Landslide site groundwater pulse detection method and system combining high-density electrical method and shallow low-temperature method

Abstract

The invention relates to a landslide site groundwater pulse detection method and system combining a high-density electrical method and a shallow low-temperature method, and the method comprises the steps: arranging an emission source at a landslide site, laying an emission electrode distance and a plurality of measurement lines, and transmitting a high-density pseudo-random multi-frequency current signal; an unmanned aerial vehicle is adopted to carry a magnetic receiver to receive electromagnetic signals converted from the pseudo-random multi-frequency current signals along a measuring line, meanwhile, a locator is carried to record position information, the apparent resistivity of the landslide site is obtained according to the electromagnetic signals, and the underground water pulse position of the landslide site is obtained by combining the apparent resistivity of the landslide site with the position information; a plurality of shallow drilling points with different depths are arranged at the underground water pulse position, heat sources are arranged in the shallow drilling points, the underground water flow velocity is determined according to the change of the temperature of the heat sources along with time, and an underground water detection result is obtained. The method is not limited by terrain and geological conditions, the detection accuracy and efficiency are improved, and the method can be used for landslide site groundwater vein detection.

Description

Technical Field

[0001] The invention relates to the technical field of underground water vein detection, and in particular to a method and system for detecting underground water veins in landslide sites by combining a high-density electrical method and a shallow low-temperature method. Background Art

[0002] In landslide disaster prevention and control, accurate detection of groundwater veins is crucial for assessing landslide stability and formulating prevention and control measures. Currently, the commonly used groundwater vein detection methods include: natural electric field method and charging method, induced polarization method (TDIP, PIP, SIP), ground penetrating radar method (GPR), ground nuclear magnetic resonance method (SNMR). The above detection methods have the following disadvantages:

[0003] The natural electric field method and the charging method are limited by terrain and geological conditions.

[0004] Induced polarization methods (TDIP, PIP, SIP) may require complex data processing and analysis.

[0005] Ground Penetrating Radar (GPR): It can provide high-resolution images of underground structures, but its ability to detect deep groundwater is limited.

[0006] Terrestrial nuclear magnetic resonance (SNMR) is expensive and requires high technical skills of the operator.

[0007] Therefore, there is an urgent need for a method and system for detecting groundwater veins in landslide sites that combines high-density electrical methods and shallow low-temperature methods to improve the accuracy and efficiency of detection without being limited by terrain and geological conditions. Summary of the invention

[0008] The present invention provides a method and system for detecting underground water veins in landslide sites by combining a high-density electrical method and a shallow low-temperature method, which is not limited by topographic and geological conditions and improves the accuracy and efficiency of detection.

[0009] In order to achieve the above object, the present invention adopts the following technical solution:

[0010] On the one hand, the present invention provides a method for detecting underground water veins in a landslide site by combining a high-density electrical method and a shallow low-temperature method, comprising:

[0011] Step 1, setting up a transmitting source at the landslide site, laying out transmitting pole distances and multiple measuring lines, and transmitting a high-density pseudo-random multi-frequency current signal;

[0012] Step 2, using a drone equipped with a magnetic receiver to receive electromagnetic signals converted from pseudo-random multi-frequency current signals along the survey line, and carrying a locator to record position information, and obtaining the apparent resistivity of the landslide site according to the electromagnetic signals;

[0013] Step 3, obtaining the location of the groundwater vein of the landslide site by combining the apparent resistivity of the landslide site with the location information;

[0014] Step 4, setting a plurality of shallow drilling points of different depths at the location of the groundwater vein, setting a heat source in the shallow drilling point, determining the groundwater flow rate by the change of the temperature of the heat source over time, and obtaining the groundwater detection result.

[0015] Optionally, the high-density pseudo-random multi-frequency current signal in step 1 specifically includes: a pseudo-random multi-frequency current signal with 7-19 main frequency points.

[0016] Optionally, the step 2 specifically includes:

[0017] Step 2.1, using a drone equipped with a magnetic receiver to receive the electromagnetic signal converted from the pseudo-random multi-frequency current signal along the measuring line, and carrying a locator to record position information, using the magnetic receiver to record the potential difference between two measuring electrodes, and at the same time recording the distance between the measuring electrodes, using the ratio of the potential difference to the distance between the measuring electrodes to obtain a single frequency electromagnetic component, and recording the multi-frequency electromagnetic components of the measuring points in the measuring line through electromagnetic signals of different frequencies;

[0018] Step 2.2, using the multi-frequency electromagnetic components to combine adjacent frequency points, and using an approximate method of first-order difference derivation to calculate the derivative of the electromagnetic field of the corresponding frequency point combination with respect to the frequency point;

[0019] Step 2.3, using the derivative to convert the apparent resistivity to obtain the apparent resistivity of the landslide site.

