expanded is arranged at the bottom of the hole; a safety counterforce closed assembly including a pressure-bearing component, a force transmission component and an anchoring component is coaxially arranged in the hole, forming an axial counterforce continuous transmission path to limit axial displacement and reduce spouting instability; a stereoscopic monitoring system is formed by arranging monitoring holes and various sensors around the test hole, and stress, deformation, seepage and damage responses are collected; a loading and monitoring closed-loop control system dynamically adjusts the loading pressure, rate, pressure maintaining and cycle parameters according to the monitoring data, completes the graded / cyclic loading, and outputs the ultimate bearing capacity, fatigue bearing capacity index and operation pressure suggestion interval.

Description

Technical Field

[0001] This invention relates to the field of testing equipment for underground gas storage engineering, and specifically to an in-situ testing system and method for the bearing capacity of surrounding rock in underground gas storage. Background Technology

[0002] During operation, the surrounding rock of underground gas storage facilities is subjected to gas pressures ranging from several megapascals to over ten megapascals over extended periods, and faces frequent gas filling and releasing cycles. The bearing capacity, fatigue damage evolution, and stability of the surrounding rock directly affect the safety of the project. Existing assessment methods mainly include indoor rock mechanics tests, numerical analysis, and a limited number of prototype or field tests. Indoor tests suffer from size effects and struggle to reflect in-situ stress, joint fissures, and groundwater conditions. Prototype tests are labor-intensive, time-consuming, and costly.

[0003] Furthermore, while existing in-situ testing devices for radial loading within boreholes (such as pressure gauges / barometers) can achieve radial pressurization of the borehole wall, their design is primarily geared towards parameter testing of soil or soft rock. Their core focus is solely on "radial loading," neglecting to address the axial reaction forces and ejection instability risks that can easily arise under high-pressure loading of compressible gases in gas storage scenarios. They also lack a reliable, safe, closed-loop reaction structure. Simultaneously, they lack a real-time control closed-loop mechanism that effectively integrates multi-source monitoring data of the surrounding rock (such as stress, deformation, and seepage) into the loading process. This makes it difficult to meet the core requirements of "safety, controllability, and repeatability" for assessment technology under long-term high-pressure cyclic conditions in gas storage facilities. Therefore, there is an urgent need for an in-situ assessment technology that relies on existing underground chambers / tunnels, requires minimal engineering work, can simulate long-term high-pressure cyclic conditions in gas storage facilities under in-situ geostress conditions, and possesses inherent safety and closed-loop controllability. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0005] To address the technical challenges of existing methods for assessing the bearing capacity of surrounding rock in underground gas storage facilities, such as the size effect of indoor tests, high costs of prototype tests, lack of a safe reaction force closure structure, and lack of a real-time control closed-loop mechanism, and to achieve a more in-situ, reliable, and information-rich assessment of the bearing capacity of surrounding rock in underground gas storage facilities, this invention provides an in-situ testing system and method for assessing the bearing capacity of surrounding rock in underground gas storage facilities.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: an in-situ testing system for the bearing capacity of surrounding rock in underground gas storage facilities, comprising an in-situ testing borehole, a high-pressure radial loading assembly, a safety reaction force closure assembly, a multi-parameter three-dimensional monitoring system, and a loading and monitoring closed-loop control system.

[0007] The in-situ test hole is opened on the sidewall of an existing underground chamber or roadway, perpendicular to the sidewall of the roadway and passing through the disturbed surrounding rock zone to enter the stress zone of the original rock. The high-pressure radial loading component is arranged at the bottom of the in-situ test hole to apply radial load to the test hole wall during the test. The safety reaction force closing component is coaxially set in the in-situ test hole and located between the high-pressure radial loading component and the hole opening to limit the axial displacement of the high-pressure radial loading component and transfer the axial reaction force it generates to the surrounding rock.

[0008] The multi-parameter three-dimensional monitoring system consists of multiple monitoring holes arranged in the surrounding rock around the in-situ test hole and a group of monitoring sensors installed in the monitoring holes. It is used to collect stress, deformation, seepage and damage response data of the surrounding rock during the loading process. The loading and monitoring closed-loop control system is connected to the high-pressure radial loading component and the multi-parameter three-dimensional monitoring system, and is used to dynamically adjust the loading pressure, loading rate, holding time and cycle parameters based on the monitoring data.

[0009] As a preferred technical solution for an in-situ testing system for the bearing capacity of surrounding rock in underground gas storage facilities, the safety reaction force closing component forms a continuous axial reaction force transmission path from the high-pressure radial loading component, through the pressure-bearing component and the force transmission component to the anchoring component, and finally to the surrounding rock at the orifice, in order to prevent axial ejection or instability under high-pressure compressible gas loading conditions.

[0010] As a preferred technical solution for an in-situ testing system for the bearing capacity of surrounding rock in an underground gas storage facility, the anchoring component includes an annular anchoring plate / flange and anchors distributed along the circumference. The anchors are one or more of anchor rods, expansion bolts, or chemical anchors, used to disperse and transfer axial reaction force to the surrounding rock at the borehole opening.

[0011] As a preferred technical solution for an in-situ testing system for the bearing capacity of surrounding rock in an underground gas storage facility, the safety reaction force closure assembly includes at least: a pressure-bearing component, a force-transmitting component arranged along the borehole axis, and an anchoring component anchored to the surrounding rock at the borehole opening. The pressure-bearing component abuts against the axial end face of the high-pressure radial loading component, and the two ends of the force-transmitting component are rigidly connected to the pressure-bearing component and the anchoring component, respectively. The force-transmitting component is a hollow rod with an internal channel to accommodate and protect the gas injection pipeline connected to the high-pressure radial loading component.

[0012] As a preferred technical solution for an in-situ testing system for the bearing capacity of surrounding rock in an underground gas storage facility, the multiple monitoring holes are arranged in a ring around the in-situ testing holes and form a three-dimensional distribution along the axial and vertical axes of the chamber / tunnel.

