Rock mass gas blasting method based on stress wave guidance

Abstract

The invention relates to a rock mass gas blasting method based on stress wave guidance. The method is suitable for the technical field of geotechnical engineering and mining. The technical problem to be solved by the invention is to provide the rock mass gas blasting method based on stress wave guidance. According to the technical scheme, the method comprises the steps that stress wave simulation is conducted on the basis of geological conditions of a target rock mass, and a stress wave simulation result of the rock mass is obtained; determining an arrangement mode and an excitation working mode of an ultrasonic excitation source and a low-frequency excitation source based on the type of the rock mass, the crack propagation target depth and the stress wave simulation result of the rock mass; wherein the low-frequency excitation source is used for reducing the rigidity of the surface of a rock mass through low-frequency excitation, increasing micro-deformation and initial micro-cracks of the rock mass, creating conditions for propagation of ultrasonic waves and locally guiding the formation position of the cracks; the ultrasonic excitation source is used for enabling ultrasonic waves to effectively reach the deep layer of the rock mass by utilizing the high penetrability of the ultrasonic waves to excite the expansion of microcracks.

Description

Technical Field

[0001] The present invention relates to a rock gas blasting method based on stress wave guidance, which is applicable to the fields of geotechnical engineering and mining technology. Background Art

[0002] The Chinese patent application number 202210322734.6 discloses a method for ultrasonic excitation-assisted carbon dioxide directional blasting, which belongs to the field of gas blasting technology. Specifically, it is a method for ultrasonic excitation-assisted carbon dioxide gas blasting to directional fracture rock mass, including seven steps: site selection, hole drilling, ultrasonic excitation, hole washing, installation of carbon dioxide blasting and fracture equipment, hole sealing and detonation.

[0003] In the above patent, ultrasonic excitation is first applied to the rock mass in the predetermined blasting and excavation direction according to the design plan, and the rock mass in the predetermined excavation direction of the geotechnical engineering is pre-cracked to reduce the dynamic properties of the rock mass and promote the formation of initial cracks inside it. Subsequently, a carbon dioxide fracturing device (or other gas explosion device) is used to blast the rock mass. This method can directionally weaken the dynamic properties of the excavated rock mass, effectively control the initiation and expansion direction of the explosive cracks in the rock mass, reduce the over-excavation and under-excavation of the rock mass, and weaken the damage and disturbance to the rock mass in the non-excavation area.

[0004] However, existing ultrasonic excitation techniques typically have a shallow propagation depth, particularly in hard or high-strength rock. Ultrasonic excitation may not effectively penetrate deeper into the rock mass. This results in insufficient initial microcrack formation depth, potentially failing to provide sufficient weakening for subsequent CO2 blasting loads. While ultrasonic excitation can indeed induce microcracks, precisely controlling the direction and location of these cracks remains a challenge. Conventional ultrasonic excitation struggles to directly and precisely control the initiation point and propagation direction of cracks, especially in complex geological conditions. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: to provide a rock gas blasting method based on stress wave guidance in response to the above-mentioned problems.

[0006] The technical solution adopted by the present invention is: a rock gas blasting method based on stress wave guidance, characterized by comprising:

[0007] Based on the geological conditions of the target rock mass, stress wave simulation is performed to obtain the stress wave simulation results of the rock mass;

[0008] Based on the rock mass type, target crack extension depth, and rock mass stress wave simulation results, determine the layout and excitation working mode of the ultrasonic excitation source and low-frequency excitation source;

[0009] Among them, the low-frequency excitation source is used to reduce the stiffness of the rock surface through low-frequency excitation, increase the micro-deformation and initial micro-cracks of the rock, create conditions for the propagation of ultrasonic waves, and locally guide the formation location of cracks;

[0010] The ultrasonic excitation source is used to utilize the high penetrability of ultrasonic waves to enable them to effectively reach deep layers of the rock mass and stimulate the expansion of microcracks.

[0011] The determining of the arrangement of the ultrasonic excitation source includes:

[0012] Based on the target rock mass type, crack extension target depth and stress wave simulation results, the ultrasonic excitation source excitation mode is determined to be multi-point excitation or directional excitation;

[0013] Based on the determined excitation mode, the arrangement mode of the ultrasonic excitation source is determined.

[0014] The determining of the excitation working mode of the ultrasonic excitation source includes:

[0015] Based on the type of target rock mass, target crack extension depth and stress wave simulation results, the optimal frequency range of ultrasonic waves is determined through simulation experiments.

[0016] The determining of the arrangement of the low-frequency excitation source includes:

[0017] The low-frequency excitation source is arranged on the surface of the rock mass or in the vicinity thereof.

