Underground water stratum advanced detection method based on induced polarization principle

Abstract

The invention discloses a groundwater stratum advanced detection method based on an induced polarization principle, and the method comprises the following steps: S1, arranging a measurement electrode system M on a tunnel face, arranging electrodes A at the periphery of the measurement electrode system M, and installing electrodes B and N at the rear part of a tunnel; s2, a cable plug is in butt joint with a'measuring cable 'socket on an induced polarization instrument host, a power supply cable is connected with an acquisition cable, and a contact coupling electrode is adjusted to be in good contact with a tunnel face; according to the underground water stratum advanced detection method based on the induced polarization principle, the problem that an existing traditional method cannot recognize tiny geological anomalies is solved; the problems that the position and the scale of an underground water layer cannot be effectively identified, the underground water layer possibly encountered in tunnel engineering cannot be detected in advance, accurate positioning information cannot be provided, the danger is large, consumed time is long, efficiency is low, and smooth construction progress is affected are solved.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel engineering, and in particular to a method for advanced detection of groundwater strata based on the principle of induced polarization. Background Art

[0002] Groundwater refers to water stored in the gaps in rocks below the ground. In a narrow sense, it refers to water in saturated aquifers below the groundwater surface. Groundwater is an important component of water resources. Due to its stable water volume and good water quality, it is one of the important water sources for agricultural irrigation, industrial conditions and cities.

[0003] The existing traditional drilling method mainly relies on manual identification and detection of geological conditions when detecting groundwater strata, and is unable to identify small geological anomalies. Due to the different characteristics of groundwater layers and other geological media, traditional methods cannot effectively identify the location and scale of groundwater layers. For groundwater layers that may be encountered in tunnel projects, it is impossible to detect in advance and provide accurate positioning information. Therefore, reasonable drainage measures cannot be formulated in advance, which may lead to water inrush accidents and is very dangerous. In addition, traditional methods are time-consuming and inefficient, affecting the smooth progress of construction. Summary of the invention

[0004] The purpose of the present invention is to provide a method for advanced detection of groundwater strata based on the principle of induced polarization, so as to solve the problems that the existing traditional methods cannot identify small geological anomalies; cannot effectively identify the location and scale of groundwater layers, cannot detect in advance and provide accurate positioning information for groundwater layers that may be encountered in tunnel projects, and are very dangerous; and are time-consuming, inefficient, and affect the smooth progress of construction.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for advanced detection of groundwater formations based on the principle of induced polarization, the method comprising the following steps:

[0006] S1: Arrange the measuring electrode system M on the tunnel face, arrange the electrode A around the measuring electrode system M, and install the electrodes B and N at the rear of the tunnel;

[0007] S2: Connect the cable plug to the "measurement cable" socket on the main unit of the induced polarization method instrument, connect the power supply and acquisition cables, and adjust the contact coupling electrode to have good contact with the tunnel face;

[0008] S3: Start the software running on the main machine of the instrument to collect power supply and potential difference data. Supply current to electrode A. After the measurement of the electrode system M is completed, move the power supply electrode system A to the rear of the face and continue to measure the potential of the array electrode M until the power supply electrode system moves to the predetermined position and the detection is completed. After the data collection is completed, invert and interpret the data, and perform inversion positioning and morphological characterization on possible adverse geological bodies.

[0009] Preferably, the electrode M in step S1 is installed on the tunnel face, and the electrode M is an array measuring electrode system composed of a plurality of measuring electrodes.

[0010] Preferably, in step S1, the electrode A is installed around the outer tunnel face of the measuring electrode system M, and the electrode A is a power supply electrode system composed of four power supply electrodes.

[0011] Preferably, the electrode B and the electrode N are power supply electrodes located at the rear of the tunnel.

[0012] Preferably, 12-14 measuring electrodes M are arranged, and non-polarizable electrodes are selected.

[0013] Preferably, the number of power supply electrode rings composed of the electrode A is 10-15, the number of power supply electrodes arranged in each ring should be 4, and the last circle of power supply electrode rings is about 80m away from the tunnel face; a power supply electrode A0 is arranged near the center of the cutterhead.

