Tunnel rockburst risk assessment method and prevention and treatment method

Abstract

The invention relates to the technical field of tunnel engineering, in particular to a tunnel rockburst risk assessment method and prevention method, and the assessment method comprises the steps: installing a plurality of first micro-seismic sensors in the circumferential direction of a tunnel wall within a preset distance range behind a tunnel face, determining an initial rockburst range based on the micro-seismic data collected by the first micro-seismic sensor; and a plurality of second micro-seismic sensors are annularly installed on the tunnel wall corresponding to the initial rockburst range, the monitoring precision of the second micro-seismic sensors is higher than that of the first micro-seismic sensors, and the final rockburst position is determined based on micro-seismic data collected by the second micro-seismic sensors. The tunnel rock burst occurrence position can be finely determined, and hydraulic slotting pressure relief is guided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tunnel engineering, and particularly relates to a tunnel rock burst risk assessment method and a prevention and treatment method. BACKGROUND

[0002] In the tunnel excavation operation in a high stress area, a large amount of elastic strain energy is stored in the rock mass in a high stress state. When this energy is released instantaneously, it will cause severe damage to the surrounding rock of the tunnel, which is specifically manifested as the burst loosening and peeling of the rock mass, and even the ejection and throwing phenomenon, i.e. rock burst. The huge energy released by the rock burst not only causes the rock to burst suddenly and eject at high speed, which directly and seriously threatens the life safety of the construction personnel, but also damages the construction equipment, increases the maintenance cost and replacement frequency of the equipment. In addition, the damaged tunnel surrounding rock also needs to be supported and repaired again, which not only delays the engineering construction period, but also greatly increases the comprehensive cost of the engineering construction. Therefore, taking proactive pressure relief measures to reduce the probability of rock burst accidents becomes a key link in the construction of high stress tunnels.

[0003] The traditional proactive prevention and treatment methods mainly include the blasting method, the drilling pressure relief method, the anchoring method and the like. Among them, the blasting method attempts to release part of the stress by blasting to create cracks in the surrounding rock. However, this method has obvious defects: the strength and range of the blasting process are difficult to accurately control, which easily causes excessive fragmentation of the surrounding rock, and not only cannot achieve effective pressure relief, but also may damage the overall stability of the surrounding rock, inducing other geological disasters; at the same time, the vibration generated by the blasting will have an adverse effect on the already constructed tunnel structure, increasing the structural safety hazard.

[0004] The core principle of the drilling pressure relief method is to drill a hole in the surrounding rock, and use the stress concentration effect around the hole to promote the rock mass to produce cracks, thereby achieving the purpose of pressure relief. However, this method is limited by the drilling depth, and the stress release effect on the deep rock mass is not good; and the drilling operation efficiency is low, which needs to consume a large amount of time and manpower, and in the tunnel engineering with a tight construction period, it is difficult to meet the construction progress requirements.

[0005] The anchoring method is to reinforce the surrounding rock by anchor rods, anchor cables and the like, aiming to improve the bearing capacity of the surrounding rock itself. However, this method cannot fundamentally reduce the high stress level in the surrounding rock, and in the area with high stress and strong rock burst tendency, the anchoring measures are difficult to resist the huge destructive energy of the rock burst, and the prevention and treatment effect on the rock burst is very limited.

[0006] Engineering practice shows that the traditional prevention and control method is difficult to adapt to the suddenness and strong destructiveness of rock burst in high stress area. At the same time, there are obvious deficiencies in the existing technology: microseismic monitoring is mostly used for post-analysis after rock burst, and it is difficult to realize early warning; the parameters (such as position, depth, shape, etc.) of water pressure cutting seam pressure relief depend on experience judgment, lack of scientific quantitative basis, resulting in unstable pressure relief effect; in addition, there is no real-time feedback mechanism after cutting seam, and the pressure relief strategy cannot be dynamically adjusted according to the stress change of surrounding rock. Therefore, developing a rock burst cooperative control method which integrates real-time monitoring, dynamic evaluation and accurate pressure relief has become a key problem to be solved in the current high stress tunnel construction. SUMMARY

[0007] The purpose of the present application is to provide a tunnel rock burst risk assessment method and prevention and control method, which can finely determine the rock burst occurrence position of the tunnel and guide the water pressure cutting seam pressure relief.

[0008] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0009] In the first aspect, the present application discloses a tunnel rock burst risk assessment method, which comprises:

[0010] A plurality of first microseismic sensors are installed along the tunnel wall in a preset distance range behind the tunnel face, and an initial rock burst range is determined based on the microseismic data collected by the first microseismic sensors;

[0011] A plurality of second microseismic sensors are installed along the tunnel wall in the initial rock burst range, the monitoring accuracy of the second microseismic sensors is higher than that of the first microseismic sensors, and a final rock burst position is determined based on the microseismic data collected by the second microseismic sensors.

[0012] Further, the number of the second microseismic sensors is eight, four of which are installed on a first cross section of the tunnel corresponding to the initial rock burst range, and the remaining four are installed on a second cross section of the tunnel corresponding to the initial rock burst range, and the distance between the first cross section and the second cross section is reasonably determined according to the size of the initial rock burst range.

