Mechanical blasting mixed excavation method suitable for large-section long footage of subway station

Abstract

The application discloses a mechanical blasting mixed excavation method suitable for large-section long footage of a subway station and relates to the technical field of underground rail transit engineering, and comprises the following steps: acquiring a tunnel section contour, a geological structure and blasting parameters, establishing a three-dimensional blasting wave propagation inversion model, identifying a closed space region forming reflection interference in combination with geological and material heterogeneity, and predicting a space point position of abnormal accumulation of blasting wave energy. The application is based on the three-dimensional blasting wave propagation inversion model, predicts an abnormal wave energy accumulation region in combination with geological heterogeneity, identifies a high-risk blasting section and reconstructs parameters, is supplemented with real-time monitoring of vibration and model feedback correction, constructs a closed-loop control system, effectively suppresses local wave peak abnormality, and improves the safety and controllability of large-section tunnel blasting construction.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of underground rail transit engineering, and in particular to a mechanical blasting mixed excavation method suitable for large-section long footage of a subway station. BACKGROUND

[0002] The "mechanical blasting mixed excavation suitable for large-section long footage of a subway station" refers to a mixed construction method combining mechanical excavation (such as a tunneling machine, a hydraulic breaking hammer, etc.) and controlled blasting (such as millisecond blasting, directional blasting, etc.) in the construction process of a subway station for complex working conditions with a large section and long footage of one-time excavation. The method flexibly deploys the advantages of machinery and blasting means, so that the excavation process has both the forming accuracy and construction continuity of mechanical excavation and the high-efficiency breaking capacity of blasting operation on hard surrounding rock, and is particularly suitable for underground space engineering with complex lithology, high surrounding rock strength, limited construction site, or tight construction period. By reasonably controlling the blasting energy and blasting sequence, auxiliary excavation and forming processing are performed with mechanical equipment, the overall footage efficiency is effectively improved, the surrounding rock disturbance is reduced, the structural stability is enhanced, and the multiple requirements of safety, efficiency, and quality for large-section long footage of a subway station construction are met.

[0003] The prior art has the following disadvantages:

[0004] In the tunnel excavation process of large-section long footage of a subway station, especially when there is a complex section structure (such as a side wall groove, an upper arch deep groove, a locally thickened or recessed area), the conventional blasting construction is easy to cause abnormal changes in the local blasting wave propagation behavior. Specifically, the high-energy shock wave generated by blasting is easy to have nonlinear staggered reflection and energy multiple superposition phenomenon in these closed or semi-closed geometric structures, resulting in a blasting wave amplitude in the local area far exceeding the design expectation, forming a high-strength energy concentration area, i.e., a "local wave peak abnormal area". This abnormal area not only causes uncontrollable over-breaking or disturbance damage to the surrounding rock structure, leading to structural safety risks such as arch top spalling and side wall collapse, but also may impact the initial support structure (such as the sprayed concrete layer or steel arch), inducing support failure, profile deformation, and connection error. At the same time, the formation mechanism of such local blasting effect has the characteristics of strong suddenness and concealment, which is difficult to avoid through conventional blasting parameter configuration, seriously threatens the stability of the tunnel structure and the construction safety, and becomes one of the key hidden risks affecting the quality control of large-section long footage mixed excavation.

[0005] The above information disclosed in the background section is only used to strengthen the understanding of the background of the present disclosure, and therefore it can include information that does not constitute prior art known to those of ordinary skill in the art. SUMMARY

[0006] The application aims to provide a mechanical blasting mixed excavation method suitable for large-section long footage of subway stations to solve the problems in the background art.

[0007] To achieve the above-mentioned purpose, the application provides the following technical solution: a mechanical blasting mixed excavation method suitable for large-section long footage of subway stations, comprising the following steps:

[0008] S1, acquiring tunnel section contour, geological structure and blasting parameters, establishing a three-dimensional blasting wave propagation inversion model, identifying a closed space region forming reflection interference in combination with geological and material heterogeneity, and predicting a spatial point position of abnormal accumulation of blasting wave energy;

[0009] S2, based on the predicted spatial point position of abnormal accumulation of blasting energy, performing structure resonance path analysis, calculating reflection wave path, energy superposition timing and wave amplitude amplification factor, and determining a high-energy change region with local wave amplitude amplification trend;

[0010] S3, according to the determined high-energy change region, constructing a vibration coupling interference evaluation index, comprehensively considering the relationship among blasting source layout, initiation timing and section geometry, and identifying a high-risk blasting section;

[0011] S4, for the high-risk blasting section, reconstructing the blasting parameters, adjusting the blasting source position, delay time and charge structure, and controlling the wave propagation path to deviate from the energy superposition region;

[0012] S5, during the implementation process of the reconstructed blasting parameters, laying vibration sensing devices, collecting propagation behavior and surrounding rock response in real time, and judging whether the wave peak distribution conforms to the expected adjustment direction;

[0013] S6, according to the difference between the vibration response data and the three-dimensional blasting wave propagation inversion model, correcting the model parameters and evaluation index, optimizing the subsequent blasting design, and realizing closed-loop control of local wave peak abnormal effect.

[0014] Preferably, step S1 comprises:

[0015] Acquiring tunnel section contour point cloud data, geological structure parameters and blasting design parameters;

[0016] Establishing a tunnel section geometry model based on point cloud data, and dividing a 0.1-meter unit grid in FLAC3D, and refining to 0.02 meters in the high-energy superposition region;

[0017] According to the geological zoning, setting different material constitutive parameters and boundary conditions, and applying initiation excitation load;

[0018] Using wave velocity field analysis and kinetic energy contour tracking method to identify the closed space region forming reflection interference, and combining with the third-order spline interpolation method to determine the spatial point position of abnormal accumulation of blasting wave energy.

[0019] Preferably, step S2 comprises:

[0020] A local propagation behavior observation area is established with each explosion energy anomaly accumulation point as the spatial center, and wave propagation path, particle velocity and energy density distribution data in the area are obtained;

[0021] The multiple reflection wave path of the target point is traced back, and the point with the highly coincident reflection path is identified;

[0022] The energy superposition timing analysis and wave amplitude amplification factor calculation are performed on the reflection path highly coincident point, and the resonance enhancement key point is screened out;

[0023] The resonance enhancement key point is projected into the three-dimensional structure model, and is clustered and divided into a high energy change area.

[0024] Preferably, step S3 comprises:

[0025] The spatial position, delay time, charge structure and excitation mode data of all explosive sources within a range of 2.5 meters around the high energy change area are obtained;

[0026] The angle between the explosive source propagation path and the target structure reflection direction is analyzed, and the spatial coupling degree is calculated;

[0027] The time difference of the wave front of each explosive source arriving at the target area is analyzed, and the timing coincidence degree is calculated;

[0028] The structure response sensitivity index is constructed in combination with the cross section geometric parameters, and the three indexes are weighted to form the excitation coupling score, and the high-risk blasting section is identified.

[0029] Preferably, step S4 comprises:

[0030] The spatial position of the explosive source is rearranged, and the staggered staggered and staggered distribution method is adopted to make the blasting wave propagation path away from the weak part of the structure;

[0031] Based on the new arrangement result, the delay time of initiation is set, the electronic detonator is controlled by zone, the initiation interval of adjacent explosive sources is pulled apart, and the wave front synchronization is dispersed;

[0032] The charge structure is optimized for each structure part, the cavity partition and energy blocking filler are set, and the continuous growth of the wave amplitude is limited;

[0033] The wave amplitude reduction, phase misplacement and energy offset effect are verified through three-dimensional simulation, and the effectiveness of the reconstruction parameters is confirmed.

