Method for comprehensive evaluation of permeability coefficient and water inflow by tunnel geophysical parameters

Abstract

This invention provides a method for comprehensively evaluating permeability coefficient and water inflow in tunnels using geophysical parameters. By testing rock cores in lithologically varying sections, the permeability coefficient, P-wave velocity, and relaxation time of the cores are obtained. A comprehensive permeability coefficient prediction model is constructed. The P-wave velocity and relaxation time distributions for the construction section are predicted using seismic wave analysis and induced polarization analysis. Based on the obtained P-wave velocity and relaxation time distributions, the permeability coefficient of each grid is calculated using the comprehensive permeability coefficient prediction model. The equivalent nodal flow rate numerical method is then used to predict the tunnel's water inflow based on the permeability coefficient distribution imaging results. This invention improves the accuracy of water inflow prediction to a certain extent and is applicable to water inflow prediction in long-distance tunnel construction, solving the problem of permeability evaluation and water inflow estimation in complex tunnel environments.

Description

Technical Field

[0001] This invention belongs to the field of tunnel exploration technology and relates to a method for comprehensively evaluating the permeability coefficient and water inflow of tunnel geophysical parameters. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] In tunnel construction, sudden water inrush is one of the most common geological hazards, easily leading to catastrophic consequences such as safety accidents involving casualties and economic losses due to tunnel structure damage and construction equipment destruction. Therefore, water inrush prediction has become a key research area of ​​great interest to scholars in the field of tunnel engineering, and is crucial for ensuring safe tunnel construction. Permeability coefficient is a prerequisite for effectively predicting water inrush ahead of the tunnel face in tunnel engineering. Currently, permeability coefficient measurement methods include indoor tests and field tests. Indoor tests face significant difficulties in accurately simulating field conditions, making it difficult to accurately obtain the actual permeability coefficient of the rock mass. Field measurement methods mainly include pumping tests, pressure tests, and seepage tests, but these tests are time-consuming and costly. These testing methods are stringent and not suitable for evaluating the permeability coefficient in the excavation area ahead of the tunnel, failing to provide timely hydrological parameters for tunnel construction. The earliest methods for predicting water inrush included drilling methods, hydrochemical methods, empirical methods, and water temperature measurement methods, but their prediction accuracy was poor, and the water inrush volume was mainly estimated empirically based on the water flow direction. In areas with poor groundwater development, predicting tunnel water inrush is even more difficult.

[0004] Currently, in practical engineering, water inflow is often estimated based on geological survey data, but the predicted results deviate significantly from the actual situation. As tunnel excavation progresses, the surrounding rock damage gradually develops, and its water conductivity increases. Therefore, obtaining the spatial distribution of the permeability characteristics of the aquifer ahead of the tunnel face is a major challenge that urgently needs to be addressed to accurately predict water inflow during tunnel construction. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a comprehensive evaluation method for permeability coefficient and water inflow volume of tunnel geophysical parameters. This invention enables rapid and accurate acquisition of the permeability distribution ahead of the tunnel face through on-site core sampling to establish a comprehensive permeability coefficient prediction model, on-site seismic wave and induced polarization method detection, permeability coefficient inversion imaging, and tunnel water inflow volume evaluation. This solves the problem of permeability evaluation and water inflow volume estimation for water-bearing structures in complex tunnel environments.

[0006] According to some embodiments, the present invention adopts the following technical solution:

[0007] A comprehensive evaluation method for tunnel geophysical parameters, including permeability coefficient and water inflow, comprises the following steps:

[0008] Test the rock core to obtain the permeability coefficient, P-wave velocity and relaxation time, and construct a comprehensive permeability coefficient prediction model;

[0009] The P-wave velocity distribution and relaxation time distribution of the construction section were predicted using the seismic wave method and the induced polarization method.

[0010] Based on the acquired longitudinal wave velocity distribution and relaxation time distribution, the permeability coefficient can be inverted and imaged.

[0011] The water inflow of the tunnel is predicted based on the permeability coefficient inversion imaging results.

[0012] As an alternative implementation method, before constructing the comprehensive prediction model, the method also includes the steps of making preliminary inferences about the engineering geological conditions and hydrogeological conditions of the construction section based on hydrogeological data, and making preliminary judgments on the lithological characteristics, geological structure, engineering geological conditions and groundwater type.

[0013] As an alternative implementation method, permeability coefficient information in the region is collected based on hydrogeological data as a reference, and the lithological variation segments are determined based on geological data.

[0014] As an alternative implementation method, a certain amount of rock cores and groundwater were collected in the lithological variation zone for indoor testing based on geological data.

[0015] As an alternative implementation method, the core samples taken on-site are saturated with groundwater from the corresponding location.

[0016] As an alternative implementation method, the relaxation time is obtained by measuring the excited polarization parameters of the saturated rock core, and the longitudinal wave velocity is obtained by measuring the acoustic parameters.

