Tunnel safety construction advanced detection method combining forward modeling and inversion analysis

Abstract

The invention discloses a tunnel safety construction advanced detection method combining forward modeling and inversion analysis. The method comprises the following steps: S1, collecting data of a tunnel construction area, performing electromagnetic wave forward modeling by using GPRMax, establishing a geologic structure model, and obtaining electromagnetic characteristic data; s2, according to geological radar actual measurement data, in combination with a GPRMax simulation result, a geological abnormal area is identified, and potential risk points are marked; s3, performing three-dimensional numerical simulation of the tunnel construction process by utilizing FLAC3D according to the geologic structure model and the potential risk point data; s4, according to a simulation result, evaluating stress distribution and a displacement field in the tunnel construction process, and optimizing a tunnel construction scheme; and S5, in the construction process, in combination with real-time monitoring data, performing comparative analysis with a simulation result, and dynamically adjusting and optimizing structural model parameters. According to the advanced detection method for tunnel safety construction, the safety risk in the tunnel construction process can be accurately predicted, and the construction safety is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel construction safety, and in particular to a tunnel safety construction advance detection method combining forward simulation and inversion analysis. Background Art

[0002] Safety issues during tunnel construction have always been a focus of attention in the engineering community. Advanced geological prediction technology is a key link in tunnel construction, mining engineering and geological exploration. Its purpose is to predict and identify potential geological risks to ensure engineering safety. At present, a variety of technical means are used in this field, including geological surveys, geophysical exploration, geochemical analysis, and numerical simulation. These methods have their own advantages and can provide preliminary information on underground structures. However, although these technologies have made significant progress in some aspects, there are still some shortcomings. First, the complexity and multi-solution of geological data make data interpretation uncertain. Second, the high cost of high-precision exploration equipment limits its application in large-scale projects. In addition, the existing numerical simulation technology is still limited in prediction accuracy and dynamic model updating, and the simulation method is relatively single.

[0003] In summary, there is an obvious demand for advanced geological prediction technology to improve prediction accuracy, reduce costs, enhance real-time monitoring capabilities and technical integration. Developing new prediction tools and technologies to overcome existing limitations is of great significance to improving engineering safety and efficiency. Therefore, a more accurate and scientific method is needed to predict and avoid potential construction risks. Summary of the invention

[0004] In view of the above-mentioned technical problems to be solved, the present invention provides a tunnel safety construction advance detection method combining forward simulation and inversion analysis to solve the problem of heterogeneous network switching and achieve smooth switching and continuous positioning in different environments.

[0005] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0006] A tunnel safety construction advance detection method combining forward simulation and inversion analysis comprises the following steps:

[0007] Step S1, collecting data of the tunnel construction area, using GPRMax to perform electromagnetic wave forward simulation on the tunnel construction area, establishing a geological structure model, and obtaining electromagnetic characteristic data of the underground structure;

[0008] Step S2, based on the measured data of geological radar and combined with the simulation results of GPRMax, identify the geological anomaly areas and mark the potential risk points;

[0009] Step S3, using FLAC3D to perform three-dimensional numerical simulation of the tunnel construction process based on the geological structure model and potential risk point data, and analyze the stability of tunnel excavation and support structure;

[0010] Step S4, evaluating the stress distribution and displacement field during the tunnel construction process according to the FLAC3D simulation results in step S3, and optimizing the tunnel construction plan;

[0011] Step S5, during the tunnel construction process, the real-time monitoring data is combined with the FLAC3D simulation results for comparative analysis, and the structural model parameters are dynamically adjusted and optimized.

[0012] As a further improvement of the above technical solution:

[0013] Preferably, the step S1 specifically includes the following contents:

[0014] S1-1, model preparation: define the geometry and electromagnetic properties of the subsurface medium and set the boundary conditions of the model;

[0015] S1-2, parameter setting: simulation parameters include center frequency, pulse width, transmission power and antenna frequency. Configure the center frequency of the simulation and select a frequency range that covers the target underground structure; set the pulse width to determine the duration of the transmission signal;

[0016] S1-3, signal configuration: set the transmission power and adjust the signal strength to adapt to different detection depths and medium attenuation; select the antenna frequency and type to optimize the signal penetration and resolution;

[0017] S1-4, forward simulation execution: run GPRMax software, perform forward simulation, and calculate the propagation and reflection of electromagnetic waves in underground media;

[0018] S1-5, Result analysis and output: Analyze the simulation results, including time domain and frequency domain data, and identify the reflection characteristics of underground structures.

