A method for predicting attenuation law of blasting vibration of a tunnel in class ii to class v surrounding rock

Abstract

The application provides a prediction method for blasting vibration attenuation law of II to V level surrounding rock of a tunnel, and relates to the field of tunnel blasting, which comprises the following steps: obtaining the surrounding rock level, the tunnel structure form and the blasting parameters of a tunnel section to be predicted; preparing rock samples of II to V level surrounding rock according to the surrounding rock level; testing the dynamic and static mechanical parameters of the rock samples of each level of surrounding rock to obtain the mechanical parameter set of each level of surrounding rock; establishing a three-dimensional blasting dynamic numerical model; using the dimension analysis method to regress and fit the blasting vibration attenuation sample set to establish a separated tunnel blasting vibration peak velocity attenuation prediction model or a small clear distance tunnel blasting vibration attenuation prediction model corresponding to each level of surrounding rock; substituting the surrounding rock level, the blasting parameters and the tunnel structure form of the tunnel section to be predicted into the corresponding blasting vibration attenuation prediction model to obtain the particle peak vibration velocity, and inversely calculating the maximum safe explosive quantity according to the allowable vibration velocity of a protection object. The application improves the prediction accuracy of the blasting vibration of the tunnel with multiple levels of surrounding rock.

Description

Technical Field

[0001] This invention relates to the field of tunnel blasting technology, and in particular to a method for predicting the vibration attenuation law of tunnel blasting in Class II to V surrounding rock. Background Technology

[0002] Drill-and-blast method is widely used in mountain tunnel and underground engineering excavation due to its strong adaptability, flexible construction organization, and suitability for complex geological conditions. During blasting excavation, part of the energy generated by the explosive detonation is used to break the rock mass and form the excavation profile, while the other part propagates to the surrounding rock and adjacent structures in the form of stress waves and vibration waves. Blasting vibrations can cause loosening of the surrounding rock, cracking of the support structure, damage to secondary lining, response of adjacent tunnel structures, and vibration exceeding limits of surface or underground protected objects. Therefore, accurate prediction of the attenuation law of tunnel blasting vibrations is an important foundation for optimizing blasting parameters and controlling construction safety.

[0003] Existing methods for predicting blasting vibrations mostly employ empirical formulas based on single-shot charge and detonation distance. These formulas are generally simple and can meet the needs of rapid estimation under typical site conditions. However, in actual tunnel construction, the surrounding rock grade often varies between Grade II and Grade V. Different grades of surrounding rock exhibit significant differences in strength, integrity, wave velocity, elastic modulus, shear modulus, Poisson's ratio, and energy dissipation capacity. The lower the surrounding rock grade, the more fractured the rock mass and the more developed its structural surfaces, resulting in more complex effects on the propagation, reflection, attenuation, and amplification of blasting vibrations. If only uniform empirical parameters are used for prediction, it is difficult to accurately reflect the differences in vibration attenuation under different surrounding rock grades. Furthermore, for tunnels with small clearance, the propagation of blasting vibrations is not only affected by the amount of explosive charge, the distance between the blast center and the surrounding rock conditions, but also by factors such as the cavity of the preceding tunnel, the transmission of rock pillars in the middle, the interaction between the two tunnels, and the reflection of the lining boundary. When the blasting vibrations propagate to the vicinity of the preceding tunnel, the following tunnel, or the middle rock pillar, local amplification or vibration velocity fluctuations may occur, making it difficult for traditional separate tunnel vibration prediction models to be directly applied to tunnels with small clearance.

[0004] Chinese invention patent application number 202111611608.4 discloses a method and system for predicting the duration of blasting vibration, electronic equipment, and storage medium. This method uses the maximum charge per blast, detonation center distance, elevation difference, rock mass damage degree, and medium mechanical parameters as variables. Based on dimensional analysis, it establishes a predictive function relationship between the duration of blasting vibration and each variable. It calculates the instantaneous energy spectrum of vibration signals generated by each blast, cumulatively quantifies the degree of rock mass damage, and modifies the prediction model using the Sadovsky formula. Finally, it determines each prediction parameter through regression fitting of field measured data. However, the prediction parameters of this method depend on the field measured vibration signals from each blast. In tunnel engineering with variable geological conditions and significant differences in surrounding rock grades, the site parameters of different surrounding rock sections are difficult to cover using uniform historical monitoring data, limiting its adaptability to different geological conditions. Summary of the Invention

[0005] In view of this, the present invention provides a method for predicting the attenuation law of blasting vibration in tunnels with surrounding rock of grades II to V, in order to solve the problem that existing blasting vibration prediction methods are difficult to apply simultaneously to multiple grades of surrounding rock, separated tunnels and tunnels with small clearance, improve the prediction accuracy of blasting vibration in tunnels with multiple grades of surrounding rock, and provide a basis for calculating the maximum safe charge and optimizing blasting schemes.

[0006] The technical solution of this invention is implemented as follows: On the one hand, the present invention provides a method for predicting the attenuation law of blasting vibration in tunnels with surrounding rock grades II to V, including: S1. Obtain the surrounding rock grade, tunnel structure, and blasting parameters of the tunnel section to be predicted; S2. Prepare Class II to Class V surrounding rock samples according to the surrounding rock grade. Class II and Class III surrounding rock samples are prepared by in-situ core sampling. Class IV and Class V surrounding rock samples are prepared by screening through acoustic testing after low-amplitude impact pre-damage treatment based on intact rock samples. S3. Perform dynamic and static mechanical parameter tests on rock samples of each level of surrounding rock to obtain the set of mechanical parameters for each level of surrounding rock. S4. Based on the mechanical parameter set of each surrounding rock level, establish a three-dimensional blasting dynamic numerical model. Verify the three-dimensional blasting dynamic numerical model with field monitoring data. Extract the peak particle vibration velocity under each surrounding rock level, construction method and blasting condition to form a blasting vibration attenuation sample set. The three-dimensional blasting dynamic numerical model includes a three-dimensional blasting dynamic numerical model for separated tunnels and a three-dimensional blasting dynamic numerical model for small clearance tunnels. S5. The dimensional analysis method is used to perform regression fitting on the sample set of blasting vibration attenuation, and a prediction model for the peak velocity attenuation of blasting vibration in separate tunnels or a prediction model for the vibration attenuation of blasting in small-distance tunnels is established based on the three-dimensional blasting dynamic numerical model. The prediction model for the vibration attenuation of blasting vibration in small-distance tunnels is obtained by introducing a cavity correction coefficient based on the prediction model for the peak velocity attenuation of blasting vibration in separate tunnels. S6. Substitute the surrounding rock grade, blasting parameters and tunnel structure of the tunnel section to be predicted into the corresponding blasting vibration attenuation prediction model to obtain the peak particle velocity, and calculate the maximum safe charge based on the allowable vibration velocity of the protected object.