[0017] As an alternative implementation method, based on the above test results, the following comprehensive permeability coefficient prediction model is established:

[0018]

[0019] In the formula, A1, A2, A3, and A4 are fitting coefficients, and V P Let τ be the longitudinal wave velocity, τ be the relaxation time, and k be the permeability coefficient.

[0020] As a further defined implementation, when the permeability coefficient distribution inversion imaging does not meet the requirements, the process returns to testing the rock core at the working face location, obtaining the permeability coefficient, P-wave velocity, and relaxation time of the rock core, and constructing a comprehensive prediction model, and then repeats the process.

[0021] As an alternative implementation method, the inflow rate can be predicted using the equivalent nodal flow rate numerical method based on the permeability coefficient inversion imaging results and the measured water head of the tunnel.

[0022] Furthermore, based on the distribution of the permeability coefficient, the finite element method can be used to obtain the overall matrix of the model and the head at each node.

[0023] Furthermore, the water inflow at any working face can be calculated using the following formula:

[0024]

[0025] In the above formula, nx and nz are the total number of nodes in two directions of the tunnel face, respectively, and b ij H represents the element value of the node in the i-th row and j-th column of the face in the general structure matrix. ij This is the head value of the node.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] This invention uses the idea of ​​calculating the permeability coefficient of each grid by means of relaxation time distribution and wave velocity distribution, which realizes a more accurate imaging of the permeability coefficient in front of the tunnel face. This leads to the formation of a comprehensive evaluation method for tunnel permeability based on the combination of induced polarization and seismic waves, which solves the problem of evaluating the permeability of water-bearing structures and estimating the inflow in complex tunnel environments.

[0028] The permeability coefficient obtained by this invention through the rock physics relationship between relaxation time, longitudinal wave velocity and permeability coefficient is more accurate than the permeability coefficient in geological exploration data. It can quickly and accurately obtain the permeability coefficient of rocks, reduce costs compared with traditional methods, and improve the accuracy of water inflow prediction to a certain extent.

[0029] This invention predicts the water inflow at the tunnel face using the equivalent nodal seepage method, enabling simultaneous excavation and exploration, and improving the accuracy of water inflow prediction to a certain extent. It is applicable to water inflow prediction in long-distance tunnel construction.

[0030] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0031] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0032] Figure 1 This is a flowchart illustrating the process of this embodiment;

[0033] Figure 2 This is a schematic diagram of the excitation polarization in this embodiment;

[0034] Figure 3This is a schematic diagram illustrating an example of obtaining relaxation time through excitation polarization in this embodiment;

[0035] Figure 4 This is a schematic diagram of the seismic wave method in this embodiment;

[0036] Figure 5 This is a schematic diagram illustrating an example of obtaining P-wave velocity using the seismic wave method in this embodiment.

[0037] Figure 6 This is a schematic diagram of the permeability coefficient inversion imaging in this embodiment.

[0038] Among them, 1. Tunnel; 2. Measuring electrode; 3. Power supply electrode A1; 4. Power supply electrode A2; 5. Power supply electrode A3; 6. Power supply electrode A4; 7. Working face; 8. Seismic source point; 9. Detector; 10. Adverse geological conditions. Detailed Implementation

[0039] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0040] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0041] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0042] Example 1

[0043] A comprehensive evaluation method for tunnel geophysical parameters, including permeability coefficient and water inflow, such as... Figure 1 As shown, the specific process includes the following:

[0044] (1) First, the engineering geological conditions and hydrogeological conditions of the construction section are preliminarily inferred through hydrogeological data, and the lithological characteristics, geological structure, engineering geological conditions and groundwater type are preliminarily determined.

[0045] (2) Indoor tests were conducted in the lithological variation zone by taking a certain amount of rock cores and groundwater according to geological data.

[0046] (3) After the core samples are saturated with the corresponding groundwater, the relaxation time, longitudinal wave velocity and permeability coefficient of the core samples are tested.

[0047] (4) Establish a comprehensive permeability coefficient prediction model based on two physical property parameters: longitudinal wave velocity and relaxation time, as shown in the following formula:

[0048]

[0049] In the formula, A1, A2, and A3 are fitting coefficients, and V P Let be the longitudinal wave velocity, τ be the relaxation time, and k be the relaxation time.

[0050] (5) Geological prediction of the geological conditions ahead of the tunnel face is carried out using the seismic wave method and the induced polarization method. The seismic wave method uses the elastic differences of artificially excited elastic waves in different media as the basis for predicting adverse geological bodies ahead of the tunnel face. Figure 2 shows the induced polarization method for detecting the conditions ahead of the tunnel face. The detection example results are as follows: Figure 3 As shown in Figure 4, the seismic wave method is used to detect the situation in front of the tunnel face. The detection results are as follows: Figure 5 As shown.

[0051] Both methods are existing methods, and their specific processes will not be elaborated here.

[0052] (6) Figure 6 As shown, the permeability coefficient of each grid is further calculated based on the comprehensive prediction model.

[0053] (7) Based on the distribution of the permeability coefficient, the finite element method can be used to obtain the general matrix of the model and the head of each node, and the equivalent node flow numerical method can be used to predict the inflow.