[0013] As a preferred technical solution for an in-situ testing system for the bearing capacity of surrounding rock in underground gas storage facilities, the monitoring sensor group includes at least one or more of the following: acoustic emission sensor, borehole stress gauge, displacement / convergence gauge, and pore pressure gauge.

[0014] As a preferred technical solution for an in-situ testing system for the bearing capacity of surrounding rock in underground gas storage facilities, the loading and monitoring closed-loop control system is configured to execute at least one control action when the monitoring data meets preset trigger conditions. The trigger conditions include: the cumulative deformation of the surrounding rock reaches a threshold, the acoustic emission event rate or energy surge reaches a threshold, and the stress increase of the surrounding rock reaches a threshold. The control actions include: reducing load, maintaining pressure, changing the loading rate, changing the cycle amplitude, or terminating loading.

[0015] As a preferred technical solution for an in-situ testing system of bearing capacity of surrounding rock in underground gas storage, the loading and monitoring closed-loop control system supports two modes: graded loading and cyclic loading. The cyclic loading mode is used to simulate the long-term operating conditions of the gas storage and output fatigue bearing capacity evaluation parameters.

[0016] This invention also discloses a testing method using the aforementioned in-situ testing system for the bearing capacity of surrounding rock in underground gas storage facilities, comprising:

[0017] S1. Drill in-situ test holes in the sidewalls of existing underground chambers or tunnels, and drill multiple monitoring holes around them and install monitoring sensor groups to form a multi-parameter three-dimensional monitoring system.

[0018] S2. Arrange a high-pressure radial loading component at the bottom of the in-situ test hole and install a safety reaction force closing component to form a continuous transmission path for the axial reaction force, thereby completing the hole closure and safety constraint.

[0019] S3. Start the loading and monitoring closed-loop control system, obtain the initial state of the surrounding rock and set the loading path;

[0020] S4. Perform hierarchical loading or cyclic loading, and collect monitoring data synchronously at each loading stage;

[0021] S5. Trigger closed-loop control based on monitoring data to dynamically adjust loading amplitude, rate, pressure holding or cyclic parameters;

[0022] S6. Based on the loading-response evolution characteristics, determine the ultimate bearing capacity and long-term fatigue bearing capacity index of the surrounding rock, and output the recommended operating pressure range of the gas storage facility.

[0023] As a preferred technical solution for a testing method, step S6 includes at least one of the following:

[0024] (a) The ultimate bearing pressure is determined by combining the nonlinear inflection point of the pressure-displacement curve, stiffness degradation and abrupt change in acoustic emission.

[0025] (b) Determine fatigue life or stability level based on residual deformation growth rate, stiffness degradation rate and damage event evolution under cyclic loading.

[0026] The beneficial effects of this invention are as follows: This invention achieves in-situ quantitative assessment of the ultimate bearing capacity, fatigue and stability of the surrounding rock by arranging in-situ test holes on the sidewall of the existing chamber and radially loading with compressible high-pressure gas, combined with a continuous transmission path of safe reaction force closure and multi-parameter three-dimensional monitoring closed-loop control. At the same time, it reduces the amount of engineering work and suppresses the risk of ejection instability, and provides a suggested range for the bearing capacity of the surrounding rock of the gas storage. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0028] Figure 1 This is a schematic diagram of the overall structure of the in-situ testing system of the present invention;

[0029] Figure 2 This is a schematic diagram showing the arrangement relationship between the rigid reaction force transmission component and the high-pressure flexible loading unit in this invention;

[0030] Figure 3 This is a schematic diagram of the three-dimensional arrangement of monitoring holes in a multi-parameter three-dimensional monitoring system.

[0031] Figure 4 This is a flowchart illustrating the in-situ testing method of the present invention.

[0032] Reference numerals: 101, underground chamber / tunnel; 102, surrounding rock; 1, in-situ test hole; 2, high-pressure flexible loading unit; 3, rigid reaction force transmission component; 31, pressure-bearing component; 32, force transmission component; 33, anchoring component; 34, anchor bolt; 4, gas injection and monitoring system; 41, high-pressure gas source device; 42, high-pressure gas injection pipeline; 43, pressure monitoring device; 44, pressure regulating component; 5, high-density three-dimensional monitoring network; 51, monitoring hole; 52, monitoring sensor group; 6, monitoring sensor signal acquisition instrument; 7, loading and monitoring closed-loop control system. Detailed Implementation

[0033] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0034] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0035] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0036] Secondly, the present invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not according to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth.

[0037] Example 1

[0038] Reference Figures 1-4 This embodiment provides an in-situ testing system for the bearing capacity of surrounding rock in an underground gas storage facility, including an in-situ test hole, a high-pressure radial loading component, a safety reaction force closure component, a multi-parameter three-dimensional monitoring system, and a loading and monitoring closed-loop control system.

[0039] In-situ test boreholes are drilled into the sidewalls of existing underground chambers or tunnels, extending perpendicular to the tunnel sidewalls and passing through the disturbed rock zone to enter the original rock stress zone. The location of these test boreholes ensures that the true mechanical response of the original rock area unaffected by the excavation of the existing chambers or tunnels can be obtained, providing a fundamental condition for accurately assessing the bearing capacity of the surrounding rock.

[0040] A high-pressure radial loading assembly is positioned at the bottom of the in-situ test borehole to apply radial loading to the borehole wall during testing. This assembly is a flexible component capable of being filled with high-pressure compressible gas and generating radial expansion. When high-pressure gas is injected into the flexible component, it expands radially, applying uniform radial pressure to the surrounding rock of the borehole wall, simulating the internal pressure load borne by the surrounding rock during gas storage facility operation. The flexible component design results in a more uniform distribution of loading pressure, avoiding the stress concentration problems that may occur with rigid loading devices.