[0014] Preferably, the distance between the electrode N and the excavation face should be no less than 10 times the distance between the power supply electrode A and the measuring electrode M, and the electrode B is farther away from the excavation face than the electrode N, and the distance between it and the electrode N is no less than 10 times the distance between the power supply electrode A and the measuring electrode M.

[0015] Preferably, the absolute value of the electrode polarity difference with the non-polarized electrode does not exceed 2mv.

[0016] It can be seen from the above technical solution that the present invention has the following beneficial effects:

[0017] This groundwater stratum advance detection method based on the principle of induced polarization is to arrange a measuring electrode system M on the tunnel face, arrange electrode A around the measuring electrode system M, install electrodes B and N at the rear of the tunnel, connect the cable plug to the "measuring cable" socket on the main unit of the induced polarization method instrument, connect the power supply and acquisition cables, adjust the contact coupling electrode to have good contact with the tunnel face, start the instrument host running software to collect power supply and potential difference data, and after the data collection is completed, invert and interpret the data, and perform inversion positioning and morphological characterization on possible poor geological bodies. This method can identify small geological anomalies and The groundwater layers encountered in tunnel projects can be detected in advance and accurate positioning information can be provided, which is helpful to formulate reasonable drainage measures, prevent water inrush accidents, and improve safety. By applying a strong current, deep geological information can be obtained, providing a more comprehensive geological forecast, reducing construction risks, and solving the problem that existing traditional methods cannot identify small geological anomalies; cannot effectively identify the location and scale of groundwater layers, and cannot detect and provide accurate positioning information in advance for groundwater layers that may be encountered in tunnel projects, which is very dangerous, time-consuming, inefficient, and affects the smooth progress of construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a flow chart of the method of the present invention;

[0019] Figure 2 It is a cross-sectional view of the observation method of the present invention;

[0020] Figure 3 A three-dimensional schematic diagram of the observation method of the present invention;

[0021] Figure 4 This is a schematic diagram of the advanced geological prediction arrangement of the tunnel TIP of the present invention;

[0022] Figure 5 This is a schematic diagram of the induced polarization imaging of the present invention. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] like Figure 1 As shown, a method for advanced detection of groundwater formations based on the principle of induced polarization comprises the following steps:

[0025] S1: Arrange the measuring electrode system M on the tunnel face, arrange the electrode A around the measuring electrode system M, and install the electrodes B and N at the rear of the tunnel;

[0026] S2: Connect the cable plug to the "measurement cable" socket on the main unit of the induced polarization method instrument, connect the power supply and acquisition cables, and adjust the contact coupling electrode to have good contact with the tunnel face;

[0027] S3: Start the software running on the main machine of the instrument to collect power supply and potential difference data. Supply current to electrode A. After the measurement of the electrode system M is completed, move the power supply electrode system A to the rear of the face and continue to measure the potential of the array electrode M until the power supply electrode system moves to the predetermined position and the detection is completed. After the data collection is completed, invert and interpret the data, and perform inversion positioning and morphological characterization on possible adverse geological bodies.

[0028] This method can identify tiny geological anomalies. For groundwater layers encountered in tunnel projects, it can detect them in advance and provide accurate positioning information, which helps to formulate reasonable drainage measures, prevent water inrush accidents, and improve safety. By applying strong currents, deep geological information can be obtained, providing more comprehensive geological forecasts and reducing construction risks.

[0029] This method takes the difference in electrical parameters between surrounding rocks and water-bearing geological structures as its physical basis. According to the distribution law of the electrical properties of the surrounding rocks under the action of the primary field and the secondary field, the distribution of water-bearing structures in the detection area is inferred. The tunnel induced polarization method first supplies an excitation current to the rock formation to generate a primary field. The positive and negative ions in the groundwater are separated under the action of the current, and then a secondary field is generated. After the current is turned off, the positive and negative ions will move in the opposite direction until they return to their original state, and the secondary field gradually decays until it disappears. The current and voltage data of the induced polarization primary field are sensitive to the position and shape of the water body; the decay time difference of the secondary field is related to the amount of water. The larger the amount of water, the longer the time difference, and the smaller the amount of water, the shorter the time difference. Therefore, the tunnel induced polarization method measures the current and voltage of the primary field to invert the water body in front, and estimates the amount of water by measuring the decay time difference.

