Shallow-buried soft rock tunnel sensitive section grading blasting construction method

Abstract

The invention discloses a graded blasting construction method for a shallow-buried soft rock tunnel sensitive section. The method comprises the steps that measuring points are arranged in a tunnel chamber, a ground surface non-cavity section and a cavity section, and blasting vibration data are obtained; peak vibration velocity prediction models are established in a partitioned mode, an attenuation model is adopted in a chamber, a correction term is introduced into a non-cavity section of the earth surface to correct the attenuation model, and a multivariable model is established for the cavity section through dimensional analysis by integrating the horizontal distance, the elevation difference, the explosive quantity, the rock mass density and the tensile strength; determining a ground surface vibration velocity safety threshold, and quantifying a cavity vibration velocity amplification coefficient and an influence range thereof; based on the peak vibration velocity probability distribution and a preset safety level, establishing a safe dose prediction model and a safe range model; and dividing control areas according to the model, and implementing graded construction. According to the method, the vibration propagation law can be accurately described, the cavity amplification effect can be quantified, dynamic prediction of the blasting safety explosive quantity and range is achieved, and disturbance of blasting vibration to surrounding rock is effectively controlled through hierarchical management and control.

Description

Technical Field

[0001] This invention relates to the field of blasting technology, and in particular to a graded blasting construction method for sensitive sections of shallow-buried soft rock tunnels. Background Technology

[0002] Shallow-buried soft rock tunnels, due to the low strength and poor self-stability of the surrounding rock, are prone to rock fissure propagation caused by blasting vibrations generated during drill-and-blast construction. Furthermore, the voids created during tunnel excavation amplify blasting vibrations (void effect), further exacerbating the risk of rock instability. Especially when traversing sensitive areas such as nature reserves and gullies, blasting vibrations not only threaten construction safety but may also damage the surrounding ecological environment.

[0003] Existing blasting control methods have the following shortcomings: First, they do not fully consider the nonlinear effects of cavitation, resulting in low vibration prediction accuracy and difficulty in adapting to complex geological conditions; second, the calculation of safe charge quantity does not incorporate probability and statistics theory, making it impossible to quantify the risks brought about by the randomness of vibration; third, construction management lacks a tiered strategy, making it difficult to balance safety and construction efficiency in sensitive areas. Therefore, there is an urgent need for a tiered blasting construction method that is universally applicable, accurate, and operable. Summary of the Invention

[0004] This invention provides a graded blasting construction method for sensitive sections of shallow-buried soft rock tunnels. Its purpose is to solve the problem of surrounding rock instability caused by amplified blasting vibration in the cavity area of ​​shallow-buried soft rock tunnels through the technical route of "segmented modeling - cavity quantification - probability control - graded management", thereby improving the safety and efficiency of blasting construction.

[0005] To achieve the above objectives, embodiments of the present invention provide a method for graded blasting construction in sensitive sections of shallow-buried soft rock tunnels, including:

[0006] S100. Measuring points were set up in the tunnel chamber, the non-cavitary section of the ground surface, and the cavitary section of the ground surface, and the peak vibration velocity and parameter waveforms of the measuring points in different areas were obtained.

[0007] S200. Segment Construction The model includes:

[0008] Using the Sadovsky model as the basic model and the horizontal proportional distance as the core variable, an attenuation model for tunnel chambers is obtained. ;

[0009] Using the attenuation model The elevation difference between the measuring point and the explosion source is introduced as a basic model. As a correction term, a coupled attenuation model for the non-cavitary segment of the surface is obtained. ;

[0010] Based on dimensional analysis, the horizontal distance between the measuring point and the blast source was selected in the surface cavity section. Elevation difference between measuring point and blast source Maximum single-stage drug dosage Rock mass density and the tensile strength of the rock mass Construct a multivariate prediction model for surface cavity segments ;

[0011] S300. Obtain the peak vibration safety threshold of the surface in surface cavity sections with different lithologies. ;

[0012] S400. Vibration velocity amplification factor The amplification effect of voids on vibration is quantified, and the vibration velocity amplification factor is fitted. The relationship between the vibration velocity amplification factor and the horizontal distance D determines the vibration velocity amplification factor. The peak position and critical influence range;

[0013] S500. Construct a security control model, including:

[0014] Based on the probability density function of peak velocity combined with a preset safety level and maximum single-stage charge The functional relationship is used as a model for predicting safe drug dosage;

[0015] Based on the obtained maximum single-segment charge and preset security level Construct the horizontal distance between a measuring point within a surface cavity and the blast source. and the elevation difference between the measuring point and the explosion source The functional relationship between them serves as a safety range model;

[0016] S600. Combining the safe dosage prediction model and the safe range model, the construction area is divided into different control zones, and different construction methods are selected in different control zones.

