Method for calculating vibration velocity of surrounding rock of water-sealed cave depot

Abstract

The invention provides a method for calculating the vibration velocity of surrounding rock of a water-sealed cave depot, and relates to the technical field of water-sealed cave depot engineering construction. The method comprises the following steps: constructing a vibration velocity calculation formula of water-sealed cave depot surrounding rock under the action of supercritical CO2 phase change fracturing on the basis of a momentum conservation law and an elastic mechanics theory; carrying out a similar model test of the underground water-sealed cave depot to obtain vibration speed response data; and a water-seal cave depot surrounding rock vibration speed calculation formula under the supercritical CO2 phase change fracturing action is compiled into Matlab for parameter analysis, optimal parameters are summarized and analyzed, and calculation of the vibration speed is completed. The method aims at solving the problems that in the prior art, under the supercritical CO2 phase change fracturing effect, the vibration speed of the surrounding rock of the underground water-sealed cave depot is difficult to accurately calculate, and parameters influencing the vibration speed cannot be effectively optimized.

Description

Technical Field

[0001] This invention relates to the field of water-sealed cavern engineering construction technology, and in particular to a method for calculating the vibration velocity of the surrounding rock of a water-sealed cavern. Background Technology

[0002] Supercritical CO2 phase change fracturing technology is a novel rock breaking method. Its principle is to pressurize liquid CO2 to a supercritical state (temperature > 31.1℃, pressure > 7.38MPa), and release a high-pressure jet after the pressure rises sharply to impact the rock. Through the combined action of stress wave superposition and gas wedging effect, the rock fissures are driven to expand until the rock breaks. It can achieve efficient rock breaking in a non-explosive environment. It has the advantages of being safe, flameless and explosion-free, green and environmentally friendly, with CO2 that can be recycled and reused, and the rock breaking strength can be precisely controlled by adjusting the filling amount and release pressure. It can be used for the excavation of underground water-sealed caverns.

[0003] There are three main problems with the application of existing technologies in underground caverns: First, conducting in-situ tests on the impact of supercritical CO2 phase change fracturing on the vibration velocity of similar objects such as underground water-sealed caverns is extremely costly and difficult to implement, requiring preliminary tests using similar physical models to explore patterns. Second, while supercritical CO2 phase change fracturing, as a novel rock fracturing method, has shown unique advantages in practical applications, it generates complex vibration effects during the fracturing process. There is a lack of precise calculation methods for the vibration velocity of water-sealed caverns under supercritical CO2 phase change fracturing, posing a significant challenge to the stability assessment of the surrounding rock and potentially increasing uncertainties in engineering design and construction, thus affecting the safety and reliability of the project. Third, the impact of supercritical CO2 blasting operations adjacent to underground water-sealed caverns on the vibration velocity of the surrounding rock has not been quantified, making it difficult to formulate reasonable construction parameter optimization schemes and surrounding rock reinforcement measures, which may lead to problems such as localized damage to the surrounding rock and groundwater leakage. Summary of the Invention

[0004] To address the aforementioned shortcomings in existing technologies, this invention provides a method for calculating the vibration velocity of surrounding rock in water-sealed caverns. This method aims to solve the problems in existing technologies where it is difficult to accurately calculate the vibration velocity of surrounding rock in underground water-sealed caverns under supercritical CO2 phase transformation-induced fracturing, and where it is impossible to effectively optimize parameters affecting vibration velocity.

[0005] To achieve the above objectives, the technical solution adopted by this invention is: a method for calculating the vibration velocity of surrounding rock in a water-sealed cavern, comprising the following steps: S1. Based on the law of conservation of momentum and the theory of elasticity, a formula for calculating the vibration velocity of the surrounding rock of a water-sealed cavern under supercritical CO2 phase transformation fracturing is constructed. S2. Conduct similar model tests on underground water-sealed caverns to obtain vibration velocity response data; S3. Initialize the parameters and calculate the vibration velocity using the vibration velocity calculation formula based on the initialized parameters. Compare the calculated vibration velocity with the vibration velocity response data obtained in S2, summarize and analyze the optimal parameters, and complete the calculation of vibration velocity.