[0013] Further, the installation of the plurality of first microseismic sensors or the plurality of second microseismic sensors along the tunnel wall comprises: forming a plurality of embedded holes radially along the tunnel wall, and the hole depth of the embedded hole is 1.2-1.5 times the radius of the tunnel.

[0014] The first microseismic sensor or the second microseismic sensor is installed in the embedded hole, and epoxy coupling agent is filled in the embedded hole to enhance signal conduction.

[0015] Further, the first microseismic sensor or the second microseismic sensor transmits data to an analysis platform in real time through a multi-channel data acquisition instrument;

[0016] The analysis platform receives data from the first microseismic sensor or the second microseismic sensor for microseismic analysis, including filtering and wave propagation analysis of microseismic information, microseismic source positioning according to the microseismic information, and obtaining the number of microseismic events, the source moment and the energy index, judging the rock burst grade and the initial rock burst range or the final rock burst position of the rock burst in the tunnel.

[0017] Further, the second microseismic sensor is connected with the multi-channel data acquisition instrument through an optical fiber.

[0018] In a second aspect, the application discloses a tunnel rock burst prevention method, which comprises:

[0019] The final rock burst position is determined by using the tunnel rock burst risk assessment method.

[0020] Obtain the rock mechanics parameters of the microseismic information and the final rock burst position area;

[0021] Determine the cutting seam parameters of the final rock burst position based on the rock mechanics parameters of the microseismic information and the final rock burst position area.

[0022] According to the determined cutting seam parameters, abrasive water jet is used to cut the seam and release pressure along the tunnel wall to prevent rock burst.

[0023] Further, the cutting seam parameters of the final rock burst position are determined based on the microseismic source radiation energy, stress and energy density concentration distribution obtained based on the microseismic information and the rock mechanics parameters of the final rock burst position area.

[0024] The microseismic source radiation energy E P,S is calculated as In the formula, ρ is the rock density, v P,S is the velocity of the longitudinal wave or the transverse wave, S is the propagation distance of the microseismic wave, μ corr is the velocity pulse in the radiation direction, t s is the duration of the microseismic event.

[0025] The calculation formula of the pressure drop Δσ is In the formula, M0 is the microseismic moment, the calculation formula is M0=μAD, μ is the shear modulus, A is the microfracture area, D is the average slip distance of the microfracture, and r is the fracture radius.

[0026] The calculation formula of the energy density concentration distribution E d is V is the fracture volume.

[0027] Further, the slotting depth is 0.8R-1.2R, and R is the radius of the surrounding rock loose circle calculated based on the Mohr-Coulomb criterion.

[0028] Further, the method further comprises: after the slotting is completed, adjusting the slotting parameters according to the change of the Lasbysson rock burst coefficient before and after the slotting in the final rock burst position area.

[0029] The application has the following unexpected beneficial effects:

[0030] The tunnel rock burst risk assessment method provided by the application realizes fine locking of the rock burst position through two-stage monitoring. In the first stage, a plurality of first microseismic sensors are installed in a preset range behind the tunnel face, and the initial rock burst range is quickly circled, so that the target area is determined for subsequent accurate monitoring, and resource waste caused by blind control is avoided. In the second stage, second microseismic sensors with higher accuracy are arranged in the initial range, and the microseismic data are analyzed in detail by using the higher monitoring accuracy, so that the final rock burst position can be accurately positioned, and the problem of ambiguous position judgment in traditional monitoring is solved, thereby providing an accurate spatial basis for rock burst risk assessment. In addition, the wide-range preliminary monitoring in the first stage can quickly screen out the risk area, thereby reducing the coverage range of the high-precision monitoring in the second stage. While ensuring the accuracy of the final positioning, the problems of high cost and data redundancy caused by full-range high-precision monitoring are avoided, so that the entire assessment process is more economical and practical, and can better adapt to the complex environment and construction period requirements of tunnel construction. At the same time, since the final rock burst position can be determined, the hydraulic slotting operation can be directly carried out on the high-risk area, thereby avoiding the invalid operation caused by inaccurate position judgment in the traditional pressure relief. The accurate target area positioning can make the slotting parameters more suitable for the actual needs, improve the pressure relief efficiency, ensure that the energy release is more concentrated in the risk point, thereby effectively reducing the rock burst occurrence probability and improving the safety of tunnel construction. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the specific embodiments of the application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the application.

[0032] Figure 1 The flowchart of the tunnel rock burst risk assessment method according to the embodiments of the application is shown.

[0033] Figure 2 The arrangement diagram of the first microseismic sensor according to the embodiments of the application is shown.

[0034] Figure 3 The arrangement diagram of the first microseismic sensor according to the embodiments of the application is shown.

[0035] Figure 4 A tunnel construction panoramic view diagram according to an embodiment of the present application.

[0036] Figure 5 A top view diagram of a second microseismic sensor arrangement according to an embodiment of the present application.

[0037] Figure 6 A diagram of a second microseismic sensor arrangement in a first section according to an embodiment of the present application.

[0038] Figure 7 A diagram of a second microseismic sensor arrangement in a second section according to an embodiment of the present application.