[0007] Based on the above technical solutions, preferably, the preparation methods for the Class IV and Class V surrounding rock samples specifically include: An intact granite specimen was selected as the base specimen, and an initial acoustic wave test was performed on the base specimen to obtain the longitudinal wave velocity before impact. A split Hopkinson pressure bar device was used to perform low-amplitude impact pre-damage treatment on the basic specimen. After each low-amplitude impact, the appearance of the sample is inspected, and samples with through cracks, obvious end face damage, edge peeling or overall breakage are rejected, thus obtaining the pre-damage retained samples for each number of impacts. Acoustic wave testing was performed on the retained samples to obtain the longitudinal wave velocity after impact. The deviation between the longitudinal wave velocity corresponding to each number of impacts and the measured longitudinal wave velocity of the surrounding rock mass corresponding to the grade of the rock to be prepared was used as the screening criterion. The pre-damaged retained sample corresponding to the number of impacts with the smallest longitudinal wave velocity deviation was determined as the equivalent weakened rock sample.

[0008] Based on the above technical solutions, preferably, the impact pressure of the low-amplitude impact pre-damage treatment is 0.1 MPa, the impact velocity is 2.4 m / s, and the number of impacts is set to 1, 2, and 3 times respectively.

[0009] Based on the above technical solutions, preferably, the set of mechanical parameters includes the density, longitudinal wave velocity, transverse wave velocity, dynamic elastic modulus, dynamic shear modulus, Poisson's ratio, uniaxial compressive strength, and dynamic response parameters of rock samples of each surrounding rock grade.

[0010] Based on the above technical solutions, preferably, the method for constructing the three-dimensional blasting dynamic numerical model specifically includes: A three-dimensional geometric model is established based on the tunnel structure of the tunnel segment to be predicted: When the tunnel structure is a separated tunnel, a three-dimensional geometric model is established that includes the surrounding rock mass, the single-tunnel excavation outline and the support structure. When the tunnel structure is a small clearance tunnel, a three-dimensional geometric model is established, including the surrounding rock mass, the excavation outline of the first tunnel, the excavation outline of the second tunnel, the interbedded rock pillars, the formed cavity of the first tunnel, and the support structure. In the three-dimensional geometric model, the surrounding rock mass and support structure are represented by Lagrange elements, while the explosive and detonation products are represented by Eulerian elements or arbitrary Lagrange-Eulerian elements. The explosive detonation pressure is transmitted to the surrounding rock mass through fluid-structure interaction. Material parameters for each surrounding rock zone are assigned based on the density, dynamic elastic modulus, dynamic shear modulus, Poisson's ratio, and uniaxial compressive strength corresponding to each surrounding rock level in the mechanical parameter set. The support structure is assigned its actual material mechanical parameters. The ground surface and each tunnel excavation face of the 3D geometric model are set as free boundaries, and the outer boundaries of the four sides and bottom of the model are set as non-reflective boundaries.

[0011] Based on the above technical solutions, the preferred method for establishing the peak velocity attenuation prediction model for split tunnel blasting vibration includes: Peak particle velocity, single-shot charge, detonation center distance, and density of surrounding rock at various levels. and longitudinal wave velocity To analyze the variables, dimensional analysis was used to derive the dimensionless parameter combination and determine the basic functional form of the prediction model for the peak velocity decay of blasting vibration in a split tunnel. Based on the basic function form, logarithmic linear regression was performed on the sample set of blasting vibration attenuation. The site coefficient and attenuation index were determined according to the surrounding rock level and construction method, and a prediction model for the peak velocity attenuation of blasting vibration in separate tunnels corresponding to each surrounding rock level was established.

[0012] Based on the above technical solutions, the preferred prediction model for the attenuation of peak velocity of blasting vibration in the separated tunnel is as follows:

[0013] in, The peak velocity of the particle. For the maximum single-shot dose, For the distance between the centers, For the first Site coefficients corresponding to Class I surrounding rock. For the first The attenuation index corresponding to grade III surrounding rock. Indicates the surrounding rock grade. Choose II, III, IV, or V.

[0014] Based on the above technical solutions, the preferred method for constructing the prediction model for blasting vibration attenuation in small-clearance tunnels is as follows: Based on the three-dimensional blasting dynamic numerical model of small-clearance tunnels, the peak particle velocity distribution along the longitudinal direction of the tunnel is extracted from each measuring point in the preceding tunnel after the subsequent tunnel blasting, and the longitudinal distribution data of the vibration velocity in the preceding tunnel is obtained. Using the longitudinal position of the measuring point as the independent variable, nonlinear regression fitting is performed on the longitudinal distribution data of the vibration velocity in the pilot tunnel. Based on the non-uniform distribution characteristics of the vibration velocity along the longitudinal direction, the center position of the vibration peak, the cavity amplification coefficient, and the cavity influence characteristic length are determined. Based on the center position of the vibration peak, the cavity amplification coefficient, and the cavity influence characteristic length, the cavity correction coefficient is determined. : Cavity correction factor By introducing a separate tunnel blasting vibration peak velocity attenuation prediction model, a small-clearance tunnel blasting vibration attenuation prediction model is obtained.

[0015] Based on the above technical solutions, the preferred prediction model for vibration attenuation during blasting in tunnels with small clearance is as follows:

[0016]

[0017] in, This represents the predicted peak velocity of a mass point at a measuring point inside the pilot tunnel of a tunnel with a small clearance. The horizontal distance between the measuring points is relative to the detonation face. This represents the longitudinal position corresponding to the peak center in the longitudinal distribution of vibration velocity in the preliminary tunnel. This is the cavity amplification factor. The cavity influence characteristic length, Indicates the first Site coefficients corresponding to Class I surrounding rock. This indicates the maximum single-shot dosage. Indicates the distance between the centers of the explosion. Indicates the first The attenuation index corresponding to grade III surrounding rock. This represents the cavity correction factor.