[0017] Preferably, a plurality of first three-dimensional velocity sensors are installed on the inner wall of the tunnel chamber. The first three-dimensional velocity sensors are arranged in the tunnel chamber according to a first density. The first three-dimensional velocity sensors installed in the sensitive area of ​​the tunnel chamber are arranged according to a second density, which is greater than the first density.

[0018] A second three-dimensional velocity sensor is installed on the surface cavity section above the tunnel chamber, and several second three-dimensional velocity sensors are arranged according to the first density.

[0019] Several third-dimensional velocity sensors are arranged on the non-cavitary section of the ground surface. The several third-dimensional velocity sensors are set according to the first density. Several pairs of second-dimensional velocity sensors and third-dimensional velocity sensors are symmetrically arranged about the explosion source.

[0020] The first three-dimensional velocity sensor, the second three-dimensional velocity sensor, and the third three-dimensional velocity sensor are rigidly fixed to the detection surface of the measuring point.

[0021] Preferably, in obtaining the attenuation model of the tunnel chamber When using horizontal proportional distance Alternate spatial proportion distance Obtain the attenuation model :

[0022]

[0023]

[0024]

[0025] in, For site coefficient, The decay exponent, The horizontal distance from the explosion source. Maximum single-stage charge;

[0026] Through the attenuation model Introducing the elevation difference between the measuring point and the blast source As a correction term, the coupling attenuation model is obtained. Coupled attenuation model of:

[0027]

[0028] in, Elevation difference influence coefficient;

[0029] Multivariate prediction model for surface cavity segments for:

[0030] .

[0031] Preferably, step S300 includes the following steps:

[0032] Obtain the rock mass density of the corresponding rock mass and the tensile strength of the rock mass The peak velocity safety threshold is derived using stress wave theory. :

[0033]

[0034] in, This refers to the longitudinal wave velocity.

[0035] Preferably, in step S400, the vibration velocity amplification factor λ quantifies the amplification effect of the void on the vibration, satisfying:

[0036]

[0037] The measured peak vibration velocity in the surface cavity area is the peak vibration velocity obtained by the second three-dimensional velocity sensor, and the measured peak vibration velocity in the surface non-cavity area is the peak vibration velocity obtained by the second three-dimensional velocity sensor.

[0038] The relationship between several magnification factors λ and their corresponding horizontal distances D is fitted using the Lorentz function:

[0039]

[0040] in, For peak amplitude, Central position This is the half-width parameter, used to describe the width of the peak. λ represents the background offset, used to indicate the baseline value or background level of the magnification factor λ when the magnification factor is far from the center position.

[0041] Preferably, in step S500, the peak velocity is assumed to follow a log-normal distribution, and the peak velocity probability density function is obtained:

[0042]

[0043] in, It is the value of the peak velocity of the random variable. It is the mean of the normal distribution corresponding to the log-normal distribution; It is the standard deviation of the normal distribution corresponding to the log-normal distribution.

[0044] Preferably, a preset safety level is used. The following condition must be met: the probability that the peak velocity is less than the peak velocity safety threshold must be greater than the preset safety level.

[0045] Safe dosage satisfy:

[0046]

[0047] in, To comprehensively consider the functional relationship between horizontal distance, elevation difference between measuring point and blast source, and safety level, According to the preset security level By consulting the Z table, This is the safe threshold for blasting vibration velocity.

[0048] Preferably, the safety range model satisfies:

[0049]

[0050] in, , , The functional relationship is to comprehensively consider the elevation difference between the measuring point and the blast source, the amount of explosive charge, and the safety level.

