Wave-absorbing and vibration-reducing method for asymmetric high-stress tunnel dynamic disturbance

Abstract

The invention relates to a wave-absorbing and vibration-reducing method for dynamic disturbance of an asymmetric high-stress tunnel, which belongs to the technical field of tunnel excavation, and specifically comprises the following steps: step 1, determining the position, range and depth of an asymmetric stress concentration area or a rockburst potential risk area behind a high-stress tunnel face, and determining the position, number and depth of grouting holes; 2, preparing and grouting a wave-absorbing material, and solidifying the wave-absorbing material, wherein the wave-absorbing material comprises the following components: cement, water, a foaming agent, polyacrylonitrile fiber and rubber powder; thirdly, monitoring holes are drilled in the middle and the two ends of the wave-absorbing grouting area, and a vibration sensor is placed in each monitoring hole; and 4, after the vibration sensor monitors that the high-energy disturbance stress wave is transmitted, obtaining an amplitude value through the waveform of the disturbance wave to obtain the main frequency of the disturbance wave. The specific position of wave-absorbing grouting is provided for a rockburst risk area, and the disturbance wave monitoring method provided by the invention can realize disturbance wave attenuation effect evaluation for various disturbance waves.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel excavation, and in particular relates to a method for absorbing and reducing vibrations of dynamic disturbances in an asymmetric high-stress tunnel. Background Art

[0002] Under the action of geological tectonic movement, the ground stress will be asymmetrically distributed. During the excavation of deep-buried high-stress hard rock tunnels, the radial stress decreases to zero, the tangential stress increases exponentially, and the surrounding rock behind the face is in a true triaxial high-ground stress state (σ1>σ2>σ3). Asymmetric stress concentration often occurs in the tunnel section, that is, an asymmetric stress concentration zone. Various multi-source dynamic disturbances in deep-buried tunnels, such as blasting, TBM vibration, earthquake, and train vibration, cause cracks in the high-stress surrounding rock. With long-term repeated disturbances, cracks gradually accumulate and the strength continues to decrease. When the bearing capacity is less than the stress level, a time-lag rockburst occurs. Therefore, dynamic disturbance becomes the main inducing factor for the occurrence of time-lag rockburst.

[0003] At present, deep buried tunnel construction is mainly carried out through two methods: drilling and blasting and TBM. As the face continues to advance, multiple cycles of blasting stress wave disturbances occur; during TBM excavation, the shield (generally 6m long) continues to vibrate for several hours. In addition, active plate areas are often affected by seismic waves, and tunnels receive dynamic disturbances caused by train vibrations during operation. When these disturbance stress waves are transmitted to stress concentration areas and their energy reaches the threshold that the surrounding rock can withstand, it is very easy to induce rock mass fractures in the area, and even cause dynamic disasters such as time-delay rock bursts.

[0004] During the construction of high-stress tunnels, the prevention and control of dynamic disturbance-triggered damage is relatively scarce. Disturbance control technologies such as shock-absorbing grooves commonly used in shallow tunnels are difficult to implement in deep high-stress tunnels, resulting in frequent dynamic disturbance-triggered damage on site.

[0005] A Chinese patent (publication number: CN116733512A, publication date: September 12, 2023) discloses a wave-absorbing and energy-absorbing anchor support method and support system, but the support method only lacks discussion on areas with high rockburst tendency and lacks specific monitoring and application methods.

[0006] A Chinese patent (publication number: CN118582211A, publication date: September 3, 2024) discloses a method for constructing long-distance, large-span tunnels with ultra-small clearance. This method only provides control over blasting and excavation disturbances, while other control performance is not disclosed. In addition, this method only pours foam concrete on the outside of the initial support of the advance tunnel, and does not provide seismic control over the deep surrounding rock mass. Summary of the invention

[0007] In view of the shortcomings of the prior art, the present invention provides a method for absorbing and reducing vibrations of asymmetric high-stress tunnel dynamic disturbances, and provides an easy-to-implement high-stress tunnel dynamic disturbance control and testing technology, which is of great significance for the prevention and control of disturbance-triggered destruction such as time-lag rock bursts.