[0034] Preferably, step S5 comprises:

[0035] Three-dimensional vibration sensing devices are arranged at the arch crown corner, the side wall groove, the inverted arch step fold line part and the steel arch connection node to form a high-density spatial monitoring network;

[0036] In the blasting implementation process, all vibration sensing devices are started, three-dimensional particle velocity time history data within 150 milliseconds are collected and transmitted to the data host station synchronously;

[0037] The measured data and the simulation prediction results are compared point by point in terms of wave peak arrival time, propagation direction and peak amplitude.

[0038] The analysis results are used to determine whether the wave peak conforms to the predicted path direction. If more than 80% of the monitoring points meet the standard and the wave amplitude decreases by more than 30%, the reconstruction is considered effective.

[0039] Preferably, the following steps are performed after the reconstruction is determined to be effective:

[0040] Based on the measured blasting wave propagation data obtained by the three-dimensional vibration sensing device, a measured-predicted difference spatial distribution map is generated.

[0041] The difference spatial distribution map is superimposed and compared with the high-risk blasting section identification result, and the local area with significant deviation in wave peak time, direction or amplitude is marked.

[0042] The blast source point, delay time and charge parameters corresponding to the deviation area are exported for subsequent blasting scheme optimization modeling input.

[0043] All vibration monitoring data are archived in the blasting construction database as historical reference for subsequent blasting design of geological paragraphs.

[0044] Preferably, step S6 comprises:

[0045] The measured wave peak arrival time, particle velocity amplitude, propagation direction and equivalent energy density are compared with the predicted values of the same coordinate points of the three-dimensional simulation model one by one to identify model deviation points with significant errors in wave speed, amplitude and direction.

[0046] For the model deviation points, the elastic modulus, shear modulus and wave impedance parameters of the corresponding surrounding rock area are adjusted, and the reflection boundary condition and joint structure parameters are corrected, and the wave propagation simulation is performed again.

[0047] According to the corrected simulation results, the excitation coupling score matrix is reconstructed, the spatial focusing coefficient, time superposition coefficient and structure amplification sensitivity coefficient are quantified, and the first-level high-coupling interference area is calibrated.

[0048] The score results are fed back to the subsequent blasting design, and for the first-level high-coupling interference area, the optimization control strategies of blast source layout offset, delay time pull-up and three-section charge structure configuration are performed.

[0049] In the above technical solutions, the present application provides the technical effects and advantages:

[0050] The application is based on a three-dimensional blasting wave propagation inversion model, combined with geological structure and material heterogeneity characteristics, accurately predicts the abnormal accumulation point of blasting wave energy, and systematically identifies high-risk blasting sections through resonance path analysis and excitation coupling index, realizes targeted reconstruction of blasting parameters. More importantly, the method introduces a real-time monitoring device on site, and dynamically compares it with the simulation model, continuously corrects the design strategy through the parameter feedback mechanism, and builds a closed-loop control system integrating "prediction-verification-correction-redesign". Compared with the traditional blasting scheme, this method significantly reduces the risk of arch collapse, side wall collapse and support failure caused by coherent superposition of blasting waves, enhances the inhibition ability of local wave peak abnormal effect, and effectively ensures the safety of large cross-section tunnel construction in complex geological conditions and the controllability of blasting operation. BRIEF DESCRIPTION OF DRAWINGS

[0051] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description only represent some embodiments described in the present application, and other drawings can also be obtained by those skilled in the art based on these drawings.

[0052] Figure 1 The method flowchart of the mechanical blasting mixed excavation method suitable for large cross-section long footage of subway station of the present application. DETAILED DESCRIPTION

[0053] Example implementations will now be described more fully with reference to the accompanying drawings. Example implementations, however, can be implemented in many different ways and should not be construed as limited to the examples set forth herein; rather, these example implementations are provided so that this disclosure will be thorough and complete, and will fully convey the inventive concept to those skilled in the art.

[0054] The present application provides a mechanical blasting mixed excavation method suitable for large cross-section long footage of subway station as shown in Figure 1 The method flowchart of the mechanical blasting mixed excavation method suitable for large cross-section long footage of subway station of the present application.

[0055] S1, obtaining tunnel excavation section contour data, geological structure parameters and construction blasting parameters, establishing a three-dimensional blasting wave propagation inversion model based on the obtained data, considering the heterogeneity of geological structure and surrounding rock material, identifying the closed space area forming reflection interference in geometric structure, and predicting the spatial point of abnormal accumulation of blasting wave energy;

[0056] To solve the problem of abnormal superposition of blasting wave energy caused by complex cross-section structure, a technical route based on fine geometry and geological information to build a three-dimensional blasting wave propagation inversion model is proposed. The following steps are realized:

[0057] Three types of core input data are acquired as the basis for model construction: first, the portable three-dimensional laser scanner is used to measure and map the tunnel to be excavated in the field, and the point cloud data of the cross section profile is obtained, ensuring that the collection accuracy is better than 5 mm, and the data covers all structural features such as the main arch section, the waist transition zone, the side wall groove, the inverted arch deep groove, the reserved pipeline slot, and the steel arch frame surrounding area; second, combined with the results of drilling sampling, seismic wave velocity testing and CT scanning analysis, detailed geological structure parameters are extracted, including rock body stratified structure, joint surface trend, rock property calibration, structure surface spacing, weathering degree, and fault influence range, and the elastic modulus, shear modulus, Poisson's ratio, density and damping coefficient of each rock layer are determined; third, the set blasting parameters are extracted from the construction design documents, including the spatial coordinate position of each blast hole, the length of the charge column and the length of the empty section, the single-hole charge amount, the type of explosive (such as 2# rock emulsion explosive), the initiation sequence (such as millisecond delay), the type of initiator (electric detonator or electronic detonator), and the blast hole arrangement (linear array or ring array).

[0058] Based on the above data, a three-dimensional blasting wave propagation inversion model is constructed. The model is constructed in the commercial finite difference simulation platform FLAC3D. First, according to the point cloud data, an accurate cross section geometric model is generated by CAD modeling software (such as SolidWorks or Rhino), and it is divided into tetrahedral or hexahedral meshes with a minimum element edge length of 0.1 meters in the preprocessor, and the mesh is refined to 0.02 meters in the energy superposition high sensitive area (such as the side wall-arch foot transition zone); second, the geological zoning is imported, and different regions such as granite, sandy mudstone, tuff, and fractured zone soft rock are respectively assigned with their corresponding material constitutive relationship, using the elastoplastic dynamic material model, and the joint zone is set with the Coulomb friction contact boundary condition; third, the blast source point is corresponded to the excitation load input position in the model, and the instantaneous pressure loading (usually 10 7 Pa, lasting 0.1 ms) at each initiation time is set according to the blasting design, realizing multi-point directional excitation input; finally, the absorbing boundary condition is set to prevent boundary reflection interference, and the blasting wave propagation simulation is performed with a total duration of not less than 150 ms.