[0006] Furthermore, the formula for calculating the vibration velocity in S1 is as follows: ; in, Indicates vibration velocity. This indicates the change in the vibration velocity of the surrounding rock. Indicates the transmission distance. This represents the instantaneous pressure generated by the supercritical CO2 phase transition inside the rupture tube. Indicates the rate of change of pressure. This represents a time variable, used to describe the continuous change of instantaneous pressure over time during the fracturing process. Indicates the density of the surrounding rock. Indicates the propagation speed of stress waves. α Indicates the attenuation coefficient. V rock Indicates the volume of the surrounding rock. This represents the elastic modulus of the surrounding rock.

[0007] Furthermore, S2 includes the following steps: S201. Determine the physical and mechanical parameters of the similar model of the underground water-sealed cavern and the fracture-cave based on the similarity theory, and determine the material mix ratio of the similar model of the underground water-sealed cavern and the fracture-cave. S202. Construct a similar model box and configure a ground stress simulation loading system; S203. Set up a data acquisition device, fix the fracturing pipe and blast it, and acquire the vibration velocity response data of the surrounding rock of the water-sealed cavern during the process.

[0008] Furthermore, step S201 includes the following steps: S2011. Determine the physical and mechanical parameters of the actual underground water-sealed cavern construction project; S2012. A 1:100 ratio is adopted as the geometric similarity ratio for underground water-sealed caverns. Based on this ratio, the geometric dimensions of the similar model of the water-sealed cavern are determined. The similar model of the water-sealed cavern is horseshoe-shaped with a span of 20cm and a cave height of 30cm. S2013. The distance between the boundary of the similar model of the fracture-cave and the boundary of the underground water-sealed cavern model is determined to be 3-5 times the cavern radius. The final size of the similar model is determined to be 1800*1300*300mm, of which the radius of the fracture-cave is 50mm and the distance from the cavern boundary is 500mm. S2014. Configure the material similarity ratio according to the physical and mechanical parameters of the similar model, and select the most suitable similarity ratio to create a similar model.

[0009] Furthermore, step S202 includes the following steps: S2021. Determine the internal dimensions of the similar model box based on the geometric dimensions of the similar model. S2022. The support section is composed of 10mm thick steel plates, and the steel plates are fixed together with angle steel and bolts. S2023. A 1800*1300*10mm steel plate is used as the rear baffle. Slide grooves are set at the corresponding positions of the left and right side baffles and the rear baffle to allow the rear baffle to move up and down. S2024. With the rear baffle placed in the chute, place the fracturing pipe and the cave mold according to the design position of the cave and the fracturing pipe. Pour similar material from the top. After the material is compacted, use a steel plate of 1800*300*20mm as the upper support plate. S2025. A hydraulic loading device and a reaction plate are installed on the upper support plate, and the same hydraulic loading device and reaction plate are installed on the right side to form a ground stress simulation loading system. The ground stress simulation loading system is controlled by a hydraulic pump and a computer, and the corresponding pressure can be set according to the design ground stress conditions.

[0010] Furthermore, step S203 includes the following steps: S2031. After the similar material has solidified, install vibration velocity monitoring components on the tunnel wall. Each component is connected to the dynamic strain monitor with wires. S2032. Slide the rear baffle upwards and arrange the fracturing hole positions according to the design spacing. Connect and fix the variable diameter fracturing tube to the welding bolts at the corresponding positions of the drill holes. Fill the gap between the variable diameter fracturing tube and the drill holes with sand. S2033. The control module is used to control the vibration velocity response data acquisition component to turn on, and the strain, pressure and velocity acquisition components transmit electrical signals to the control module in real time to acquire vibration velocity response data. S2034. Connect the fracturing tube inflation head and inflation conduit, use inflation equipment to inflate the fracturing tube, causing the variable diameter fracturing tube to break from the middle, thereby generating impact pressure on the cavern model. S2035. Stop collecting vibration velocity response data of the surrounding rock of the water-sealed cavern.