[0008] A method for absorbing and reducing vibration of dynamic disturbance in an asymmetric high-stress tunnel, specifically comprising the following steps:

[0009] Step 1: Determine the location, quantity and depth of the grouting holes according to the location, range and depth of the asymmetric stress concentration area or rock burst potential risk area behind the high-stress tunnel face;

[0010] Step 2: Prepare and grout the absorbing material and wait for it to solidify:

[0011] Step 3: Drill monitoring holes in the middle and at both ends of the wave-absorbing grouting area, and place a vibration sensor in each monitoring hole;

[0012] Step 4: After the vibration sensor detects the transmission of the high-energy disturbance stress wave, the amplitude and main frequency of the disturbance wave are obtained through the disturbance wave waveform.

[0013] In the step 1, based on the geological data of the tunnel surrounding rock, according to the asymmetric stress distribution and the geometric characteristics of the tunnel section, the position, range and depth of the asymmetric stress concentration area behind the high stress tunnel face are determined;

[0014] Or determine the location, scope, and depth of potential rockburst risk areas based on real-time monitoring of microseismic events and energy accumulation areas.

[0015] The depth of the grouting holes is 3m-5m; the spacing between the grouting holes is determined according to the development of the surrounding rock cracks and is 0.7m-1.5m; the length of the grouting holes along the tunnel axis is not more than 10m, and the height does not exceed 5m.

[0016] The step 2 is specifically as follows: after the components are mixed and stirred sufficiently, the absorbing material is prepared; at the same time, parallel plum blossom-shaped grouting holes are arranged in the asymmetric stress concentration area or the potential rock burst risk area; and then the configured absorbing material is injected into the grouting holes in combination with the PVC grouting pipe using a grouting truck.

[0017] In the step 2, cement, water, foaming agent, polyacrylonitrile fiber and rubber powder are selected as components of the absorbing material.

[0018] The mass ratio of water to cement is 0.4 to 1.0;

[0019] The proportion of foaming agent added is 1% to 1.5% of the volume of water added;

[0020] The particle size of the rubber powder is less than 2.5 mm, and the mass fraction of the rubber powder is 15% to 30% of the mass of the cement;

[0021] The length of the polyacrylonitrile fiber is 5 mm to 12 mm, and the mass fraction of the polyacrylonitrile fiber is 0.5% to 2% of the mass fraction of the cement.

[0022] First, cement, rubber powder and polyacrylonitrile fiber materials are added into a mixer and stirred thoroughly to form a mixture. Subsequently, a foaming agent is diluted with water to form a foaming liquid, and a high-pressure foaming machine is used to foam the foaming liquid. The foaming liquid is added into the mixer and stirred evenly with the mixture.

[0023] The grouting holes are spaced 1 m left and right and 0.5 m up and down, and their depths are consistent with the radial depth of the stress concentration zone.

[0024] The number of the monitoring holes is 3 to 5, with a diameter of 10 cm and a depth of 8 cm.

[0025] In the step three, the vibration sensor is fixed in the monitoring hole by using high-strength quick-setting gypsum; after the high-strength gypsum solidifies, the vibration sensor is turned on to adjust the sensor parameters, the acquisition mode is set to continuous acquisition, the acquisition time is set to 1s, and the sampling rate is set to 4kHz.

[0026] The beneficial effects of the present invention are as follows: the present invention proposes a wave absorbing and vibration reducing method for the disturbance transmission process in the surrounding rock, provides a specific location for wave absorbing grouting for the rock burst risk area, and can target a variety of disturbance waves, thereby realizing the evaluation of the disturbance wave attenuation effect.

[0027] The present invention is simple to implement and can achieve the effect of attenuating various disturbance waves. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic flow chart of the wave absorbing method for asymmetric high stress tunnel dynamic disturbance provided by the present invention;

[0029] Figure 2 is a schematic diagram of the location of the asymmetric stress concentration area;

[0030] Figure 3 This is a schematic diagram of the location of the potential risk area for rock burst;

[0031] Figure 4 This is a working principle diagram of the wave-absorbing grouting material used in the present invention;

[0032] Figure 5 A schematic diagram of the arrangement of wave-absorbing grouting holes and monitoring holes in the embodiment provided by the present invention;

[0033] Figure 6 A schematic diagram of a sensor monitoring a disturbance stress wave in an embodiment provided by the present invention;

[0034] Figure 7 It is a typical vibration wave spectrum diagram before and after the disturbance stress wave passes through the wave-absorbing grouting area;