[0018] Furthermore, step S6 specifically includes: Based on the surrounding rock grade and tunnel structure of the tunnel section to be predicted, the corresponding blasting vibration attenuation prediction model is selected: When the tunnel structure is a separated tunnel, select the prediction model for the peak velocity attenuation of blasting vibration in a separated tunnel with the corresponding surrounding rock level. When the tunnel structure is a small clearance tunnel, select the blasting vibration attenuation prediction model for small clearance tunnels with corresponding surrounding rock grade. When the blast center distance and blasting parameters of the tunnel section to be predicted are substituted into the corresponding blasting vibration prediction model, the predicted value of the peak particle velocity at the measuring point is obtained. Using the allowable vibration velocity of the protected object as a constraint, the maximum safe charge is calculated by substituting the separated tunnel or the tunnel with small clearance into the corresponding blasting vibration attenuation prediction model. ; Will Compare the actual single-shot charge quantity with the blasting plan to determine whether the blasting plan meets the vibration safety control requirements of the protected object. If the actual single-shot charge quantity exceeds... The demolition plan will then be adjusted.

[0019] The present invention has the following advantages over the prior art: (1) Representative rock samples were prepared for Class II to Class V surrounding rocks, and basic parameters corresponding to different surrounding rock levels were obtained by dynamic and static mechanical parameter testing, so that the blasting vibration prediction model could reflect the differences in mechanical properties of multi-level surrounding rocks. (2) For Class IV and Class V surrounding rocks, equivalent weakened rock samples were prepared by low-amplitude impact pre-damage method, and rock samples corresponding to the target surrounding rock level were screened by acoustic wave test, which improved the operability of obtaining indoor test parameters for low-level surrounding rocks. (3) Combining indoor rock sample tests, on-site blasting vibration monitoring and three-dimensional dynamic numerical simulation can improve the reliability of the blasting vibration attenuation prediction model and avoid the problem of limited applicability of purely empirical formulas; (4) Prediction models were established for separate tunnels and tunnels with small clearance, and a cavity correction coefficient was introduced into the tunnel with small clearance model to characterize the influence of cavity in the pilot tunnel, transmission of rock columns in the middle and interaction between the two tunnels on the propagation of blasting vibration. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a flowchart of a method for predicting the vibration attenuation law of blasting tunnels in Class II to V surrounding rock according to the present invention. Figure 2 This is a schematic diagram of the preparation process of equivalent weakened rock samples for Class IV and Class V surrounding rock in the method for predicting the attenuation law of blasting vibration in tunnels of Class II to V surrounding rock according to the present invention. Figure 3 This is a schematic diagram of the acoustic testing principle of a method for predicting the attenuation law of blasting vibration in tunnels of Class II to V surrounding rock according to the present invention. Figure 4This is a schematic diagram of a three-dimensional dynamic numerical model of split tunnel blasting, which is a method for predicting the vibration attenuation law of tunnel blasting in Class II to V surrounding rock according to the present invention. Figure 5 This is a schematic diagram of a three-dimensional dynamic numerical model of a small-clearance tunnel for predicting the vibration attenuation law of tunnel blasting in Class II to V surrounding rock, according to the present invention. Figure 6 This is a schematic diagram of the monitoring point layout for a method to predict the attenuation law of blasting vibration in tunnels of Class II to V surrounding rock according to the present invention. Figure 7 This is a comparison of numerical simulation and field monitoring blasting velocity waveforms of a method for predicting the attenuation law of blasting vibration in tunnels of Class II to V surrounding rock, according to the present invention. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] like Figure 1 As shown, this invention provides a method for predicting the attenuation law of blasting vibration in tunnels with surrounding rock grades II to V, comprising: S1. Obtain the surrounding rock grade, tunnel structure, and blasting parameters of the tunnel section to be predicted; among which, the surrounding rock grade includes Grade II, Grade III, Grade IV, and Grade V; the tunnel structure includes separated tunnels and tunnels with small clearance; the blasting parameters include borehole layout, charge structure, single-shot charge, total charge, detonation sequence, and delay time.

[0024] This can be understood as setting up monitoring points and protected objects in the tunnel section to be predicted. The monitoring points include those inside the tunnel, on the surface, in the preceding tunnel, in the following tunnel, in the interlocking rock pillars, and near the protected objects. The protected objects include the tunnel secondary lining, overlying gas pipelines, unstable rocks at the tunnel entrance, and other structures or rock masses sensitive to blasting vibrations.

[0025] S2. Prepare Class II to Class V surrounding rock samples according to the surrounding rock grade. Class II and Class III surrounding rock samples are prepared by on-site core sampling. Class IV and Class V surrounding rock samples are prepared by screening through acoustic testing after low-amplitude impact pre-damage treatment based on intact rock samples.

[0026] like Figure 2 As shown, in one embodiment of the present invention, the method for preparing Class IV and Class V surrounding rock samples specifically includes: An intact granite specimen was selected as the base specimen, and an initial acoustic wave test was performed on the base specimen to obtain the longitudinal wave velocity before impact. A split Hopkinson pressure bar device was used to perform low-amplitude impact pre-damage treatment on the base sample. The purpose of low-amplitude impact pre-damage treatment is to induce microcrack propagation and reduce wave velocity inside the base sample without causing overall damage to the sample. After each low-amplitude impact, the appearance of the sample is inspected, and samples with through cracks, obvious end face damage, edge peeling or overall breakage are rejected, thus obtaining the pre-damage retained samples for each number of impacts. Acoustic wave testing was performed on the retained samples to obtain the longitudinal wave velocity after impact. The deviation between the longitudinal wave velocity corresponding to each number of impacts and the measured longitudinal wave velocity of the surrounding rock mass corresponding to the grade of the rock to be prepared was used as the screening criterion. The pre-damaged retained sample corresponding to the number of impacts with the smallest longitudinal wave velocity deviation was determined as the equivalent weakened rock sample.

