Tunnel chain type rockburst risk assessment method based on rock mass structural plane characteristics

Abstract

The invention provides a tunnel chain type rockburst risk assessment method based on rock mass structural plane characteristics, and relates to the technical field of geological exploration. Through the processes of static prediction, dynamic early warning, advanced detection, structural plane parameterization and tendency index, typed identification and directional evaluation of chain rock burst are realized. Structural surface features (position, scale, dip angle and included angle) are taken as a core, a stress control type and a structural surface control type are firstly distinguished, then the occurrence risk of strain-structural surface slippage type rockburst and chain type rockburst is judged, and axial chain type rockburst, radial chain type rockburst and axial-radial chain type rockburst are further identified according to the included angle between a structural surface and a tunnel axis and the dip angle of the structural surface. According to the method, multiple chain type rockburst modes can be identified and evaluated at the same time, the limitation that in the prior art, only single-time rockburst can be evaluated or only one specific type of chain type rockburst is limited is made up, and a scientific basis is provided for forepoling and dynamic construction management.

Description

Technical Field

[0001] This invention relates to the field of geological exploration technology, and in particular to a method for assessing the risk of chain rockbursts in tunnels based on the characteristics of rock mass structural surfaces. Background Technology

[0002] During the excavation of deep-buried tunnels under high ground stress, the phenomenon of multiple rockbursts occurring sequentially along the same area is called chain rockburst. Based on its spatial distribution characteristics, chain rockbursts can be divided into axial chain rockbursts and radial chain rockbursts. Axial chain rockbursts refer to multiple consecutive rockbursts along the tunnel axis, while radial chain rockbursts refer to repeated rockbursts occurring at the same crater location. Compared to single rockbursts, chain rockbursts cause more extensive damage, last longer, and result in greater hazards.

[0003] As my country's transportation infrastructure continues to extend into the southwestern region with its complex terrain and geological conditions, tunnel engineering projects are generally characterized by long routes, great burial depths, and high stress, making chain rockburst hazards increasingly prominent. Existing risk assessments mostly focus on the timing of occurrence (instantaneous rockbursts, time-delayed rockbursts) or the formation mechanism (strain-induced rockbursts, strain-structure slip rockbursts, fracture-induced rockbursts), identifying and issuing early warnings for specific types of single rockbursts. However, systematic assessments of multiple failures at the same location (radial chain rockbursts) or sequential failures at adjacent locations (axial chain rockbursts) remain insufficient.

[0004] Invention patent CN118707590A discloses a method for predicting radial chain rockbursts under the influence of weak strips in TBM tunnels. This method emphasizes that the occurrence conditions of chain rockbursts are affected by the rock mass structure and uses microseismic parameters (number of events, cumulative apparent volume, cumulative apparent stress, etc.) to predict whether the rockburst type is radial chain rockburst. However, this method fails to propose a method for assessing and predicting the risk of chain rockbursts based on the characteristics of rock mass structural surfaces (such as location, size, dip, dip angle, etc.).

[0005] In summary, current technologies lack a chain rockburst assessment system with rock mass structural planes as the core controlling factor. They also fail to clarify the differentiated impacts of various structural plane characteristics on the chain rockburst incubation process and lack further differentiation of complex patterns involving simultaneous axial and radial development in a few cases. Therefore, there is an urgent need to propose an feasible assessment method that reveals the controlling role of structural planes in chain rockbursts. This method has significant theoretical and practical value for improving tunnel construction safety under complex geological conditions. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a tunnel chain rockburst risk assessment method based on the characteristics of rock mass structural surfaces, addressing the shortcomings of the prior art.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] A method for assessing the risk of chain rockburst in tunnels based on the characteristics of rock mass structural surfaces, comprising the following steps:

[0009] Step 1: Conduct static prediction before construction and dynamic early warning during construction to make a preliminary assessment of whether there is a risk of rockburst during the excavation process;

[0010] Step 2: Conduct advance detection of the unexcavated area in front of the tunnel face to identify whether potential rockbursts are controlled by structural planes and classify them as stress-controlled rockbursts or structural plane-controlled rockbursts.