[0019] Preferably, in step S2, identifying the geological anomaly area specifically includes:

[0020] S2-1, obtain the radar detection image of the survey line, analyze and infer the medium properties and interface position according to the time, phase, frequency, amplitude and waveform characteristics of the reflected signal;

[0021] S2-2, calculate the target's buried depth L based on the time difference Δt between the face reflection and the target reflection:

[0022]

[0023] Where: L is the target burial depth, υ is the electromagnetic wave propagation speed, Δt is the time difference between the tunnel face reflection and the target reflection, and x is the offset distance;

[0024] S2-3, reflection coefficient and wave velocity are:

[0025]

[0026] Where: γ is the reflection coefficient, v is the velocity, ε is the relative dielectric constant, and c is the speed of light.

[0027] Preferably, in step S3, the specific steps are as follows:

[0028] S3-1, establishing a geological model: creating a geological model based on the geological anomaly areas and potential risk points identified in step S2; defining initial stress states and boundary conditions;

[0029] S3-2, Load application and construction simulation: Apply loads step by step to simulate the construction process or geological changes; apply displacement boundary conditions and force boundary conditions;

[0030] S3-3, perform numerical simulation: run the simulation to solve the stress, displacement and plastic zone development of the model under load;

[0031] S3-4, Result analysis: Analyze stress distribution, displacement field and support structure response.

[0032] The tunnel safety construction advance detection method of combined forward simulation and inversion analysis provided by the present invention has the following advantages compared with the prior art:

[0033] The tunnel safety construction advance detection method of the present invention combines forward simulation and inversion analysis, combines GPRMax and FLAC3D technologies, and fully combines the advantages of the two technologies, which can more accurately predict the safety risks in the tunnel construction process, improve construction safety, and reduce the occurrence of construction accidents. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a GPRMax forward simulation optimization flow chart of the geological structure of the tunnel construction area of ​​the present invention.

[0035] Figure 2 It is a flow chart of FLAC3D inversion analysis and tunnel construction scheme optimization of the present invention. DETAILED DESCRIPTION

[0036] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0037] like Figure 1 and Figure 2 As shown, the tunnel safety construction advance detection method of the present invention combining forward simulation and inversion analysis comprises the following steps:

[0038] Step S1, collect geological, hydrogeological and geophysical data of the tunnel construction area, use GPRMax to perform electromagnetic wave forward simulation of the tunnel construction area, establish a geological structure model, and obtain electromagnetic characteristic data of the underground structure.

[0039] This step is mainly to determine how to construct a geological structure model in GPRMax. In this embodiment, the main parameters for constructing the geological structure model are the geometric structure and electromagnetic properties of the underground medium, including defining the dielectric constant and conductivity parameters of the underground medium, and adding possible undesirable geological targets such as faults, cracks, and caves to the model.

[0040] Specifically include the following:

[0041] S1-1, Model preparation: Define the geometry and electromagnetic properties of the underground medium, including dielectric constant and conductivity, and add possible unfavorable geological targets to the model at corresponding locations and depths as needed; set the boundary conditions of the model, such as perfectly matched layers (PML) to simulate open space.

[0042] S1-2, parameter setting: simulation parameters include center frequency, pulse width, transmission power and antenna frequency. Configure the center frequency of the simulation and select a frequency range that can cover the target underground structure; set the pulse width to determine the time length of the transmitted signal to control the spatial resolution.

[0043] S1-3, Signal Configuration: Set the transmit power and adjust the signal strength to adapt to different detection depths and medium attenuation; select the antenna frequency and type to optimize the signal penetration and resolution.

[0044] S1-4, forward simulation execution: After configuring all parameters, run the GPRMax software to perform forward simulation and calculate the propagation and reflection of electromagnetic waves in the underground medium.

[0045] S1-5, Result analysis and output: Analyze the simulation results, including time domain and frequency domain data, and identify the reflection characteristics of underground structures.