[0041] A safety reaction force closure assembly is coaxially mounted within the in-situ test borehole, located between the high-pressure radial loading assembly and the borehole opening. It restricts the axial displacement of the high-pressure radial loading assembly and transmits its generated axial reaction force to the surrounding rock. This assembly includes at least a pressure-bearing member, a force-transmitting member arranged axially along the borehole, and an anchoring member anchored to the surrounding rock at the borehole opening. The pressure-bearing member abuts against the axial end face of the high-pressure radial loading assembly, directly bearing the axial expansion force generated by the high-pressure gas. The force-transmitting member is rigidly connected at both ends to the pressure-bearing member and the anchoring member, forming a continuous axial force transmission path. The safety reaction force closure assembly forms a continuous axial reaction force transmission path from the high-pressure radial loading assembly, through the pressure-bearing member and the force-transmitting member to the anchoring member, and finally to the surrounding rock at the borehole opening. This effectively prevents axial ejection or instability under high-pressure compressible gas loading conditions, ensuring the safety and reliability of the testing process.

[0042] The anchoring components include annular anchor plates / flanges and circumferentially distributed anchors, which are one or more of anchor bolts, expansion bolts, or chemical anchors. The annular anchor plates / flanges are tightly fitted to the surface of the surrounding rock at the borehole opening, and the anchors penetrate the anchor plates and extend into the interior of the surrounding rock, dispersing and transferring the axial reaction force to the surrounding rock at the borehole opening, thus avoiding rock damage caused by excessive local stress.

[0043] In a preferred embodiment, the force-transmitting component is a hollow rod with an internal channel to accommodate and protect the gas injection pipeline connected to the high-pressure radial loading assembly. This design ensures the structural strength of the force-transmitting component while providing a protective channel for high-pressure gas delivery, preventing damage to the gas injection pipeline under high-pressure conditions.

[0044] The multi-parameter three-dimensional monitoring system consists of multiple monitoring holes arranged in the surrounding rock around the in-situ test holes and a group of monitoring sensors installed in the monitoring holes. It is used to collect data on stress, deformation, seepage, and damage response of the surrounding rock during loading. The multiple monitoring holes are arranged in a ring around the in-situ test holes, forming a three-dimensional distribution along the axial and vertical axes of the chamber / tunnel to cover the key influence zone of the surrounding rock around the in-situ test holes. This three-dimensional monitoring network can comprehensively capture the multi-field coupled response characteristics of the surrounding rock under radial loading. The monitoring sensor group includes at least one or more of the following: acoustic emission sensors, borehole stress gauges, displacement / convergence gauges, pore pressure gauges, and temperature sensors. Acoustic emission sensors are used to monitor micro-fracture activity within the surrounding rock; borehole stress gauges measure changes in the stress state of the surrounding rock; displacement / convergence gauges monitor deformation characteristics of the surrounding rock; pore pressure gauges measure changes in pore fluid pressure; and temperature sensors monitor the temperature field distribution.

[0045] The loading and monitoring closed-loop control system is connected to the high-pressure radial loading component and the multi-parameter three-dimensional monitoring system. It dynamically adjusts the loading pressure, loading rate, holding time, and cycle parameters based on monitoring data, creating a real-time closed-loop feedback between the loading process and the surrounding rock response. This enables in-situ assessment of the ultimate bearing capacity and long-term fatigue bearing capacity of the surrounding rock. The control system is configured to execute at least one control action when the monitoring data meets preset trigger conditions. These trigger conditions include surrounding rock stiffness degradation reaching a threshold, residual deformation accumulation reaching a threshold, acoustic emission event rate or energy surge reaching a threshold, and abnormal increase in seepage pressure reaching a threshold. When surrounding rock stiffness degradation reaches the preset threshold, it indicates a significant decrease in the bearing capacity of the surrounding rock; when residual deformation accumulation reaches the threshold, it indicates irreversible plastic deformation of the surrounding rock; when acoustic emission event rate or energy surges, it indicates intensified internal fracturing activity of the surrounding rock; and when seepage pressure rises abnormally, there may be a risk of increased permeability of the surrounding rock. Corresponding control actions include load reduction, pressure holding, changing the loading rate, changing the cycle amplitude, or terminating loading to ensure the safety of the testing process and obtain effective evaluation data.

[0046] Triggering conditions and control actions reference examples:

[0047] The loading and monitoring closed-loop control system is configured to execute the following active feedback control strategy:

[0048] Based on acoustic emission precursor-based fuse control: The system receives the ringing count rate signal fed back by the acoustic emission sensor in the monitoring hole in real time; when the system detects that the slope of the ringing count rate change exceeds the preset fracture penetration slope threshold, the controller sends an opening command to the electromagnetic fast exhaust valve of the gas injection system to execute a millisecond-level emergency deload action to prevent the fracture from unstablely expanding.

[0049] Fatigue loading control based on stiffness evolution: In cyclic loading mode, the system synchronously collects the gas pressure signal inside the bag and the radial displacement signal fed back by the displacement sensor in the monitoring hole, and calculates the secant modulus of the surrounding rock in real time; when the attenuation of the secant modulus reaches the preset stiffness failure threshold (e.g., 60%-80% of the initial modulus), the system automatically stops pressurization and maintains the pressure holding state, or controls the pressure regulating valve to perform staged unloading to obtain the unloading rebound characteristic data of the surrounding rock;

[0050] Stress anomaly-based pressure stabilization control: When the surrounding rock stress value fed back by the borehole stress gauge undergoes a sudden change (sudden increase or sudden decrease) exceeding the preset fluctuation threshold within a predetermined time, the system determines that the surrounding rock is in an unstable rheological state, and then controls the high-pressure gas source device to suspend pressure regulation and maintain a constant volume state until the stress monitoring value returns to linear change characteristics.