[0027] This invention prepares representative rock samples for Class II to Class V surrounding rocks and obtains basic parameters corresponding to different surrounding rock classes through dynamic and static parameter testing, so that the blasting vibration prediction model can reflect the differences in mechanical properties of surrounding rocks at multiple levels.

[0028] In one embodiment of the present invention, the preparation method of Class II and Class III surrounding rock samples is as follows: Representative intact rock masses were selected from the Class II and Class III surrounding rock sections at the site of the tunnel project to be predicted. Core drilling, cutting, grinding and dimensional trimming were performed on them to prepare standard cylindrical specimens. Specimens with through cracks, obvious joints, damaged ends or peeling edges were removed by checking the integrity of the appearance, the accuracy of the dimensions and the flatness of the end face.

[0029] This invention addresses the problem of difficulty in directly preparing complete samples from Class IV and Class V fractured surrounding rocks. It employs a low-amplitude impact pre-damage method to prepare equivalent weakened rock samples and uses acoustic testing to screen rock samples corresponding to the target surrounding rock level, thereby improving the operability of obtaining indoor test parameters for low-level surrounding rocks.

[0030] In one embodiment of the present invention, the standard cylindrical sample has a diameter of 50 mm and a height of 100 mm.

[0031] In one embodiment of the present invention, the impact air pressure of the low-amplitude impact pre-damage treatment is 0.1 MPa, the impact velocity is 2.4 m / s, and the number of impacts is set to 1, 2 and 3 times respectively.

[0032] In one embodiment of the present invention, the P-wave velocity of the Class IV surrounding rock foundation sample before impact was 4.08 km / s, while the target site rock mass wave velocity was 3.25 km / s. After one impact, the P-wave velocity was 3.72 km / s; after two impacts, it was 3.42 km / s; and after three impacts, it was 2.38 km / s. For the Class V surrounding rock foundation sample, the P-wave velocity before impact was 3.56 km / s, while the target site rock mass wave velocity was 2.65 km / s. After one impact, the P-wave velocity was 3.18 km / s; after two impacts, it was 2.82 km / s; and after three impacts, the sample was destroyed and could no longer be used as a valid sample. Therefore, the rock sample after two impacts was selected as the equivalent weakened rock sample corresponding to Class IV and Class V surrounding rock.

[0033] S3. Perform dynamic and static mechanical parameter tests on rock samples of each level to obtain a set of mechanical parameters for each rock level. The set of mechanical parameters includes the density, longitudinal wave velocity, transverse wave velocity, dynamic elastic modulus, dynamic shear modulus, Poisson's ratio, uniaxial compressive strength, and dynamic response parameters of the rock samples of each rock level. The dynamic and static mechanical parameter tests include uniaxial compressive strength test, acoustic wave test, and dynamic impact test.

[0034] In one embodiment of the present invention, in the uniaxial compressive strength test, the average uniaxial compressive strength of the Class II surrounding rock sample is 134.2 MPa, the average uniaxial compressive strength of the Class III surrounding rock sample is 101.4 MPa, the average uniaxial compressive strength of the Class IV surrounding rock sample is 85.2 MPa, and the average uniaxial compressive strength of the Class V surrounding rock sample is 30.5 MPa.

[0035] In one embodiment of the present invention, the rock sample used for uniaxial compressive strength test and acoustic wave test is processed into a cylindrical specimen with a diameter of 50 mm and a height of 100 mm; the rock sample used for dynamic impact test is processed into a short cylindrical specimen with a diameter of 50 mm and a height of 25 mm.

[0036] In one embodiment of the present invention, during acoustic wave testing, a transmitting transducer and a receiving transducer are respectively disposed on both ends of the rock sample, and a coupling agent is placed between the transducer and the end face of the rock sample to ensure stable transmission of acoustic wave signals. The longitudinal wave velocity and transverse wave velocity of the rock sample are calculated by measuring the time required for the longitudinal and transverse waves to traverse the rock sample.

[0037]

[0038] in, Indicates the longitudinal wave velocity. This indicates the axial distance between the two end faces of the rock sample. This indicates the time required for the longitudinal wave to traverse the rock sample. Indicates the transverse wave velocity. This indicates the time required for a shear wave to traverse the rock sample.

[0039] like Figure 3 As shown, the main unit has a transmitter interface and a receiver interface, which are connected to the corresponding transducers. When testing the longitudinal wave velocity, the P-wave transmitter and receiver are placed against the upper and lower end faces of the rock sample, respectively. The sound wave propagates along the sample axis as a longitudinal compression wave. When testing the transverse wave velocity, the S-wave transducer assembly is replaced, with the S-wave transmitter and receiver also placed against the rock sample end faces. The sound wave propagates as a shear wave. The main unit records the propagation time of the sound wave from the transmitter to the receiver, and combined with the axial length of the rock sample, calculates the longitudinal and transverse wave velocities of the rock sample.

[0040] S4. A three-dimensional blasting dynamic numerical model is established based on the mechanical parameter set of each surrounding rock level. The three-dimensional blasting dynamic numerical model is verified by field monitoring data. The peak particle velocity is extracted under each surrounding rock level, construction method and blasting condition to form a blasting vibration attenuation sample set. The three-dimensional blasting dynamic numerical model includes a three-dimensional blasting dynamic numerical model of a split tunnel and a three-dimensional blasting dynamic numerical model of a small clearance tunnel. The blasting vibration attenuation sample set includes surrounding rock level, tunnel structure, construction method, single-shot charge, blast center distance, measuring point location and peak particle velocity.

[0041] In one embodiment of the present invention, LS-DYNA software is used to establish three-dimensional blasting dynamic numerical models for separated tunnel sections and small-clearance tunnel sections, respectively.