[0030] In the specific implementation process, Figure 2 and Figure 3As shown in the figure, a number of measuring electrodes are arranged on the tunnel face to form an array measuring electrode system (electrode M), and four power supply electrodes are arranged around the outer face of the measuring electrode system to form a power supply electrode system (electrode A). The power supply electrode B and the power supply electrode N are located at infinity behind the tunnel. During detection, the four power supply electrode systems A are supplied with the same current, and one power supply electrode is arranged on the tunnel face at the same time. The array measuring electrode M measures the potential. After each measuring electrode in the array measuring electrode system has finished measuring, the power supply electrode system A is moved to the rear of the tunnel face, and the potential of the array electrode M is continuously measured until the power supply electrode system moves to the predetermined position and the detection is completed. The three-dimensional observation mode has the advantages of backward shielding and forward focusing. The use of multiple isotropic sources for power supply has the advantage of theoretically reducing the interference of abnormal bodies near the electrodes, and can suppress the sensitivity of abnormal bodies near the tunnel face. The multiple isotropic source electrodes are moved to the rear of the tunnel face for detection, and there is no need to continuously detect with the tunnel excavation. The receiving mode of the array electrode can realize three-dimensional inversion imaging of the abnormal body. By inverting the apparent resistivity profile, the resistivity profile of the surrounding rock in the detection area is obtained, which shows low resistance for water-bearing structures and high resistance for complete surrounding rocks, thereby achieving the purpose of detecting the geological conditions in the detection area. The low-resistance part of the three-dimensional imaging represents the water-bearing geological structure.

[0031] For the instruments used, the transmitter should be a constant current source and should have multi-channel output function. The power supply current can be adjusted in a large range to meet the requirements of different detection environments. The receiver should have a multi-channel acquisition function to be able to collect parameters such as voltage, current, and apparent resistivity; the sampling frequency should not be less than 1000Hz, and the measurement current resolution should not be less than 0.01mA.

[0032] Specifically, Figure 4 As shown in the figure, 12 to 14 measuring electrodes M are arranged according to the specific conditions of the tunnel face. Non-polarized electrodes should be selected. The number of power supply electrode rings composed of multiple isotropic power supply electrodes (electrode A) should be 10-15, and the number of power supply electrodes arranged in each ring should be 4. The last circle of power supply electrode rings is about 80m away from the tunnel face; a power supply electrode (electrode A0) is arranged near the center of the cutterhead and should be arranged behind the excavation face. The distance between electrode N and the excavation face should be no less than 10 times the distance between the power supply electrode A and the measuring electrode M. Electrode B is farther from the excavation face than electrode N, and the distance between electrode B and electrode N is no less than 10 times the distance between the power supply electrode A and the measuring electrode M.

[0033] During the data collection process, the tunnel face needs to be cleared in advance to ensure the safety of the advance forecast work and to ensure that the tunnel face is basically flat. During the collection process, other electrical forecasting work should not be carried out at the same time. High-power electrical equipment such as welding machines and motors should be turned off. There should be no strong electromagnetic interference in the collection area. The error of repeated measurements should be less than 5%, the number of bad point data should not exceed 1% of all data, and bad points cannot appear continuously.

[0034] like Figure 5 As shown in the figure, during the data processing, special induced polarization processing software is used to analyze and invert the parameters such as the polarizability, resistivity and half-time difference of the data, and the resistivity and polarizability structure of the rock mass in front of the face are obtained. By analyzing the resistivity and polarizability structure of the rock mass, the detection of water-bearing caves, underground rivers and other structures in front is achieved.