[0051] Preferably, in S600, n safety levels are set, where n≥2, to determine the safe dosage. Using the vertical axis as the ordinate and the safe distance output by the safety range model corresponding to each safety level as the horizontal axis, n safety curves are formed to divide the construction area into different control zones.

[0052] The above-described solution of the present invention has the following beneficial effects:

[0053] This invention accurately describes the propagation law of blasting vibration through a segmented attenuation model, quantifying the influence range and intensity of the void effect; a safety control model established by combining probability and statistics theory enables dynamic prediction of safe charge and safe range; and a graded control strategy adapts to the construction needs of areas with different levels of sensitivity, effectively controlling the disturbance of blasting vibration to the surrounding rock.

[0054] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0055] Figure 1 is a schematic diagram of the tunnel internal and external measuring point layout scheme of the present invention, wherein:

[0056] Figure 1a This is the main view;

[0057] Figure 1b It is a top view;

[0058] Figure 2 This is a Lorentz model fitting curve of the vibration velocity amplification factor;

[0059] Figure 3 This is a diagram illustrating the safe range;

[0060] Figure 4 It is a tiered control area division. Detailed Implementation

[0061] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0062] exist Figure 1a and Figure 1b In the diagram, the boxes represent the installation locations of the three-dimensional velocity sensors.

[0063] As shown in Figure 1- Figure 4As shown, an embodiment of the present invention provides a graded blasting construction method for shallow-buried soft rock tunnels in sensitive sections, comprising the following steps:

[0064] S100. Measuring points were set up in the tunnel chamber, the non-cavitary section of the ground surface, and the cavitary section of the ground surface, and the peak vibration velocity and parameter waveforms of the measuring points in different areas were obtained.

[0065] Specifically, measuring points are deployed in tunnel chambers, surface cavities, and non-cavity surface sections to meet the principle of "full regional coverage and denser deployment in sensitive areas":

[0066] Several first three-dimensional velocity sensors are installed on the inner wall of the tunnel chamber. The first three-dimensional velocity sensors are arranged in the tunnel chamber according to a first density. The first three-dimensional velocity sensors installed in the sensitive area of ​​the tunnel chamber are arranged according to a second density, which is greater than the first density.

[0067] The first three-dimensional velocity sensor is installed along the length of the tunnel, at the top and sides of the tunnel.

[0068] A second three-dimensional velocity sensor is installed on the surface cavity section above the tunnel chamber, and several second three-dimensional velocity sensors are arranged according to the first density.

[0069] Several third-dimensional velocity sensors are arranged on the non-cavitary section of the ground surface. The third-dimensional velocity sensors are set according to the first density. The second-dimensional sensors and the third-dimensional sensors are arranged symmetrically in pairs about the blast source along the length of the tunnel. Each pair of second-dimensional sensors and third-dimensional sensors respectively acquires blasting vibration data of measuring points at the same distance from the blast source.

[0070] Each three-dimensional velocity sensor synchronously collects blasting vibration data in the X (axial), Y (radial), and Z (gravity) directions to obtain peak particle velocity (PPV) and waveform parameters in different regions.

[0071] The first three-dimensional velocity sensor, the second three-dimensional velocity sensor, and the third three-dimensional velocity sensor are rigidly fixed to the detection surface of the measuring point.

[0072] Before fixing the sensors, each three-dimensional velocity sensor is leveled using a spirit level and then filled and fixed with plaster powder to ensure that each three-dimensional velocity sensor is in close contact with the detection surface and to avoid data distortion.

[0073] S200. Segment Construction The model includes:

[0074] Using the Sadovsky model as the basic model and the horizontal proportional distance as the core variable, an attenuation model for tunnel chambers is obtained. ;

[0075] Tunnel Chamber Attenuation Model Introducing the elevation difference between the measuring point and the blast source As a correction term, a coupled attenuation model for the non-cavitary segment of the surface is obtained. ;

[0076] Based on dimensional analysis, the horizontal distance between the measuring point and the blast source was selected in the surface cavity section. Elevation difference between measuring point and blast source Maximum single-stage drug dosage Rock mass density and the tensile strength of the rock mass Construct a multivariate prediction model for surface cavity segments ;