[0039] Figure 8 A diagram of a cut construction area arrangement according to an embodiment of the present application.

[0040] Figure 9 A diagram of a cut section according to an embodiment of the present application.

[0041] Figure 10 A diagram of a monitoring device arrangement fixed at the cut position according to an embodiment of the present application.

[0042] In the diagram, 1 - first microseismic sensor, 2 - second microseismic sensor, 3 - data acquisition instrument, 4 - analysis platform, 5 - optical fiber, 6 - cut, 7 - borehole stress sensor, 8 - pre-buried hole, 9 - epoxy coupling agent, 10 - tunnel face, 11 - first section, 12 - second section, 20 - cut area. DETAILED DESCRIPTION

[0043] Other advantages and effects of the present application can be easily understood by those skilled in the art from the above description of the preferred embodiments of the present application. The present application can also be implemented or applied in other different specific embodiments, and the details in the specification can be modified or changed based on different views and applications without departing from the spirit of the present application. It should be understood that the preferred embodiments are only for illustrating the present application, and are not intended to limit the protection scope of the present application.

[0044] It should be noted that the diagrams provided in the following embodiments only schematically illustrate the basic concept of the present application, and the components related to the present application are shown in the diagrams, but not drawn according to the number, shape and size of the components in actual implementation. The type, number and ratio of the components in actual implementation can be arbitrarily changed, and the component layout type can also be more complex.

[0045] In an embodiment, the present application provides a tunnel rock burst risk assessment method, as shown in FIG. 1, which comprises the following steps. Figures 1 to 6 ​

[0046] A plurality of first microseismic sensors 1 are installed along the tunnel wall in a preset distance range behind the tunnel face 10, and the initial rock burst range is determined based on the microseismic data collected by the first microseismic sensors 1;

[0047] A plurality of second microseismic sensors 2 are installed along the tunnel wall corresponding to the initial rock burst range, the monitoring accuracy of the second microseismic sensors 2 is higher than that of the first microseismic sensors 1, and the final rock burst position is determined based on the microseismic data collected by the second microseismic sensors 2.

[0048] The tunnel rock burst risk assessment method of the present application realizes the fine locking of the rock burst position through two-stage monitoring. In the first stage, a plurality of first microseismic sensors 1 are installed in a preset range along the tunnel wall behind the tunnel face 10, and the initial rock burst range is quickly circled, which defines the target area for subsequent accurate monitoring and avoids resource waste caused by blind control. In the second stage, second microseismic sensors 2 with higher accuracy are arranged in the initial range, and the microseismic data is analyzed in detail using the higher monitoring accuracy of the second microseismic sensors 2, which can accurately locate the final rock burst position and solve the problem of ambiguous position judgment in traditional monitoring, providing an accurate spatial basis for rock burst risk assessment.

[0049] Moreover, the large-scale preliminary monitoring in the first stage can quickly screen out the risk area, reducing the coverage range of the high-precision monitoring in the second stage. Further, while ensuring the accuracy of the final positioning, the high cost and data redundancy caused by full-range high-precision monitoring are avoided, making the entire evaluation process more economical and practical, and better adapting to the complex environment and time requirements of tunnel construction.

[0050] At the same time, since the final rock burst position can be determined, the water jetting operation can be directly carried out in the high-risk area, avoiding the invalid operation caused by inaccurate position judgment in traditional pressure relief. Precise target area positioning can make the cutting parameters more suitable for actual needs, improve the efficiency of pressure relief, and ensure that energy release is more concentrated in the risk point, thereby effectively reducing the probability of rock burst and improving the safety of tunnel construction.

[0051] As a preferred embodiment of the present application, referring to Figures 4 to 7 As shown in the figure, the number of second microseismic sensors 2 is eight, of which four second microseismic sensors 2 are installed on the first section 11 of the tunnel corresponding to the initial rock burst range, and the remaining four second microseismic sensors 2 are installed on the second section 12 of the tunnel corresponding to the initial rock burst range. The spacing of the first section 11 and the second section 12 is reasonably determined according to the size of the initial rock burst range.

[0052] The preferred embodiment improves positioning accuracy through multi-sensor cooperative monitoring. Specifically, eight second microseismic sensors 2 are used for monitoring. Compared with a smaller number of sensors, more dimensions of microseismic signals can be captured, and through cross-validation and analysis of multiple sets of data, the error of single sensor monitoring can be effectively reduced, and the positioning accuracy of the final rock burst location can be greatly improved. Especially in a complex tunnel surrounding rock environment, the monitoring network formed by multiple sensors can more comprehensively cover the initial rock burst range, reduce the signal blind area, and ensure the integrity and reliability of the microseismic data, providing more solid data support for accurately locking the rock burst risk point.