[0051] The loading and monitoring closed-loop control system supports two modes: graded loading and cyclic loading. The graded loading mode determines the ultimate bearing capacity of the surrounding rock by gradually increasing the loading pressure; the cyclic loading mode is used to simulate the long-term operating conditions of the gas storage facility and output fatigue bearing capacity evaluation parameters. Through repeated loading-unloading cycles, the stability and fatigue characteristics of the surrounding rock under long-term cyclic loading are evaluated.

[0052] This in-situ testing system applies radial pressure to the surrounding rock through a high-pressure radial loading component, ensures test safety through a safety reaction closure component, comprehensively collects surrounding rock response data through a multi-parameter three-dimensional monitoring system, and achieves intelligent control through a loading and monitoring closed-loop control system. This forms a complete in-situ evaluation system for the bearing capacity of surrounding rock, which can accurately assess the ultimate bearing capacity and long-term stability of the surrounding rock of underground gas storage facilities.

[0053] Example 2

[0054] This invention provides an in-situ testing method for evaluating the bearing capacity of surrounding rock in gas storage facilities using an in-situ testing system. This method, implemented based on the in-situ testing system, can accurately assess the bearing capacity and long-term stability of surrounding rock in underground gas storage facilities.

[0055] S1. Drilling Layout and Monitoring System Construction: In-situ test boreholes are drilled into the sidewalls of existing underground chambers or tunnels. These boreholes extend radially, passing through the disturbed rock zone and entering the original rock stress zone. Multiple monitoring boreholes are drilled around the in-situ test boreholes, arranged in a ring around them and forming a three-dimensional distribution along the axial and vertical axes of the chamber / tunnel to cover the key influence zone of the surrounding rock. Monitoring sensor arrays are installed in each monitoring borehole, including acoustic emission sensors, borehole stress gauges, displacement / convergence gauges, pore pressure gauges, and temperature sensors, forming a multi-parameter three-dimensional monitoring system. This monitoring system can comprehensively collect data on stress, deformation, seepage, and damage response of the surrounding rock during loading, providing comprehensive data support for assessing the bearing capacity of the surrounding rock.

[0056] S2. Loading and Reaction System Installation: A high-pressure radial loading assembly is installed at the bottom of the in-situ test borehole. This assembly is a flexible component capable of being filled with high-pressure compressible gas and generating radial expansion, applying radial loading to the borehole wall through radial expansion. A safety reaction closure assembly is installed, coaxially positioned within the in-situ test borehole between the high-pressure radial loading assembly and the borehole opening. This assembly includes a pressure-bearing component, a force-transmitting component arranged along the borehole axis, and an anchoring component anchored to the surrounding rock at the borehole opening. The pressure-bearing component abuts against the axial end face of the high-pressure radial loading assembly, and the force-transmitting component is rigidly connected at both ends to the pressure-bearing component and the anchoring component, respectively. This forms a continuous axial reaction force transmission path from the high-pressure radial loading assembly, through the pressure-bearing component and the force-transmitting component to the anchoring component, and finally to the surrounding rock at the borehole opening. This ensures a continuous axial reaction force transmission path, completing the borehole closure and safety constraint. This design effectively prevents axial ejection or instability under high-pressure compressible gas loading conditions, ensuring the safety of the testing process.

[0057] In a preferred embodiment, the anchoring component includes an annular anchor plate / flange and circumferentially distributed anchors, which are one or more of anchor bolts, expansion bolts, or chemical anchors, used to disperse and transfer axial reaction forces to the surrounding rock at the borehole opening, thereby improving the reliability and stability of the anchoring.

[0058] In another preferred embodiment, the force-transmitting component is a hollow rod with an internal channel to accommodate and protect the gas injection pipeline connected to the high-pressure radial loading component, thus ensuring the force-transmitting function of the structure and providing protection for gas delivery.

[0059] S3. System Initialization and Loading Path Setting: The loading and monitoring closed-loop control system is activated. This system is connected to the high-pressure radial loading component and the multi-parameter three-dimensional monitoring system. The initial state of the surrounding rock is acquired through the monitoring system, including basic parameters such as the initial stress field, deformation state, and seepage conditions. Based on the actual operational requirements of the gas storage facility and the characteristics of the surrounding rock, a reasonable loading path is set, including parameters such as loading pressure level, loading rate, and holding time, providing a control benchmark for subsequent staged loading or cyclic loading.

[0060] S4. Staged Loading and Synchronous Data Acquisition: A staged or cyclic loading procedure is executed by injecting high-pressure gas into the high-pressure radial loading component, causing radial expansion and applying radial pressure to the borehole wall. During each loading stage, a multi-parameter three-dimensional monitoring system simultaneously acquires data on stress changes, deformation response, seepage characteristics, and damage evolution of the surrounding rock. The loading process adopts a progressively increasing approach, maintaining a certain duration after each loading stage to observe the creep characteristics and long-term stability of the surrounding rock. Cyclic loading simulates the inflation-deflation cycle process in actual gas storage operation to evaluate the fatigue characteristics of the surrounding rock.

[0061] S5. Closed-Loop Control and Parameter Optimization: The loading and monitoring closed-loop control system triggers a closed-loop control mechanism based on real-time collected monitoring data, dynamically adjusting the loading pressure, loading rate, holding time, and cycle parameters according to the monitoring data. When monitoring data shows abnormal responses in the surrounding rock, the system automatically adjusts the loading parameters to ensure the safety of the testing process and the validity of the data. This closed-loop feedback mechanism creates a real-time closed-loop feedback between the loading process and the surrounding rock response, achieving intelligent control of the testing process.