[0077] Specifically, based on the Sadovsky model Horizontal proportional distance Alternate spatial proportion distance Thus, the attenuation model is obtained. :

[0078]

[0079]

[0080]

[0081] in, For site coefficient, The decay exponent, The horizontal distance from the explosion source. Maximum single-stage charge;

[0082] Through the attenuation model Obtain the coupling attenuation model Coupled attenuation model :

[0083]

[0084] in, For site coefficient, The decay exponent, The elevation difference influence coefficient. The horizontal distance from the explosion source. Maximum single-stage charge, The elevation difference between the measuring point and the blast source;

[0085] Based on dimensional analysis, the horizontal distance of the measuring point from the blast source was selected for the surface cavity section. Elevation difference between measuring point and blast source Maximum single-stage drug dosage Rock mass density and the tensile strength of the rock mass Construct a multivariate prediction model for surface cavity segments ;

[0086]

[0087] in, The elevation difference between the measuring point and the blast source, For site coefficient, The decay exponent, The elevation difference influence coefficient. The horizontal distance from the explosion source. Maximum single-stage charge, this multivariate prediction model It covers the maximum single-stage charge, horizontal distance from the blast source, and cavity morphology, and is adapted to the nonlinear propagation characteristics of vibration in surface cavity sections.

[0088] S300. Obtain the peak vibration safety threshold of the surface in surface cavity sections with different lithologies. ;

[0089] Specifically, rock samples are obtained from the area to be blasted ahead of the tunnel, and the rock mass density is determined through rock mechanics experiments. and the tensile strength of the rock mass Derivation of peak velocity safety threshold using stress wave theory :

[0090]

[0091] in, For longitudinal wave velocity;

[0092] S400. Vibration velocity amplification factor The amplification effect of voids on vibration is quantified, and the vibration velocity amplification factor is fitted. The relationship between the vibration velocity amplification factor and the horizontal distance D determines the vibration velocity amplification factor. The peak position and critical influence range;

[0093] The vibration velocity amplification factor λ quantizes the amplification effect of the void on vibration, which satisfies the following:

[0094] ;

[0095] Among them, the measured peak vibration velocity in the surface cavity area and the measured peak vibration velocity in the surface non-cavity area are the peak vibration velocities obtained by the second three-dimensional velocity sensor and the third three-dimensional velocity sensor with the same horizontal distance D from the explosion source, respectively.

[0096] The relationship between several magnification factors λ and the corresponding horizontal distance D is fitted using the Lorentz function:

[0097]

[0098] in, For peak amplitude, Central position This is the half-width parameter, used to describe the width of the peak. Background offset, used to represent the baseline value or background level of the magnification factor λ when far from the center position. The horizontal distance from the blast source;

[0099] S500. Construct a safety control model. This model, centered on "quantifying vibration randomness + dynamically adapting to engineering conditions," combines probability and statistics theory with on-site measured data to achieve precise calculations of safe dosage and safety range. This includes:

[0100] Based on the probability density function of peak velocity combined with a preset safety level and maximum single-stage charge The functional relationship is used as a model for predicting safe drug dosage;

[0101] Assuming the peak velocity follows a log-normal distribution, the peak velocity probability density function is:

[0102]

[0103] in, It is the value of the peak velocity of the random variable. It is the mean of the normal distribution corresponding to the log-normal distribution; It is the standard deviation of the normal distribution corresponding to the log-normal distribution, and e is the Euler number.

[0104] Based on the probability density function of the log-normal distribution and combined with a preset safety level To obtain a safe dosage:

[0105]

[0106] in, To comprehensively consider the horizontal distance D and the elevation difference between the measuring point and the blast source and preset security level The functional relationship, According to the preset security level By consulting the Z table, The safe threshold for blasting vibration velocity, Here, e is the field coefficient, and e is the Euler number. The horizontal distance between the measuring point and the blast source. The decay exponent, This represents the influence coefficient of elevation difference.

[0107] It is important to note the preset security level. It should meet the following requirement: the probability that the peak vibration velocity is less than the peak vibration velocity safety threshold needs to be greater than the preset safety level.