[0011] Furthermore, step S3 includes the following steps: In the Matlab environment, the parameters were initialized, with the pressure change rate set to 1000 GPa / s and the rock mass density set to 2700 kg / m³. 3The elastic modulus is set to 50 GPa, Poisson's ratio is set to 0.3, the distance between the CO2 fracturing pipe and the cavern wall is set to 0.5 m, and the attenuation coefficient is set to 0.1. Substituting the initialized parameters into the calculation formula for the vibration velocity of the surrounding rock of the water-sealed cavern under supercritical CO2 phase transformation fracturing, the vibration velocity of the surrounding rock of the water-sealed cavern under the current conditions is calculated. The vibration velocity is compared with the vibration velocity response data obtained by S2, the optimal parameters are summarized and analyzed, and the vibration velocity is calculated.

[0012] The beneficial effects of this invention are: (1) By establishing a specialized calculation model, the vibration velocity of the surrounding rock is accurately calculated, and the parameters affecting the change of vibration velocity are analyzed in depth. Optimization methods are proposed to provide a more scientific and reliable theoretical basis and technical support for the design, construction and operation of underground water-sealed caverns, ensuring their stability and safety under the supercritical CO2 phase transformation fracturing effect.

[0013] (2) The present invention can accurately calculate the vibration velocity of the surrounding rock based on the actual geological conditions, providing reliable data for the stability assessment of water-sealed caverns and effectively improving the calculation accuracy.

[0014] (3) This invention utilizes similarity theory to construct a similar model of underground water-sealed caverns, which simplifies experimental operations, reduces costs, and enhances the representativeness of experimental results. This invention integrates the influence of multiple factors, optimizes the construction parameters of supercritical CO2 phase change-induced fracturing, and improves the safety, efficiency, and economic benefits of the construction and operation of underground water-sealed caverns. Attached Figure Description

[0015] Figure 1 This is a flowchart of the method of the present invention.

[0016] Figure 2 This is a structural diagram of a similar model box that was made.

[0017] Figure 3 This is a schematic diagram illustrating the effect of the rate of change of pressure on vibration velocity.

[0018] Figure 4 This is a schematic diagram illustrating the effect of the elastic modulus of the surrounding rock on vibration velocity.

[0019] Figure 5 This is a schematic diagram illustrating the effect of surrounding rock density on vibration velocity.

[0020] Figure 6 This is a schematic diagram illustrating the effect of Poisson's ratio of the surrounding rock on vibration velocity.

[0021] Figure 7 This is a schematic diagram illustrating the effect of distance on vibration velocity.

[0022] Among them, 1-model box, 2-vertical loading device, 3-support frame, 4-surrounding rock similar model, 5-lateral loading device, 6-vibration velocity sensor, 7-water-sealed cavern structure, 8-CO2 fracturing pipe. Detailed Implementation

[0023] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0024] Example like Figure 1 As shown, this invention provides a method for calculating the vibration velocity of the surrounding rock in a water-sealed cavern, the implementation of which is as follows: S1. Based on the law of conservation of momentum and the theory of elasticity, a formula for calculating the vibration velocity of the surrounding rock of a water-sealed cavern under supercritical CO2 phase transformation fracturing is constructed.

[0025] In this embodiment, when supercritical CO2 phase transformation fracturing acts on the surrounding rock of an underground water-sealed cavern, it will induce vibrations in the surrounding rock. To accurately calculate the vibration velocity, it is necessary to comprehensively consider multiple factors and their interactions. The derivation process of the formula will be explained in detail below, addressing the lack of theoretical guidance for the application of CO2 phase transformation fracturing technology in underground water-sealed caverns.

[0026] During the process of high-pressure gas ejected from the fracturing pipe to fracture the rock mass, the vibration velocity of the surrounding rock in the cavern is affected by various factors. Based on the law of conservation of momentum and the theory of elasticity, the vibration velocity calculation formula is established as follows: In the hypothetical fracturing process, the pressure generated by the CO2 phase transformation mainly propagates to the surrounding rock in the form of stress waves; the surrounding rock is considered to be a homogeneous, isotropic linear elastic body; the stress waves will attenuate during propagation, and the degree of attenuation is related to the propagation distance.