[0062] S6. Bearing Capacity Assessment and Result Output: Based on the analysis of loading-response evolution characteristics, the ultimate bearing capacity and long-term fatigue bearing capacity of the surrounding rock are determined through a comprehensive evaluation of key parameters such as stress-strain relationship, failure mode, and permeability changes. Considering the actual operating requirements of the gas storage facility and taking into account safety and economic factors, a recommended operating pressure range for the gas storage facility is output. This method enables in-situ assessment of the ultimate bearing capacity and long-term fatigue bearing capacity of the surrounding rock, providing a scientific basis for the safe operation of the gas storage facility.

[0063] This in-situ testing method, through a systematic testing process, enables a comprehensive assessment of the bearing capacity of the surrounding rock of a gas storage facility. It can not only determine the ultimate bearing capacity of the surrounding rock, but also evaluate its fatigue characteristics and long-term stability under cyclic loading, providing important technical support for the design optimization and safe operation of gas storage facilities.

[0064] Furthermore, this method achieves an accurate evaluation of the bearing capacity of the surrounding rock through a systematic testing process and multi-dimensional data analysis.

[0065] The core of this method lies in the bearing capacity evaluation stage in step S6, employing multiple judgment criteria to ensure the reliability and accuracy of the evaluation results. In terms of static bearing capacity assessment, the ultimate bearing pressure is determined by jointly considering the nonlinear inflection point of the pressure-displacement curve, stiffness degradation, and abrupt changes in acoustic emission. Specifically, during graded loading, a high-density three-dimensional monitoring network is used to collect deformation response data of the surrounding rock in real time, and a pressure-displacement relationship curve is plotted. When the surrounding rock approaches its ultimate bearing state, a significant nonlinear inflection point appears on this curve, indicating a transition from elastic deformation to plastic deformation. Simultaneously, by continuously monitoring changes in the stiffness of the surrounding rock, significant stiffness degradation indicates the onset of microcracks or damage accumulation within the rock. The acoustic emission monitoring system captures acoustic emission signals generated by crack propagation within the surrounding rock; a sudden increase in acoustic emission events or a sharp rise in energy signifies that the surrounding rock is about to reach its bearing limit. By comprehensively analyzing the changing characteristics of these three key indicators, the ultimate bearing pressure of the surrounding rock can be accurately determined, avoiding errors that may arise from judging based on a single indicator.

[0066] In terms of dynamic load-bearing capacity assessment, this method determines fatigue life or stability level based on residual deformation growth rate, stiffness degradation rate, and damage event evolution under cyclic loading conditions. A cyclic loading regime is implemented through a gas injection and monitoring system to simulate periodic pressure changes in actual gas storage operation. In each loading cycle, the cumulative residual deformation of the surrounding rock is monitored, and the residual deformation growth rate is calculated. When the growth rate remains stable or shows a decreasing trend, it indicates that the surrounding rock has good cyclic load-bearing capacity; when the growth rate continues to increase, it indicates that the surrounding rock may experience fatigue failure. Simultaneously, the degree of load-bearing capacity degradation is assessed by analyzing the degradation law of the surrounding rock stiffness during cyclic loading. The changing trend of the stiffness degradation rate can reflect the development speed and accumulation degree of damage within the surrounding rock. Damage event evolution analysis tracks the initiation, propagation, and penetration of cracks within the surrounding rock through acoustic emission monitoring and microseismic monitoring, establishing a damage evolution model. Based on the comprehensive analysis of these multi-dimensional data, the fatigue life of the surrounding rock under long-term cyclic loading can be predicted, and the corresponding stability level can be determined.

[0067] The advantage of this evaluation method lies in its multi-parameter joint judgment mechanism, which improves the reliability of the evaluation results. The pressure-displacement curve can intuitively reflect the macroscopic mechanical response of the surrounding rock, the stiffness degradation index reveals the attenuation law of the surrounding rock's bearing capacity, and acoustic emission monitoring captures the real-time development of internal damage in the surrounding rock from a microscopic perspective. These three elements corroborate each other, forming a complete evaluation system. In cyclic loading assessment, the residual deformation growth rate reflects the plastic accumulation characteristics of the surrounding rock, the stiffness degradation rate characterizes the rate of attenuation of bearing capacity, and the damage event evolution reveals the development process of the failure mechanism. This multi-dimensional evaluation method can comprehensively reflect the bearing capacity characteristics of the surrounding rock under complex stress environments, providing a scientific basis for the long-term safe operation of gas storage facilities.

[0068] This evaluation method enables the establishment of quantitative evaluation standards for the bearing capacity of surrounding rock, providing important technical support for optimizing gas storage design parameters and setting operating pressures, and ensuring the safe and stable operation of gas storage facilities throughout their service life.

[0069] Example 3

[0070] like Figure 1 As shown in the figure, an in-situ testing system for evaluating the bearing capacity of the surrounding rock of a gas storage facility is arranged on the side wall of an existing underground chamber. It includes an in-situ testing hole 1, a high-pressure flexible loading unit 2, a rigid reaction force transmission component 3, a gas injection and monitoring system 4, and a high-density three-dimensional monitoring network 5.

[0071] It is installed on an underground chamber, or it can be an underground tunnel. The in-situ test hole 1 is opened on the surrounding rock 102 of the side wall.

[0072] Furthermore, in-situ test borehole 1 is drilled from the sidewall of the existing underground chamber, with its axis roughly pointing radially towards the depth of the surrounding rock. Its depth is preferably greater than three times the equivalent diameter D of the chamber, so that the stress state near the bottom of the borehole closely approximates the stress field of the original rock. The diameter of in-situ test borehole 1 is determined based on the construction equipment and testing requirements, and can be 100–300 mm.

[0073] The high-pressure flexible loading unit 2 is arranged at the bottom region of the in-situ test hole 1. It is a flexible component, such as a flexible bag, that can be filled with high-pressure gas and expand radially. The size of the high-pressure flexible loading unit 2 is adapted to the inner diameter of the in-situ test hole 1. It can be smoothly inserted into the bottom of the hole when it is not inflated, and can form good contact with the hole wall after inflation to apply radial loading pressure to the hole wall.