[0020] Optionally, the apparent resistivity of the landslide site is obtained as:

[0021]

[0022] Among them, μ is the magnetic permeability, r is the distance between the center of the dipole moment and the observation point, ω is the angular frequency, i is the emission current, dl is the length of the dipole emission source, represents the partial derivative, Ex represents the component of the electric field in the x direction, ρ i represents the apparent resistivity at the ith frequency point.

[0023] Optionally, the step 3 specifically includes:

[0024] Step 3.1, obtaining the terrain information of the landslide site, dividing the landslide site into three-dimensional grids based on the terrain information, and combining the apparent resistivity with the location information to obtain the resistivity in each grid;

[0025] Step 3.2, obtaining the location of the groundwater veins at the landslide site by inverting the resistivity within each grid.

[0026] Optionally, obtaining the resistivity within each grid includes:

[0027] The smooth constrained least squares inversion algorithm is used to obtain the resistivity in each grid. The resistivity inversion objective function is:

[0028] (G T G+λC T C) Δm=G T Δd

[0029] Among them, Δd is the residual vector between the observed data d and the forward theoretical calculated value d; G is the coefficient matrix; Δm is the modification vector of the initial model m, C is the model smoothing matrix; λ is the smoothing damping factor.

[0030] Optionally, step 4 specifically includes:

[0031] Step 4.1, after the heat source is powered on and generates heat, record the temperature change data detected by each temperature probe over time;

[0032] Step 4.2, according to the relationship between the temperature value detected by the temperature probe and time, the temperature detected by each temperature probe at the same time is taken as the vector magnitude, and the direction from the linear heat source to each probe is taken as the vector direction, to determine the vector corresponding to each probe;

[0033] Step 4.3, according to the principle of vector superposition, the direction obtained after superposition of each vector is determined as the groundwater flow direction. According to the relationship between the temperature change detected by each probe and time, the groundwater flow velocity is calculated. The groundwater flow velocity is determined by combining the flow velocity values ​​obtained by each probe.

[0034] On the other hand, in order to achieve the above-mentioned purpose, the present invention also provides a landslide site groundwater vein detection system combining high-density electrical method and shallow low-temperature method, comprising:

[0035] The signal transmitting unit sets a transmitting source at the landslide site, arranges transmitting pole distances and multiple measuring lines, and transmits high-density pseudo-random multi-frequency current signals;

[0036] A signal receiving unit, using a drone equipped with a magnetic receiver to receive the electromagnetic signal converted from the pseudo-random multi-frequency current signal along the measuring line, and carrying a locator to record position information;

[0037] A position detection unit, which obtains the apparent resistivity of the landslide site according to the electromagnetic signal, and obtains the position of the underground water vein of the landslide site by combining the apparent resistivity of the landslide site with the position information;

[0038] The flow velocity detection unit sets a plurality of shallow drilling points of different depths at the location of the groundwater vein, sets a heat source in the shallow drilling point, determines the groundwater flow velocity by the change of the temperature of the heat source over time, and obtains the groundwater detection result.

[0039] The beneficial effects of the present invention are:

[0040] The present invention detects underground water veins in a landslide site by combining a high-density electrical method with a shallow low-temperature method, uses an unmanned aerial vehicle equipped with a magnetic receiver to receive electromagnetic signals converted from the pseudo-random multi-frequency current signal along a survey line, obtains the apparent resistivity of the landslide site, obtains the location of the underground water veins in the landslide site by combining the apparent resistivity of the landslide site with the location information, and further determines the groundwater flow rate based on the change of the temperature of the heat source over time, obtains the groundwater detection result, and improves the accuracy and efficiency of groundwater vein detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0042] Figure 1 The present invention is a flowchart of a method for detecting underground water veins in a landslide site by combining a high-density electrical method and a shallow low-temperature method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0043] 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.

[0044] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] High-density electrical method is an effective technology in groundwater detection. It measures the resistivity of underground strata by sending direct current underground to infer the distribution of groundwater. The following are some key points about the application of high-density electrical method in groundwater detection:

[0046] The basic principle of high-density electrical method: High-density electrical method uses direct current to pass into the ground to measure the resistivity of underground formations, and thereby determine the interface between different materials. The measured result is the resistivity profile.