[0011] Step 3: Based on the location and size of the structural surface, rockbursts controlled by the structural surface are classified into strain-structural surface slip rockbursts and chain rockbursts. Strain-structural surface slip rockbursts are single rockbursts occurring along the structural surface, while chain rockbursts are multiple rockbursts occurring along the structural surface. The risk of chain-like development of the structural surface is then determined.

[0012] Step 4: For potential chain rockburst sections, determine the spatial evolution type of chain rockburst based on the dip angle of the structural surface and the angle between the structural surface and the tunnel axis: axial chain rockburst, radial chain rockburst, and axial-radial chain rockburst, to achieve spatial evolution identification;

[0013] Step 5: Using the location, size, type, dip, and inclination angle of the structural surface as independent variables, construct a correlation heatmap for different rockburst types; establish the occurrence tendency index and threshold range of structural surface characteristic parameters for different types of rockbursts, forming occurrence tendency index and risk classification for each type of rockburst, and make judgments on the occurrence risks of strain-type rockbursts, strain-structural surface slip rockbursts, axial chain rockbursts, radial chain rockbursts, and axial-radial chain rockbursts, which are used to guide advanced support and construction organization plans.

[0014] Furthermore, in step one, the pre-construction static prediction is achieved through on-site investigation, in-situ stress testing, and indoor rock mechanics tests, and a variety of empirical criteria are used to conduct a preliminary assessment of rockburst risk;

[0015] The field investigation included determining the lithology, mineral composition, and degree of joint and fracture development of the surrounding rock, and calculating the rock quality index RQD and rock mass integrity coefficient through core drilling. RQD is calculated using the following formula:

[0016] ;

[0017] In the formula, The core segment must be at least 10 cm in length. This refers to the drilling and coring depth.

[0018] Rock mass integrity coefficient Calculation using the P-wave velocity method:

[0019] ;

[0020] In the formula, The longitudinal wave velocity of the rock mass. The longitudinal wave velocity of the intact rock sample;

[0021] The larger the RQD, the The larger the rock mass, the more intact it is, the stronger its energy accumulation capacity, and the higher the risk of rockburst.

[0022] In-situ stress testing is used to measure the magnitude and direction of the three principal stresses and to establish a stress profile along the tunnel, which characterizes the spatial variation of the maximum principal stress σ1, intermediate principal stress σ2, and minimum principal stress σ3. Laboratory rock mechanics testing includes determining the uniaxial compressive strength of the rock. Uniaxial tensile strength Elastic modulus Poisson's ratio ,density ;

[0023] The various empirical criteria include stress intensity ratio. Rock brittleness index B, elastic strain energy index ; The larger the size, the higher the risk of rockburst. The larger the value, the more pronounced the brittleness and the stronger the tendency for rockburst. The larger the value, the stronger the rock's energy storage capacity, and the higher the risk of rockburst; stress intensity ratio Rock brittleness index B, elastic strain energy index Calculate according to the following formulas:

[0024] ; ; ;

[0025] In the formula, This represents the maximum tangential stress at the excavation outline.

[0026] Furthermore, in step one, the dynamic early warning during construction period uses a microseismic monitoring system to continuously collect micro-fracture activity of the surrounding rock at the working face. By analyzing the spatiotemporal distribution of microseismic events, the continuous increase in the density of microseismic events and the rapid increase in the number of events in a short period of time are used as precursor information for rockbursts, thereby achieving real-time dynamic early warning for the area in front of the working face and making accurate judgments.