[0042] like Figure 4 and Figure 5 As shown, the specific method for constructing a three-dimensional blasting dynamic numerical model includes: A three-dimensional geometric model is established based on the tunnel structure of the tunnel section to be predicted: the overall size of the geometric model is 100m×100m×120m, and the tunnel cross-section size is 14m×10m. When the tunnel structure is a separated tunnel, a three-dimensional geometric model is established that includes the surrounding rock mass, the single-tunnel excavation outline and the support structure. When the tunnel structure is a small clearance tunnel, a three-dimensional geometric model is established, including the surrounding rock mass, the excavation outline of the first tunnel, the excavation outline of the second tunnel, the interbedded rock pillars, the formed cavity of the first tunnel, and the support structure. In the three-dimensional geometric model, the surrounding rock mass and support structure are represented by Lagrange elements, while the explosive and detonation products are represented by Eulerian elements or arbitrary Lagrange-Eulerian elements. The explosive detonation pressure is transmitted to the surrounding rock mass through fluid-structure interaction. Material parameters for each surrounding rock zone are assigned based on the density, dynamic elastic modulus, dynamic shear modulus, Poisson's ratio, and uniaxial compressive strength corresponding to each surrounding rock level in the mechanical parameter set. The support structure is assigned its actual material mechanical parameters. The ground surface and each tunnel excavation face of the 3D geometric model are set as free boundaries, and the outer boundaries of the four sides and bottom of the model are set as non-reflective boundaries.

[0043] In one embodiment of the present invention, the surrounding rock mass, support structure, and lining structure are simulated using Lagrange elements; the explosive and detonation products are simulated using Eulerian elements or arbitrary Lagrange-Eulerian elements; the explosive detonation pressure is transferred to the surrounding rock medium through fluid-structure interaction, and the specific parameters are shown in Table 1. Table 1 Parameters of the 3D Geometric Model

[0044] After establishing the three-dimensional geometric model, blasting vibration monitoring points were set up on site to collect blasting vibration velocity time history data and extract the peak vibration velocity monitored on site.

[0045] In one embodiment of the present invention, starting from the lower step face, a monitoring point is arranged every 5 meters along the tunnel direction, for a total of 5 monitoring points, such as... Figure 6 As shown; The numerical simulation peak velocity was compared with the field-monitored peak velocity, and the error was:

[0046] in, δ This represents the peak velocity error. V s To numerically simulate peak vibration velocity, V m For on-site monitoring of peak vibration velocity; when δ If the percentage is no greater than 10%, the three-dimensional blasting dynamic numerical model is deemed to meet the verification requirements. The verification results are shown below. Figure 7 As can be seen from the figure, the vibration velocity waveform of the numerical simulation results is basically consistent with the overall field monitoring, and the peak vibration velocity error is within 10%, indicating that the numerical simulation has high reliability.

[0047] S5. The dimensional analysis method is used to perform regression fitting on the sample set of blasting vibration attenuation, and a prediction model for the peak velocity attenuation of blasting vibration in separate tunnels or a prediction model for the vibration attenuation of blasting in small-distance tunnels is established based on the three-dimensional blasting dynamic numerical model. The prediction model for the vibration attenuation of blasting vibration in small-distance tunnels is obtained by introducing a cavity correction coefficient based on the prediction model for the peak velocity attenuation of blasting vibration in separate tunnels. In one embodiment of the present invention, the method for establishing a prediction model for the peak velocity attenuation of blasting vibration in a split tunnel includes: Peak particle velocity, single-shot charge, detonation center distance, and density of surrounding rock at various levels. and longitudinal wave velocity To analyze the variables, dimensional analysis was used to derive the dimensionless parameter combination and determine the basic functional form of the prediction model for the peak velocity decay of blasting vibration in a split tunnel. Based on the basic function form, logarithmic linear regression was performed on the sample set of blasting vibration attenuation. The site coefficient and attenuation index were determined according to the surrounding rock grade and construction method, and a prediction model for the peak velocity attenuation of blasting vibration in separated tunnels corresponding to each surrounding rock grade was established.

[0048] in, The peak velocity of the particle. For the maximum single-shot dose, For the distance between the centers, For the first Site coefficients corresponding to Class I surrounding rock. For the first The attenuation index corresponding to grade III surrounding rock. Indicates the surrounding rock grade. Choose II, III, IV, or V; and The rock mass level and construction method were determined by log-linear regression fitting.

[0049] This invention combines indoor rock sample testing, on-site blasting vibration monitoring, and three-dimensional dynamic numerical simulation, which can improve the reliability of the blasting vibration attenuation prediction model and avoid the problem of limited applicability of purely empirical formulas.

[0050] In one embodiment of the present invention, frequency domain analysis can be performed on the vibration velocity time history output by on-site blasting vibration monitoring or a three-dimensional blasting dynamic numerical model, specifically including: The vibration velocity time history v(t) of each measuring point is extracted and subjected to fast Fourier transform to obtain the frequency domain amplitude spectrum V(f); In the frequency domain amplitude spectrum V(f), the frequency corresponding to the peak amplitude is determined as the dominant frequency fp of the blasting vibration at that measuring point; The dominant frequency f of blasting vibration under different surrounding rock grades, different detonation center distances, and different single-shot charge weights was statistically analyzed. p The explosive charge and the distance from the detonation center were used as independent variables, and the dominant frequency of the blasting vibration was f. p By performing regression fitting on the dependent variable, the dominant frequency prediction model is obtained:

[0051] in, f p The dominant frequency of blasting vibration, Q For the maximum single-shot dose, R For the distance between the centers, a iLet be the dominant frequency site coefficient corresponding to the i-th level of surrounding rock. b i Let be the dominant frequency attenuation index corresponding to the i-th level of surrounding rock, where i represents the surrounding rock level and i can be II, III, IV or V.

[0052] Understandably, the dominant frequency prediction model is used to help reflect the frequency characteristics of blasting vibrations; in cases where the dominant frequency sample set has not been fitted, the peak particle velocity prediction model and the back-calculation results of the maximum safe charge are still used as the main basis for safety control.