[0035] Figure 8 This is a diagram of the rockburst attenuation effect of Example 2. DETAILED DESCRIPTION

[0036] In order to better explain the present invention and facilitate understanding, the technical solutions and effects of the present invention are described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0037] Example 1

[0038] This embodiment provides a method for absorbing and reducing vibrations in dynamic disturbances of an asymmetric high-stress tunnel. First, the location of an asymmetric stress concentration area or a potential rock burst risk area in the tunnel is determined according to the direction and magnitude of the principal stress in the tunnel section or the aggregation of microseismic events. Grouting holes are drilled in the above-mentioned area, and absorbing grouting materials are arranged. Then, vibration sensors are arranged inside and outside the absorbing grouting area to monitor the disturbance stress waves during the tunnel excavation process, and the disturbance wave data and microseismic data are compared to verify the absorbing effect. Figure 1 As shown, the specific steps are as follows:

[0039] Step 1: Based on the geological data of the tunnel surrounding rock, according to the stress distribution and the geometric cross-section characteristics of the tunnel, determine the location, range, and depth of the asymmetric stress concentration area behind the high-stress tunnel face, and determine the location of the grouting hole as the asymmetric stress concentration area based on the asymmetric stress concentration area, such as Figure 2 As shown, the depth and range of the grouting holes are consistent with the asymmetric stress concentration area, i.e., the dangerous area where rock burst may occur. In this embodiment, the number of grouting holes is 8, the horizontal spacing of the grouting holes is 1m, the hole depth is 3m, the length of the grouting area is 5m, and the height is 2m, forming a wave-absorbing grouting area.

[0040] Step 2: Prepare and grout the absorbing material:

[0041] Cement, water, foaming agent, polyacrylonitrile fiber and rubber powder are selected as the components of the absorbing material, and the components are mixed and stirred in a certain proportion. At the same time, plum blossom-shaped grouting holes are arranged according to the grouting area obtained in the asymmetric stress concentration area, and then the configured absorbing material is injected into the grouting hole with the PVC grouting pipe using a grouting truck.

[0042] In this embodiment, the mass ratio of water to cement is 0.4; the proportion of foaming agent added is 1% of the volume of the added water; the particle sizes of the rubber powder are 0.425, 0.85, and 2 mm, respectively, the mass fraction of the rubber powder is 20% of the mass of the cement, and the three particle sizes each account for 1 / 3; the length of the polyacrylonitrile fiber is 9 mm, and the mass fraction of the polyacrylonitrile fiber is 0.5% of the mass fraction of the cement.

[0043] The preparation method of the wave absorbing material is as follows: in this embodiment, a foaming agent and water are first prepared at a volume ratio of 1%, and then stirred at a fixed speed of 1000r / min for 3 minutes, and then cement, rubber powder and polyacrylonitrile fiber are added in sequence.

[0044] The pores formed by adding foaming agent to the absorbing material can block the transmission of disturbance stress waves, increase the reflection of disturbance stress waves, and reduce the impact of stress waves on the surrounding rock behind the absorbing area; the rubber in the material can cause elastic deformation of the absorbing material, further attenuating the propagation of stress waves. Due to the impedance effect and loss mechanism of the absorbing material on stress waves, the stress wave amplitude, that is, the stress wave energy and frequency, are greatly attenuated after transmission. The absorbing principle diagram is shown in the figure below. Figure 4 shown.

[0045] In this embodiment, the location of the plum blossom-shaped grouting holes is arranged in the asymmetric stress concentration area (see Figure 4 ), use a rock drill to drill grouting holes, use a grouting truck to inject the prepared and evenly stirred absorbing material and PVC plastic pipe into the grouting holes, and wait for it to solidify.

[0046] Step 3: In this embodiment, four monitoring holes with a diameter of 10 cm and a depth of 8 cm are drilled in the middle and at both ends of the wave-absorbing grouting area, and a vibration sensor is placed inside each monitoring hole. The vibration sensor is fixed in the monitoring hole using high-strength quick-setting gypsum. Figure 5-6 shown.

[0047] After the high-strength gypsum solidifies, turn on the vibration sensor to adjust the sensor parameters, set the acquisition mode to continuous acquisition, the acquisition time to 1s, and the sampling rate to 4kHz, and monitor the speed and acceleration of the disturbance stress wave before and after passing through the absorbing area in real time.