[0027] Furthermore, in Step 2, geological radar GPR and acoustic wave reflection method TSP are used for advanced detection to identify structural planes. The GPR emits high-frequency electromagnetic waves to the surrounding rock. When the electromagnetic waves encounter an interface with a dielectric constant difference, reflection and refraction occur. Structural planes such as joints, fissures, and faults form strong reflection signals due to the dielectric constant difference, thereby identifying the presence and continuity of the structural planes. The TSP generates low-frequency acoustic waves or ultrasonic waves by arranging acoustic wave emission sources. When the acoustic waves propagate to the structural plane, partial reflection occurs due to changes in the medium density and elastic modulus. The receiver records the reflection signal, and the position and nature of the structural plane are judged based on the arrival time, amplitude, and spectral characteristics of the reflected wave. According to the influence strength of the structural plane, potential rock bursts are divided into: stress-controlled rock bursts and structural plane-controlled rock bursts; when the detected continuous length of the structural plane is greater than the size threshold , and the minimum distance from the structural plane to the excavation contour is less than the position threshold , if this condition is not met, it is judged as a stress-controlled rock burst. If this condition is met, it is judged as a structural plane-controlled rock burst, and Step 3 is entered.

[0028] Furthermore, in Step 3, the influence of the structural plane position on strain-structural plane slip-type rock bursts and chain-type rock bursts is characterized by the minimum distance from the structural plane to the excavation contour; when , the structural plane in the near zone is vulnerable to the influence of excavation unloading, and the probability of multiple failures along the structural plane is high, and the risk of chain-type rock bursts is high, where is the equivalent excavation radius; when 0.5R < d ≤ 1.5R, the structural plane in the middle zone may be partially exposed during a single rock burst process, which is likely to induce strain-structural plane slip-type rock bursts and has a certain possibility of chain-type rock bursts; when , the structural plane in the far zone is difficult to directly induce rock bursts, and the risk of chain-type rock bursts is low;

[0029] The influence of the structural plane size on strain-structural plane slip-type rock bursts and chain-type rock bursts is characterized by the equivalent extension length of the structural plane; for small-scale structural planes with a length less than m, due to poor continuity, it is difficult to effectively control rock bursts, and the risk of chain-type rock bursts is low; for medium-scale structural planes with a length between

[0030] When the structural plane-controlled rock burst satisfies the characteristics of the near zone and large scale, that is and M, it is judged that the current section has a high risk of chain-type rock bursts; when it is in the near zone and medium scale, that is and At m, it is preferably determined to be a strain-structure plane slip rockburst type with the possibility of chain rockburst; when it is near the area and small in scale, i.e. and At m, the risk of chain rockburst is low.

[0031] Furthermore, in step four, the orientation of the structural planes includes the dip direction. With tilt angle Set the inclination and tilt angle thresholds as follows: and ,in accordance with and Chain type determination is performed based on the combination relationship:

[0032] when When the risk of axial chain rockburst increases, it is determined that the risk is high. Over time, the chain effect gradually weakens;

[0033] when When the risk of radial chain rockburst increases, it is determined that the risk is increased; when At this time, it is not easy to form a continuous sliding effect, and it manifests as static brittle failure, which weakens the trend of rockburst developing radially;

[0034] when and At that time, it was determined that the risk of axial-radial chain rockburst was increased, that is, axial chain rockburst and radial chain rockburst developed simultaneously;

[0035] when and At this time, rockbursts do not tend to develop along the axial or radial direction, and the risk of chain rockbursts is relatively low.

[0036] Furthermore, step five specifically includes sample construction, correlation analysis, propensity score calculation, and risk grading output;

[0037] The sample construction uses a single-cycle advance unit as the sample and records structural surface feature parameters, including the minimum distance from the structural surface to the excavation profile. Equivalent extension length of structural surface , Structural plane type, Structural plane tendency Structural surface inclination angle And record the corresponding rockburst type, including stress-controlled type / structure plane controlled type, as well as strain type, strain-structure plane slip type, axial chain type, radial chain type, and axial-radial chain type;

[0038] The correlation analysis calculates the correlation coefficient between structural surface feature parameters and the occurrence frequency or probability of each type of rockburst, forms a correlation matrix of structural surface features and rockburst type and draws a heat map to identify the set of sensitive parameters.