[0053] In one embodiment of the present invention, the method for constructing a prediction model for vibration attenuation during blasting in tunnels with small clearance is as follows: Based on the three-dimensional blasting dynamic numerical model of small-clearance tunnels, the peak particle velocity distribution along the longitudinal direction of the tunnel is extracted from each measuring point in the preceding tunnel after the subsequent tunnel blasting, and the longitudinal distribution data of the vibration velocity in the preceding tunnel is obtained. Using the longitudinal position of the measuring point as the independent variable, nonlinear regression fitting is performed on the longitudinal distribution data of the vibration velocity in the pilot tunnel. Based on the non-uniform distribution characteristics of the vibration velocity along the longitudinal direction, the center position of the vibration peak, the cavity amplification coefficient, and the cavity influence characteristic length are determined. Based on the center position of the vibration peak, the cavity amplification coefficient, and the cavity influence characteristic length, the cavity correction coefficient is determined. The cavity correction coefficient is used to correct the effects of the cavity in the pilot tunnel, the transmission of rock columns in the middle, the reflection of the lining boundary, and the interaction between the two tunnels on the propagation of blasting vibration. Cavity correction factor By introducing a prediction model for the peak velocity attenuation of blasting vibration in separated tunnels, a prediction model for the vibration attenuation of blasting in tunnels with small clearances is obtained:

[0054]

[0055] in, This represents the predicted peak velocity of a mass point at a measuring point inside the pilot tunnel of a tunnel with a small clearance. The horizontal distance between the measuring points is relative to the detonation face. This represents the longitudinal position corresponding to the peak center in the longitudinal distribution of vibration velocity in the preliminary tunnel. This is the cavity amplification factor, used to characterize the additional amplification of vibration velocities near the reference position by the cavity boundary. The cavity influence characteristic length is used to characterize the attenuation range of the cavity influence along the tunnel longitudinal direction. , and The values ​​were obtained through nonlinear regression fitting and were assigned according to the surrounding rock grade and the tunnel location.

[0056] This invention is achieved through , and Three parameters describe the influence of the cavity effect in the pilot tunnel of a small-clearance tunnel on the propagation of blasting vibration, which can improve the applicability of peak particle velocity prediction under small-clearance tunnel conditions.

[0057] In one embodiment of the present invention, A g , x 0 and L g Values ​​are taken separately according to the surrounding rock grade, construction method, and tunnel location; when the predicted working condition is consistent with the fitted working condition, the values ​​under the corresponding surrounding rock grade, construction method, and tunnel location are directly adopted. A g , x 0 and L g When the predicted working condition is not completely consistent with the fitted working condition, the validated model parameters that are closest in terms of surrounding rock grade, construction method and tunnel location shall be given priority and corrected in combination with the field monitoring results.

[0058] Understandable. A g , x 0 and L g This study is used to characterize the cavity effect of the pilot tunnel and the influence of the interaction between the two tunnels on the propagation of blasting vibration under established working conditions with small clearance. It does not involve the determination of the parameter evolution law under different excavation advance states of the pilot tunnel.

[0059] In one embodiment of the present invention, the parameters of the blasting vibration attenuation prediction model corresponding to different construction methods and different surrounding rock grades in a separated tunnel are shown in Table 2: Table 2 Parameters of the Prediction Model for Peak Velocity Attenuation of Blasting Vibration in Separated Tunnels

[0060] Table 3 shows the parameters of the blasting vibration attenuation prediction model for different construction methods and different surrounding rock grades in tunnels with small clearance. Table 3 Parameters for the Prediction Model of Peak Velocity Attenuation of Blasting Vibration in Small-Clear-Distance Tunnels During Subsequent Tunneling

[0061] Table 4 shows the parameters of the blasting vibration attenuation prediction model for different construction methods and different surrounding rock grades in tunnels with small clearance. Table 4 Parameters for the Prediction Model of Peak Velocity Attenuation of Blasting Vibration in the Pilot Tunnel of Small-Clearance Tunnels

[0062] Table 5 shows the parameters of the blasting vibration attenuation prediction model corresponding to different construction methods and different surrounding rock grades above the tunnel face: Table 5 Parameters of the Prediction Model for Vibration Attenuation during Blasting at the Tunnel Face

[0063] S6. Substitute the surrounding rock grade, blasting parameters and tunnel structure of the tunnel section to be predicted into the corresponding blasting vibration attenuation prediction model to obtain the peak particle velocity, and calculate the maximum safe charge based on the allowable vibration velocity of the protected object.

[0064] Specifically, step S6 includes: Based on the surrounding rock grade and tunnel structure of the tunnel section to be predicted, the corresponding blasting vibration attenuation prediction model is selected: When the tunnel structure is a separated tunnel, select the prediction model for the peak velocity attenuation of blasting vibration in a separated tunnel with the corresponding surrounding rock level. When the tunnel structure is a small clearance tunnel, select the blasting vibration attenuation prediction model for small clearance tunnels with corresponding surrounding rock grade. When the blast center distance and blasting parameters of the tunnel section to be predicted are substituted into the corresponding blasting vibration prediction model, the predicted value of the peak particle velocity at the measuring point is obtained. Using the allowable vibration velocity of the protected object as a constraint, the maximum safe charge is calculated by substituting the separated tunnel or the tunnel with small clearance into the corresponding blasting vibration attenuation prediction model. ; Will Compare the actual single-shot charge quantity with the blasting plan to determine whether the blasting plan meets the vibration safety control requirements of the protected object. If the actual single-shot charge quantity exceeds... The demolition plan will then be adjusted.

[0065] In one embodiment of the present invention, the maximum safe charge is calculated using the secondary lining as the protected object, and the allowable particle vibration velocity of the secondary lining is taken as 1.5 cm / s. Based on the blasting vibration attenuation prediction model corresponding to different tunnel structure forms, construction methods, and surrounding rock grades, the maximum safe charge under the secondary lining control conditions is shown in Table 6. Table 6 Maximum Safe Dosage

[0066] When considering the protection of secondary lining, gas pipelines and dangerous rocks at the tunnel entrance, the maximum safe charge under the allowable vibration velocity control for each protected object is calculated for each working condition, and the minimum value is taken as the comprehensive maximum safe charge for that working condition.

[0067] In one embodiment of the present invention, the actual dosage, maximum safe dosage, and determination results after comprehensive protection object control are shown in Table 7: Table 7. Judgment Results After Comprehensive Protection Target Control

[0068] As shown in Table 7, in the case of reserved core soil method for Class V surrounding rock of the separated tunnel, the actual amount of explosives is 8.64 kg, and the comprehensive maximum safe amount of explosives is 6.38 kg, with a difference of 35.42%. It is determined that there is a risk of excessive blasting vibration in this case.