[0018] The excitation working mode of determining the ultrasonic excitation source and the low-frequency excitation source includes:

[0019] The low-frequency excitation source works first, and then switches to the ultrasonic excitation source;

[0020] Among them, the start-up timing of the ultrasonic excitation source is determined based on the rock stress response and crack development obtained through real-time monitoring.

[0021] The excitation working mode of determining the ultrasonic excitation source and the low-frequency excitation source includes:

[0022] Determine the low-frequency excitation time t of the low-frequency excitation source by genetic algorithm LF and the ultrasonic excitation time t of the ultrasonic excitation source US ;

[0023] The fitness function of the genetic algorithm is expressed as:

[0024] F(t LF ,t US )=w1·D(t LF ,t US )-w2·Δσ(t LF ,t US )

[0025] Where D is the crack extension depth based on the low-frequency excitation time t LF and ultrasonic excitation time t US function; Δσ is the rock damage based on low-frequency excitation time t LF and ultrasonic excitation time t US function; w1 and w2 are weight coefficients.

[0026] Construct a function of crack extension depth D and rock damage Δσ:

[0027] Crack extension depth D(t LF , t US ): Relies on a nonlinear combination of low-frequency excitation and ultrasonic excitation, for example:

[0028]

[0029] Among them, a1, a2, a3, and a4 are constants obtained through experiments or numerical models.

[0030] Rock mass damage Δσ(t LF , t US ): It can also depend on nonlinear functions of low frequency and ultrasonic excitation:

[0031] Δσ(t LF , t US )=b1·t LF +b2·t US +b3·exp(-c1·t LF -c2·t US )+b4

[0032] Among them, b1, b2, b3, c1, c2, and b4 are constants.

[0033] How to get the specific crack growth depth and rock damage at each iteration:

[0034] In each iteration, according to the current low-frequency excitation time t LF and ultrasonic excitation time t US Calculate crack growth depth and rock damage:

[0035] Calculation of crack extension depth D: Combine the current excitation time (t LF , t US ) into the crack extension depth function D(t LF , t US ).

[0036] Calculation of rock mass damage Δσ: Combine the current excitation time (t LF , t US) into the rock mass damage function Δσ(t LF , t US ).

[0037] New fitness function:

[0038] The fitness function is calculated using the values ​​of crack extension depth D and rock damage Δσ:

[0039] F(t LF , t US )=w1·D(t LF , t US )+w2·Δσ(t LF , t US )

[0040] Through these steps, each iteration calculates the specific crack extension depth and rock damage according to the current excitation time combination, and evaluates the quality of the solution through the fitness function.

[0041] The stress wave simulation is a stress wave simulation experiment that combines geological modeling with digital twin technology.

[0042] The frequency range of the ultrasonic excitation source is between 20kHz and 1MHz; the frequency range of the low-frequency excitation source is between 20Hz and 200Hz.

[0043] The beneficial effects of this invention are as follows: by combining ultrasonic and low-frequency excitation sources to excite the rock mass, it can effectively reduce rock stiffness and increase the formation and expansion of microcracks. Low-frequency excitation (such as vibration or impact) produces micro-deformations on the rock mass surface, reducing internal stress in the rock mass, thereby providing a more ideal propagation environment for ultrasonic excitation. Ultrasonic excitation can precisely guide the direction of crack propagation, thereby effectively weakening the rock mass and reducing the energy and load required for subsequent blasting.

[0044] Through stress wave simulation experiments that combine geological modeling with digital twin technology, the present invention can comprehensively evaluate the stress field, crack propagation pattern, and ultrasonic wave propagation effect of the rock mass before blasting, enabling customized technical solutions for different rock mass areas to ensure that cracks propagate along predetermined paths. This effectively avoids the construction risks caused by the uncertainty of crack propagation direction in traditional blasting, thereby enhancing the controllability of crack guidance.

[0045] By precisely controlling the timing and intensity of the ultrasonic and low-frequency excitation sources, this method enables them to work synergistically within a predetermined timeframe, ensuring that rock cracks propagate in the desired direction and depth. By optimizing the timing and intensity of the excitation sources, the energy release during blasting can be precisely controlled, minimizing unnecessary vibration and rock damage. Lower blasting loads also reduce impact on equipment and the environment.

[0046] The combination of the multi-point excitation method and the directional excitation method of the present invention makes the generation and expansion of cracks more directional, avoiding the problems of uneven cracks or uncontrolled expansion in traditional blasting methods, providing an ideal basis for the precise implementation of subsequent gas blasting, and improving the success rate and accuracy of blasting. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 A flowchart of an embodiment.