[0039] The aforementioned tendency index calculation establishes a tendency score for each type of rockburst. :

[0040] ;

[0041] in, For structural surface characteristic parameters ( ); This is a normalization function that outputs values ​​between 0 and 1. The weighting coefficients are determined based on the correlation analysis results and the calibration of engineering samples.

[0042] Will It is divided into four levels: low, medium, high, and very high, with the ranges set as follows:

[0043] Low: ;

[0044] middle: ;

[0045] high: ;

[0046] Extremely high: ;

[0047] The risk classification output includes: high-risk mileage, chain rockburst type, and construction organization recommendations.

[0048] The beneficial effects of adopting the above technical solution are as follows: The tunnel chain rockburst risk assessment method based on rock mass structural surface characteristics provided by this invention achieves typological identification and directional assessment of chain rockbursts through a process of static prediction + dynamic early warning + advanced detection + structural surface parameterization + tendency indicators. Based on structural surface characteristics (location...) ,scale ,inclination Angle With this method as its core, the invention first distinguishes between stress-controlled and structural plane-controlled rockbursts, then determines the risk of strain-structural plane slip rockbursts and chain rockbursts, and further identifies axial, radial, and axial-radial chain rockbursts based on the angle between the structural plane and the tunnel axis and the inclination angle of the structural plane. This invention can simultaneously identify and evaluate multiple chain rockburst modes, overcoming the limitations of existing technologies that can only evaluate single rockbursts or are limited to a specific type of chain rockburst, thus providing a scientific basis for developing advanced support and dynamic construction management. Attached Figure Description

[0049] Figure 1 A flowchart of a tunnel chain rockburst risk assessment method based on rock mass structural surface characteristics provided in an embodiment of the present invention;

[0050] Figure 2Structural surface position parameters provided for embodiments of the present invention d A schematic diagram illustrating the impact of chain rockburst risk;

[0051] Figure 3 A schematic diagram illustrating the impact of structural surface dimension parameter L on the risk of chain rockburst, provided in an embodiment of the present invention.

[0052] Figure 4 The included angle between the structural surface and the tunnel axis provided in the embodiments of the present invention Schematic diagram illustrating the impact on chain rockburst risk;

[0053] Figure 5 The structural surface tilt angle provided in the embodiments of the present invention Schematic diagram illustrating the impact on chain rockburst risk;

[0054] Figure 6 The structural surface tilt angle provided in the embodiments of the present invention and the included angle of the tunnel axis Schematic diagram illustrating the influence of combination relationships on the manifestation of chain rockbursts;

[0055] Figure 7 The thermal map showing the correlation between structural surface feature parameters and different types of rockbursts provided in the embodiments of the present invention;

[0056] Figure 8 An actual diagram of an axial chain rockburst occurring, provided for an embodiment of the present invention;

[0057] Figure 9 This is a real-world diagram illustrating a radial chain rockburst, provided as an embodiment of the present invention. Detailed Implementation

[0058] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that the following embodiments are used to explain the present invention, and not to limit the scope of protection of the present invention.

[0059] like Figure 1 As shown, the method in this embodiment includes the following steps.

[0060] Step 1: Identify the risk of rockburst ahead of the tunnel face using static prediction (empirical criteria) and dynamic early warning (microseismic monitoring).

[0061] In static prediction, lithology and joint / fracture development are obtained through field investigation, and RQD is calculated. :

[0062] ;

[0063] ;

[0064] in, The core segment must be at least 10 cm in length. This refers to the drilling and coring depth. The longitudinal wave velocity of the rock mass. The longitudinal wave velocity of the intact rock sample.