[0108] Based on the obtained maximum single-segment charge and preset security level Construct the horizontal distance between a point within a surface cavity and the blast source. and the elevation difference between the measuring point and the explosion source The functional relationship between them serves as a safety range model;

[0109] The safety range model satisfies:

[0110]

[0111] in, , , To comprehensively consider the elevation difference between the measuring point and the blast source , charge amount and preset security level The functional relationship, This is the site coefficient. The safe threshold for blasting vibration velocity, where e is the Euler number. According to the preset security level By consulting the Z table, The decay exponent, This represents the influence coefficient of elevation difference.

[0112] S600. Combining the safe dosage prediction model and the safe range model, the construction area is divided into different control zones, and different construction methods are selected in different control zones.

[0113] Specifically, set n preset security levels. , where n is an integer greater than or equal to 2. In this embodiment, n=3, meaning there are 3 preset safety levels. ,in,

[0114] With safe dosage The first safety curve is formed by using the safety distance output in the safety range model corresponding to the first safety level as the vertical axis and the horizontal axis as the horizontal axis.

[0115] Similarly, the second safety level and the corresponding safety distance form the second safety curve;

[0116] The third safety level and the corresponding safety distance form the third safety curve.

[0117] Among them, the range of the first safety level is smaller than the range of the second safety level, and the range of the second safety level is smaller than the range of the third safety level;

[0118] Take any value for the safe dosage on the vertical axis, and it will form point 1 on the first safety curve, point 2 on the second safety curve, and point 3 on the third safety curve.

[0119] As can be seen from points 1 and 3, under the current safe charge, the area with a distance greater than the x-coordinate corresponding to point 3 is the safe zone; the area with a distance less than the x-coordinate corresponding to point 1 is the danger zone. The intermediate area between the x-coordinate ranges corresponding to points 1 and 3 can be further subdivided by point 2, such as into a relatively safe zone and a relatively dangerous zone.

[0120] by Figure 3 For example, the first safety level is greater than 0.99, the second safety level is greater than 0.98 and less than 0.99, and the third safety level is less than 0.98 and greater than 0.95. Three safety curves are formed by the three safety levels and their corresponding safety distances.

[0121] When the maximum single-segment charge At this time, it forms points 1 (25.621, 18.6) and 3 (32.042, 18.6) with the first, second, and third safety curves, respectively. From these two points, it can be seen that when The area within 25.621m of the blast source is designated as a danger zone, marked in red; the area between 25.621m and 32.042m is designated as an intermediate zone, marked in yellow; and the area beyond 32.042m of the blast source is designated as a safe zone, marked in green. Different excavation methods are used for different zones to avoid collapses caused by blasting.

[0122] Similarly, when the safety distance on the horizontal axis is chosen to be consistent, the intersection point formed by intersecting with each safety curve indicates the maximum single-segment charge used in the corresponding area. Less than the corresponding maximum single-stage charge .

[0123] Taking a certain double-track tunnel as an example, the tunnel is in Class V surrounding rock and passes through a national nature reserve and gully landform:

[0124] Project Overview:

[0125] The left tunnel is 1660m long and the right tunnel is 1730m long. The surrounding rock is mainly sandstone and argillaceous sandstone (density 2450kg / m³, tensile strength 0.35MPa, longitudinal wave velocity 2000m / s). The elevation difference between the shallowest measuring point and the blast source is 6m. There are two gullies on the ground surface (elevation difference between the measuring point and the blast source is 28~35m). It is necessary to control the impact of blasting vibration on the nature reserve.

[0126] On-site blasting vibration monitoring implementation:

[0127] The NUBOX-8016 blast vibration meter was used in conjunction with a TP3V-4.5 three-dimensional velocity sensor, with a sampling frequency of 50kHz, a trigger negative delay of -100ms, and a trigger level of 0.1cm / s.

[0128] Eight measuring points (4m apart) are set up on the left sidewall of the tunnel chamber, and 20 measuring points are set up along the axis on the ground surface (3m apart in the gully area and 8m apart in the ordinary area).

[0129] A total of 120 sets of valid data were collected. After removing outliers, 100 sets were retained for model fitting.