[0059] During the simulation process, the closed space region forming the reflection interference is identified by analyzing the reflection behavior of the blast wave in the geometric discontinuous region. The wave velocity field analysis and kinetic energy contour tracking method is used to extract the wave propagation path trajectory at the arch top corner, wall foot concave area, inverted arch thickening section, etc. By comparing the energy attenuation slope and velocity vector coincidence degree on different paths, it is determined which regions have more than three wave path intersection phenomena, and the occurrence time and maximum wave amplitude position are recorded. Further, the particle velocity peak value and kinetic energy density cumulative value of the region in the range of 0~50 ms after blasting are counted, and the space body with wave field overlap degree greater than 80% and wave amplitude increase more than 3 times the original excitation value is selected as the reflection interference closed region. In addition, the dynamic change trend of the space body is reconstructed by the multi-time snapshot synthesis analysis technology, and the energy focusing ability of the space body with time evolution is confirmed, which provides a basis for subsequent point calibration.

[0060] The "wave velocity field analysis and kinetic energy contour tracking method" refers to a method of observing the velocity distribution of wave propagation at different time nodes and the kinetic energy spatial distribution map in three-dimensional blast wave propagation simulation, and dynamically identifying the path and trend of wave propagation, reflection and aggregation in space. Its role in the blasting inversion model is to locate and analyze the actual propagation trajectory of the blast wave in the geometric mutation region of the tunnel structure, especially to identify dangerous regions that may have multiple reflections and energy superposition, such as arch top turning points, wall recesses, and inverted arch step thickening sections.

[0061] The specific steps are as follows:

[0062] In the three-dimensional simulation results, wave velocity distribution data at multiple time points after blasting is extracted to generate "wave velocity field" images. The wave velocity field shows the size and direction of particle velocity at different spatial positions, and higher wave velocity areas indicate that the wave front has just passed through, and low wave velocity areas are areas that have not been reached or have been reflected.

[0063] The superimposed kinetic energy contour distribution map is a contour surface with the same kinetic energy density in the model, which is used to identify space regions with concentrated energy. By continuously tracking the evolution of these contours on the time axis, the bending, focusing or repeated reflection trend of wave motion in specific structural areas (such as arch top corners) can be observed.

[0064] By comparing these characteristic regions in time sequence, the evolution path of kinetic energy contours at structural corners can be analyzed, and combined with the direction of wave velocity vector, the propagation trajectory of blast wave in these special-shaped structures can be clearly depicted. For example, if the wave velocity vector in the wall recess appears multiple times in the same direction, combined with the repeated accumulation of kinetic energy contours at this point, it indicates that there is a high-frequency reflection path in this region, which is a closed space with abnormal energy accumulation.

[0065] The trajectory is connected with the superimposed area and projected onto the tunnel section map to accurately locate the reflection path convergence point as the input basis for subsequent analysis of the high-risk area of "local wave peak anomaly".

[0066] In the identified closed space area, key points with strong energy accumulation trend are extracted. By comparing the particle velocity time history curves of each point, a wave amplitude variation rate curve is fitted using a cubic spline interpolation method, and the wave amplitude growth rate, superposition time consistency coefficient and instantaneous power density of each point are calculated. Finally, the blast wave abnormal accumulation points that show strong nonlinear growth trend in the initial stage (0-20 ms) of blast excitation and multiple reflection waves superimposed at the same time are screened out. Further, the coordinates of these points are projected back to the tunnel excavation section geometric model to locate their corresponding component parts in the actual structure (such as arch top spray mixing area, steel arch connection node, inverted arch concrete joint), as high-risk area key control points, providing spatial input basis for subsequent implementation of blast structure resonance path analysis, excitation disturbance control and fine parameter reconstruction.

[0067] The cubic spline interpolation method is a commonly used smoothing fitting technique in data analysis. The basic idea is to connect a series of cubic curve segments to make the curves smoothly transition between each data point, thereby accurately restoring the continuous change trend of the data in time or space. In the present invention, the cubic spline interpolation method is used to finely fit the wave amplitude variation data of each point in the blast wave propagation simulation process to capture the dynamic change characteristics in the initial stage (0-20 ms) of blast excitation and identify the spatial points that may have local wave peak anomalies.

[0068] In specific operation, first, the particle velocity time history data of each monitoring point in the initial stage of blast excitation is extracted from the simulation results, and a discrete data point sequence is constructed at equal time intervals. Then, the cubic spline interpolation method is used to fit these discrete data points into a continuous and smooth wave amplitude variation curve, so that the curve meets the data trend and has good derivative continuity in each time period, avoiding sharp jumps or unrealistic fluctuations. Next, by analyzing the slope change of the fitted curve on the time axis, the wave amplitude growth rate of each point in a short time is extracted to judge its energy concentration degree. At the same time, the degree of time sequence overlap of multiple reflection waves arriving at the point is compared, and the "superposition time consistency coefficient" reflecting the synchronization of multiple wave superposition is calculated to further determine whether it is a reflection focus with multiple wave enhancement. Finally, combined with the local kinetic energy change rate of the point in the same time period, the instantaneous power density level is estimated, and whether the point has significant nonlinear growth trend and blast wave abnormal accumulation characteristics is judged from the wave amplitude growth rate, time sequence coincidence and energy density.

[0069] Through this method, those key points that show obvious energy anomaly characteristics in the early stage of excitation can be effectively screened from thousands of model calculation points, serving as the core basis for subsequent hazard zone identification and blasting parameter reconstruction, effectively improving prediction accuracy and intervention pertinence.

[0070] The purpose of this step is to provide a blasting wave propagation base model with high spatial precision and geological response capability for subsequent prediction and control of local blasting wave peak abnormal effect in large-section long footage tunnels in subway stations. By obtaining tunnel excavation section contour data, geological structure parameters and construction blasting parameters, the geometric feature, surrounding rock structure and actual blasting boundary conditions of the construction area can be fully mastered, thereby providing real input basis for numerical simulation. The three-dimensional blasting wave propagation inversion model established on this basis can dynamically simulate the propagation, reflection, refraction and interference process of blasting waves in different lithology zones, section geometry changes and charge layout after blasting excitation, and truly reproduce the spatio-temporal evolution path of blasting waves in complex spatial structures. In particular, by introducing the modeling of the heterogeneity of surrounding rock materials (such as impedance difference between different rock layers and fracture development degree), the nonlinear and asymmetric behavior of energy propagation in actual engineering can be effectively captured, making the model more close to the real engineering situation. The ultimate goal of this model is to identify closed space regions formed by multiple reflections and interferences of waves in complex geometric regions (such as arch top grooves, side wall corners and inverted arch thickening zones), and locate the blasting wave abnormal accumulation points with significant energy superposition strength and highly coincident propagation path in these regions. Such points are usually the core source area of local wave peak abnormality formation in subsequent blasting, which is prone to induce arch top spalling, side wall damage or initial support failure. Therefore, accurate prediction through this step in advance is not only a necessary prerequisite for subsequent blasting optimization design, but also a key control means to ensure the stability of complex tunnel structure and construction safety.