[0053] Secondly, the split surface layout realizes fine monitoring in the spatial dimension. The eight second microseismic sensors 2 are placed in the first section 11 and the second section 12, and the distance between the two sections is reasonably determined according to the size of the initial rock burst range. This layout breaks the limitations of single-section monitoring and forms a three-dimensional monitoring space along the axial direction of the tunnel. Through comparative analysis of the microseismic signals of the two sections, not only can the position of the rock burst risk point in the ring direction be determined, but also the depth and range of the rock burst risk point in the axial direction can be more accurately judged, so that the positioning of the final rock burst location is upgraded from a plane to a three-dimensional space, providing more accurate spatial coordinates for subsequent targeted pressure relief and avoiding the deviation of pressure relief caused by the ambiguity of axial positioning. Specifically, the specific position of the rock burst in the tunnel section is determined by the time sequence of the triggering of the eight second microseismic sensors 2.

[0054] Furthermore, the flexibility of the layout scheme adapts to different engineering scenarios. The distance between the two sections can be adjusted according to the size of the initial rock burst range, which means that this scheme can adapt to rock burst risk areas of different sizes and shapes. For an initial rock burst area with a larger range, the section spacing can be appropriately increased to expand the monitoring coverage; for a risk area with a smaller range and concentration, the spacing can be reduced to achieve more intensive monitoring, ensuring that the monitoring effort matches the characteristics of the risk area. This flexibility makes this method more applicable in diverse tunnel construction environments and better meets the individual needs of actual projects.

[0055] Finally, the monitoring resource configuration is optimized, taking into account efficiency and cost. The number of eight second microseismic sensors 2 not only ensures the monitoring accuracy and coverage, but also avoids data redundancy and cost increases caused by too many sensors. The split surface layout improves monitoring efficiency without increasing the number of sensors, making the limited monitoring resources work to the maximum, ensuring the evaluation effect while controlling the project cost, and having high practical value.

[0056] By way of example, the first section 11 is arranged close to the tunnel face 10, and the second section is arranged away from the tunnel face 10. Referring to Figure 6As shown, the four second microseismic sensors 2 arranged on the first section 11 are respectively located at the upper left, upper right, lower left and lower right positions of the section, see Figure 7 As shown, the four second microseismic sensors 2 arranged on the second section 12 are respectively located at the upper end, lower end, left end and right end of the section.

[0057] It should be noted that the first microseismic sensors 1 can also be arranged in two rows or three rows.

[0058] Exemplarily, as shown in Figure 2 As shown, the first microseismic sensors 1 are arranged in two rows. In order to achieve three-dimensional coverage, a total of eight first microseismic sensors 1 are used, four first microseismic sensors 1 are arranged on each section D1 and D2, two first microseismic sensors 1 are arranged on the left and right walls respectively, and the eight first microseismic sensors 1 are at different heights from the ground, that is, there is a height difference between the eight first microseismic sensors 1. The distance L1 between the section D1 and the tunnel face 10 is 45-80 m, and the distance L2 between the section D2 and the section D1 is 25-30 m.

[0059] Exemplarily, as shown in Figure 3 As shown, the first microseismic sensors 1 are arranged in three rows. One first microseismic sensor 1 is arranged on the left and right walls and the arch of the section D3, one first microseismic sensor 1 is arranged on the left and right walls of the section D4, and one first microseismic sensor 1 is arranged on the left and right walls and the arch of the section D5. The distance L3 between the section D3 and the tunnel face 10 is 40-80 m, and the distance L4 between the section D4 and the section D3 and the distance L5 between the section D5 and the section D4 are 20-25 m.

[0060] As a preferred embodiment of the present application, the plurality of first microseismic sensors 1 or the plurality of second microseismic sensors 2 are installed along the tunnel wall in a circumferential direction, which specifically comprises: as shown in Figure 6 and Figure 7 As shown, a plurality of pre-buried holes 8 are formed in the radial direction along the tunnel wall, and the hole depth of the pre-buried hole 8 is 1.2-1.5 times the radius of the tunnel. The first microseismic sensor 1 or the second microseismic sensor 2 is installed in the pre-buried hole 8, and the pre-buried hole 8 is filled with epoxy resin coupling agent 9 to enhance signal conduction.

[0061] In the preferred embodiment, by setting the hole depth of the pre-buried hole to 1.2-1.5 times the radius of the tunnel, the limitation of monitoring only on the surface of the tunnel is broken, and the sensor can be closer to the rock mass in the deep high stress area. Under high ground stress conditions, the incubation and energy accumulation of rockburst often occur within a certain depth range of the surrounding rock, and an installation position that is too shallow may miss the key microseismic signals. A depth of 1.2-1.5 times the radius can cover the key area with high risk of rockburst, while avoiding the increased difficulty and cost of drilling too deep, achieving a balance between monitoring range and engineering feasibility. Moreover, in tunnel construction, there are more surface disturbances such as mechanical equipment vibration and personnel activity, while the microseismic signals of the deep rock mass can more directly reflect the true state of rockburst incubation. After the first microseismic sensor 1 or the second microseismic sensor 2 is deeply buried, the disturbance of surface interference on the monitoring data can be reduced, and the signal-to-noise ratio of the signal can be improved.