[0130] Fitting results of the segment PPV decay model:

[0131] Tunnel chamber: After screening 40 sets of data, the following results were obtained through fitting:

[0132] =86.178×D^(-1.437)×Q^(0.380) (correlation coefficient is 0.887);

[0133] Non-cavitary sections of the surface: After introducing elevation difference correction, the fitted result is:

[0134]

[0135] (Correlation coefficient is 0.888);

[0136] Surface of the cavity section: Based on dimensional analysis fitting, the following results are obtained:

[0137] =14.717×(D / Q^(1 / 3))^(-0.375)×(h / D)^(-0.037) (Correlation coefficient is 0.913, and the average relative error of prediction is 0.098).

[0138] Safety threshold and void effect quantification:

[0139] Safety threshold: Substitute The formula yields a PPV safety threshold of 7.719 cm / s for sandstone and conglomerate.

[0140] Hollow effect: The relationship between λ and D was fitted using the Lorentz function: λ = 1.262 / (1 + ((D - 14.578) / 8.2)^2) + 0.988 (correlation coefficient is 0.976). The peak position of λ is D = 14.578 m (1.04 times the hole diameter), and the amplification effect is most significant when h / D = 2.11.

[0141] Application effect of the safety control model:

[0142] Safe charge: Corresponding to different D values in the 2# gully (h = 28 m, P0 = 0.98): :

[0143] D = 20 m: = 15.6 kg;

[0144] D = 25 m: = 20.8 kg;

[0145] D = 30 m: = 26.5 kg;

[0146] Safety range: Corresponding to different h values for Q = 43.2 kg (second bench blasting) ( ( = 0.98):

[0147] h = 6 m: = 21.2 m;

[0148] h = 15 m: = 18.5 m;

[0149] h = 28 m: = 15.8 m;

[0150] Implementation effect of staged blasting control

[0151] Dangerous area (core area of gully, D ≤ 15 m): Excavated using a roadheader, with the surface settlement rate controlled within 2.5 mm / d and no ecological damage;

[0152] Middle area (15 m < D ≤ 40 m): Three-bench presplitting blasting was implemented, with the spacing of presplitting holes being 0.4 m, the linear charge density being 180 g / m, Qmax = 20.8 kg, and the measured PPV ≤ 7.5 cm / s, meeting the safety threshold;

[0153] Safe area (D > 40 m): Conventional blasting was used, with the charge amount being 35 - 43 kg. Through dynamic adjustment by the safety model, the construction efficiency was increased by 20%.

Claims

1. A method for graded blasting construction in sensitive sections of shallow-buried soft rock tunnels, characterized in that, include: S100. Measuring points were set up in the tunnel chamber, the non-cavitary section of the ground surface, and the cavitary section of the ground surface, and the peak vibration velocity and parameter waveforms of the measuring points in different areas were obtained. S200. Segment Construction The model includes: Using the Sadovsky model as the basic model and the horizontal proportional distance as the core variable, an attenuation model for tunnel chambers is obtained. ; Using the attenuation model The elevation difference between the measuring point and the explosion source is introduced as a basic model. As a correction term, a coupled attenuation model for the non-cavitary segment of the surface is obtained. ; Based on dimensional analysis, the horizontal distance between the measuring point and the blast source was selected in the surface cavity section. Elevation difference between measuring point and blast source Maximum single-stage drug dosage Rock mass density and the tensile strength of the rock mass Construct a multivariate prediction model for surface cavity segments ; S300. Obtain the peak vibration safety threshold of the surface in surface cavity sections with different lithologies. ; S400. Vibration velocity amplification factor The amplification effect of voids on vibration is quantified, and the vibration velocity amplification factor is fitted. The relationship between the vibration velocity amplification factor and the horizontal distance D determines the vibration velocity amplification factor. The peak position and critical influence range; S500. Construct a security control model, including: Based on the probability density function of peak velocity combined with a preset safety level and maximum single-stage charge The functional relationship is used as a model for predicting safe drug dosage; Based on the obtained maximum single-segment charge and preset security level Construct the horizontal distance between a measuring point within a surface cavity and the blast source. and the elevation difference between the measuring point and the explosion source The functional relationship between them serves as a safety range model; S600. Combining the safe dosage prediction model and the safe range model, the construction area is divided into different control zones, and different construction methods are selected in different control zones.