[0027] According to the momentum theorem, the impulse generated by the change in pressure is equal to the change in momentum of the surrounding rock: ; in, This represents the change in momentum of the surrounding rock. Indicates external impulse. This indicates the initial moment when the pressure pulse begins to act on the surrounding rock. This indicates the termination time when the pressure pulse ends and the impulse transmission is complete. Indicates force, In d Indicates the transmission distance. tThis represents a time variable, used to describe the continuous change of instantaneous pressure over time during the fracturing process. This represents the rate of change of pressure, here. d To express differentiation, Indicates the surface area of ​​the cavern. This represents the complete duration of the pressure pulse's effect on the surrounding rock. , Indicates the quality of the surrounding rock. This indicates the change in the vibration velocity of the surrounding rock.

[0028] The quality of the surrounding rock is expressed as: ; in, Indicates the density of the surrounding rock. V rock Indicates the volume of the surrounding rock. L This indicates the depth affected by vibration in the surrounding rock.

[0029] Combining the above equations, we get: ; in, This indicates the change in the vibration velocity of the surrounding rock.

[0030] Further considering the propagation speed and attenuation of stress waves, according to the elastic wave velocity theory, the propagation speed of stress waves in the surrounding rock is: ; in, c p E represents the propagation speed of stress waves. rock V represents the elastic modulus of the surrounding rock. rock It represents Poisson's ratio.

[0031] Depth of influence of surrounding rock vibration L It can be represented as: ; Substituting the depth L affected by the surrounding rock vibration into the expression for the change in the surrounding rock vibration velocity Δv: ; Considering the attenuation of stress waves during propagation, the vibration velocity and propagation distance d Related to attenuation coefficient α It can be represented as: ; The final formula for calculating the vibration velocity of the surrounding rock is as follows: ; in, Indicates vibration velocity. This indicates the change in the vibration velocity of the surrounding rock. Indicates the transmission distance. This represents the instantaneous pressure generated by the supercritical CO2 phase transition inside the rupture tube. Indicates the rate of change of pressure. This represents a time variable, used to describe the continuous change of instantaneous pressure over time during the fracturing process. Indicates the density of the surrounding rock. Indicates the propagation speed of stress waves. α Indicates the attenuation coefficient. V rock Indicates the volume of the surrounding rock. This represents the elastic modulus of the surrounding rock.

[0032] S2. Conduct similar model tests on underground water-sealed caverns to obtain vibration velocity response data. The implementation method is as follows: S201. Based on similarity theory, determine the physical and mechanical parameters of the similar model of the underground water-sealed cavern and the fractured hole, and determine the material mix ratio of the similar model of the underground water-sealed cavern and the fractured hole. The implementation method is as follows: S2011. Determine the physical and mechanical parameters of the actual underground water-sealed cavern construction project; S2012. A 1:100 ratio is adopted as the geometric similarity ratio for underground water-sealed caverns. Based on this ratio, the geometric dimensions of the similar model of the water-sealed cavern are determined. The similar model of the water-sealed cavern is horseshoe-shaped with a span of 20cm and a cave height of 30cm. S2013. The distance between the boundary of the similar model of the fracture-cave and the boundary of the underground water-sealed cavern model is determined to be 3-5 times the cavern radius. The final size of the similar model is determined to be 1800*1300*300mm, of which the radius of the fracture-cave is 50mm and the distance from the cavern boundary is 500mm. S2014. Configure the material similarity ratio according to the physical and mechanical parameters of the similar model, and select the most suitable similarity ratio to make a similar model; S202. Construct a similar model box and configure a geostress simulation loading system. The implementation method is as follows: S2021. Determine the internal dimensions of the similar model box based on the geometric dimensions of the similar model. S2022. The support section is composed of 10mm thick steel plates, and the steel plates are fixed together with angle steel and bolts. S2023. A 1800*1300*10mm steel plate is used as the rear baffle. Slide grooves are set at the corresponding positions of the left and right side baffles and the rear baffle to allow the rear baffle to move up and down. S2024. With the rear baffle placed in the chute, place the fracturing pipe and the cave mold according to the design position of the cave and the fracturing pipe. Pour similar material from the top. After the material is compacted, use a steel plate of 1800*300*20mm as the upper support plate. S2025. A hydraulic loading device and a reaction plate are installed on the upper support plate, and the same hydraulic loading device and reaction plate are installed on the right side to form a ground stress simulation loading system. The ground stress simulation loading system is controlled by a hydraulic pump and a computer, and the corresponding pressure can be set according to the design ground stress conditions. S203. Deploy data acquisition devices, fix the fracturing pipe and blast it, and acquire vibration velocity response data of the surrounding rock of the water-sealed cavern during the process. The implementation method is as follows: S2031. After the similar material has solidified, install vibration velocity monitoring components on the tunnel wall. Each component is connected to the dynamic strain monitor with wires. S2032. Slide the rear baffle upwards and arrange the fracturing hole positions according to the design spacing. Connect and fix the variable diameter fracturing tube to the welding bolts at the corresponding positions of the drill holes. Fill the gap between the variable diameter fracturing tube and the drill holes with sand. S2033. The control module controls the vibration velocity response data acquisition component to start. The strain, pressure and velocity acquisition components transmit electrical signals to the control module in real time to acquire vibration velocity response data. The control module is a computer and corresponding software. For example, starting the strain acquisition software will turn on the control module.