[0065] The maximum principal stress σ1, intermediate principal stress σ2, minimum principal stress σ3, and their directional distribution were obtained through in-situ stress testing. Uniaxial compressive strength was determined by indoor tests. Uniaxial tensile strength Elastic modulus Poisson's ratio ,density Calculate the stress intensity ratio Rock brittleness index Elasticity index ,in, This represents the maximum tangential stress at the excavation outline. A higher stress-intensity ratio indicates a higher risk of rockburst. A higher rock brittleness index ratio indicates more significant rock brittleness and a stronger tendency for rockburst. A higher elastic strain energy index indicates a stronger ability of the rock to store elastic energy, and a higher risk of rockburst.

[0066] The dynamic early warning is achieved through a microseismic monitoring system, which collects micro-fracture events in the surrounding rock ahead of the tunnel face and analyzes the spatiotemporal distribution and clustering characteristics of these events. When the density of microseismic events continues to increase and the number of events grows rapidly in a short period, it serves as a precursor to rockburst, enabling real-time, dynamic risk tracking and early warning ahead of the tunnel face, and allowing for accurate judgment.

[0067] Step 2: Use advanced forecasting technologies such as ground-penetrating radar (GPR) and acoustic reflection method (TSP) to identify the structural surface ahead and determine whether the potential rockburst risk zone is controlled by the structural surface.

[0068] The ground-penetrating radar emits high-frequency electromagnetic waves into the surrounding rock. When these waves encounter geological interfaces with different dielectric constants, reflection and refraction occur. Joints, fissures, faults, and other structural surfaces in the surrounding rock generate strong reflection signals due to differences in dielectric constant, thus allowing the identification of these structural surfaces. Alternatively, a sound wave reflection method can be used, deploying a sound wave source to generate low-frequency or ultrasonic waves. When these sound waves propagate to structural surfaces (such as joints, fissures, and faults) in the surrounding rock, partial reflection occurs due to changes in the medium's density and elastic modulus. The receiver records the reflected signals. When a continuous length exceeding a size threshold is detected... (In this embodiment) The structural plane (m), or the minimum distance from the structural plane to the excavation profile. Less than the position threshold (In this embodiment) Values If the structural plane significantly overlaps with the area where microseismic events are concentrated, it is determined to be a structural plane-controlled rockburst and proceeds to step three; otherwise, it is determined to be a stress-controlled rockburst and continues to implement early warning and control according to step one.

[0069] Step 3: Based on the structural plane position parameters With dimensional parameters Structural plane-controlled rockbursts are classified into strain-structural plane slip rockbursts, which are single rockbursts occurring along the geological structure, and chain rockbursts, which are multiple rockbursts occurring along the geological structure.

[0070] like Figure 2 As shown, the location of the structural surface is defined by the minimum distance from the structural surface to the excavation profile. Characterization, divided into near region ( ), Central District ( ) and distant area ( Near-surface structural planes are more prone to forming continuous failure paths along the structural plane under unloading disturbances, resulting in a high risk of chain-like failures. The location of the structural plane affects strain-structural plane slip-type rockbursts and chain-like rockbursts because when the structural plane is near the excavation profile, continuous failure along the structural plane is more likely to occur. Structural planes in the middle range of the excavation profile are generally locally exposed during strain-structural plane slip-type rockbursts. However, structural planes in the far range of the excavation profile are unlikely to directly cause rockbursts during excavation.

[0071] like Figure 3 As shown, the structural dimensions are in terms of the extended length. Characterization is divided into small-scale ( m), mesoscale ( m) and large scale ( Small-scale structural surfaces, due to their extremely poor continuity, are difficult to effectively control rockburst formation. Medium-scale structural surfaces can induce rockbursts, but due to their generally low ductility, they are unlikely to trigger a chain reaction. Large-scale structural surfaces have strong extension, reaching tens of meters, and pose a high risk of chain rockbursts. When a structural surface meets the characteristics of a near-field and large-scale area, it is identified as a potential chain rockburst zone and proceeds to step four.