[0048] Vibration sensors arranged in this way can monitor multi-source dynamic disturbance waves in front of and behind the wave-absorbing grouting area, including tunnel face blasting disturbance waves, TBM vibration disturbance waves, seismic disturbance waves, rock burst stress waves, etc.

[0049] Step 4: After the vibration sensor detects the transmission of high-energy disturbance stress waves, the disturbance stress wave data recorded by the vibration sensor is exported. The amplitude is obtained through the disturbance wave waveform and the disturbance wave waveform is subjected to fast Fourier transform to obtain the main frequency of the disturbance wave.

[0050] To compare the wave absorbing effect, refer to formula (1):

[0051] A=(P A -P B ) / P A (1)

[0052] Where:

[0053] A-vibration wave amplitude reduction rate, which is the ratio of the amplitude change of the stress wave passing through the wave-absorbing grouting area and the two ends of the wave-absorbing grouting area;

[0054] P A -Amplitude of surrounding rock disturbance waves when no absorbing material is grouted;

[0055] P B -Amplitude of disturbance waves in surrounding rock after grouting of wave-absorbing materials.

[0056] Refer to formula (2):

[0057] Q=(F A -F B ) / F A (2)

[0058] Where:

[0059] Q-vibration wave frequency reduction rate, which is the ratio of the main frequency transformation of the stress wave passing through the wave-absorbing grouting area and the two ends of the wave-absorbing area;

[0060] F A -Main frequency of surrounding rock disturbance wave when no absorbing material is grouted;

[0061] F B -The main frequency of the surrounding rock disturbance wave after grouting the wave-absorbing material.

[0062] like Figure 7 As shown in the figure, in this embodiment, the surrounding rock disturbance wave amplitude P is A is 0.521. When the absorbing material is not injected, the main frequency of the surrounding rock disturbance wave is F A is 177.73Hz; the surrounding rock disturbance wave amplitude after grouting the absorbing material is P B is 0.250, and the main frequency of the surrounding rock disturbance wave after grouting the absorbing material is F B The amplitude of the disturbance wave is 45.069% attenuated and the main frequency is 34.868% attenuated according to equations (1) and (2). The amplitude and main frequency of the disturbance stress wave after the wave-absorbing grouting area are significantly lower than those before the wave-absorbing grouting area.

[0063] It can be seen from this that the wave absorbing method provided in the present application can significantly weaken the propagation of dynamic disturbance stress waves, reduce their disturbance effects, and to a large extent ensure the stability of the asymmetric stress concentration zone.

[0064] This application provides an absorbing material composed of cement, water, foaming agent, polyacrylonitrile fiber and rubber powder by selecting the components of the absorbing material, and determines the composition ratio of the absorbing material. Drilling and grouting are performed on the basis of determining the position of the asymmetric stress concentration area after excavation, and multiple vibration sensors are arranged in the grouting area and at the front and rear ends, providing a high-stress tunnel dynamic disturbance-triggered rock burst grouting absorbing technology and a field test method, which realizes attenuation after the disturbance wave passes through the absorbing material, effectively reduces the vibration amplitude and frequency, and monitors the speed, acceleration and other characteristics of various disturbance stress waves before and after the application of the absorbing material in real time. The present invention can attenuate the disturbing effect of the disturbance wave on the stress concentration area of ​​the high-stress tunnel, avoid the occurrence of dynamic disasters such as time-lag rock burst, and ensure the safety of construction personnel and equipment.

[0065] Example 2

[0066] The difference between this embodiment and embodiment 1 is that in step 1, the location, range, and depth of the potential rock burst risk area are determined based on the distribution of microseismic events and energy concentration areas monitored in real time by microseismic monitoring technology, and the location of the grouting hole is determined as the potential rock burst risk area based on the potential rock burst risk area, such as Figure 3 As shown, the depth and range of the grouting holes are consistent with the potential risk area of ​​rock burst, that is, the dangerous area where rock burst may occur. The remaining steps are completely consistent with Example 1.

[0067] In addition to judging the wave absorption effect through vibration attenuation and the above-mentioned amplitude-frequency comparison, this embodiment can also know the effect of wave absorption grouting on reducing rock burst risk through the changes in the number of microseismic events and microseismic energy in the rock burst risk area before and after wave absorption. The rock burst attenuation effect of this embodiment is shown in Figure 8 , reducing the risk of rock burst.