[0033] S2034. Connect the fracturing tube inflation head and inflation conduit, use inflation equipment to inflate the fracturing tube, causing the variable diameter fracturing tube to break from the middle, thereby generating impact pressure on the cavern model. S2035. Stop collecting vibration velocity response data of the surrounding rock of the water-sealed cavern.

[0034] In this embodiment, the water-sealed cavern similarity model and the fracture-cave similarity model only consider the geometric similarity ratio, while the surrounding rock similarity model mainly considers the material strength similarity ratio. The similarity model in this invention mainly refers to the material, which can be replaced by the surrounding rock similarity model.

[0035] In this embodiment, the physical and mechanical parameters of the underground water-sealed cavern and the fracture-cave similarity model are determined according to similarity theory, and the material mix ratio of the similarity model is further determined as follows: The physical and mechanical parameters of the actual water-sealed cavern construction project (cave shape, geometric dimensions, rock density, tensile / compressive strength, elastic modulus, and Poisson's ratio) were determined. A 1:100 scale was adopted as the geometric similarity ratio for the underground water-sealed cavern. Based on this, the geometric dimensions of the similar model of the water-sealed cavern were determined. The water-sealed cavern model was determined to be horseshoe-shaped with a span of 20cm and a height of 30cm. To avoid size effects, the distance between the model boundary and the cavern model boundary was determined to be 3-5 times the cavern radius. The final similar model size was determined to be 1800*1300*300mm, with a fracture hole radius of 50mm (due to the small geometric similarity size, only load similarity was considered), and a distance of 500mm from the cavern boundary. Based on the physical and mechanical parameters of the similar model, the material similarity ratio was further configured, and the most suitable similarity ratio was selected for model making.

[0036] In this embodiment, as Figure 2 As shown, a model box was constructed and a geostress simulation loading system was configured, specifically as follows: The internal dimensions of the similar model box 1 are determined based on the geometric dimensions of the similar model. A 1820*1500*10mm steel plate is used as the base plate, a 1500*1500*10mm steel plate as the left side baffle, and a 1500*1300*10mm steel plate as the right side support plate (with a 50mm radius circular hole in the center for the right-side stress loading device to pass through). A 300*1300*10mm steel plate is used as the right side baffle (which can move freely). The support parts are composed of 10mm thick steel plates, which are fixed together with angle steel and bolts. An 1800*1300*10mm steel plate is used as the rear baffle. Slots are provided at corresponding positions on the left and right side baffles and the rear baffle to allow the rear baffle to move up and down. With the rear baffle placed in the slots, the fracturing pipe and the cavern mold are placed according to the design positions of the cavern and fracturing pipe. The similar material is poured in from the top. After the material is compacted, a 1800*300*20mm steel plate is used as the upper support plate. A hydraulic loading device and a reaction plate are installed on the upper support plate. The same structure is set on the right side to form a ground stress simulation loading system. The ground stress simulation loading system is controlled by a hydraulic pump and a computer. The corresponding pressure can be set according to the design ground stress conditions. In the figure, 1 is the model box, which is used to fill similar materials; 2 is the vertical loading device, which is used to simulate vertical ground stress; 3 is the support frame, which is used to fix the model box; 4 is the surrounding rock similar model, which is used to simulate the surrounding rock material of the water-sealed cavern with a certain similarity ratio; 5 is the horizontal loading device, which is used to simulate horizontal ground stress; 6 is the vibration velocity sensor, which is used to collect vibration velocity signals; 7 is the water-sealed cavern structure, which is used to simulate a scaled-down version of the water-sealed cavern structure with a certain geometric similarity ratio; 8 is the CO2 fracturing pipe, which is used to release the CO2 phase change fracturing pressure.