[0062] In the preferred embodiment, filling the pre-buried hole 8 with epoxy coupling agent 9 can eliminate the medium gap and ensure continuous vibration conduction. If there is an air gap between the first microseismic sensor 1 or the second microseismic sensor 2 and the hole wall, it will cause the seismic wave (microseismic signal) to be greatly attenuated due to reflection and refraction during propagation, and even lose the key signals. As a high-strength and high-adhesion coupling material, the epoxy coupling agent 9 can tightly fill the gap between the sensor and the rock mass, enabling the mechanical vibration generated by microseismic to be conducted from the rock mass to the sensor without a gap, significantly improving the transmission efficiency and integrity of the signal. Moreover, the tunnel construction environment is complex, and the surrounding rock may have slight deformation or vibration. If the first microseismic sensor 1 or the second microseismic sensor 2 is not installed firmly, it is easy to cause the monitoring data to drift due to loosening. After the epoxy coupling agent 9 is cured, the sensor and the rock mass can be firmly combined, avoiding errors caused by position changes during long-term monitoring, and ensuring the stability and consistency of the data. At the same time, the surrounding rock of the tunnel is often accompanied by water seepage or humid environment, and the epoxy resin has good water resistance and chemical stability, which can effectively protect the sensor from failure due to moisture and corrosion, prolong the service life, and reduce the maintenance cost.

[0063] This installation method provides double protection for microseismic monitoring from the hardware level through the combination of depth optimization and coupling reinforcement: on the one hand, deep installation ensures that the sensor can capture early microseismic signals during the incubation stage of rockburst, such as the vibration of internal rock mass crack initiation and expansion, providing more sufficient data support for early warning of rockburst risk; on the other hand, efficient signal conduction makes the monitoring data more truly reflect the actual state of the rock mass, reducing false positives and false negatives caused by signal attenuation or interference, and improving the accuracy of rockburst location, laying a reliable foundation for subsequent precise pressure relief.

[0064] As a preferred embodiment of the present application, refer to Figure 3As shown, the first microseismic sensor 1 or the second microseismic sensor 2 transmits data to the analysis platform 4 in real time through the multi-channel data acquisition instrument 3; the analysis platform 4 receives data from the first microseismic sensor 1 or the second microseismic sensor 2 for microseismic analysis, including filtering and spectrum analysis of microseismic information, microseismic source positioning according to microseismic information, and obtaining the number of microseismic events, source moment and energy index, judging the rock burst grade and the initial rock burst range or the final rock burst position of the rock burst in the tunnel.

[0065] In the preferred embodiment, the first microseismic sensor 1 and the second microseismic sensor 2 transmit data to the analysis platform 4 in real time through the multi-channel data acquisition instrument 3, and real-time data transmission and processing are performed, which improves the timeliness of risk response. The time difference from the collection of microseismic signals (such as vibrations generated by rock mass rupture) to the transmission to the analysis platform 4 is greatly compressed, ensuring that the dynamic changes in the rock burst incubation process can be captured in time. For sudden rock burst risks in high ground stress tunnels, real-time means that more warning time can be gained for the construction party, which facilitates timely adoption of emergency measures such as temporary support and personnel evacuation, thereby reducing accident losses.

[0066] The filtering and spectrum analysis of the analysis platform 4 on the microseismic information eliminates interference from the data source and extracts effective signals, laying a high-quality foundation for subsequent analysis. There are a large number of interference signals (such as mechanical equipment vibration, blasting aftershocks, personnel activity noise, etc.) in the tunnel construction environment. Through the filtering algorithm (such as wavelet transform, band-pass filtering) of filtering processing, noise other than the microseismic signals related to rock burst can be eliminated, avoiding misjudgment caused by interference signals. Spectrum analysis can distinguish different types of rock mass activities, such as slow crack propagation and violent rupture, by analyzing the frequency, amplitude and other characteristics of microseismic signals, further accurately identifying rock burst precursor signals and reducing the interference of non-rock burst events on risk assessment.

[0067] The analysis platform 4 builds a multi-dimensional rock burst risk assessment system through microseismic source positioning, microseismic event quantity statistics, source moment and energy index calculation. Among them, the microseismic source positioning can accurately determine the spatial position of the microseismic event, providing a direct basis for delineating the initial rock burst range and the final rock burst position, ensuring the accuracy of the risk area lock. The number of microseismic events can reflect the frequency of internal rupture activities of the rock mass. A sudden increase in the number of events in a short period of time usually indicates a decrease in rock mass stability and an increase in rock burst risk. The source moment can reflect the scale of rock mass rupture, such as crack length and displacement, and the energy index is directly related to the release strength of elastic strain energy. The combination of the two can quantitatively assess the potential damage of rock burst, and further judge the rock burst grade, such as slight, moderate and strong, providing data support for formulating differentiated prevention strategies.

[0068] As a preferred embodiment of the present application, the second microseismic sensor 2 is connected with the multi-channel data acquisition instrument 3 through the optical fiber 5.

[0069] Compared with traditional cable transmission, optical fiber transmission has significant anti-interference advantage. There are a large number of strong electromagnetic equipment (such as shield machine, electric welder, ventilator, etc.) in the tunnel construction environment, and the traditional cable is easy to be interfered by electromagnetic signal, resulting in noise, distortion or even loss of microseismic data. While optical fiber transmits data through optical signal, does not produce electromagnetic radiation, and is not affected by external electromagnetic interference, which can ensure that the high-precision microseismic signals (such as weak rock fracture vibration) collected by the second microseismic sensor 2 are transmitted to the data acquisition instrument 3 without distortion, and provide high-quality raw data for accurate analysis of the subsequent analysis platform 4. Moreover, the signal transmission loss of optical fiber is much lower than that of cable, especially in long-distance transmission scenarios, which can effectively avoid signal attenuation caused by too long distance and ensure the monitoring sensitivity of deep or remote microseismic events.