[0072] Step 4: For potential chain rockburst zones, based on the dip angle of the structural plane... With structural tendency Determine whether the rockburst propagates radially, axially, or both radially and axially. Dip angle. The angle between the orientation of the structural surface and the tunnel axis is defined by the angle between the two surfaces, with a range of values ​​of [value missing]. .

[0073] like Figure 4 As shown, when (In this embodiment) When this occurs, the axial chain risk increases significantly; for example... Figure 5As shown, when (In this embodiment) When this occurs, the radial chain risk increases. For example... Figure 6 As shown, based on and Determining the chain type of combination relationship:

[0074] Axial chain rockburst;

[0075] Radial chain rockburst;

[0076] and : Axial-radial chain rockburst;

[0077] and The risk of chain rockburst is extremely low. Proceed to step five for assessment.

[0078] Axial chain rockbursts exhibit a strong dependence on the dip of the structural plane, while radial chain rockbursts are greatly influenced by the spatial distribution of the structural plane dip angle. Based on the distribution of the structural plane's attitude intervals, a dynamic judgment is made regarding the occurrence tendency of different types of rockbursts. When the angle between the structural plane and the tunnel axis is less than 10°, the risk of axial chain rockbursts increases significantly. Conversely, when the dip angle of the structural plane is greater than 80°, the risk of radial chain rockbursts increases. When a steeply dipping structural plane with a small angle to the tunnel axis is present (…),… and Chain rockbursts are very likely to exhibit a trend of simultaneous axial and radial development.

[0079] Step 5: Using the location, scale, type, dip, and dip angle of the structural surface as independent variables, construct a correlation heatmap for different rockburst types, and establish occurrence tendency indicators and risk classifications.

[0080] like Figure 7 The correlation coefficients between structural surface characteristic parameters and the frequency / probability of different rockburst types are calculated, forming a correlation matrix and heatmap to determine the set of sensitive parameters and their weights. A tendency score is established for each type of rockburst.

[0081] ;

[0082] in, For structural surface characteristic parameters ( ); This is a normalization function that outputs values ​​between 0 and 1. The weighting coefficients are determined based on the correlation analysis results and the calibration of the engineering samples.

[0083] Will It is divided into four levels: low, medium, high, and very high (thresholds are set to 0.25, 0.50, and 0.75, respectively), and the ranges are set as follows:

[0084] Low: ;

[0085] middle: ;

[0086] high: ;

[0087] Extremely high: .

[0088] Output high-risk mileage sections, chain rockburst types (axial / radial / axial-radial), and construction organization suggestions.

[0089] like Figure 8 The image shows the actual situation of an axial chain rockburst, characterized by a series of craters appearing in adjacent sections along the tunnel axis; as shown... Figure 9 As shown, this is a real-world example of radial chain rockburst, characterized by repeated damage at the same crater location, verifying the applicability of the type determination in step four.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope defined by the present invention.

Claims

1. A tunnel chain rock burst risk assessment method based on rock mass structure surface characteristics, characterized by: The specific steps include: Step one: static prediction before construction and dynamic early warning during construction to preliminarily identify whether there is rock burst risk in the excavation process; Step two: advance detection of the unexcavated area in front of the working face to identify whether the potential rock burst is controlled by the structure surface and distinguish between stress-controlled rock burst and structure surface-controlled rock burst; Step three: according to the position and size of the structure surface, the structure surface-controlled rock burst is divided into strain-structure surface slip rock burst and chain rock burst; wherein, the strain-structure surface slip rock burst is single rock burst along the structure surface, and the chain rock burst is multiple rock bursts along the structure surface, and it is determined whether the structure surface has the risk of chain development; Step four: for the potential chain rock burst section, based on the structure surface inclination and the angle between the structure surface and the tunnel axis, the spatial evolution type of the chain rock burst is determined: axial chain rock burst, radial chain rock burst and axial-radial chain rock burst, to realize spatial evolution identification; Step five: taking the position, size, type, tendency and inclination of the structure surface as independent variables, a correlation heat map of different rock burst types is constructed; the characteristic parameters of the structure surface are used to establish the tendency index and threshold interval of different types of rock burst, to form the occurrence tendency index and risk classification of each type of rock burst, to judge the occurrence risk of strain rock burst, strain-structure surface slip rock burst, axial chain rock burst, radial chain rock burst and axial-radial chain rock burst, to guide the advance support and construction organization plan.