[0037] In this embodiment, a data acquisition device is installed, a fracturing tube is fixed and blasted, and vibration information of the surrounding rock of the water-sealed cavern is acquired during the process, specifically as follows: After the similar material solidifies, vibration velocity monitoring components are installed on the tunnel wall, and each component is connected to the dynamic strain monitor with wires; the rear baffle is slid upward, and the fracturing hole positions are arranged according to the design spacing. The welded bolts at the corresponding positions of the variable diameter fracturing tube and the borehole are connected and fixed, and sand is used to fill the gap between the variable diameter fracturing tube and the borehole; the control module controls the data acquisition components to start, and the strain, pressure and velocity acquisition components transmit the electrical signals of the acquired data to the control module in real time; the fracturing tube inflation head and inflation conduit are connected, and the fracturing tube is inflated with an inflation device to cause the variable diameter fracturing tube to break from the middle, thereby generating impact pressure on the tunnel model; data acquisition is stopped.

[0038] S3. Initialize the parameters and calculate the vibration velocity using the vibration velocity calculation formula based on the initialized parameters. Compare the calculated vibration velocity with the vibration velocity response data obtained in S2, summarize and analyze the optimal parameters, and complete the calculation of vibration velocity. The implementation method is as follows: In the Matlab environment, the parameters were initialized, with the pressure change rate set to 1000 GPa / s and the rock mass density set to 2700 kg / m³. 3 The elastic modulus is set to 50 GPa, Poisson's ratio is set to 0.3, the distance between the CO2 fracturing pipe and the cavern wall is set to 0.5 m, and the attenuation coefficient is set to 0.1. Substituting the initialized parameters into the calculation formula for the vibration velocity of the surrounding rock of the water-sealed cavern under supercritical CO2 phase transformation fracturing, the vibration velocity of the surrounding rock of the water-sealed cavern under the current conditions is calculated. The vibration velocity is compared with the vibration velocity response data obtained by S2, the optimal parameters are summarized and analyzed, and the vibration velocity is calculated.

[0039] In this embodiment, within the MATLAB environment, the pressure change rate is initially set to 1000 GPa / s and the rock mass density is set to 2700 kg / m³. 3 The elastic modulus was set to 50 GPa, Poisson's ratio to 0.3, the distance between the CO2 fracturing tube and the cavern wall to 0.5 m, and the attenuation coefficient to 0.1. These parameters were chosen based on actual experimental conditions and theoretical calculation requirements, aiming to simulate the real fracturing environment of a water-sealed underground cavern. The experiments conducted in S2 were based on these parameters, and Matlab parameter range analysis was performed on top of these parameters.

[0040] Based on the above initialization parameters, the initial vibration velocity under the current conditions is calculated using the derived vibration velocity calculation formula. This calculation process strictly follows the formula to ensure the accuracy of the results.

[0041] like Figures 3 to 7 As shown, to deeply analyze the influence of various parameters on vibration velocity, a systematic parameter analysis was conducted. Taking the pressure change rate as an example, different pressure change rate values ​​were selected in 100 GPa / s intervals within the range of 500 GPa / s to 2000 GPa / s. For each selected pressure change rate value, the corresponding vibration velocity value was calculated by substituting it into the formula. These results were then plotted into a curve, intuitively demonstrating the positive correlation between the pressure change rate and vibration velocity.