[0070] In an embodiment, the application discloses a tunnel rock burst prevention method, which comprises:

[0071] The final rock burst position is determined by using the tunnel rock burst risk assessment method described above;

[0072] Obtain the microseismic information and the rock mechanics parameters of the final rock burst position area;

[0073] Determine the slotting parameters of the final rock burst position based on the microseismic information and the rock mechanics parameters of the final rock burst position area;

[0074] According to the determined slotting parameters, abrasive water jet is used to cut and release pressure along the tunnel wall, to prevent rock burst.

[0075] The tunnel rock burst prevention method integrates accurate assessment and scientific pressure relief means, forming a systematic rock burst risk control scheme, and its beneficial effects mainly reflect in the following aspects:

[0076] Firstly, the accuracy and targeting of rock burst prevention are realized. The method takes the final rock burst position determined accurately as the core to carry out prevention and control operation, which completely changes the blindness of the traditional wide-net pressure relief measures. With the high-risk area determined by the early risk assessment, combined with the slotting parameters calculated by the microseismic information and rock mechanics parameters, the slotting operation can strictly match the actual stress state and rock mass characteristics of the risk point, ensuring that the pressure relief measures directly hit the risk source. This closed-loop process of accurate positioning, scientific parameters and directional pressure relief avoids invalid operation and resource waste, and significantly improves the pertinence and effectiveness of rock burst prevention.

[0077] Secondly, the risk of rock burst is reduced from the source by scientific pressure relief mechanism. The core logic of the prevention and control method is to provide space for the deformation of surrounding rock through the ring cutting, directly reduce the surface ring stress, and reduce the accumulation of elastic strain energy. This mechanism directly attacks the essence of rock burst, that is, the instantaneous release of high stress and energy. Compared with the traditional anchoring method which only relies on passive defense to resist stress, it can better weaken the material basis of rock burst from the source. At the same time, the design of cutting to make stress transfer to the interior of the rock mass and weaken the surface surrounding rock further optimizes the stress state of the surrounding rock: the stress concentration phenomenon of the surface is alleviated, and the bearing capacity of the deep rock mass is reasonably utilized, forming a double guarantee of pressure relief and stress redistribution, greatly reducing the probability of sudden energy release.

[0078] Furthermore, the use of abrasive water jet cutting technology improves the safety and controllability of pressure relief operations. Compared with the violent disturbance of traditional blasting method and the low efficiency of drilling pressure relief method, abrasive water jet technology has the following advantages: first, the cutting process can accurately control the depth, range and shape, avoiding the disadvantages of excessive fragmentation of surrounding rock or uncontrolled stress release by blasting method, and maintaining the overall stability of the rock mass while effectively relieving pressure; second, the operation process has no strong vibration and impact, which will not cause additional safety hazards to the constructed tunnel structure, and also reduce the risk of inducing other geological disasters; third, the efficient cutting characteristics of abrasive water jet can improve the construction progress and better meet the time requirements of tunnel engineering.

[0079] Finally, a coordinated system of evaluation, parameter design and pressure relief execution is formed, improving the engineering economy. Because the rock burst risk assessment, parameter calculation and pressure relief construction are closely linked, the whole process not only avoids the waste of cost caused by blind prevention and control, such as ineffective drilling and excessive anchoring, but also reduces the time delay, equipment damage and secondary repair cost caused by accidents by reducing the rock burst rate. At the same time, accurate cutting parameter design can optimize resource inputs such as abrasive consumption and operation time on the premise of ensuring pressure relief effect, achieving the balance between maximum prevention and control effect and optimal engineering cost.

[0080] In summary, through the combination of precise positioning, scientific parameters, efficient pressure relief and mechanism optimization, this prevention and control method not only improves the reliability of rock burst prevention and control from a technical point of view, but also takes into account safety, economy and construction efficiency in engineering practice, providing a more adaptive and effective solution for rock burst control of high geostress tunnels.

[0081] It should be noted that, as shown in Figure 8 and Figure 9 , the abrasive water jet is used to cut and relieve pressure along the ring of the tunnel wall, and the cuttings 6 are not connected along the ring of the tunnel wall, but are distributed along the ring of the tunnel wall.

[0082] As a preferred embodiment of the present application, the microseismic source radiation energy, stress and energy density concentration distribution are obtained based on the microseismic information and the rock mechanics parameters of the final rock burst location area, and the cut joint parameters of the final rock burst location are determined according to the microseismic source radiation energy, stress and energy density concentration distribution;

[0083] The calculation formula of the microseismic source radiation energy E P,S is In the formula, ρ is the rock density, v P,S is the velocity of the longitudinal wave or the transverse wave, S is the propagation distance of the microseismic wave, μ corr is the velocity pulse of the radiation direction, t s is the microseismic event duration;

[0084] The calculation formula of the pressure drop Δσ is In the formula, M0 is the microseismic moment, the calculation formula is M0=μAD, μ is the shear modulus, A is the microfracture area, D is the average slip distance of the microfracture, and r is the fracture radius;

[0085] The calculation formula of the energy density concentration distribution E d is V is the fracture volume.