[0071] S2, according to the predicted blasting energy abnormal accumulation space points, perform blasting wave structure resonance path analysis, calculate the reflection wave path, energy superposition timing and wave amplitude amplification factor of the corresponding points, and determine the high-energy change area with local wave amplitude amplification trend;

[0072] In order to further identify the multi-path reflection and local energy enhancement behavior of blasting waves in complex geometric structures, based on the predicted blasting energy abnormal accumulation space points, further blasting wave structure resonance path analysis is carried out. This analysis includes the following steps:

[0073] Extract all the blasting energy anomaly accumulation points identified by the three-dimensional blasting wave propagation inversion model in the previous stage, and establish a local propagation behavior observation area one by one. Take each point as the spatial center, set a cubic analysis unit with a side length of 2.0 meters, and divide it into a spatial grid with a precision of not less than 0.05 meters. In each local analysis unit, the particle velocity data, energy density distribution data, and direction vector data within the full time range of the blasting simulation are retrieved to construct the complete wave propagation record of the point within the 0 to 100 millisecond time window after blasting excitation. On this basis, the main propagation path of the blasting wave from the initial excitation point to the target point is analyzed, the propagation direction, propagation speed, and arrival time of the wave front are tracked, and the path trajectory diagram is drawn for subsequent reflection behavior analysis.

[0074] Identify the reflection path for each target point. Through the three-dimensional visualization analysis platform, take the target point as the receiving point, and reverse trace the main wave and reflection wave paths received by the target point at multiple time nodes. The spatial angle, incident boundary attribute, and propagation time of each propagation path are comprehensively judged. For example, when the path comes from the tunnel arch corner, the inverted arch recess area, or the side wall reflection surface, and the reflection times are not less than twice, and the propagation paths appear high-angle intersection in space, the path is marked as a multiple reflection path. If a target point receives reflected waves from three or more different directions, and the difference between the incident angle and the reflection angle of the reflection path is less than 15 degrees, and the included angle between the propagation paths is less than 30 degrees, it indicates that the point is in a multi-path coupling focal point area with obvious resonance focusing characteristics, and is recorded as a "reflection path highly overlapping point".

[0075] On the points with multi-path reflection characteristics, carry out energy superposition timing analysis and wave amplitude amplification factor calculation. The specific operation is as follows: Extract the particle velocity curve of the point with time from the model data, smooth the waveform by using the cubic spline interpolation method, and determine the main wave peak position and corresponding time. Calculate the time interval between adjacent wave peaks to determine whether it is concentrated within 20 milliseconds after blasting; if two or more wave peaks with similar heights and time intervals less than 2 milliseconds appear within this time period, it indicates that there is a synchronous superposition trend. Further, compare the maximum wave peak amplitude with the wave peak value of the initial excitation point within the same time period to calculate the wave amplitude amplification factor. If the wave amplitude amplification factor is greater than 3.0, and the time interval between the superposition wave peaks is less than 1 millisecond, it indicates that the point has a significant local wave amplitude amplification effect, and is determined as a "resonance enhancement key point".

[0076] All resonance-enhanced key points are projected back to the three-dimensional tunnel structure model, and their corresponding structure positions are determined according to their spatial coordinates. If a point falls in the concave corner area under the lower edge of the arch, the connection between the steel arch and the shotcrete support, the abrupt segment of the inverted arch concrete bottom surface, or the lateral transition area of the side wall, it will be classified as a structure vulnerable to high-energy change area. Through spatial grouping and clustering analysis, multiple adjacent high-energy points are merged into a "high-energy change area", and the average wave amplitude amplification factor, energy superposition frequency and reflection path density in this area are calculated, which are used as quantitative reference for subsequent blasting disturbance control and parameter optimization of dangerous section.

[0077] The purpose of this step is to further analyze the reflection propagation characteristics and energy time superposition mechanism of the structure space where these points are located based on the identified spatial points with abnormal aggregation of blasting wave energy, so as to accurately identify the key areas that are most likely to occur resonance focusing and local wave amplitude abnormal amplification during blasting. By calculating the reflection wave path of each point, the specific direction, propagation order and path coincidence degree of the multiple reflections of blasting waves in the structure geometric form mutation area (such as arch foot, side wall groove, inverted arch step) can be determined, and whether there is a phenomenon of high-frequency convergence of reflection waves in space can be judged. Combined with the analysis of the arrival order of these reflection waves in time, whether multiple wave fronts can synchronously arrive at the same position in a very short time and form a high degree of consistency in energy superposition time sequence can be further identified. If the calculated wave amplitude amplification factor is much higher than the initial excitation value, it indicates that there is a significant resonance effect at this point, and the surrounding space is likely to develop into a high-energy impact area. In the actual construction process of tunnel excavation, such high-energy change areas are usually the inducing sources of risk events such as arch top spalling, support cracking or profile deviation. Therefore, by identifying and quantitatively evaluating these areas in advance through this step, not only does it provide a scientific basis for the precise control of subsequent blasting parameters, but also lays a technical foundation for the structure reinforcement and support warning of high-risk sections. This analysis plays a bridge role in blasting control, converting the simulation prediction results into implementable and intervenable spatial objects, and realizing the key conversion from "finding problems" to "preventing risks".

[0078] S3, according to the determined high-energy change area, constructing a vibration coupling disturbance evaluation index, comprehensively quantifying the coupling relationship between the blasting source position, the delay sequence of initiation and the geometric structure of the tunnel section, and identifying the high-risk blasting section prone to nonlinear concentration of blasting energy;

[0079] To effectively identify the high-risk areas that may appear nonlinear concentration of blasting wave energy during blasting construction, and thus cause structural disturbance, based on the high-energy change areas identified in the previous step, a vibration coupling disturbance evaluation index is constructed. This evaluation method comprehensively analyzes the energy focusing characteristics of the spatial distribution of blasting sources, the delay time configuration of initiation, and the geometric structure of the tunnel section, and determines the blasting risk level point by point. The process includes the following steps:

[0080] The coordinates of the high-energy change areas identified in the three-dimensional simulation analysis are projected back into the tunnel entity structure corresponding to the construction design drawings, and combined with the three-dimensional laser measurement model, it is determined that these areas are located in the crown annular re-entrant corner area, the edge wall-invert connection, the haunch variable cross-section location, the invert step turn-around section and other structural geometric mutation areas. On this basis, all the explosive source information within a radius of 2.5 meters is searched, including the three-dimensional spatial coordinates of the explosive source point, the delay time of initiation, the type of explosive used (such as emulsion explosive, ammonium oil explosive), the charging structure (cylindrical charge or segmented charge), the single-hole charge amount (unit: kg) and the initiation method (such as millisecond electric detonator, electronic detonator). This data is used as the full set of input factors for the excitation of the high-energy area, a corresponding data list is established, and it is recorded into the simulation analysis platform for subsequent coupling modeling.

[0081] The coupling relationship between the above explosive source data and the high-energy change area is analyzed in space and time dimensions. In terms of space, the Euclidean space distance between each explosive point and the center point of the high-energy area is calculated, and the wave propagation direction vector is extracted to analyze whether it is co-directional with the main reflection path direction of the target area; if the path angle is less than 20 degrees, it is determined to have directional focusing tendency. In terms of time, the delay initiation sequence of all related explosive sources is analyzed, a delay time axis graph is drawn, a time sequence array is formed, and the time nodes of the arrival of the waves from multiple explosive sources to the target area are calculated to determine whether multiple explosive waves form superposition within a time window of not more than 5 milliseconds. If both the spatial directionality and the time coincidence are satisfied, it is considered that the target area may be affected by the multi-point coordinated excitation and has the potential risk of forming energy nonlinear concentration.