[0042] A similar systematic approach was used to analyze the influence of the elastic modulus. Different elastic modulus values ​​were selected in 5 GPa intervals within the range of 30 GPa to 70 GPa. For each selected elastic modulus value, keeping other parameters constant, the corresponding vibration velocity was calculated using the formula, and the results were plotted as a curve, demonstrating the inverse correlation between the elastic modulus and vibration velocity.

[0043] For the analysis of rock mass density, it is 2200 kg / m³. 3 Up to 3200kg / m 3 Within the range, at 100kg / m 3 Different rock mass density values ​​were selected at intervals. Each selected rock mass density value was substituted into the formula for calculation to obtain the corresponding vibration velocity, and a curve was plotted to show the inverse correlation between rock mass density and vibration velocity.

[0044] When analyzing the influence of Poisson's ratio, different Poisson's ratio values ​​were selected in intervals of 0.02 within the range of 0.25 to 0.35. Each selected Poisson's ratio value was substituted into the formula for calculation to obtain the corresponding vibration velocity, and a curve was plotted to show the complex relationship between Poisson's ratio and vibration velocity.

[0045] Finally, in analyzing the influence of the distance between the fracturing pipe and the cavern wall, different distance values ​​were selected in 0.1m intervals within the range of 0.3m to 0.7m. Each selected distance value was substituted into the formula for calculation to obtain the corresponding vibration velocity, and a curve was plotted to show the inverse correlation between the distance between the fracturing pipe and the cavern wall and the vibration velocity.

[0046] These graphs clearly show that, all other things being equal, an increase in the rate of change of pressure leads to an increase in vibration velocity, while an increase in rock density, elastic modulus, Poisson's ratio, and the distance between the fracture tube and the cavern wall leads to a decrease in vibration velocity.

[0047] According to the diagram, the condition for the minimum vibration velocity is: , , , , However, in actual engineering projects, the calculated vibration velocity must be determined based on the specific engineering environmental conditions.

Claims

1. A method for calculating the vibration velocity of surrounding rock in a water-sealed cavern, characterized in that, Includes the following steps: S1. Based on the law of conservation of momentum and the theory of elasticity, a formula for calculating the vibration velocity of the surrounding rock of a water-sealed cavern under supercritical CO2 phase transformation fracturing is constructed. S2. Conduct similar model tests on underground water-sealed caverns to obtain vibration velocity response data; S3. Initialize the parameters and calculate the vibration velocity using the vibration velocity calculation formula based on the initialized parameters. Compare the calculated vibration velocity with the vibration velocity response data obtained in S2, summarize and analyze the optimal parameters, and complete the calculation of vibration velocity.

2. The method for calculating the vibration velocity of the surrounding rock of a water-sealed cavern according to claim 1, characterized in that, The formula for calculating the vibration velocity in S1 is as follows: ； in, Indicates vibration velocity. This indicates the change in the vibration velocity of the surrounding rock. Indicates the transmission distance. This represents the instantaneous pressure generated by the supercritical CO2 phase transition inside the rupture tube. Indicates the rate of change of pressure. This represents a time variable, used to describe the continuous change of instantaneous pressure over time during the fracturing process. Indicates the density of the surrounding rock. Indicates the propagation speed of stress waves. α Indicates the attenuation coefficient. V rock Indicates the volume of the surrounding rock. This represents the elastic modulus of the surrounding rock.

3. The method for calculating the vibration velocity of the surrounding rock of a water-sealed cavern according to claim 1, characterized in that, S2 includes the following steps: S201. Determine the physical and mechanical parameters of the similar model of the underground water-sealed cavern and the fracture-cave based on the similarity theory, and determine the material mix ratio of the similar model of the underground water-sealed cavern and the fracture-cave. S202. Construct a similar model box and configure a ground stress simulation loading system; S203. Set up a data acquisition device, fix the fracturing pipe and blast it, and acquire the vibration velocity response data of the surrounding rock of the water-sealed cavern during the process.