[0069] In the case of a pre-reserved core soil method for Class IV surrounding rock in a separated tunnel, the actual charge was 13.68 kg, while the maximum safe charge was 12.38 kg, a difference of 10.50%. It was determined that this case posed a risk of excessive blasting vibration.

[0070] In the case of the stepped method for Class III surrounding rock in a separated tunnel, the actual amount of explosives was 25.30 kg, and the maximum safe amount of explosives was 30.84 kg, with a difference of -17.96%. It was determined that the working condition met the safety control requirements.

[0071] In the case of the step-by-step method for Class II surrounding rock in a separated tunnel, the actual charge was 22.00 kg, and the maximum safe charge was 54.24 kg, with a difference of -62.98%. It was determined that the case met the safety control requirements.

[0072] In the CD method working condition of Class V surrounding rock in a tunnel with small clearance, the actual charge was 11.88 kg, while the maximum safe charge was 7.40 kg, with a difference of 60.54%. It was determined that there was a risk of excessive blasting vibration in this working condition.

[0073] In the CD method working condition of Class IV surrounding rock in a tunnel with small clearance, the actual charge was 18.81 kg, while the maximum safe charge was 14.64 kg, with a difference of 28.48%. It was determined that there was a risk of excessive blasting vibration in this working condition.

[0074] In the case of a tunnel with a small clearance and Class V surrounding rock using the double-sided pilot tunnel method, the actual charge was 11.88 kg, while the maximum safe charge was 7.93 kg, a difference of 49.81%. It was determined that there was a risk of excessive blasting vibration in this case.

[0075] Therefore, it can be seen that for Class II and Class III surrounding rock, due to the relatively good rock mass integrity and bearing capacity, the actual charge quantity is less than the maximum safe charge quantity in most working conditions; for Class IV and Class V surrounding rock, due to the higher degree of rock mass fragmentation and weaker resistance to disturbance, the maximum safe charge quantity is significantly reduced, and in some working conditions, the actual charge quantity exceeds the maximum safe charge quantity, requiring adjustments to the blasting plan.

[0076] For operating conditions determined to be out of range, one or more of the following safety control measures may be taken: Reduce the maximum single-shot charge; adjust the borehole layout; optimize the charge structure; optimize the detonation network; increase the delay time; adjust the construction method; strengthen the support structure; and increase the frequency of on-site blasting vibration monitoring.

[0077] This invention can calculate the maximum safe charge based on the allowable vibration velocity of the protected object, providing a quantitative basis for blasting parameter optimization, construction safety evaluation and on-site vibration control, while improving the accuracy of blasting vibration prediction for tunnels in multi-level surrounding rock.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for predicting the vibration attenuation law of blasting in tunnels with surrounding rock grades II to V, characterized in that, include: S1. Obtain the surrounding rock grade, tunnel structure, and blasting parameters of the tunnel section to be predicted; S2. Prepare Class II to Class V surrounding rock samples according to the surrounding rock grade. Class II and Class III surrounding rock samples are prepared by in-situ core sampling. Class IV and Class V surrounding rock samples are prepared by screening through acoustic testing after low-amplitude impact pre-damage treatment based on intact rock samples. S3. Perform dynamic and static mechanical parameter tests on rock samples of each level of surrounding rock to obtain the set of mechanical parameters for each level of surrounding rock. S4. Based on the mechanical parameter set of each surrounding rock level, establish a three-dimensional blasting dynamic numerical model. Verify the three-dimensional blasting dynamic numerical model with field monitoring data. Extract the peak particle vibration velocity under each surrounding rock level, construction method and blasting condition to form a blasting vibration attenuation sample set. The three-dimensional blasting dynamic numerical model includes a three-dimensional blasting dynamic numerical model for separated tunnels and a three-dimensional blasting dynamic numerical model for small clearance tunnels. S5. The dimensional analysis method is used to perform regression fitting on the sample set of blasting vibration attenuation, and a prediction model for the peak velocity attenuation of blasting vibration in separate tunnels or a prediction model for the vibration attenuation of small-clearance tunnels is established based on the three-dimensional blasting dynamic numerical model. The prediction model for the attenuation of blasting vibration in small-clearance tunnels is based on the prediction model for the attenuation of peak velocity of blasting vibration in separated tunnels, and is obtained by introducing a cavity correction coefficient. S6. Substitute the surrounding rock grade, blasting parameters and tunnel structure of the tunnel section to be predicted into the corresponding blasting vibration attenuation prediction model to obtain the peak particle velocity, and calculate the maximum safe charge based on the allowable vibration velocity of the protected object.

2. The method for predicting the vibration attenuation law of blasting in tunnels of Class II to V surrounding rock as described in claim 1, characterized in that: The specific methods for preparing the Class IV and Class V surrounding rock samples include: An intact granite specimen was selected as the base specimen, and an initial acoustic wave test was performed on the base specimen to obtain the longitudinal wave velocity before impact. A split Hopkinson pressure bar device was used to perform low-amplitude impact pre-damage treatment on the basic specimen. After each low-amplitude impact, the appearance of the sample is inspected, and samples with through cracks, obvious end face damage, edge peeling or overall breakage are rejected, thus obtaining the pre-damage retained samples for each number of impacts. Acoustic wave testing was performed on the retained samples to obtain the longitudinal wave velocity after impact. The deviation between the longitudinal wave velocity corresponding to each number of impacts and the measured longitudinal wave velocity of the surrounding rock mass corresponding to the grade of the rock to be prepared was used as the screening criterion. The pre-damaged retained sample corresponding to the number of impacts with the smallest longitudinal wave velocity deviation was determined as the equivalent weakened rock sample.

3. The method for predicting the vibration attenuation law of blasting in tunnels of Class II to V surrounding rock as described in claim 2, characterized in that: The impact pressure of the low-amplitude impact pre-damage treatment is 0.1 MPa, the impact velocity is 2.4 m / s, and the number of impacts is set to 1, 2, and 3 times respectively.