[0082] An excitation coupling disturbance evaluation index is constructed to quantitatively calculate the above coupling relationship. Three indexes are specifically set: the first one is a spatial coupling degree index, which reflects the consistency of the explosive source propagation path direction and the main reflection path of the target structure, and the direction angle cosine value is normalized, the closer to 1, the higher the spatial coupling degree; the second one is a time coincidence degree index, which reflects the synchronization of the wave front overlap in the target area, and a Gaussian weight factor is constructed based on the wave front arrival time difference for unified normalization; the third one is a structure response sensitivity index, which is modeled according to the geometric mutation characteristics of the target area in the three-dimensional cross-section model, including curvature radius, recess depth, variable cross-section angle and other parameters, to obtain the structure response index of the focusing ability of the blasting wave reflection. After standardization, the three indexes are given a weighted coefficient for linear superposition, and finally a comprehensive excitation coupling score is formed, with a numerical range of 0 to 1, the higher the score, the stronger the coupling effect and the greater the structure disturbance risk.

[0083] Based on the excitation coupling score, the risk judgment threshold is set, usually taking 0.75 as the dividing line, and all high-energy areas are classified. The area with a score greater than or equal to 0.75 is determined as a "first-level high-risk blasting section", the score between 0.5 and 0.75 is a "second-level intervention section", and the rest is a "regular control section". For the first-level high-risk section, control measures such as blast source rearrangement, charge structure optimization, and initiation time sequence offset adjustment should be implemented in subsequent blasting design, while the support thickness, material strength, and node rigidity in this area should be strengthened, and multiple vibration monitoring points should be set to achieve real-time feedback control. This process not only realizes the quantitative identification of high-risk blasting sections, but also provides decision-making basis for subsequent implementation of precision controlled blasting.

[0084] The role of this step is to further identify the high-risk blasting section in the blasting process that may be induced by the non-linear concentration effect of blasting energy due to unreasonable excitation source configuration, based on the high-energy change area that has been identified. By analyzing the distribution position of the blast source in space, the excitation direction, and the propagation path angle between the high-energy area, it can be determined whether the excitation energy has a spatial focusing trend. By analyzing the time difference of the initiation delay sequence, it can be determined whether the blasting waves released by multiple blast sources are superimposed in a very short time window, thereby forming the time synchronization of the instantaneous energy peak. On this basis, combined with the geometric features of the tunnel cross-section structure, such as arch foot curvature, inverted arch step mutation, and edge wall groove angle, the response sensitivity of the target area to blasting wave reflection and focusing can be further judged. By comprehensively quantifying the above three factors, the excitation coupling disturbance evaluation index constructed can not only be used to judge the structural disturbance risk implied in the current blasting design scheme, but also provide reliable basis for subsequent blasting parameter optimization, initiation sequence reconstruction, and blast source rearrangement. Through the risk classification output of this index, the high-risk blasting section that is most likely to cause energy abnormal convergence and induce surrounding rock over-crushing, initial support damage, or profile deformation in the blasting process can be identified in advance, thereby realizing the change from "passive response" to "active prediction" in construction risk management. This step plays a key role in the whole blasting design closed-loop control process, and is a basic analysis link for realizing precision blasting, controlling structural disturbance, and ensuring construction safety.

[0085] S4, for the identified high-risk blasting section, the blasting parameters are reconstructed, the spatial layout of the blast source, the initiation delay time, and the charge structure configuration are re-set, the blasting wave propagation path is adjusted to avoid high-energy superposition area, and the diffusion and phase offset of the blasting wave energy are realized;

[0086] For identified high-risk blasting sections, to avoid multi-source coupling and superposition of blast waves in structurally complex areas, resulting in abnormally enhanced local amplitudes and causing construction hazards such as over-fractured surrounding rock, damage to initial support structures, or excavation profile deviation, a blasting parameter reconstruction strategy based on energy path regulation and peak misalignment control needs to be implemented. This strategy includes resetting the spatial layout of blast sources, the configuration of initiation delay time, and the composition of the charge structure to ensure that the blast wave propagation path avoids high-energy superposition zones, achieving directional diffusion and phase difference control. Specifically, it includes the following steps:

[0087] Based on the spatial coordinates of the three-dimensional high-risk blasting section, the original blast source layout scheme was globally adjusted. Taking construction sections as units, the blast source arrangement was redesigned on the cross-sections to avoid concentrating multiple blast sources in structurally weak areas, such as the upper edge of the arch, the junction of sidewall recesses, or the corner of the invert arch steps. In the optimized design, a "staggered arrangement + layered distribution" method was adopted: in the circumferential arrangement, blast sources were arranged in a spiral cross pattern, with a longitudinal offset of 0.6 meters between each adjacent row; in the axial direction, the spacing between each blast source row was maintained at no less than 1.5 meters, and an asymmetrical configuration was set according to the structural direction. This guided the blast wavefront during propagation towards areas with relatively higher structural strength (such as straight sections of sidewalls or the bottom surface of the invert arch), reducing the wavefront concentration tendency at structural geometric transitions.

[0088] Based on the rearranged blast source locations, a new detonation delay time program was developed. A millisecond-level electronic detonator control device was employed, assigning each blast source point an independent delay configuration. The detonation sequence strictly adhered to the principles of "staggered main reflection directions" and "delayed critical structural nodes": the blast source delay time corresponding to the concave corner area of ​​the arch was set to +80 milliseconds after the reference blast source, +60 milliseconds at the sidewall recess, and +100 milliseconds in the invert arch turning-back area. This ensured that the blast wave fronts generated by blast sources at different locations were staggered as much as possible on the time axis, preventing them from synchronously reaching high-risk structural areas. The detonation interval between adjacent blast source points was no less than 20 milliseconds. By "spacing out" the timing, synchronicity was disrupted, effectively dispersing the focused energy in the time domain.

[0089] According to the reconstructed position of the explosion source and the delay sequence, the special design optimization of the charge structure is implemented for each blast hole. In terms of charge material selection, low-velocity emulsion explosive is used in the vault and inverted arch area, with a detonation velocity of 3,000 to 3,200 meters per second; ammonium oil explosive is used in the side wall and structure response sensitive area, with a detonation velocity of 2,500 to 2,800 meters per second, delaying the wave front propagation speed. In terms of charge method, the "interval cavity charge + energy barrier filler" structure is adopted, that is, two segments of explosive columns are set inside each blast hole, with a non-explosive high-density polyethylene inert material layer inserted in between, with a length not less than 10 centimeters. This structure can form an energy interruption zone when the explosion occurs, significantly reducing the wave front continuity and reducing the possibility of phase interference. At the same time, the total charge amount of a single hole is controlled to be not more than 80% of the original design charge amount, by reducing the peak blast energy release rate, increasing the wave amplitude difference, and further interfering with the aggregation conditions of the reflection path.

[0090] Based on the above reconstruction results, a three-dimensional blasting wave propagation simulation platform (such as a dynamic analysis model based on FLAC3D or LS-DYNA) is called to simulate the propagation path prediction of the new scheme. By comparing the blasting wave propagation path, wave amplitude distribution curve and energy concentration area position change in the original design scheme and the reconstruction scheme, the wave amplitude peak value of the original high-risk blasting section is monitored to see if it has dropped by more than 30%, the phase arrival time difference is more than 5 milliseconds, and the maximum energy density position deviates from the original identified point by more than 0.5 meters. If all three indicators are met, it means that the reconstruction scheme effectively breaks the energy coupling path, realizes wave peak misalignment and diffusion control, and verifies that the interference control target is achieved. Finally, the reconstruction scheme will be used as the basis for design optimization of the construction drawing, and will be fed back to the support design department at the same time, used for synchronous reinforcement design coordination, and transmitted to the field blasting process instruction book as the basis for the implementation of the blasting construction control parameters.