4. The method for calculating the vibration velocity of the surrounding rock of a water-sealed cavern according to claim 3, characterized in that, S201 includes the following steps: S2011. Determine the physical and mechanical parameters of the actual underground water-sealed cavern construction project; S2012. A 1:100 ratio is adopted as the geometric similarity ratio for underground water-sealed caverns. Based on this ratio, the geometric dimensions of the similar model of the water-sealed cavern are determined. The similar model of the water-sealed cavern is horseshoe-shaped with a span of 20cm and a cave height of 30cm. S2013. The distance between the boundary of the similar model of the fracture-cave and the boundary of the underground water-sealed cavern model is determined to be 3-5 times the cavern radius. The final size of the similar model is determined to be 1800*1300*300mm, of which the radius of the fracture-cave is 50mm and the distance from the cavern boundary is 500mm. S2014. Configure the material similarity ratio according to the physical and mechanical parameters of the similar model, and select the most suitable similarity ratio to create the similar model.

5. The method for calculating the vibration velocity of the surrounding rock of a water-sealed cavern according to claim 4, characterized in that, S202 includes the following steps: S2021. Determine the internal dimensions of the similar model box based on the geometric dimensions of the similar model. S2022. The support section is composed of 10mm thick steel plates, and the steel plates are fixed together with angle steel and bolts. S2023. A 1800*1300*10mm steel plate is used as the rear baffle. Slide grooves are set at the corresponding positions of the left and right side baffles and the rear baffle to allow the rear baffle to move up and down. S2024. With the rear baffle placed in the chute, place the fracturing pipe and the cave mold according to the design position of the cave and the fracturing pipe. Pour similar material from the top. After the material is compacted, use a steel plate of 1800*300*20mm as the upper support plate. S2025. A hydraulic loading device and a reaction plate are installed on the upper support plate, and the same hydraulic loading device and reaction plate are installed on the right side to form a ground stress simulation loading system. The ground stress simulation loading system is controlled by a hydraulic pump and a computer, and the corresponding pressure can be set according to the design ground stress conditions.

6. The method for calculating the vibration velocity of the surrounding rock of a water-sealed cavern according to claim 3, characterized in that, S203 includes the following steps: S2031. After the similar material has solidified, install vibration velocity monitoring components on the tunnel wall. Each component is connected to the dynamic strain monitor with wires. S2032. Slide the rear baffle upwards and arrange the fracturing hole positions according to the design spacing. Connect and fix the variable diameter fracturing tube to the welding bolts at the corresponding positions of the drill holes. Fill the gap between the variable diameter fracturing tube and the drill holes with sand. S2033. The control module is used to control the vibration velocity response data acquisition component to turn on, and the strain, pressure and velocity acquisition components transmit electrical signals to the control module in real time to acquire vibration velocity response data. S2034. Connect the fracturing tube inflation head and inflation conduit, use inflation equipment to inflate the fracturing tube, causing the variable diameter fracturing tube to break from the middle, thereby generating impact pressure on the cavern model. S2035. Stop collecting vibration velocity response data of the surrounding rock of the water-sealed cavern.

7. The method for calculating the vibration velocity of the surrounding rock of a water-sealed cavern according to claim 1, characterized in that, S3 includes the following steps: In the Matlab environment, the parameters were initialized, with the pressure change rate set to 1000 GPa / s and the rock mass density set to 2700 kg / m³. 3 The elastic modulus is set to 50 GPa, Poisson's ratio is set to 0.3, the distance between the CO2 fracturing pipe and the cavern wall is set to 0.5 m, and the attenuation coefficient is set to 0.

1. Substituting the initialized parameters into the calculation formula for the vibration velocity of the surrounding rock of the water-sealed cavern under supercritical CO2 phase transformation fracturing, the vibration velocity of the surrounding rock of the water-sealed cavern under the current conditions is calculated. The vibration velocity is compared with the vibration velocity response data obtained by S2, the optimal parameters are summarized and analyzed, and the vibration velocity is calculated.

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