[0054] The water inflow at any working face can be calculated using the following formula:

[0055]

[0056] In the above formula, nx and nz are the total number of nodes in two directions of the tunnel face, respectively, and b ij H represents the element value of the node in the i-th row and j-th column of the face in the general structure matrix. ij This is the head value of the node.

[0057] Example 2

[0058] A comprehensive evaluation method for tunnel geophysical parameters, including permeability coefficient and water inflow, comprises the following steps:

[0059] 1. Collect hydrological and geological data along the tunnel route, obtain permeability coefficient information of the study area based on hydrological data as a reference, and roughly determine the lithological variation sections based on geological data;

[0060] 2. Obtain on-site rock cores and groundwater, and test the relaxation time, P-wave velocity, and permeability coefficient of the rock cores under the groundwater saturation condition;

[0061] 3. Establish a comprehensive permeability coefficient prediction model based on field core data;

[0062] 4. Conduct seismic wave detection at the tunnel site to obtain the P-wave velocity distribution of that section. Furthermore, significant abrupt changes in P-wave velocity can also serve as a reference for determining whether the lithology has changed.

[0063] 5. Conduct induced polarization detection at the tunnel site to obtain induced polarization data for this section, and perform induced polarization inversion to obtain the relaxation time distribution;

[0064] 6. Based on the relaxation time distribution and wave velocity distribution collected on-site, the permeability coefficient inversion imaging in front of the tunnel face is obtained through the comprehensive permeability coefficient prediction model;

[0065] 7. Evaluate tunnel permeability based on the inversion imaging results of the permeability coefficient. If the imaging effect is not good, return to step 1.

[0066] The other processes are the same as in Example 1, and will not be described again here.

[0067] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for comprehensively evaluating tunnel geophysical parameters, including permeability coefficient and water inflow, characterized by: Includes the following steps: Based on geological data, a comprehensive permeability prediction model was established by taking a certain amount of rock cores and groundwater samples in lithological variation zones and conducting indoor tests. The comprehensive prediction model is as follows: In the formula, A1, A2, A 3、 A4 is the fitting coefficient, V P Let τ be the longitudinal wave velocity and τ be the relaxation time. Permeability coefficient; The P-wave velocity distribution and relaxation time distribution in front of the tunnel face are obtained by using the seismic wave method and the induced polarization method. Using a comprehensive permeability coefficient prediction model, the permeability coefficient of each grid is calculated based on the obtained P-wave velocity distribution and relaxation time distribution. The water inflow of the tunnel is predicted based on the permeability imaging results.

2. The method for comprehensively evaluating the permeability coefficient and water inflow of tunnel geophysical parameters as described in claim 1, characterized in that, Before constructing a comprehensive prediction model, the process also includes preliminary inferences about the engineering geological and hydrogeological conditions of the construction section based on hydrogeological data, and preliminary judgments on the lithological characteristics, geological structure, engineering geological conditions, and groundwater type.

3. The method for comprehensively evaluating the permeability coefficient and water inflow of tunnel geophysical parameters as described in claim 1, characterized in that, Based on geological data, a certain amount of rock cores and groundwater were collected in the lithological variation zone for indoor testing.

4. The method for comprehensively evaluating the permeability coefficient and water inflow of tunnel geophysical parameters as described in claim 1, characterized in that, After saturating the collected rock cores with the corresponding groundwater, the relaxation time, P-wave velocity, and permeability coefficient of the rock cores were tested.

5. The method for comprehensively evaluating the permeability coefficient and water inflow of tunnel geophysical parameters as described in claim 1, characterized in that, Based on the permeability coefficient distribution, the finite element method can be used to obtain the overall matrix of the model within the prediction area and the head at each node.

6. The method for comprehensively evaluating the permeability coefficient and water inflow of tunnel geophysical parameters as described in claim 1, characterized in that, The inflow rate can be predicted using the equivalent nodal flow rate numerical method based on the permeability coefficient inversion imaging results and the measured water head in the tunnel.

7. The method for comprehensively evaluating the permeability coefficient and water inflow of tunnel geophysical parameters as described in claim 6, characterized in that, The water inflow at any working face can be calculated using the following formula: In the above formula, nx and nz are the total number of nodes in two directions of the tunnel face, respectively. Let be the element value of the node in the i-th row and j-th column on the tunnel face in the general structure matrix. This is the head value of the node.

8. The method for comprehensively evaluating the permeability coefficient and water inflow of tunnel geophysical parameters as described in claim 1, characterized in that, When performing inversion imaging of permeability coefficient distribution, it is combined with preliminary judgment of stratigraphic lithology, geological structure, engineering geological conditions, and groundwater type.

9. The method for comprehensively evaluating the permeability coefficient and water inflow of tunnel geophysical parameters as described in claim 1, characterized in that, When the permeability distribution inversion imaging does not meet the requirements, the process returns to testing the core sample at the working face to obtain the permeability, P-wave velocity, and relaxation time of the core sample, and then constructs a comprehensive prediction model. This process is repeated.

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