[0048] Figure 2 Schematic diagram of the precise synchronous control flow of ultrasonic and low-frequency excitation sources in the embodiment. DETAILED DESCRIPTION

[0049] This embodiment is a rock gas blasting method based on stress wave guidance. In this blasting method, the rock mass in the predetermined excavation direction of the geotechnical engineering is pre-fractured. Specifically, the following steps are included:

[0050] S1. Based on the geological conditions of the target rock mass, stress wave simulation is performed to obtain stress wave simulation results of the rock mass.

[0051] In this embodiment, the geological conditions of the target rock mass are evaluated to obtain physical properties such as density, strength, and elastic modulus. Through stress wave simulation experiments combining geological modeling with digital twin technology, the physical properties of different rock mass areas and the propagation effects of ultrasonic waves are evaluated in advance.

[0052] Stress wave simulation is a preliminary step in the entire process. By simulating the physical properties and stress field of the rock mass, it provides important information about rock mass response, stress distribution, and crack formation. The results of this module provide the basis for the subsequent selection of ultrasonic excitation and low-frequency excitation sources.

[0053] In this embodiment, by combining geological modeling and digital twin technology, the stress field, crack expansion pattern and ultrasonic propagation effect of different rock mass areas are simulated. This can help evaluate the heterogeneity and mechanical properties of the rock mass, as well as the penetration effect of ultrasonic waves in different areas. The simulation results can guide the specific selection of ultrasonic and low-frequency excitation sources (frequency, intensity, excitation location, etc.), ensuring that the physical properties of the rock mass are maximized.

[0054] The rock mass property data provided by the stress wave simulation results can help select the appropriate excitation source and determine how to effectively combine the two excitation sources (ultrasonic and low-frequency excitation sources in this case). By evaluating different combinations of frequency, intensity, and waveform, the propagation depth and efficiency of the wave can be maximized.

[0055] S2. Based on the rock mass type, crack propagation target depth, and rock mass stress wave simulation results, determine the layout and excitation working mode of the ultrasonic excitation source and low-frequency excitation source.

[0056] In this case, an ultrasonic and low-frequency excitation system for the rock mass was established, and the propagation direction and excitation position of the ultrasonic wave were determined to maximize its penetration depth. The specific steps included the arrangement of the ultrasonic source, frequency and waveform optimization, low-frequency excitation source selection, and synchronous layout of the excitation sources.

[0057] 1) Ultrasonic source placement: The ultrasonic excitation source placement is determined based on the target rock mass area (e.g., the expected microcrack formation area). Based on the target rock mass type, target crack propagation depth, and stress wave simulation results, the ultrasonic excitation source excitation mode is determined as multi-point excitation or directional excitation. Based on the determined excitation mode, the ultrasonic excitation source placement is determined.

[0058] This embodiment determines the specific design (frequency, power, layout position, etc.) of ultrasonic excitation and low-frequency excitation sources based on the multi-point excitation method and the directional excitation method. It is necessary to optimize the specific deployment and operation mode of these excitation sources through the multi-point excitation method and the directional excitation method to further ensure the precise guidance of the cracks.

[0059] In this embodiment, the wave motion may be emitted to the rock mass through a sensor or an ultrasonic transducer. If the rock mass is relatively hard, it may be necessary to enhance the effect through multi-point excitation.

[0060] 2) Frequency and waveform optimization: Based on the target rock type, crack propagation target depth, and stress wave simulation results, the optimal frequency range of ultrasound (e.g., 20 kHz to 1 MHz) is determined through simulation experiments. Lower-frequency ultrasound has better penetration and can penetrate deeper rock layers, but may have lower resolution. Based on the response characteristics of the rock mass, a suitable frequency range is selected to ensure that ultrasound can be effectively transmitted at greater depths.

[0061] 3) Low-frequency excitation source selection: Select a low-frequency excitation source (such as low-frequency vibration or mechanical shock) and use it in conjunction with the ultrasonic excitation system to enhance the micro-crack formation effect in the rock mass, especially in areas where ultrasonic waves cannot penetrate deeply.

[0062] In this embodiment, a suitable low-frequency vibration device or mechanical impact source is selected based on the thickness and hardness of the target rock mass and the desired effect. For example, a low-frequency vibration source can use a vibration source with a frequency range of 20 Hz to 200 Hz, while a mechanical impact source can generate shock waves through high-speed impact.

[0063] The low-frequency excitation source is positioned appropriately based on the rock mass structure and stress distribution. It is typically located on the rock mass surface or in an adjacent area. Combining this with an ultrasonic source ensures the two excitation modes interact to maximize their effectiveness.