[0074] A rigid reaction force transmission component 3 is installed inside the in-situ test hole 1 to seal the hole opening and transmit the axial expansion reaction force generated by the high-pressure flexible loading unit 2 to the surrounding rock. The rigid reaction force transmission component 3 includes at least a pressure-bearing component 31, a force-transmitting component 32, an anchoring component 33, and an anchor rod 34. The pressure-bearing component 31 is arranged on the side of the high-pressure flexible loading unit 2 facing the hole opening to bear the axial expansion reaction force of the high-pressure flexible loading unit 2; one end of the force-transmitting component 32 is connected to the pressure-bearing component 31 and extends axially along the in-situ test hole 1 to the hole opening area; the anchoring component 33 is arranged around the hole opening of the in-situ test hole 1 and fixed to the surrounding rock by an anchoring structure, and the other end of the force-transmitting component 32 is connected to the anchoring component 33, thereby transmitting the axial expansion reaction force of the high-pressure flexible loading unit 2 to the surrounding rock through the pressure-bearing component 31, the force-transmitting component 32, the anchoring component 33, and the anchor rod 34.

[0075] The force transmission component 32 is a hollow force transmission rod, which can have a channel inside for arranging part of the gas pipeline of the gas injection and monitoring system 4, so that the gas pipeline is arranged more compactly and protected in the in-situ test hole 1.

[0076] Because this invention uses high-pressure gas as the loading medium, and gas has high compressibility energy, if the borehole wall is damaged or the seal fails, the high-pressure gas may be released instantaneously, causing the loading unit to be ejected like a "bullet". Therefore, the rigid reaction force transmission component 3 in this embodiment plays a crucial "blowout preventer" role, directly transmitting the huge axial thrust to the anchoring component 33 and dispersing it to the surrounding rock at the borehole opening through the force transmission component 32, ensuring the inherent safety of the testing process.

[0077] The gas injection and monitoring system 4 includes a high-pressure gas source device 41, a high-pressure gas injection pipeline 42, and a pressure monitoring device 43. The high-pressure gas source device 41 can be an air compressor or other device capable of providing stable and adjustable gas pressure. One end of the high-pressure gas injection pipeline 42 is connected to the high-pressure gas source device 41, and the other end is connected to the air inlet of the high-pressure flexible loading unit 2. The pressure monitoring device 43 is installed on the high-pressure gas injection pipeline 42 to monitor the internal gas pressure of the high-pressure flexible loading unit 2 in real time and can transmit the pressure signal to the data acquisition and control system. If necessary, the gas injection and monitoring system 4 can also be equipped with safety protection devices such as a safety relief valve, i.e., a pressure regulating component 44.

[0078] The high-density three-dimensional monitoring network 5 consists of multiple monitoring holes 51 arranged around the in-situ test hole 1 and a group of monitoring sensors 52 installed in the monitoring holes 51. Figure 3 As shown, monitoring holes 51 can be drilled around the in-situ test hole 1 according to a predetermined spatial arrangement. For example, several monitoring holes can be arranged above, below, and laterally of the in-situ test hole 1 to form a certain monitoring coverage area of ​​the surrounding rock around the in-situ test hole 1. The monitoring sensor group 52 may include one or more of acoustic emission sensors, borehole stress gauges, and other applicable sensors, selected according to the test requirements. After the sensor arrangement is completed, the monitoring holes 51 can be sealed with grouting material to ensure good coupling between the sensors and the surrounding rock.

[0079] With the above structure, the in-situ testing system of this embodiment can apply controllable radial gas loading to the bottom area of ​​the in-situ testing hole 1 using the high-pressure flexible loading unit 2, safely transmit axial reaction force through the rigid reaction force transmission component 3, and monitor the multi-field response of the surrounding rock in real time through the high-density three-dimensional monitoring network 5.

[0080] The monitoring sensor signal acquisition instrument 6 is connected to the monitoring sensor group 52 and the gas injection and monitoring system 4 via a signal line, and is used to monitor pressure signals and receive data from the monitoring hole in real time.

[0081] The loading and monitoring closed-loop control system 7 is connected to the monitoring sensor signal acquisition instrument 6 and the gas injection and monitoring system 4, and is used to make judgments based on the monitored data and then control the on and off of high-pressure gas injection.

[0082] Furthermore, the corresponding in-situ testing methods are as follows:

[0083] This embodiment presents an in-situ testing method for evaluating the bearing capacity of surrounding rock in a gas storage facility using an in-situ testing system.

[0084] Step S1: Drilling and monitoring hole arrangement.

[0085] At the construction site of the proposed gas storage facility, a representative section of the existing underground chamber or tunnel is selected, and in-situ test boreholes 1 are drilled on its sidewalls according to design requirements, extending radially to the original rock stress zone. Based on the characteristics of the surrounding rock and monitoring needs, multiple monitoring boreholes 51 are arranged around the in-situ test boreholes 1 along the axial and vertical directions of the existing underground chamber or tunnel to form a high-density three-dimensional monitoring network 5.

[0086] Step S2: Install and seal the monitoring sensor group.

[0087] A predetermined type and number of monitoring sensor groups 52 are installed in each monitoring hole 51. For example, acoustic emission sensors, borehole stress gauges, and borehole pressure sensors are arranged at different depths and connected to the data acquisition and control system on the ground or inside the tunnel via cables or optical fibers. After the sensors are installed, the monitoring holes 51 are grouted and sealed with grout to ensure good mechanical and signal coupling between the monitoring sensor groups 52 and the surrounding rock.

[0088] Step S3: Loading and reaction structure installation.