[0091] The purpose of this step is to fundamentally intervene in the propagation path and interference characteristics of the blasting wave in the complex structure area by reconstructing the blasting parameters for the identified high-risk blasting section, avoiding the risk of structure disturbance, surrounding rock over-crushing or initial support damage caused by multi-source superposition and energy focusing of blasting waves in space. In traditional blasting design, the blast source often adopts symmetrical and equidistant arrangement, and the charge structure and delay time are configured by experience, ignoring the amplification effect of different section structures on wave propagation direction and phase combination, especially in the geometric discontinuous areas such as tunnel vault re-entrant angle, side wall corner or inverted arch step, which is easy to form a high-amplitude local wave peak due to the multi-path convergence of blasting waves in a short time, resulting in structure stress over-limit. This step reconfigures the spatial distribution of the blast source to avoid high energy coupling areas, and through staggered configuration of the delay time of the initiation, the wave front generated by each blast source is phase-shifted in the time axis, avoiding synchronous energy superposition. In addition, by adjusting the charge structure, such as using cavity charging, segmented charging, low-explosive combination and other means, the blasting energy release presents discontinuity and dispersion, thereby effectively reducing the wave peak amplitude, disturbance concentration and reflection coincidence rate. Finally, the reconstructed blasting scheme can make the blasting wave propagation in the structure present directional diffusion and time staggered characteristics, realizing the energy interference control of the original high-risk blasting section. This process not only optimizes the blasting energy release law, but also provides an accurate design basis for subsequent blasting monitoring and structure response control, which is a key technical link to realize high-precision, low-disturbance and safe and controllable blasting operation.

[0092] S5, during the implementation of the reconstructed blasting parameters, multi-point vibration sensing devices are laid out to collect real-time blasting wave propagation behavior and surrounding rock vibration response data, and to determine whether the actual blasting wave peak distribution conforms to the predicted path adjustment direction;

[0093] To verify whether the blasting parameter reconstruction has realized effective regulation and control of the blasting wave propagation path, high-precision vibration sensing devices need to be laid out on site to monitor the wave propagation behavior and surrounding rock vibration response in real time during the blasting process. By comparing the measured data with the simulation prediction results point by point, the closed-loop verification of the wave peak propagation trajectory deviation, energy concentration trend and direction control effect is realized, ensuring that the blasting energy will not be focused again in the high-risk section. This process includes the following steps:

[0094] High-density vibration sensing devices were laid out in the tunnel construction section to collect real-time responses of blast wave propagation. According to the main propagation path and energy reflection focus point identified in the three-dimensional blasting simulation model, the sensing point layout position was selected preferentially, focusing on covering the vault corner, side wall groove, inverted arch step fold line part and steel arch connection node. Each sensing point used a three-axis electric vibration velocity sensor (model SVS1000, frequency range 0.5 Hz-1 kHz), and was equipped with a high-precision collector. The sampling frequency was set to 20 kHz, and the sampling accuracy reached ±0.1 mm / s. The sensing points were laid out at an interval of 3 meters in the ring direction and 2.5 meters in the longitudinal direction, using a longitudinal and transverse layout method. Three layers of vertical sensing panels were set up in typical structural sections to form a three-dimensional multi-point time and space monitoring network. The sensors were installed on the outer surface of the surrounding rock spray mix layer through waterproof packaging shells, and were fixed by chemical anchor + steel support double consolidation to ensure continuous and reliable data collection under the action of blasting load.

[0095] In the blasting implementation phase, the initiation command was issued by the blasting command system, and the collection program of all vibration sensing devices was started at the same time. Each device collected complete wave response data from the initiation time to 150 milliseconds, including particle velocity three-dimensional component time history curve, first arrival time of blast wave front, peak value time of wave amplitude, frequency response energy spectrum, etc. The collected data was connected to the field data processing master station in real time through the optical fiber communication line and entered the multi-channel synchronous processing. The processing software generated wave peak propagation animation, equal amplitude line distribution graph and structure response energy spectrum in real time, forming a visual image and data integrated result, which was convenient for the construction technical group to make synchronous research and judgment.

[0096] The measured data collected and the prediction results of the simulation model established before and after the reconstruction of the blasting parameters were compared and analyzed point by point. The comparison contents included three core indicators: first, the time error between the first arrival time of the wave peak and the predicted time, with the control target set as an error of not more than ±3 milliseconds; second, the directional deviation between the measured propagation direction and the predicted main propagation path, with the directional angle deviation set as not more than ±15 degrees; third, the amplitude difference of particle velocity peak value and simulation result, with the control target set as within ±25%. If the measured data meets the above standards, it is considered that the blasting wave propagation behavior conforms to the expected control path; if it exceeds the limit, it needs to be further evaluated whether it is an abnormal phenomenon caused by local geological mutation or blast wave coherent interference, and marked as an area that needs further intervention. All monitoring point results were integrated and output in the form of spatial coordinates to generate a "measured-predicted difference spatial distribution map", and were superimposed with the original high-risk area identification results for comprehensive comparison and analysis.

[0097] Based on the comparison analysis results, the effect of the blasting parameter reconstruction strategy is determined. If more than 80% of the monitoring points meet the control targets of wave peak time, direction and amplitude, and the measured wave amplitude of the sensing points in the high-risk area is reduced by more than 30% compared with the original design scheme, and the wave front synchronization arrival probability is reduced to less than 20%, it is determined that the blasting parameter reconstruction scheme is effective, and the wave field regulation and control target is achieved. Otherwise, the blasting source layout or delay scheme needs to be adjusted according to the monitoring feedback, and the simulation modeling and field verification are re-performed. The determination results are prepared by the construction unit into a special analysis report, and submitted to the supervision, design and safety technology person in charge for joint review, as the basis for subsequent blasting section parameter optimization or support structure design revision. At the same time, all monitoring data are archived into the blasting construction database as prior data for future blasting design parameter configuration under similar geological conditions.

[0098] The role of this step is to build a three-dimensional sensing network covering the key structure area by laying out multi-point high-precision vibration sensing devices on the blasting construction site, to realize real-time monitoring and data collection of the whole process of blasting wave propagation behavior and surrounding rock vibration response, and to judge whether the reconstructed blasting parameters meet the preset control targets of "energy diffusion" and "wave peak misalignment". In the construction of complex cross-section tunnels, even if the blasting parameters are theoretically optimized and simulated, they may still be affected by factors such as geological heterogeneity, construction disturbance and equipment precision, resulting in deviation of the actual wave front propagation path from the original set path, and thus unexpected local wave amplitude enhancement phenomenon. Therefore, this step reinforces the design model through field monitoring, which is a key link in the realization of the "prediction-verification-optimization" closed-loop control. Specifically, the vibration sensing device can collect dynamic data such as particle velocity, acceleration and kinetic energy density of each point after blasting excitation, and determine the real path, arrival time and amplitude peak of the blasting wave front in three-dimensional space. By comparing the measured data with the predicted path in the blasting wave propagation inversion model, it can be accurately judged whether the wave peak successfully avoids the high-energy change area, whether time misalignment is formed at the sensitive structure part, and whether the preset control intervention effect is achieved. If the measured wave peak direction, timing and amplitude are consistent with the predicted results, it means that the blasting parameter reconstruction scheme is effective; otherwise, it needs to be fed back to the parameter design link for secondary optimization. This step not only improves the verifiability of blasting design, but also enables the blasting control to have a data-driven adaptive ability, which is the technical guarantee core of realizing high-quality, safe and controllable blasting construction.