[0047] Application in groundwater detection: High-density electrical method is often used to find groundwater resources and explore underground caves, seawater intrusion, landslide exploration, dam, reservoir and embankment leakage, karst collapse and goaf area investigation, etc.

[0048] Case study: In the Heifangtai area, due to the loess landslide problem caused by agricultural irrigation, high-density electrical method was used to detect the distribution of groundwater in the loess layer. The results show that the groundwater in the area has a high mineralization degree, which mainly comes from agricultural irrigation; the groundwater level in the loess layer inside the tableland is relatively flat, while the water level at the edge of the tableland drops sharply, and the trend is basically consistent with the landslide terrain.

[0049] Comparison with borehole data: In the study of Heifangtai area, the detection results of high-density electrical method were basically consistent with the results of borehole data, which proved the reliability of high-density electrical method for groundwater level detection.

[0050] Application in other areas: In Fangchenggang area, high-density electrical method is used to identify high-quality water supply sources. The results show that the depth, thickness and spatial distribution of groundwater aquifers in the area can be obtained more accurately.

[0051] Application in environmental survey: High-density electrical method is also used to investigate urban groundwater and soil organic pollution. Through exploration, high-resistance abnormal areas are found. These areas are all pollution halos affected by high concentrations of organic pollutants.

[0052] Shallow cryogenic groundwater detection, also known as shallow geothermometry, is a technique that uses the effect of groundwater flow on formation temperature to detect groundwater distribution. Here are some key information about shallow cryogenic groundwater detection:

[0053] Principle: The shallow geothermal measurement method is based on the influence of flowing groundwater veins on normal formation temperature. By distributing shallow boreholes of a certain depth and density in the survey area, a high-precision thermometer is used to measure the ground temperature at each point at the depth, and an isotherm map is drawn to invert the path distribution of the flowing groundwater veins.

[0054] Ease of operation: This method has the advantages of fast speed, high efficiency, low cost, simple and easy method, and little influence by terrain. It can easily obtain information such as the spatial distribution and reserves of groundwater veins.

[0055] Application areas: Shallow geothermal measurement is widely used in areas such as landslide groundwater distribution and reservoir dam bottom leakage.

[0056] Measuring depth: The 1-meter-deep geothermal measurement borehole is shallow, less affected by daily changes, and is widely used.

[0057] Detection conditions: Experiments have shown that when the temperature difference between groundwater and normal strata is greater than 2.5°C, this method can be used to detect the spatial distribution, reserves and other information of underground waterways.

[0058] Result correction: Since shallow ground temperature will be affected by factors such as annual ground temperature, microtopography, landform and geology, the results need to be corrected before they can be used for analysis.

[0059] Case application: In a typical gully erosion area in Wuhua County, eastern Guangdong, the shallow geothermal method was used to explore the distribution of groundwater, and the role of groundwater in the formation of gully erosion was discussed from the perspective of hydraulic erosion.

[0060] Result analysis: After correction, the maximum temperature difference of all the measurement points is 6.8℃, and the average water temperature of the spring point is 7.2℃ different from the normal stratum temperature, indicating that the shallow geothermal measurement method is applicable to the experimental area. The isotherm map can intuitively reflect the changes in the temperature field in the domain. The areas where the isotherms are densely distributed are the areas where the temperature field changes violently and reaches the extreme value, thus inferring the flow path of groundwater veins.

[0061] In summary, high-density electrical method and shallow low-temperature method for groundwater detection is an effective technology that can detect groundwater resources at a lower cost and higher efficiency, and is of great significance for water resources management and environmental investigation.

[0062] It should be noted that the following implementation is also applicable to other detection methods. The following is only an example of the above method for detection description: The technology for visualizing underground water veins in a plane and two dimensions related to the detection and confirmation system of underground water veins in a specific land area of ​​the present invention is a 4-dimensional water cycle reproduction, analysis, prediction, and visualization simulation system that uses a computer to reproduce, analyze, predict, and visualize the water cycle status from the past to the future in a certain range of the land, etc., and is realized through the following structure:

[0063] A three-dimensional topographic and geological model of the surface and underground of a certain range of the earth's surface generated using satellite image data, local measured data, and currently published topographic and geological data, or using any of the satellite image data or the local measured data and the currently published topographic and geological data, is stored in a storage component, and an initialization model is generated by executing a simulation program compiled based on the clarification of the analytical topic for solving the requested water problem, by initializing the underground of the three-dimensional topographic and geological model as a saturated zone. For the initialization model, based on the execution of the simulation program, the data from the input component and the meteorological, hydrological, topographic, and land data used for the reproduction of the past and modern times and the prediction of the future are used to generate the initialization model. The various parameters related to utilization, geology, soil and sand, water utilization, man-made objects, fluid properties, and chemical substance characteristics are input to perform simulation based on the calculation processing performed by the calculation unit and the image generation processing performed by the image generation processing unit. The simulation results are verified by water quality and water quantity numerical analysis methods, topographic and geological analysis methods, and historical fact comparison methods. The topographic and geological models are corrected as needed to improve the simulation accuracy. The simulation results are stored in the storage unit, and 2D or 3D static images and dynamic images are processed and displayed on the display unit, so as to reproduce, analyze, predict, and visualize the 4D water cycle conditions from the past to the future in the geosphere within a certain range.

[0064] In addition, the technology for drilling holes at the positioning points to enable the position of the groundwater (or water source) in the groundwater veins that can be visualized two-dimensionally and three-dimensionally in the groundwater veins of the specific site area is realized by the following structure:

[0065] The structure comprises: a plurality of electrode groups arranged along a measuring line in a specific ground area; a measuring point switching unit, which uses two of the four electrodes in the electrode group forming a dipole-dipole configuration as potential electrodes and the other two electrodes as current electrodes, combines and switches them, and implements horizontal exploration and underground vertical exploration of a specific ground area by a resistivity method and a Wenner method; a measuring unit, which applies a voltage including two high and low frequencies to the two potential electrodes forming the dipole-dipole configuration, and uses the other two current electrodes to detect the current divided by the high and low frequencies flowing between the potential electrodes for each measuring point of the entire specific ground area. The measurement of the current divided by the high and low frequencies; a resistivity calculation component for each measuring point, which calculates the resistivity values ​​divided by the high and low frequencies in the horizontal and vertical directions at each measuring point of the corresponding specific site area for each measuring point, based on the voltages including the high and low frequencies and the detected current divided by the high and low frequencies; and an impedance effect calculation component for each measuring point, which calculates the impedance effect of each measuring point including (resistance value corresponding to the high frequency) / (resistance value corresponding to the low frequency) based on the calculated resistivity values ​​divided by the high and low frequencies at each measuring point, so that the measuring point position with impedance effect > 1 can be inferred as having underground water veins.

[0066] The following is only a description of the detection method:

[0067] S1. According to the spatial conditions of the open-pit mine and the geological detection tasks in the goaf, a high-density seismic and electrical joint observation system is designed. The parameters of the high-density seismic and electrical joint observation system are determined according to the spatial conditions of the mine and the geological detection tasks; to achieve full coverage and effective detection of the target detection depth. The high-density seismic and electrical joint observation system includes the deployment of seismic and electrical joint detection lines in the detection work area, the installation of seismographs in the detection work area, and the long-row electrical electrode system and power supply station installed on the joint detection line, as well as the seismic source and detector installed on the joint detection line. The seismic offset distance is not less than 20m, the number of detector channels is not less than 12, and the number of multiple coverages is greater than or equal to 6 times; the power supply station is set according to the length of the electrode arrangement, and a power supply station is added every 60 meters of the long row of electrode lines. The distance between seismic detector channels is the same as the electrode distance, which is 1 to 2m. S2. Use a high-density seismic and electrical joint observation system to collect seismic data and electrical data, and process the collected seismic data and electrical data to obtain seismic profiles and electrical detection profiles. The present invention uses a high-density seismic and electrical joint observation system to collect seismic and electrical data. The seismic source excitation needs to be able to generate effective reflected waves with sufficient energy and rich high-frequency signals. When using an artificial mechanical source, multiple enhancement methods are used to suppress noise. The electrical power supply has sufficient power, and the power supply voltage and current can be appropriately adjusted according to the depth of the target layer to be detected. The collected signals are saved and recorded after being qualified by quality judgment.

[0068] S2. The process of processing the collected seismic data and electrical data specifically includes: preprocessing of seismic data, extraction of traces, static correction, velocity analysis, dynamic correction, stacking, and prestack migration; the migration method adopts Kirchhoff integral method prestack migration; multi-point rounding, smoothing, filtering, and resistivity tomography of electrical data distortion; after processing, seismic profiles and electrical profiles are obtained. The migration method adopts Kirchhoff integral method pre-stack migration, and the seismic profile of the detection line is obtained after processing. The seismic profile after the processing of the survey line data is shown, and the reflection wave group of the survey line is compared and analyzed. The effective signal is determined in combination with the existing geological data in the detection area and the phase axes of different wave groups are tracked. The continuity, amplitude and phase changes and spatial distribution of the phase axes of the wave group are used to analyze and finely analyze the geological anomaly body ahead of the detection, and comprehensively analyze the geological conditions ahead of the detection; specifically, the migration processing uses Kirchhoff integral method pre-stack migration in data processing; the steps of processing high-density electrical data include: distortion multi-point smoothing, smoothing, filtering, resistivity inversion imaging of electrical data; after processing, the high-density electrical detection profile is obtained.