[0064] 4) Synchronous layout of excitation sources: Low-frequency excitation can be combined with ultrasonic excitation to form an interactive wave field by controlling the application time and intensity. During the generation of rock cracks, low-frequency vibration can effectively reduce the stiffness of the rock mass and enhance the rock mass's response to ultrasonic waves.

[0065] Low-frequency excitation (such as low-frequency vibration or mechanical impact) can reduce the stiffness of the rock surface, increase the micro-deformation and initial micro-cracks of the rock mass. The formation of these micro-cracks provides a channel for ultrasonic excitation and can control the initial expansion direction of the cracks. Low-frequency excitation creates conditions for the propagation of ultrasonic waves and can also locally guide the formation location of cracks. The high-frequency characteristics of ultrasonic excitation can propagate deep inside the rock mass and guide the expansion direction of the cracks through precise wave propagation.

[0066] The high penetrability of ultrasound enables it to effectively reach deep into the rock mass, stimulating the expansion of microcracks, and through the design of different frequencies and waveforms, the crack expansion path can be precisely controlled.

[0067] In order to achieve precise synchronous control of the ultrasonic and low-frequency excitation sources so that they can work together within a certain period of time to achieve the ideal rock weakening effect, in this example, the excitation time of the ultrasonic and low-frequency excitation sources is precisely controlled by a control system (for example, based on a PLC or digital control system).

[0068] In actual application of this embodiment, a low-frequency excitation source (such as a low-frequency vibration source or a mechanical impact source) is started first, and usually a lower frequency vibration or shock wave is selected, for example, a frequency between 20Hz and 200Hz. These fluctuations can act on the surface of the rock mass and produce tiny rock deformations through low-frequency vibrations. The initial micro-deformation creates more favorable conditions for subsequent ultrasonic excitation, reduces the stiffness of the rock mass, makes it easier for the rock mass to crack, and allows ultrasonic waves to propagate to deep layers in a more efficient manner.

[0069] For example, on a piece of rock, a low-frequency exciter is first used to generate vibrations of about 100 Hz on the surface, with an action time of about 1-2 seconds. This can effectively reduce the internal stress on the rock surface and produce microcracks or microdeformations.

[0070] Once the micro-deformation or micro-cracks caused by low-frequency excitation stabilize, the ultrasonic excitation source (such as an ultrasonic transducer with a frequency of 20kHz to 1MHz) is immediately started to further act on the rock mass through high-frequency shock waves. Ultrasonic waves have a higher frequency and better penetration ability, and can penetrate deeper into the rock mass, promote the expansion of micro-cracks, and accurately guide the direction of crack expansion. For example: 0.5 seconds after the end of low-frequency excitation, ultrasonic excitation is started. Ultrasonic waves generate efficient stress waves through the micro-cracks in the rock mass, accurately guiding the cracks to further expand.

[0071] This embodiment uses a control system (such as a PLC or digital control system) to accurately adjust the timing of the low-frequency vibration source and the ultrasonic source. The system controls the start-up timing of the excitation source according to the set parameters (such as the type of rock mass, the required crack extension depth, etc.) and ensures coordination between the two excitation sources.

[0072] For example, using a PLC control system, set the low-frequency vibration excitation source to work for 2 seconds first, and then switch to the ultrasonic excitation source to work for 3 seconds to ensure that the action time of the two is connected to each other to avoid interference.

[0073] In practical applications, the duration of low-frequency and ultrasonic excitation needs to be appropriately adjusted. Excessive low-frequency excitation can cause excessive rock deformation, affecting ultrasonic propagation, while too short a duration may not create a suitable propagation environment for ultrasonic waves. In this example, a genetic algorithm was used to adjust the duration of low-frequency and ultrasonic excitation to find the optimal excitation time combination for rock weakening.

[0074] The fitness function of the genetic algorithm is expressed as:

[0075] F(t LF ,t US )=w1·D(t LF ,t US )-w2·Δσ(t LF ,t US )

[0076] Where D is the crack extension depth based on the low-frequency excitation time t LF and ultrasonic excitation time t US function; Δσ is the rock damage based on low-frequency excitation time t LF and ultrasonic excitation time t US function; w1 and w2 are weight coefficients.

[0077] In this embodiment, by real-time monitoring of the stress response and crack development of the rock mass, the feedback control system adjusts the parameters of the excitation source to ensure that ultrasonic excitation and blasting are started at the appropriate time to ensure the transmission and weakening effects of the wave.

[0078] In this embodiment, the start timing and time interval between the low-frequency excitation source and the ultrasonic excitation source are precisely adjusted through a control system (such as a PLC or a digital control system).