2. The tunnel chain rockburst risk assessment method based on rock mass structural plane characteristics according to claim 1, characterized in that: In step one, the static prediction before construction is realized through field investigation, in-situ stress test and indoor rock mechanics test, and a variety of empirical criteria are used to preliminarily evaluate the rock burst risk; The field investigation includes finding out the surrounding rock lithology, mineral composition, joint fissure development degree, and calculating rock quality index RQD and rock mass integrity coefficient through drilling core taking ; wherein, the RQD is calculated according to the following formula: ； In the formula, is the length of a core section not less than 10 cm, is the length of the drilling core footage; Rock mass integrity factor Using longitudinal wave velocity method: ； wherein Vp is the longitudinal wave velocity of the rock mass, Vp is the longitudinal wave velocity of the intact rock sample; The greater the RQD is, the more complete the rock mass is, the stronger the energy accumulation ability is, and the higher the rock burst risk is; In-situ stress test is used to measure the magnitude and direction of three principal stresses, to establish the stress profile along the tunnel, to characterize the spatial variation of the maximum principal stress σ1, the intermediate principal stress σ2 and the minimum principal stress σ3 , uniaxial compressive strength , uniaxial tensile strength , elastic modulus , Poisson's ratio ; The plurality of empirical criteria include stress intensity ratio , rock brittleness index B, elastic strain energy index ; The greater the stress intensity ratio, the higher the rockburst risk; The greater the rock brittleness index, the more significant the brittleness, and the stronger the rockburst tendency; The greater the elastic strain energy index, the stronger the rock energy storage capacity, and the higher the rockburst risk; stress intensity ratio , rock brittleness index B, elastic strain energy index are respectively calculated according to the following formula: ； ； ； wherein is the maximum tangential stress at the excavation profile.

3. The tunnel chain rockburst risk assessment method based on rock mass structural plane characteristics according to claim 2, characterized in that: In step one, the dynamic early warning during construction is realized through the microseismic monitoring system, which continuously collects the microfracture activity of the surrounding rock of the working face, and through the analysis of the spatial and temporal distribution of microseismic events, the continuous rise of microseismic event density and the rapid growth of event number in a short period of time are regarded as the precursor information of rock burst, to realize the real-time dynamic early warning in front of the working face and make accurate judgment.

4. The tunnel chain rockburst risk assessment method based on rock mass structural plane characteristics according to claim 3, characterized in that: The step two, the advanced detection adopts the geological radar GPR and the acoustic reflection method TSP to identify the structural plane; the GPR emits high-frequency electromagnetic wave to surrounding rock, and electromagnetic wave meets the interface of dielectric constant difference and produces reflection and refraction; joint, fracture, fault these structural planes form strong reflection signal due to the dielectric constant difference, so as to identify the existence and continuity of the structural plane; the TSP generates low-frequency acoustic wave or ultrasonic wave by arranging acoustic wave emission source, the acoustic wave propagates to the structural plane and partially reflects due to the change of medium density and elastic modulus, the receiver records the reflection signal, and the position and nature of the structural plane are judged by the reflection wave arrival time, amplitude and spectrum characteristics; according to the influence strength of the structural plane, the potential rock burst is divided into stress-controlled rock burst and structural plane-controlled rock burst; the continuous length of the detected structural plane is greater than the size threshold , and the minimum distance from the structural plane to the excavation contour is less than the position threshold , when the condition is not met, it is determined as stress-controlled rock burst, if the condition is met, it is determined as structural plane-controlled rock burst, and enters step three.