Claims

1. A method for absorbing and reducing vibrations of dynamic disturbances in an asymmetric high-stress tunnel, characterized in that: The specific steps include: Step 1: Determine the location, quantity and depth of the grouting holes according to the location, range and depth of the asymmetric stress concentration area or rock burst potential risk area behind the high-stress tunnel face; Step 2: Prepare and grout the absorbing material and wait for it to solidify: Step 3: Drill monitoring holes in the middle and at both ends of the wave-absorbing grouting area, and place a vibration sensor in each monitoring hole; Step 4: After the vibration sensor detects the transmission of the high-energy disturbance stress wave, the amplitude and main frequency of the disturbance wave are obtained through the disturbance wave waveform.

2. The method for absorbing and reducing vibration of asymmetric high-stress tunnel dynamic disturbance according to claim 1 is characterized in that: In the step 1, based on the geological data of the tunnel surrounding rock, according to the asymmetric stress distribution and the geometric characteristics of the tunnel section, the position, range and depth of the asymmetric stress concentration area behind the high stress tunnel face are determined; Or determine the location, scope, and depth of potential rockburst risk areas based on real-time monitoring of microseismic events and energy accumulation areas.

3. The method for absorbing and reducing vibration of dynamic disturbance in an asymmetric high-stress tunnel according to claim 1 is characterized in that: The depth of the grouting holes is 3m-5m; the spacing between the grouting holes is determined according to the development of the surrounding rock cracks and is 0.7m-1.5m; the length of the grouting holes along the tunnel axis is not more than 10m, and the height does not exceed 5m.

4. The method for absorbing and reducing vibration of asymmetric high-stress tunnel dynamic disturbance according to claim 1 is characterized in that: The step 2 is specifically as follows: after the components are mixed and stirred sufficiently, the absorbing material is prepared; at the same time, parallel plum blossom-shaped grouting holes are arranged in the asymmetric stress concentration area or the potential rock burst risk area; and then the configured absorbing material is injected into the grouting holes in combination with the PVC grouting pipe using a grouting truck.

5. The method for absorbing and reducing vibration of asymmetric high-stress tunnel dynamic disturbance according to claim 1, characterized in that: In the step 2, cement, water, foaming agent, polyacrylonitrile fiber and rubber powder are selected as components of the absorbing material.

6. The method for absorbing and reducing vibration of asymmetric high-stress tunnel dynamic disturbance according to claim 5, characterized in that: The mass ratio of water to cement is 0.4 to 1.0; The proportion of foaming agent added is 1% to 1.5% of the volume of water added; The particle size of the rubber powder is less than 2.5 mm, and the mass fraction of the rubber powder is 15% to 30% of the mass of the cement; The length of the polyacrylonitrile fiber is 5 mm to 12 mm, and the mass fraction of the polyacrylonitrile fiber is 0.5% to 2% of the mass fraction of the cement.

7. The method for absorbing and reducing vibration of asymmetric high-stress tunnel dynamic disturbance according to claim 6 is characterized in that: First, cement, rubber powder and polyacrylonitrile fiber materials are added into a mixer and stirred thoroughly to form a mixture. Subsequently, a foaming agent is diluted with water to form a foaming liquid, and a high-pressure foaming machine is used to foam the foaming liquid. The foaming liquid is added into the mixer and stirred evenly with the mixture.

8. The method for absorbing and reducing vibration of asymmetric high-stress tunnel dynamic disturbance according to claim 4 is characterized in that: The grouting holes are spaced 1 m left and right and 0.5 m up and down, and their depths are consistent with the radial depth of the stress concentration zone.

9. The method for absorbing and reducing vibration of asymmetric high-stress tunnel dynamic disturbance according to claim 1, characterized in that: The number of the monitoring holes is 3 to 5, with a diameter of 10 cm and a depth of 8 cm.

10. The method for absorbing and reducing vibration of asymmetric high-stress tunnel dynamic disturbance according to claim 1, characterized in that: In the step three, the vibration sensor is fixed in the monitoring hole by using high-strength quick-setting gypsum; after the high-strength gypsum solidifies, the vibration sensor is turned on to adjust the sensor parameters, the acquisition mode is set to continuous acquisition, the acquisition time is set to 1s, and the sampling rate is set to 4kHz.

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