[0099] S6, based on the comparison results between the collected vibration response data and the three-dimensional blasting wave propagation inversion model, dynamically correcting the propagation model parameters and excitation coupling interference evaluation index, and optimizing the subsequent blasting design strategy to realize the whole process closed-loop control of the local blasting wave peak abnormal effect in the complex cross-section;

[0100] To achieve the whole-process closed-loop control of the abnormal effect of local blasting wave peak in complex cross-section, after the completion of blasting construction and on-site vibration response data collection, based on the comparison results of measured data and three-dimensional blasting wave propagation inversion model, the key parameters of the model and the excitation coupling disturbance evaluation index are dynamically modified, and the subsequent blasting design strategy is further optimized to ensure the effective and continuous realization of the control target. The process includes the following steps:

[0101] The measured data collected by the vibration sensing devices laid in the tunnel vault edge, side wall transition zone, inverted arch step bottom and steel arch node area are standardized. The key parameters extracted from each monitoring point include the first arrival time of the wave peak (in milliseconds, accuracy 0.1 ms), the wave peak particle velocity amplitude (unit: mm / s, accuracy 0.01 mm / s), the main propagation direction (in azimuth angle, range 0° to 360°) and the equivalent energy density (unit: J / m 3 ). The total amount of collected data is not less than 30 monitoring points, which are classified into the database according to the construction section number and compared with the predicted values of the same coordinate points in the three-dimensional simulation model one by one. If the difference between the wave peak arrival time of a certain monitoring point and the model prediction is greater than 3 milliseconds, the particle velocity difference is greater than ±0.8 mm / s, and the propagation direction angle error is greater than 20°, it is marked as "model deviation point", and the proportion of each type of deviation point in the entire section is counted for error trend analysis.

[0102] Based on the identified model deviation points, the physical parameters in the propagation model are modified one by one. For the areas where the measured wave speed is faster than the model value, the elastic modulus of the corresponding surrounding rock is adjusted from 3.5 GPa to 4.2 GPa, the shear modulus is adjusted from 1.4 GPa to 1.8 GPa, and the wave impedance is increased to 4000 kg / m 2 ·s; for the points where the wave amplitude is significantly higher than the model value, check the local reflection boundary condition setting, and add an equivalent rigid structure in the simulation model with a thickness of 0.3 m, a density of 2.6 t / m 3 , and a high stiffness material unit with a Poisson's ratio of 0.32. In addition, the joint surface development area is discretely processed, and 3 groups of tangential joint interfaces are set within 0.8 m around the deviation points with a joint spacing of 0.25 m, a friction angle of 28°, and a cohesive force of 500 kPa to reflect the actual geological discontinuity. The modified model is re-simulated for wave propagation, and the particle velocity time history and wave energy contour distribution are output, and the simulation results of the key points are required to be consistent with the measured values with a coincidence rate of not less than 90%.

[0103] According to the modified simulation results, the parameters of the excitation coupling interference evaluation index are reconstructed. Taking the high-energy response point as the center, the spatial distance (accuracy 0.1 m) from the three nearest explosion source points, the delay difference (unit: millisecond, time interval according to the actual detonator configuration) and the location geometric curvature radius (unit: meter, directly extracted from the CAD structure profile) are counted. After normalizing the above three types of data, a new "excitation coupling score matrix" is constructed, in which the spatial focusing coefficient is set to 0.4, the time superposition coefficient is set to 0.35, and the structure amplification sensitivity coefficient is set to 0.25. The total score range is 0 to 1. For regions with a score greater than 0.75, they are determined as first-level high coupling interference regions and need to be controlled in subsequent design. The score matrix will be integrated with the blasting design software as input parameters for the rearrangement of explosion sources and the setting of the initiation sequence.

[0104] The above modification results are fed back to the subsequent blasting section design link as the core basis of the dynamic optimization control strategy. In the construction design adjustment, the explosion source points in the first-level high coupling interference region are forced to be rearranged. The specific scheme is to offset the original explosion source point by 0.5 meters along the normal direction, set the delay to be greater than 60 milliseconds, and use a "main charge-cavity-isolation filling" three-section structure, with the main charge section length controlled at 0.3 meters, the cavity section at 0.1 meters, and the filling section using high-density polyurethane energy-absorbing material. The adjusted blasting scheme is submitted to the design review group for expert evaluation, and after the evaluation is passed, it can be executed. After each subsequent blasting, real-time data collection is performed, and the propagation model and control strategy are iteratively optimized according to the above process, forming a dynamic updating mechanism to realize the "measurement-simulation-design" trinity closed-loop regulation and control of blasting wave propagation behavior.

[0105] The role of this step is to establish a dynamic closed-loop mechanism of "data feedback-model correction-index reconstruction-strategy optimization", ensuring that blasting design not only stays at the theoretical prediction level, but also continuously adjusts and optimizes based on field measurement results, thereby achieving precise control of local blasting wave peak abnormal effects in complex cross-sections. In the construction of large cross-section long-length subway station tunnels, due to geological heterogeneity, fluctuation of surrounding rock physical parameters, and complex structure geometry, etc., blasting waves in the actual propagation process are prone to deviation, focusing or interference beyond the prediction model, leading to local wave amplitude increase, energy concentration, and thus causing surrounding rock damage, support deformation, and contour overbreak. Therefore, relying solely on static blasting simulation design cannot meet the requirements of full-process control, and a dynamic adjustment mechanism based on measured data must be introduced.

[0106] By laying high-density vibration sensing devices to collect blast wave propagation data, and comparing with the predicted results of the three-dimensional blast wave propagation inversion model point by point, it can clearly identify which areas have problems such as propagation path deviation, wave peak arrival time error and energy response out of control. On this basis, the key parameters such as wave velocity, impedance, boundary conditions and joint structure in the model are dynamically corrected, so that the model can more truly reflect the geological environment and structural characteristics of the construction site. At the same time, combined with the simulation results after correction, the disturbance index system of the coupling between the blast source position, initiation sequence and section geometry is reconstructed, and the high-risk section of the next round is identified, providing a scientific basis for the iterative design of blasting parameters.

[0107] Finally, by introducing the corrected model and optimization index into the blasting design process, the spatial arrangement of the blast source, delay arrangement and charge structure are optimized in linkage, so that the propagation direction and phase of the blast wave in the structure are precisely controlled, the local wave amplitude overlap and high-frequency focusing effect are avoided, and the blasting profile forming quality and supporting structure safety redundancy are improved. This step is not only the core link of the closed-loop verification of the prediction model, but also the key technical support for building a high-precision and self-adaptive blasting control system, which has significant engineering practicality.

[0108] The mechanical blasting mixed excavation method suitable for large-section long footage of subway station can realize precise control of the whole process of blast wave propagation behavior in complex section structure, and significantly improve the safety, stability and forming quality of tunnel excavation construction. Based on the three-dimensional blast wave propagation inversion model, the method accurately predicts the abnormal accumulation point of blast wave energy combined with the geological structure and material heterogeneity, and systematically identifies high-risk blasting sections through resonance path analysis and excitation coupling index to realize the reconstruction of blasting parameters. More importantly, the method introduces on-site vibration sensing devices for real-time monitoring and dynamic comparison with the simulation model, and continuously corrects the design strategy through the parameter feedback mechanism, forming a closed-loop control system integrating "prediction-verification-correction-redesign". Compared with the traditional blasting scheme, the method significantly reduces the engineering risks such as arch collapse, side wall collapse and support failure caused by coherent superposition of blast waves, enhances the inhibition ability of local wave peak abnormal effect, and effectively ensures the construction safety and controllability of large-section tunnel in complex geological conditions of subway station.