[0086] In the preferred embodiment, the microseismic source radiation energy E P,S (reflecting the total energy released by the rock mass fracture), the pressure drop Δσ (reflecting the stress adjustment amplitude), and the energy density E d (reflecting the energy concentration degree) are accurately calculated by using the formula based on the microseismic monitoring data and the rock mechanics parameters. The abstract rock burst risk is converted into a calculable physical quantity, and the cut joint parameters are upgraded from empirical judgment to formula derivation, which greatly improves the scientific nature of the pressure relief design.

[0087] The core goal of the cut joint is to release the accumulated elastic strain energy of the rock burst in a targeted manner. In the embodiment, the energy and stress analysis is used to realize the accurate matching of the pressure relief parameters and the rock burst energy: if the microseismic source radiation energy E P,S is large, and the energy density E d is high, it indicates that the rock mass in this area has accumulated a large amount of energy and has a large rock burst potential, and a deeper and denser cut joint needs to be designed to ensure sufficient pressure relief. If the pressure drop Δσ shows that the local stress concentration is significant, the stress can be released in a targeted manner by adjusting the direction of the cut joint (such as perpendicular to the maximum principal stress), so as to avoid the secondary concentration of stress. In this way, the problems of insufficient or excessive pressure relief can be effectively reduced, and the prevention and control efficiency is improved.

[0088] As a preferred embodiment of the present application, referring to Figure 9 , the depth of the cut joint 6 is 0.8R-1.2R, and R is the surrounding rock relaxation circle radius calculated based on the Mohr-Coulomb criterion.

[0089] Specifically, the calculation formula of the loose circle radius is In the formula, r0 is the tunnel radius, is the internal friction angle of the rock, c is the cohesion of the rock, and P0 is the initial ground stress.

[0090] The slot 6 depth is set to 0.8R-1.2R, which can ensure that the slot penetrates the confining pressure plastic zone, so that the slot action range covers the surrounding rock loose circle. The surrounding rock loose circle is the area where the surrounding rock stress is adjusted, plastic deformation or failure occurs, and reasonable slotting in this range can effectively release the elastic strain energy accumulated in the loose circle, reduce the probability of rock burst, and also improve the stress distribution of the surrounding rock and enhance the stability of the surrounding rock. It should be noted that in actual engineering, the parameters of the surrounding rock may have certain discreteness, and this interval gives the construction adjustment space, as long as the slot depth is selected within this range according to the accurately calculated R, the pressure relief effect and construction operability can be considered, and different tunnel engineering scenes can be adapted.

[0091] As a preferred embodiment of the present application, the tunnel rock burst prevention method of the present application further comprises: determining the slot position of the tunnel rock burst construction surface according to the microseismic monitoring technology, referring to Figures 8 to 10 As shown in the figure, a plurality of borehole stress sensors 7 are arranged at the slot area 20 of the working surface to monitor the stress distribution of the surrounding rock around the construction surface. Take the field sample for laboratory rock property detection, and finally obtain the sample rock mechanics property parameters of the tunnel construction surface and the surrounding stress size distribution. According to the surrounding rock loose circle theory, the stress is mainly concentrated in the plastic zone of the rock, and unloading the plastic zone can effectively prevent stress concentration to produce rock burst phenomenon. Based on the Mohr-Coulomb criterion, the radius R of the surrounding rock loose circle is calculated, and the slot depth is designed as 0.8R-1.2R to ensure that it penetrates the plastic zone.

[0092] According to the slot position, slot depth and shape of the tunnel, the abrasive water jet equipment is controlled to perform slotting perpendicular to the working surface in the circumferential direction. After the slotting is completed, a displacement monitoring sensor 13 is arranged to observe the pressure relief effect after the slotting.

[0093] The reasonable cut joint shape can achieve better pressure relief effect, and can be divided according to different rock properties and Protodyakonov coefficient: when Protodyakonov coefficient f is greater than or equal to 8, the rock type is brittle rock, the mechanical property is high compressive strength and low toughness, and the rock is prone to burst, the cut joint shape is V-shaped or prismatic joint, the stress concentration at the tip guides the directional expansion of the crack, and the risk of random rupture is reduced; the prismatic bottom flares to release energy. When Protodyakonov coefficient 4 is less than or equal to f and greater than 8, the rock type is ductile rock, the mechanical property is medium strength and strong plastic deformation capacity, the cut joint shape is rectangular joint + trapezoidal flared, a uniform deformation space is provided, the trapezoidal flared reduces the stress concentration at the opening, and the plastic deformation is adapted. When Protodyakonov coefficient f is less than 4, the rock type is bedding and joint development rock, the mechanical property is that the structural plane is more and the strength anisotropy is significant, the cut joint shape is wave-shaped or sawtooth-shaped cut joint, the stress is dispersed by the wave fluctuation, the expansion along the structural plane is avoided, and the sawtooth enhances the friction anchoring effect of the cut joint and the surrounding rock.