2. The method for graded blasting construction in sensitive areas of shallow-buried soft rock tunnels according to claim 1, characterized in that: Several first three-dimensional velocity sensors are installed on the inner wall of the tunnel chamber. The first three-dimensional velocity sensors are arranged in the tunnel chamber according to a first density. The first three-dimensional velocity sensors installed in the sensitive area of ​​the tunnel chamber are arranged according to a second density, which is greater than the first density. A second three-dimensional velocity sensor is installed on the surface cavity section above the tunnel chamber, and several second three-dimensional velocity sensors are arranged according to the first density. Several third-dimensional velocity sensors are arranged on the non-cavitary section of the ground surface. The several third-dimensional velocity sensors are set according to the first density. Several pairs of second-dimensional velocity sensors and third-dimensional velocity sensors are symmetrically arranged about the explosion source. The first three-dimensional velocity sensor, the second three-dimensional velocity sensor, and the third three-dimensional velocity sensor are rigidly fixed to the detection surface of the measuring point.

3. The method for graded blasting construction in sensitive areas of shallow-buried soft rock tunnels according to claim 1, characterized in that: In obtaining the attenuation model of the tunnel chamber When using horizontal proportional distance Alternate spatial proportion distance Obtain the attenuation model : ； ； ； in, For site coefficient, The decay exponent, The horizontal distance from the explosion source. Maximum single-stage charge; Through the attenuation model Introducing the elevation difference between the measuring point and the blast source As a correction term, the coupling attenuation model is obtained. Coupled attenuation model of: ； in, Elevation difference influence coefficient; Multivariate prediction model for surface cavity segments for: 。 4. The graded blasting construction method for sensitive sections of shallow-buried soft rock tunnels according to claim 3, characterized in that: Step S300 includes the following steps: Obtain the rock mass density of the corresponding rock mass and the tensile strength of the rock mass The peak velocity safety threshold is derived using stress wave theory. : ； in, This refers to the longitudinal wave velocity.

5. The method for graded blasting construction in sensitive areas of shallow-buried soft rock tunnels according to claim 4, characterized in that: In step S400, the vibration velocity amplification factor λ quantifies the amplification effect of the void on the vibration, satisfying the following: ； The measured peak vibration velocity in the surface cavity area is the peak vibration velocity obtained by the second three-dimensional velocity sensor, and the measured peak vibration velocity in the surface non-cavity area is the peak vibration velocity obtained by the second three-dimensional velocity sensor. The relationship between several magnification factors λ and their corresponding horizontal distances D is fitted using the Lorentz function: ； in, For peak amplitude, As the center position, This is the half-width parameter, used to describe the width of the peak. λ represents the background offset, used to indicate the baseline value or background level of the magnification factor λ when the magnification factor is far from the center position.

6. The method for graded blasting construction in sensitive areas of shallow-buried soft rock tunnels according to claim 5, characterized in that: In step S500, assuming the peak velocity follows a log-normal distribution, the peak velocity probability density function is obtained: ； in, It is the value of the peak velocity of the random variable. It is the mean of the normal distribution corresponding to the log-normal distribution; It is the standard deviation of the normal distribution corresponding to the log-normal distribution.

7. The method for graded blasting construction in sensitive areas of shallow-buried soft rock tunnels according to claim 6, characterized in that: Preset security level The following condition must be met: the probability that the peak velocity is less than the peak velocity safety threshold must be greater than the preset safety level. Safe dosage satisfy: ； in, To comprehensively consider the functional relationship between horizontal distance, elevation difference between measuring point and blast source, and safety level, According to the preset security level By consulting the Z table, This is the safe threshold for blasting vibration velocity.

8. The method for graded blasting construction in sensitive areas of shallow-buried soft rock tunnels according to claim 7, characterized in that: The safety range model satisfies: ； in, , , The functional relationship is to comprehensively consider the elevation difference between the measuring point and the blast source, the amount of explosive charge, and the safety level.

9. The method for graded blasting construction in sensitive areas of shallow-buried soft rock tunnels according to claim 8, characterized in that: In S600, n safety levels are set, where n≥2, with a safe dosage. Using the vertical axis as the ordinate and the safe distance output by the safety range model corresponding to each safety level as the horizontal axis, n safety curves are formed to divide the construction area into different control zones.

Images