[0046] Step S2, based on the measured data of geological radar and combined with the GPRMax simulation results, identify geological abnormal areas such as faults, cracks, and voids, and mark potential risk points.

[0047] Specifically:

[0048] S2-1, electromagnetic wave signals propagate in the medium and will produce reflection, dispersion and attenuation when encountering interfaces with different dielectric properties. The transmitting and receiving antennas move synchronously at the same interval on the survey line to obtain the radar detection image of the survey line. The medium properties and interface position are analyzed and inferred based on the time, phase, frequency, amplitude and waveform characteristics of the reflected signal.

[0049] S2-2, ground penetrating radar belongs to the reflection wave detection method. Its basic principle is similar to that of air-to-air radar. According to the time difference Δt between the reflection of the face and the reflection of the target, the burial depth L of the target can be calculated:

[0050]

[0051] Where: L is the target burial depth (distance from the tunnel face), v is the electromagnetic wave propagation speed, Δt is the time difference between the tunnel face reflection and the target reflection, and x is the offset distance (the distance between the transmitting antenna and the receiving antenna). The calculation method of the depth of the abnormal area location is obtained.

[0052] S2-3, for the high-frequency electromagnetic pulses used by ground penetrating radar, the medium usually encountered in engineering surveys and detection is a low-loss medium dominated by displacement current. In this type of medium, the reflection coefficient and wave velocity mainly depend on the dielectric constant, as shown in the following formula:

[0053]

[0054] Where: γ is the reflection coefficient, ε is the relative dielectric constant, and c is the speed of light.

[0055] The positive and negative values ​​of the reflection coefficient can be used to compare the dielectric constants between different regions, and the properties of the medium can be verified by combining the frequency, amplitude and waveform characteristics; the location and depth information of the abnormal area can be further obtained through the wave velocity. That is, the electromagnetic wave propagation velocity c is obtained through the above formula, and the electromagnetic wave propagation velocity is brought into step S2-2 to calculate the location and depth of the abnormal area.

[0056] Step S3, using FLAC3D software, based on the geological structure model and potential risk point data, a three-dimensional numerical simulation of the tunnel construction process is performed to analyze the stability of the tunnel excavation and support structure.

[0057] In this step, the medium properties, interface position, and depth of the abnormal area in step S2 are used to determine whether there is a water-bearing cave behind the tunnel face, and its specific location, volume, etc. are obtained. This information is the potential risk point data, which is used to perform more accurate FLAC3D inversion simulation analysis.

[0058] In this embodiment, constructing a geological model in FLAC3D involves more detailed geological parameters and construction conditions, including:

[0059] (1) Material properties: Assign specific material properties to different geological layers, such as elastic modulus, Poisson's ratio, internal friction angle, cohesion, etc.

[0060] (2) Initial stress state: Define the initial stress state such as geostress and hydrostatic pressure.

[0061] (3) Boundary conditions: Set displacement boundary conditions and force boundary conditions to simulate load application and geological changes during the construction process.

[0062] (4) Grid division: Appropriate grid division is performed according to the complexity of the geological structure to ensure the accuracy and computational efficiency of the simulation.

[0063] The specific steps for analyzing the stability of tunnel excavation and support structure using FLAC3D software are as follows:

[0064] S3-1, establish geological model: create a geological model based on the geological anomaly areas and potential risk points identified in step S2, including geometric dimensions, grid division and material property allocation, including at least elastic modulus, Poisson's ratio, internal friction angle, cohesion, etc.; define the initial stress state and boundary conditions, including at least hydrostatic pressure, ground stress, initial displacement, and velocity conditions.

[0065] S3-2, Load application and construction simulation: Apply loads gradually to simulate the construction process or geological changes; apply displacement boundary conditions (such as fixed boundaries, free boundaries) and force boundary conditions.

[0066] S3-3, Perform numerical simulation: Run simulations to solve the stress, displacement, and plastic zone development of the model under load, paying attention to the responses near geological anomalies and potential risk points.

[0067] S3-4, Result analysis and visualization: Analyze stress distribution, displacement field and support structure response; use FLAC3D visualization tools to display simulation results.