[0109] The above only describes certain exemplary embodiments of the present application by way of illustration, without doubt, for ordinary skilled in the art, the described embodiments can be modified in various ways without departing from the spirit and scope of the present application. Therefore, the above figures and description are illustrative in nature and should not be construed as limiting the scope of the claims of the present application.

Claims

1. A mechanical blasting and mixed excavation method applicable to large-section, long-expansion excavation of subway stations, characterized in that, Includes the following steps: S1. Obtain the tunnel cross-sectional profile, geological structure and blasting parameters, establish a three-dimensional blasting wave propagation inversion model, combine geological and material heterogeneity, identify closed spatial regions that form reflection interference, and predict the spatial locations of abnormal accumulation of blasting wave energy. S2. Based on the predicted spatial locations of abnormal accumulation of blasting energy, structural resonance path analysis is performed to calculate the reflected wave path, energy superposition time sequence and amplitude amplification factor, and to determine the high-energy change region with a local amplitude amplification trend. S3. Based on the identified high-energy change region, construct an excitation coupling interference assessment index, and identify high-risk blasting sections by comprehensively considering the blast source layout, detonation sequence and cross-sectional geometry. S4, for high-risk blasting sections, reconstructs blasting parameters, adjusts the blast source location, delay time and charge structure, and controls the wave propagation path to deviate from the energy superposition zone; S5, during the implementation of the reconstructed blasting parameters, a vibration sensing device is deployed to collect the propagation behavior and surrounding rock response in real time, and to determine whether the peak distribution meets the expected adjustment direction. S6. Based on the difference between the vibration response data and the three-dimensional blast wave propagation inversion model, the model parameters and evaluation indicators are corrected to optimize the subsequent blasting design and achieve closed-loop control of the local peak anomaly effect. Step S4 includes: The spatial location of the blast source was rearranged, and a staggered and layered distribution method was adopted to keep the propagation path of the blast wave away from the weak parts of the structure. Based on the new layout results, the detonation delay time is set, and electronic detonators are used for zoned control to increase the detonation interval between adjacent detonation sources and disrupt wavefront synchronization. The charge structure was optimized for each structural part, and cavity partitions and energy-blocking fillers were set to limit the continuous increase of wave amplitude. The effects of amplitude reduction, phase misalignment, and energy shift were verified through three-dimensional simulation, confirming the effectiveness of the reconstruction parameters.

2. The mechanical blasting and mixed excavation method for large-section, long-expansion subway station excavation as described in claim 1, characterized in that, Step S1 includes: Acquire tunnel cross-sectional contour point cloud data, geological structure parameters, and blasting design parameters; A geometric model of the tunnel cross section was established based on point cloud data, and a 0.1-meter unit mesh was divided in FLAC3D, which was further refined to 0.02 meters in the high-energy superposition region. Different material constitutive parameters and boundary conditions are set according to geological zones, and detonation excitation loads are applied. The closed spatial region that forms reflection interference is identified by wave velocity field analysis and kinetic energy contour tracing method, and the spatial location of the abnormal accumulation of blast wave energy is determined by combining the third-order spline interpolation method.

3. The mechanical blasting and mixed excavation method for large-section, long-distance excavation of subway stations according to claim 1, characterized in that, Step S2 includes: Establish a local propagation behavior observation area with each point of abnormal accumulation of blast energy as the spatial center, and obtain wave propagation path, particle velocity and energy density distribution data within the area; By tracing the multiple reflected wave paths of the target point in reverse, points with highly overlapping reflection paths can be identified. Energy superposition time series analysis and amplitude amplification factor calculation were performed on the points where the reflection paths highly overlapped to screen out key points for resonance enhancement. The key points of resonance enhancement are projected onto the three-dimensional structural model and clustered into high-energy change regions.

4. The mechanical blasting and mixed excavation method for large-section, long-expansion subway stations according to claim 3, characterized in that, Step S3 includes: Acquire data on the spatial location, delay time, charge structure, and excitation method of all explosion sources within a 2.5-meter radius of the high-energy change area; Analyze the angle between the propagation path of the explosion source and the reflection direction of the target structure, and calculate the spatial coupling degree; Analyze the time difference between the arrival of each explosion source wavefront in the target area and calculate the temporal overlap. By combining cross-sectional geometric parameters, a structural response sensitivity index is constructed, and the three indices are weighted to form an excitation coupling score to identify high-risk blasting sections.

5. The mechanical blasting and mixed excavation method for large-section, long-expansion subway station excavation as described in claim 4, characterized in that, Step S5 includes: Three-dimensional vibration sensing devices are deployed at the corners of the arch, the grooves of the side walls, the broken lines of the inverted arch steps, and the connection nodes of the steel arch frame to form a high-density spatial monitoring network. During the blasting process, all vibration sensing devices were activated to collect three-dimensional particle velocity time history data within 150 milliseconds and transmit it synchronously to the data master station. A point-by-point comparative analysis was conducted between the measured data and the simulation prediction results, focusing on three aspects: peak arrival time, propagation direction, and peak amplitude. The analysis results determine whether the peak conforms to the predicted path direction. If more than 80% of the monitoring points meet the standard and the amplitude decreases by more than 30%, the reconstruction is considered effective.

6. The mechanical blasting and mixed excavation method for large-section, long-expansion subway station excavation as described in claim 5, is characterized in that... Once the reconstruction is deemed valid, perform the following steps: Based on the measured data of blast wave propagation obtained by the three-dimensional vibration sensing device, a spatial distribution map of the measured-predicted difference is generated. By overlaying and comparing the spatial distribution map of the differences with the identification results of high-risk blasting sections, local areas with significant deviations in peak time, direction, or amplitude are marked. Export the blast source location, delay time and charge parameters corresponding to the deviation area for subsequent blasting scheme optimization modeling input; All vibration monitoring data will be archived into the blasting construction database as a historical reference for subsequent blasting designs in geological sections.

7. The mechanical blasting and mixed excavation method for large-section, long-expansion subway station excavation as described in claim 6, is characterized in that... Step S6 includes: The measured wave peak arrival time, particle velocity amplitude, propagation direction and equivalent energy density are compared one by one with the predicted values ​​of the three-dimensional simulation model at the same coordinate point to identify model deviation points with significant errors in wave velocity, wave amplitude and direction. For the deviation points in the model, the elastic modulus, shear modulus and wave impedance parameters of the corresponding surrounding rock area were adjusted, and the reflection boundary conditions and joint structure parameters were corrected. Wave propagation simulation was then performed again. Based on the corrected simulation results, the excitation coupling scoring matrix was reconstructed, the spatial focusing coefficient, the time superposition coefficient and the structural amplification sensitivity coefficient were quantified, and the first-level high coupling interference zone was calibrated. The scoring results are fed back to subsequent blasting designs. For the first-level high-coupling interference zone, optimized control strategies are implemented, including offsetting the blast source layout, increasing the delay time, and configuring the three-stage charge structure.

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