[0035] In the drilling and blasting section detection process, firstly, according to the on-site conditions and detection needs, the appropriate positions and the appropriate number of points are selected on the face, and the measuring electrode system M is arranged as evenly as possible on the face by drilling holes, and the electrodes B and N are installed at infinity, and the cable plug is connected to the "measuring cable" socket on the host of the induced polarization method instrument; the detection personnel carry the electrode equipment box to the rear of the face of the drilling and blasting tunnel, connect the power supply and acquisition cables, adjust the contact coupling electrode to have good contact with the face, start the instrument, and run the software on the host of the equipment to collect power supply and potential difference data, and collect data. After the data collection is completed, the data is inverted and interpreted, and the possible poor geological bodies are inverted and located and the morphology is characterized.

[0036] Among them, during continuous forecasting, the two forecast ranges before and after should overlap by more than 5m, the contact between the electrode and the surrounding rock should be checked, and the nearby electromagnetic interference sources should be removed or avoided in the collection area; when they cannot be removed or avoided, the location should be noted and marked in the record, and the measuring electrode of the induced polarization method should be a non-polarized electrode. For the non-polarized electrode, the electrode extreme difference should be checked, and its absolute value should not exceed 2mv. The infinity electrode B and the infinity electrode N should be arranged behind the excavation face, and the distance between electrode N and the excavation face should be not less than 10 times the distance between the power supply electrode A and the measuring electrode M. Electrode B is farther from the excavation face than electrode N, and the distance between it and electrode N is not less than 10 times the distance between the power supply electrode A and the measuring electrode M.

[0037] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for advanced detection of groundwater formations based on the principle of induced polarization, characterized in that: The method comprises the following steps: S1: Arrange the measuring electrode system M on the tunnel face, arrange the electrode A around the measuring electrode system M, and install the electrodes B and N at the rear of the tunnel; S2: Connect the cable plug to the "measurement cable" socket on the main unit of the induced polarization method instrument, connect the power supply and acquisition cables, and adjust the contact coupling electrode to have good contact with the tunnel face; S3: Start the software running on the main machine of the instrument to collect power supply and potential difference data. Supply current to electrode A. After the measurement of the electrode system M is completed, move the power supply electrode system A to the rear of the face and continue to measure the potential of the array electrode M until the power supply electrode system moves to the predetermined position and the detection is completed. After the data collection is completed, invert and interpret the data, and perform inversion positioning and morphological characterization on possible adverse geological bodies.

2. The method for advanced detection of groundwater strata based on the induced polarization principle according to claim 1 is characterized in that: In the step S1, the electrode M is installed on the tunnel face, and the electrode M is an array measuring electrode system composed of a plurality of measuring electrodes.

3. The method for advanced detection of groundwater strata based on the induced polarization principle according to claim 1 is characterized in that: In the step S1, the electrode A is installed around the outer tunnel face of the measuring electrode system M, and the electrode A is a power supply electrode system composed of four power supply electrodes.

4. The method for advanced detection of groundwater strata based on the induced polarization principle according to claim 1 is characterized in that: The electrode B and the electrode N are power supply electrodes and are located at the rear of the tunnel.

5. The method for advanced detection of groundwater strata based on the induced polarization principle according to claim 1 is characterized in that: The measuring electrodes M are arranged in 12-14 numbers and are non-polarized electrodes.

6. The method for advanced detection of groundwater strata based on the induced polarization principle according to claim 1 is characterized in that: The number of power supply electrode rings composed of the electrode A is 10-15, the number of power supply electrodes arranged in each ring should be 4, and the last circle of power supply electrode rings is about 80m away from the tunnel face; a power supply electrode A0 is arranged near the center of the cutterhead.

7. The method for advanced detection of groundwater strata based on the induced polarization principle according to claim 1 is characterized in that: The distance between the electrode N and the excavation face should be no less than 10 times the distance between the power supply electrode A and the measuring electrode M. The electrode B is farther away from the excavation face than the electrode N, and the distance between it and the electrode N is no less than 10 times the distance between the power supply electrode A and the measuring electrode M.

8. The method for advanced detection of groundwater strata based on the induced polarization principle according to claim 5 is characterized by: The absolute value of the electrode difference with respect to the non-polarized electrode does not exceed 2mv.

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