5. The tunnel chain rockburst risk assessment method based on rock mass structural plane characteristics according to claim 4, characterized in that: In step three, the influence of the structural plane position on strain-structural plane slip type rockburst and chain rockburst is characterized by the minimum distance from the structural plane to the excavation contour When , the structural plane in the near zone is susceptible to excavation unloading, and the probability of multiple failures along the structural plane is high, and the risk of chain rockburst is high, wherein is the equivalent radius of excavation; when 0.5R , the structural plane in the far zone is difficult to directly induce rockburst, and the risk of chain rockburst is low; The influence of the structural plane size on strain-structural plane slip type rockburst and chain rockburst is characterized by the equivalent extension length of the structural plane characterization; for Small scale structural plane of m, due to poor continuity, it is difficult to effectively control rockburst, and the risk of chain rockburst is low; for Medium scale structural plane of m, inducing local single failure along the structural plane, the risk of strain-structural plane slip type rockburst is high; for Large scale structural plane of m, due to strong extension, it is easy to form multiple failures along the structural plane, and the risk of chain rockburst is high; When the structure plane control rock burst meets the characteristics of near zone and large scale, i.e. and m, it is determined that the current section has a high risk of chain rock burst; when it is near zone and medium scale, i.e. and m, it is preferably determined as strain-structure plane slip rock burst type and has the possibility of chain rock burst; when it is near zone and small scale, i.e. and m, the risk of chain rock burst is low.

6. The tunnel chain rockburst risk assessment method based on rock mass structure plane characteristics according to claim 5, characterized in that: In the step four, the structural plane occurrence includes dip direction and dip angle ; The inclination tendency and inclination angle threshold values are set respectively as and , the chain type is determined according to the combination relationship of and . When the axial chain rockburst risk is elevated; when the chain effect is gradually weakened; When , it is determined that the radial chain rockburst risk is increased; when , the continuous sliding effect is not easy to form, showing static brittle failure, and weakening the trend of radial development of rockburst. When and the axial-radial chain rockburst risk is determined to be elevated, i.e., the axial chain rockburst and the radial chain rockburst develop simultaneously; When and , rock burst does not have the tendency to develop in axial or radial direction, and the risk of chain rock burst is low.

7. The tunnel chain rockburst risk assessment method based on rock mass structural plane characteristics according to claim 6, characterized in that: Step five specifically includes sample construction, correlation analysis, tendency index calculation and risk classification output; The sample construction takes a single-cycle footage unit as a sample, records structural plane characteristic parameters, including the minimum distance from the structural plane to the excavation profile , the equivalent extension length of the structural plane , the structural plane type and the structural plane inclination , the structural plane dip angle , and records the corresponding rock burst type, including stress-controlled / structural plane-controlled, and strain type, strain-structural plane slip type, axial chain type, radial chain type, axial-radial chain type; The correlation analysis calculates the correlation coefficient between the characteristic parameters of the structure surface and the occurrence frequency or probability of each type of rock burst, forms the correlation matrix of structure surface characteristics-rock burst type and draws a heat map, which is used to identify the sensitive parameter set; The said index of proneness is calculated, for each rockburst-prone class, a proneness score : ； wherein, is a structural plane characteristic parameter, ; is a normalization function, outputting a value between 0 and 1; is a weight coefficient, determined according to correlation analysis results and engineering sample calibration; Will be divided into low, medium, high, and very high four levels, interval settings as follows: Low: ; middle: ; High: ; Extremely high: ; The risk classification output includes high-risk mileage, chain rock burst type and construction organization suggestion.

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