[0068] Step S4, based on the FLAC3D simulation results, evaluate the stress distribution and displacement field during the tunnel construction process, and optimize the tunnel construction plan, including adjusting the support design and improving the construction process.

[0069] Step S5, during the tunnel construction process, combined with real-time monitoring data, the real-time monitoring data includes surface settlement, surrounding rock stress, support structure strain and groundwater level, and the monitoring data is compared and analyzed with the FLAC3D simulation results, and the structural model parameters are dynamically adjusted to improve the accuracy of simulation analysis and conclusions, so as to ensure construction safety.

[0070] Step S6: After the construction is completed, FLAC3D software is used to conduct a post-construction evaluation to ensure the long-term stability of the tunnel.

[0071] The above implementation cases are only preferred embodiments of the present invention and are not intended to limit the present invention in any form. Although the present invention has been disclosed as above with preferred embodiments, they are not intended to limit the present invention. Therefore, any simple modification, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A tunnel safety construction advance detection method combining forward simulation and inversion analysis, characterized in that: The following steps are involved: Step S1, collecting data of the tunnel construction area, using GPRMax to perform electromagnetic wave forward simulation on the tunnel construction area, establishing a geological structure model, and obtaining electromagnetic characteristic data of the underground structure; Step S2, based on the measured data of geological radar and combined with the simulation results of GPRMax, identify the geological anomaly areas and mark the potential risk points; Step S3, using FLAC3D to perform three-dimensional numerical simulation of the tunnel construction process based on the geological structure model and potential risk point data, and analyze the stability of tunnel excavation and support structure; Step S4, evaluating the stress distribution and displacement field during the tunnel construction process according to the FLAC3D simulation results in step S3, and optimizing the tunnel construction plan; Step S5, during the tunnel construction process, the real-time monitoring data is combined with the FLAC3D simulation results for comparative analysis, and the structural model parameters are dynamically adjusted and optimized.

2. The tunnel safety construction advance detection method based on combined forward simulation and inversion analysis according to claim 1 is characterized in that: The step S1 specifically includes the following contents: S1-1, model preparation: define the geometry and electromagnetic properties of the subsurface medium and set the boundary conditions of the model; S1-2, parameter setting: simulation parameters include center frequency, pulse width, transmission power and antenna frequency. Configure the center frequency of the simulation and select a frequency range that covers the target underground structure; set the pulse width to determine the duration of the transmission signal; S1-3, signal configuration: set the transmission power and adjust the signal strength to adapt to different detection depths and medium attenuation; select the antenna frequency and type to optimize the signal penetration and resolution; S1-4, forward simulation execution: run GPRMax software, perform forward simulation, and calculate the propagation and reflection of electromagnetic waves in underground media; S1-5, Result analysis and output: Analyze the simulation results, including time domain and frequency domain data, and identify the reflection characteristics of underground structures.

3. The tunnel safety construction advance detection method based on combined forward simulation and inversion analysis according to claim 1 is characterized in that: In step S2, identifying the geological anomaly area is specifically as follows: S2-1, obtain the radar detection image of the survey line, analyze and infer the medium properties and interface position according to the time, phase, frequency, amplitude and waveform characteristics of the reflected signal; S2-2, calculate the target's buried depth L based on the time difference Δt between the face reflection and the target reflection: Where: L is the target burial depth, υ is the electromagnetic wave propagation speed, Δt is the time difference between the tunnel face reflection and the target reflection, and x is the offset distance; S2-3, reflection coefficient and wave velocity are: Where: γ is the reflection coefficient, v is the velocity, ε is the relative dielectric constant, and c is the speed of light.

4. The tunnel safety construction advance detection method based on combined forward simulation and inversion analysis according to claim 1 is characterized in that: In step S3, the specific steps are as follows: S3-1, establishing a geological model: creating a geological model based on the geological anomaly areas and potential risk points identified in step S2; defining initial stress states and boundary conditions; S3-2, Load application and construction simulation: Apply loads step by step to simulate the construction process or geological changes; apply displacement boundary conditions and force boundary conditions; S3-3, perform numerical simulation: run the simulation to solve the stress, displacement and plastic zone development of the model under load; S3-4, Result analysis: Analyze stress distribution, displacement field and support structure response.

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