4. The method for predicting the vibration attenuation law of blasting in tunnels of Class II to V surrounding rock as described in claim 1, characterized in that: The set of mechanical parameters includes the density, longitudinal wave velocity, transverse wave velocity, dynamic elastic modulus, dynamic shear modulus, Poisson's ratio, uniaxial compressive strength, and dynamic response parameters of rock samples of each surrounding rock grade.

5. The method for predicting the vibration attenuation law of blasting in tunnels of Class II to V surrounding rock as described in claim 4, characterized in that: The method for constructing the three-dimensional blasting dynamic numerical model specifically includes: A three-dimensional geometric model is established based on the tunnel structure of the tunnel segment to be predicted: When the tunnel structure is a separated tunnel, a three-dimensional geometric model is established that includes the surrounding rock mass, the single-tunnel excavation outline and the support structure. When the tunnel structure is a small clearance tunnel, a three-dimensional geometric model is established, including the surrounding rock mass, the excavation outline of the first tunnel, the excavation outline of the second tunnel, the interbedded rock pillars, the formed cavity of the first tunnel, and the support structure. In the three-dimensional geometric model, the surrounding rock mass and support structure are represented by Lagrange elements, while the explosive and detonation products are represented by Eulerian elements or arbitrary Lagrange-Eulerian elements. The explosive detonation pressure is transmitted to the surrounding rock mass through fluid-structure interaction. Material parameters for each surrounding rock zone are assigned based on the density, dynamic elastic modulus, dynamic shear modulus, Poisson's ratio, and uniaxial compressive strength corresponding to each surrounding rock level in the mechanical parameter set. The support structure is assigned its actual material mechanical parameters. The ground surface and each tunnel excavation face of the 3D geometric model are set as free boundaries, and the outer boundaries of the four sides and bottom of the model are set as non-reflective boundaries.

6. The method for predicting the vibration attenuation law of blasting in tunnels of Class II to V surrounding rock as described in claim 1, characterized in that: The method for establishing the peak velocity attenuation prediction model for split-type tunnel blasting vibration includes: Peak particle velocity, single-shot charge, detonation center distance, and density of surrounding rock at various levels. and longitudinal wave velocity To analyze the variables, dimensional analysis was used to derive the dimensionless parameter combination and determine the basic functional form of the prediction model for the peak velocity decay of blasting vibration in a split tunnel. Based on the basic function form, logarithmic linear regression fitting was performed on the sample set of blasting vibration attenuation. The site coefficient and attenuation index were determined according to the surrounding rock level and construction method, and a prediction model for the peak velocity attenuation of blasting vibration in separate tunnels corresponding to each surrounding rock level was established.

7. The method for predicting the vibration attenuation law of blasting in tunnels of Class II to V surrounding rock as described in claim 6, characterized in that: The prediction model for the attenuation of peak vibration velocity in split-type tunnel blasting is as follows: in, The peak velocity of the particle. For the maximum single-shot dose, For the distance between the centers, For the first Site coefficients corresponding to Class I surrounding rock. For the first The attenuation index corresponding to grade III surrounding rock. Indicates the surrounding rock grade. Choose II, III, IV, or V.

8. The method for predicting the vibration attenuation law of blasting in tunnels of Class II to V surrounding rock as described in claim 1, characterized in that: The method for constructing the prediction model for vibration attenuation during blasting in tunnels with small clearance is as follows: Based on the three-dimensional blasting dynamic numerical model of small-clearance tunnels, the peak particle velocity distribution along the longitudinal direction of the tunnel is extracted from each measuring point in the preceding tunnel after the subsequent tunnel blasting, and the longitudinal distribution data of the vibration velocity in the preceding tunnel is obtained. Using the longitudinal position of the measuring point as the independent variable, nonlinear regression fitting is performed on the longitudinal distribution data of the vibration velocity in the pilot tunnel. Based on the non-uniform distribution characteristics of the vibration velocity along the longitudinal direction, the center position of the vibration peak, the cavity amplification coefficient, and the cavity influence characteristic length are determined. Based on the center position of the vibration peak, the cavity amplification coefficient, and the cavity influence characteristic length, the cavity correction coefficient is determined. : Cavity correction factor By introducing a separate tunnel blasting vibration peak velocity attenuation prediction model, a small-clearance tunnel blasting vibration attenuation prediction model is obtained.

9. The method for predicting the vibration attenuation law of blasting in tunnels of Class II to V surrounding rock as described in claim 8, characterized in that: The prediction model for vibration attenuation during blasting in tunnels with small clearance is as follows: in, This represents the predicted peak velocity of a mass point at a measuring point inside the pilot tunnel of a tunnel with a small clearance. The horizontal distance between the measuring points is relative to the detonation face. This represents the longitudinal position corresponding to the peak center in the longitudinal distribution of vibration velocity in the preliminary tunnel. This is the cavity amplification factor. The cavity influence feature length, Indicates the first Site coefficients corresponding to Class I surrounding rock. This indicates the maximum single-shot dosage. Indicates the distance between the centers of the explosion. Indicates the first The attenuation index corresponding to grade III surrounding rock. This represents the cavity correction factor.

10. The method for predicting the vibration attenuation law of blasting in tunnels of Class II to V surrounding rock as described in claim 1, characterized in that: Step S6 specifically includes: Based on the surrounding rock grade and tunnel structure of the tunnel section to be predicted, the corresponding blasting vibration attenuation prediction model is selected: When the tunnel structure is a separated tunnel, select the prediction model for the peak velocity attenuation of blasting vibration in a separated tunnel with the corresponding surrounding rock level. When the tunnel structure is a small clearance tunnel, select the blasting vibration attenuation prediction model for small clearance tunnels with corresponding surrounding rock grade. When the blast center distance and blasting parameters of the tunnel section to be predicted are substituted into the corresponding blasting vibration prediction model, the predicted value of the peak particle velocity at the measuring point is obtained. Using the allowable vibration velocity of the protected object as a constraint, the maximum safe charge is calculated by substituting the separated tunnel or the tunnel with small clearance into the corresponding blasting vibration attenuation prediction model. ; Will Compare the actual single-shot charge quantity with the blasting plan to determine whether the blasting plan meets the vibration safety control requirements of the protected object. If the actual single-shot charge quantity exceeds... The demolition plan will then be adjusted.

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