[0079] In this example, a low-frequency excitation source (such as a vibration or impact source) is first activated to induce tiny deformations on the rock surface, reducing rock stiffness and creating conditions for crack initiation. Once the micro-deformation generated by the low-frequency excitation source stabilizes, the ultrasonic excitation source is immediately activated. At this time, the ultrasonic waves can propagate along the micro-cracks and guide the cracks to continue to expand, maintaining the directionality of the cracks. The low-frequency excitation creates a suitable propagation environment for the propagation of ultrasonic waves through physical deformation, allowing the ultrasonic waves to generate effective stress waves along the crack path, guiding the cracks to expand in the predetermined direction.

[0080] In this embodiment, the excitation time is optimized by using a genetic algorithm or the like to ensure that the duration of the low-frequency excitation and the ultrasonic excitation are relatively coordinated, thereby avoiding excessive deformation or excessively short excitation that may lead to unsatisfactory crack propagation.

[0081] This embodiment deploys stress sensors, strain gauges, and microseismic sensors within the rock mass to collect real-time rock mass response data, particularly data on the formation and expansion of microcracks. Through data analysis, the evolution of these microcracks is captured in real time and fed back to the control system. Based on this monitoring data, the power, frequency, and excitation pattern of the excitation source can be optimized to ensure crack formation at the desired depth and direction.

Claims

1. A rock gas blasting method based on stress wave guidance, characterized in that: include: Based on the geological conditions of the target rock mass, stress wave simulation is performed to obtain the stress wave simulation results of the rock mass; Based on the type of rock mass, the target depth of crack extension, and the stress wave simulation results of the rock mass, determine the layout and excitation working mode of the ultrasonic excitation source and the low-frequency excitation source; Among them, the low-frequency excitation source is used to reduce the stiffness of the rock surface through low-frequency excitation, increase the micro-deformation and initial micro-cracks of the rock, create conditions for the propagation of ultrasonic waves, and locally guide the formation position of cracks; The ultrasonic excitation source is used to utilize the high penetration of ultrasonic waves so that they can effectively reach deep layers of the rock mass and stimulate the expansion of microcracks.

2. The rock mass gas blasting method based on stress wave guidance according to claim 1, characterized in that: The method of determining the arrangement of the ultrasonic excitation source comprises: Based on the type of target rock mass, the target depth of crack extension and the stress wave simulation results, the excitation mode of the ultrasonic excitation source is determined to be multi-point excitation or directional excitation; Based on the determined excitation mode, the arrangement mode of the ultrasonic excitation source is determined.

3. The rock mass gas blasting method based on stress wave guidance according to claim 1, characterized in that: The method of determining the excitation working mode of the ultrasonic excitation source includes: Based on the type of target rock mass, target crack extension depth and stress wave simulation results, the optimal frequency range of ultrasonic waves is determined through simulation experiments.

4. The rock mass gas blasting method based on stress wave guidance according to claim 1, characterized in that: The method of determining the arrangement of the low-frequency excitation source comprises: The low frequency excitation source is arranged on the surface of the rock mass or in the vicinity thereof.

5. The rock mass gas blasting method based on stress wave guidance according to claim 1, characterized in that: The excitation working mode of determining the ultrasonic excitation source and the low-frequency excitation source includes: The low-frequency excitation source works first, and then switches to the ultrasonic excitation source; Among them, the start-up timing of the ultrasonic excitation source is determined based on the rock stress response and crack development obtained through real-time monitoring.

6. The rock mass gas blasting method based on stress wave guidance according to claim 5, characterized in that: The excitation working mode of determining the ultrasonic excitation source and the low-frequency excitation source includes: Determine the low-frequency excitation time t of the low-frequency excitation source by genetic algorithm LF and the ultrasonic excitation time t of the ultrasonic excitation source US ; The fitness function of the genetic algorithm is expressed as: F(t LF ,t US )=w1·D(t LF ,t US )-w2·Δσ(t LF ,t US ) Where D is the crack extension depth based on the low-frequency excitation time t LF and ultrasonic excitation time t US function; Δσ is the rock mass damage based on low-frequency excitation time t LF and ultrasonic excitation time t US function; w1 and w2 are weight coefficients.

7. The rock mass gas blasting method based on stress wave guidance according to claim 1, characterized in that: The stress wave simulation is a stress wave simulation experiment that combines geological modeling with digital twin technology.

8. The rock mass gas blasting method based on stress wave guidance according to claim 1, characterized in that: The frequency range of the ultrasonic excitation source is between 20kHz and 1MHz; the frequency range of the low-frequency excitation source is between 20Hz and 200Hz.

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