[0089] A high-pressure flexible loading unit 2 is arranged at the bottom of the in-situ test hole 1 and connected to the front end of the high-pressure gas injection pipeline 42. A pressure-bearing member 31 is installed on the side of the high-pressure flexible loading unit 2 facing the hole opening, and one end of a force-transmitting member 32 is connected to the pressure-bearing member 31. The force-transmitting member 32 extends axially along the in-situ test hole 1 to the hole opening area. Anchoring members 33 are arranged around the hole opening of the in-situ test hole 1, for example, by pre-drilling anchoring holes and installing anchor rods 34, so that the anchoring members 33 are reliably anchored to the surrounding rock. The other end of the force-transmitting member 32 is fixedly connected to the anchoring member 33, so that the rigid reaction force transmission component 3 forms a continuous mechanical transmission path.

[0090] Step S4: System assembly and inspection.

[0091] The high-pressure gas injection pipeline 42 is led to the air inlet of the high-pressure flexible loading unit 2 through the internal channel of the force transmission component 32 or the internal space of the in-situ test hole 1, and connected to the high-pressure gas source device 41. A pressure monitoring device 43 is installed at a suitable location on the high-pressure gas injection pipeline 42, and the relevant signal lines are connected to the data acquisition and control system. The entire system is then checked for sealing and functionality to ensure there are no obvious leaks or structural loosening.

[0092] Step S5: Staged gas loading and data acquisition.

[0093] The high-pressure gas source device 41 is activated, injecting high-pressure gas into the high-pressure flexible loading unit 2 in stages according to a predetermined loading path. For example, several pressure stages can be used, with each stage increasing the pressure by a certain value, and the pressure is maintained for a period of time after each stage is applied. During the loading and pressure holding process, the pressure monitoring device 43 records the gas pressure inside the high-pressure flexible loading unit 2 in real time; the high-density three-dimensional monitoring network 5 collects multi-field response data such as stress, deformation, seepage, and damage of the surrounding rock at each monitoring hole 51.

[0094] The aforementioned pre-defined loading program includes:

[0095] An example of hierarchical loading:

[0096] 1. In-place sealing: Place the high-pressure radial loading assembly at the bottom of the hole, connect the air injection line, and perform P... init =0.2MPa check.

[0097] 2. Monotonic graded loading (gradual, holding pressure):

[0098] Step A: Increase the pressure to P1 = 2.0 MPa and maintain it for 60 minutes;

[0099] Step B: Increase the pressure to P2 = 4.0 MPa and maintain it for 60 minutes;

[0100] Step C: Increase the pressure to P3 = 6.0 MPa and maintain it for 60 minutes;

[0101] Step D: Increase the pressure to P4=8.0MPa (test target) and maintain it for 60 minutes.

[0102] 3. After the test, gradually depressurize and remove the equipment.

[0103] An example of loading in a loop:

[0104] 1. In-place sealing: Place the high-pressure radial loading assembly at the bottom of the hole, connect the air injection line, and perform P... init =0.2MPa check.

[0105] 2. Cyclic loading (fatigue load capacity test): 10 cycles, each cycle consisting of P min =2.0MPa increased to P max =8.0MPa (pressurize for 30 minutes), maintain at 8.0MPa for 30 minutes, reduce to 2.0MPa and maintain for 30 minutes (i.e., each cycle is about 90 minutes).

[0106] 3. After the test, gradually depressurize and remove the equipment.

[0107] Step S6: Evaluation of the bearing capacity of the surrounding rock.

[0108] Based on the collected pressure-time curves and multi-field response data of the surrounding rock, the stress, deformation, and damage evolution characteristics of the surrounding rock during various loading and pressure holding processes are analyzed, including but not limited to: changes in the apparent stiffness of the surrounding rock, stress redistribution patterns at monitoring points, nonlinear evolution of displacement with loading, and abrupt changes in damage indication signals. Through these analytical results, the bearing capacity and stability characteristics of the surrounding rock are determined, and a reasonable range and safety recommendations for the operating pressure of the proposed gas storage facility are provided.

[0109] Example 3: Optional structure of flexible loading unit and rigid reaction force component

[0110] This embodiment, based on Embodiment 1, provides an optional implementation of the structure of the high-pressure flexible loading unit and the rigid reaction force transmission component to further illustrate the application scope of the system of the present invention. The structure in this embodiment is supplementary to the present invention and does not constitute a necessary limitation of the present invention.

[0111] The high-pressure flexible loading unit can employ a multi-layer flexible material composite structure, such as an inner high-pressure resistant rubber layer, a middle reinforcing fiber layer or mesh skeleton layer, and an outer wear-resistant protective layer, to improve durability and damage resistance under high-pressure circulating gas loading. A detachable sealing joint can be installed at the air inlet of the high-pressure flexible loading unit for easy installation and replacement.

[0112] The pressure-bearing component in the rigid reaction force transmission assembly can adopt a disc-shaped or dish-shaped structure with a diameter slightly smaller than the diameter of the in-situ test hole, and reinforcing ribs can be set on the pressure-bearing surface to improve the load-bearing capacity. The force transmission component can adopt a hollow rod structure, with gas pipelines or other functional components arranged inside the hollow cavity. The anchoring component can include an annular anchor plate and several anchors, which are distributed circumferentially to uniformly transmit the reaction force to the surrounding rock.

[0113] The above-mentioned optional structures further improve the reliability and applicability of the system under high-pressure gas loading conditions. However, the basic concept of the present invention is not limited thereto. Those skilled in the art can carry out various forms of structural design and optimization of the high-pressure flexible loading unit and rigid reaction force transmission component according to actual engineering needs.

[0114] Furthermore, an example of an evaluation method based on multiple monitoring data is as follows:

[0115] Based on Example 2, a multi-field data comprehensive analysis approach can be used to evaluate the bearing capacity of surrounding rock. For example, during each stage of pressure loading and holding, pressure-displacement relationship curves, stress change curves, and seepage pressure change curves of key monitoring points in the surrounding rock are established. Combined with changes in damage indication signals, the transition process of the surrounding rock from an approximately linear elastic stage to a nonlinear stage, and from a slightly damaged stage to a significantly damaged stage can be identified.