[0094] As a preferred embodiment of the present application, further comprising: after the completion of the cut joint, adjusting the cut joint parameters according to the change of the pre- and post-cut joint Rasomson rockburst coefficient in the final rockburst position area. If the post-cut joint Rasomson rockburst coefficient is lower than the initial Rasomson rockburst coefficient, and the post-cut joint Rasomson rockburst coefficient is reduced by 10%, and the cut joint 6 is obviously extruded and closed, it can be explained that the cut joint 6 can obviously relieve pressure in this area. Otherwise, the spacing and number of the cut joint are appropriately adjusted, the tunnel needs to be cut again, the spacing of the cut joint is reduced to 70%-80% of the original design, the number of parallel cut joints is increased by 1-2, the total length of the cut joint is not more than 40% of the length of the relaxation circle, and the stability of the surrounding rock is avoided to be excessively weakened.

[0095] The above examples are only preferred examples for fully illustrating the present application, and the protection scope of the present application is not limited thereto. The equivalent replacement or transformation of the skilled in the art on the basis of the present application is within the protection scope of the present application.

Claims

1. A method of assessing the risk of rockburst in a tunnel, characterized in that, include: Within a predetermined distance behind the tunnel face, multiple first microseismic sensors are installed circumferentially along the tunnel wall. The initial rockburst range is determined based on the microseismic data collected by the first microseismic sensors. Multiple second microseismic sensors are installed circumferentially on the tunnel wall corresponding to the initial rockburst range. The monitoring accuracy of the second microseismic sensors is higher than that of the first microseismic sensors. The final rockburst location is determined based on the microseismic data collected by the second microseismic sensors.

2. The tunnel rockburst risk assessment method according to claim 1, characterized in that: The number of the second microseismic sensors is eight. Four of the second microseismic sensors are installed on the first section of the tunnel corresponding to the initial rockburst range, and the remaining four are installed on the second section of the tunnel corresponding to the initial rockburst range. The distance between the first section and the second section is reasonably determined according to the size of the initial rockburst range.

3. The tunnel rockburst risk assessment method according to claim 1, characterized in that, Installing multiple first microseismic sensors or multiple second microseismic sensors circumferentially along the tunnel wall specifically includes: forming multiple pre-embedded holes radially along the tunnel wall, wherein the depth of the pre-embedded holes is 1.2 to 1.5 times the tunnel radius; The first or second micro-vibration sensor is installed in the pre-embedded hole, and the pre-embedded hole is filled with epoxy resin coupling agent to enhance signal transmission.

4. The tunnel rockburst risk assessment method of claim 1, wherein: The first or second microseismic sensor transmits data to the analysis platform in real time via a multi-channel data acquisition instrument. The analysis platform receives data from the first or second microseismic sensor and performs microseismic analysis, including filtering and spectral analysis of the microseismic information, locating the microseismic source based on the microseismic information, and obtaining the number of microseismic events, focal moment, and energy index, as well as determining the rockburst level and the initial rockburst range or final rockburst location in the tunnel.

5. The tunnel rockburst risk assessment method of claim 4, wherein: The second micro-vibration sensor is connected to a multi-channel data acquisition instrument via optical fiber.

6. A method of preventing rock burst in a tunnel, characterized by, include: The final rockburst location is determined using the tunnel rockburst risk assessment method according to any one of claims 1 to 5; Acquire microseismic information and rock mechanical parameters of the final rockburst location area; The cutting parameters at the final rockburst location are determined based on microseismic information and rock mechanical parameters in the area where the final rockburst occurred. Based on the determined cutting parameters, abrasive water jets are used to cut and release pressure along the circumferential direction of the tunnel wall to prevent rock bursts.

7. The method of rockburst prevention of a tunnel according to claim 6, characterized by: Based on microseismic information and rock mechanical parameters of the final rockburst location area, the distribution of microseismic source radiation energy, stress, and energy density is obtained. Based on the distribution of microseismic source radiation energy, stress, and energy density, the cutting parameters of the final rockburst location are determined. The microseismic source radiates energy E P,S The calculation formula is In the formula, p is the density of rock, v P,S is the velocity of P or S wave, S is the propagation distance of microseismic wave, μ corr is the velocity pulse of radiation direction, t s is the duration of microseismic event; The calculation formula of the pressure drop Δσ is In the formula, M0 is the microseismic moment, the calculation formula of which is M0=μAD, μ is the shear modulus, A is the microfracture surface area, D is the average slip distance of the microfracture, and r is the fracture radius. The energy density concentration distribution case E d The calculation formula is V is the fracture volume.

8. The tunnel rockburst prevention method according to claim 6, characterized in that: The cut depth is 0.8R to 1.2R, where R is the radius of the loosened zone of the surrounding rock calculated based on the Mohr-Coulomb criterion.

9. The tunnel rockburst prevention method according to claim 6, characterized by, Also includes: After the slotting is completed, the slotting parameters are adjusted based on the changes in the Rasmussen rockburst coefficient before and after slotting in the final rockburst location area.

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