[0116] In practical applications, several evaluation indicators can be selected based on monitoring data, such as stiffness degradation ratio, residual deformation, stress redistribution amplitude, and the frequency and energy of damage events. The gas pressure range within which the surrounding rock can operate safely for a long period can then be determined based on the changing trends of these indicators. This embodiment is merely an example of an evaluation method, and the present invention is not limited to specific evaluation indicators and algorithms.

[0117] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An in-situ testing system for the bearing capacity of surrounding rock in underground gas storage facilities, characterized in that: This includes in-situ test holes, high-pressure radial loading components, safety reaction force closing components, multi-parameter three-dimensional monitoring systems, and loading and monitoring closed-loop control systems. The in-situ test hole is opened on the sidewall of an existing underground chamber or roadway, perpendicular to the sidewall of the roadway and passing through the disturbed surrounding rock zone to enter the stress zone of the original rock. The high-pressure radial loading component is arranged at the bottom of the in-situ test hole to apply radial load to the test hole wall during the test. The safety reaction force closing component is coaxially set in the in-situ test hole and located between the high-pressure radial loading component and the hole opening to limit the axial displacement of the high-pressure radial loading component and transfer the axial reaction force it generates to the surrounding rock. The multi-parameter three-dimensional monitoring system consists of multiple monitoring holes arranged in the surrounding rock around the in-situ test hole and a group of monitoring sensors installed in the monitoring holes. It is used to collect stress, deformation, seepage and damage response data of the surrounding rock during the loading process. The loading and monitoring closed-loop control system is connected to the high-pressure radial loading component and the multi-parameter three-dimensional monitoring system, and is used to dynamically adjust the loading pressure, loading rate, holding time and cycle parameters based on the monitoring data. The safety reaction force closing component forms a continuous axial reaction force transmission path from the high-pressure radial loading component, through the pressure-bearing component and the force transmission component to the anchoring component and finally to the surrounding rock at the orifice, which is used to prevent axial ejection or instability under high-pressure compressible gas loading conditions. The safety reaction force closure assembly includes at least: a pressure-bearing member, a force-transmitting member arranged along the borehole axis, and an anchoring member anchored to the surrounding rock at the borehole opening, wherein the pressure-bearing member abuts against the axial end face of the high-pressure radial loading assembly, and the two ends of the force-transmitting member are rigidly connected to the pressure-bearing member and the anchoring member, respectively; the force-transmitting member is a hollow rod with a channel inside to accommodate and protect the gas injection pipeline connected to the high-pressure radial loading assembly.

2. The in-situ testing system for the bearing capacity of surrounding rock in underground gas storage facilities according to claim 1, characterized in that: The anchoring components include annular anchor plates / flanges and circumferentially distributed anchors, which are one or more of anchor rods, expansion bolts, or chemical anchors, used to disperse and transfer axial reaction forces to the surrounding rock at the borehole opening.

3. The in-situ testing system for the bearing capacity of surrounding rock in underground gas storage facilities according to claim 2, characterized in that: Multiple monitoring holes are arranged in a ring around the in-situ test holes, forming a three-dimensional distribution along the axial and vertical axes of the chamber / tunnel.

4. The in-situ testing system for the bearing capacity of surrounding rock in underground gas storage facilities according to claim 3, characterized in that: The monitoring sensor group includes at least one or more of the following: acoustic emission sensor, borehole stress gauge, displacement / convergence gauge, and pore pressure gauge.

5. The in-situ testing system for the bearing capacity of surrounding rock in underground gas storage facilities according to claim 4, characterized in that: The loading and monitoring closed-loop control system is configured to execute at least one control action when the monitoring data meets preset trigger conditions. The trigger conditions include: the surrounding rock stiffness degradation reaches a threshold, the residual deformation accumulation reaches a threshold, the acoustic emission event rate or energy surge reaches a threshold, and the seepage pressure rises abnormally to a threshold. The control actions include: reducing load, maintaining pressure, changing the loading rate, changing the cycle amplitude, or terminating loading.

6. The in-situ testing system for the bearing capacity of surrounding rock in underground gas storage facilities according to claim 5, characterized in that: The loading and monitoring closed-loop control system supports two modes: graded loading and cyclic loading. The cyclic loading mode is used to simulate the long-term operating conditions of the gas storage facility and output fatigue bearing capacity evaluation parameters.

7. A testing method using the in-situ testing system for the bearing capacity of surrounding rock of an underground gas storage facility as described in any one of claims 1 to 6, characterized in that: include, S1. Drill in-situ test holes in the sidewalls of existing underground chambers or tunnels, and drill multiple monitoring holes around them and install monitoring sensor groups to form a multi-parameter three-dimensional monitoring system. S2. Arrange a high-pressure radial loading component at the bottom of the in-situ test hole and install a safety reaction force closing component to form a continuous transmission path for the axial reaction force, thereby completing the hole closure and safety constraint. S3. Start the loading and monitoring closed-loop control system, obtain the initial state of the surrounding rock and set the loading path; S4. Perform hierarchical loading or cyclic loading, and collect monitoring data synchronously at each loading stage; S5. Trigger closed-loop control based on monitoring data to dynamically adjust loading amplitude, rate, pressure holding or cyclic parameters; S6. Based on the loading-response evolution characteristics, determine the ultimate bearing capacity and long-term fatigue bearing capacity index of the surrounding rock, and output the recommended operating pressure range of the gas storage facility.

8. The test method according to claim 7, characterized in that: Step S6 includes at least one of (a) or (b) below: (a) The ultimate bearing pressure is determined by combining the nonlinear inflection point of the pressure-displacement curve, stiffness degradation and abrupt change in acoustic emission. (b) Determine fatigue life or stability level based on residual deformation growth rate, stiffness degradation rate and damage event evolution under cyclic loading.

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