[0069] S3, extract seismic attribute data from the obtained seismic profile, and then optimize and analyze the extracted seismic attribute data, fuse the optimized seismic attribute data sensitive to the goaf with the electrical resistivity data sensitive to water content, form a seismic and electrical attribute profile after attribute fusion, calibrate and track the target layer of the attribute profile, and analyze and detect the spatial occurrence morphology and water content of the hidden goaf below. In S3, extract seismic attribute data sensitive to the goaf from the obtained seismic profile, including multiple seismic attributes related to amplitude, phase and frequency, optimize the extracted multiple seismic attribute data, and obtain seismic attribute data and electrical attribute data sensitive to the goaf structure and water content. In S3, the seismic attribute data sensitive to the goaf and the electrical resistivity data sensitive to water content are fused. The data fusion specifically includes: standardization of different attribute data, solving correlation coefficients, calculating eigenvalues ​​and eigenvectors, converting fused attributes and calculating fused attribute contribution rates, and selecting the attribute value with the highest fused attribute contribution rate as the fused data to form a profile. The target layer of the attribute profile in S3 is calibrated according to the exploration and verification drilling and logging data of the goaf area in the detection area, and the target layer tracking analysis is carried out by combining the two profile data. The continuity, amplitude and phase changes and spatial distribution of the seismic wave group phase axis are used to analyze the spatial occurrence state of the hidden goaf area, and the electrical resistivity characteristics are used to determine the water content of the goaf. Specifically, the fusion of sensitive seismic attribute data and electrical resistivity data adopts the main attribute analysis method. The main attribute analysis analyzes and processes multiple groups of attribute data, removes the overlapping information of these attribute variables, and recombine them into new and fewer variable groups. There is an unrelated relationship between the new variable groups obtained by recombination, and while removing the overlapping parts between the data, the main attribute variables obtained retain the information of the original data as much as possible. Through the above-mentioned main attribute analysis method, seismic and electrical data were substituted into the calculation, and the characteristic value contribution rate and cumulative contribution rate of the main attributes A1 and A2 after the main fusion, as well as the correlation coefficient between the original data and the data converted into the main attributes, were calculated. The main attributes with high contribution rate were selected as the fused data, and the profile of the fusion results of seismic and electrical data was obtained. The horizon was calibrated using the exploration verification drilling and logging data, and the target horizon was tracked and analyzed by combining the two profile data. The continuity, amplitude and phase changes and spatial distribution of the seismic wave group phase axis were used to analyze the spatial occurrence state of the hidden goaf, and the electrical resistivity characteristics were used to determine the water content of the goaf.

[0070] like Figure 1As shown, this embodiment discloses a method for detecting groundwater veins in a landslide site by combining a high-density electrical method and a shallow low-temperature method, comprising: step 1, setting a transmitting source at the landslide site, laying out transmitting pole distances and multiple survey lines, and emitting a high-density pseudo-random multi-frequency current signal; step 2, using an unmanned aerial vehicle equipped with a magnetic receiver to receive electromagnetic signals converted from the pseudo-random multi-frequency current signal along the survey line, and carrying a locator to record position information, and obtaining the apparent resistivity of the landslide site according to the electromagnetic signal; step 3, obtaining the position of the groundwater veins in the landslide site by combining the apparent resistivity of the landslide site with the position information; step 4, setting multiple shallow drill points of different depths at the position of the groundwater veins, setting a heat source in the shallow drill point, determining the groundwater flow rate by the change of the temperature of the heat source over time, and obtaining the groundwater detection result.

[0071] Furthermore, step 1 specifically includes:

[0072] Select the transmitting source at the appropriate location of the landslide site, and arrange the transmitting poles A and B. The straight-line distance between the AB poles is 1 km to 2 km, depending on the specific terrain conditions; connect the AB electrodes to the AB output port of the transmitter through cables, and the cables must meet the transmitting current carrying capacity requirements; the transmitter transmits a high-power pseudo-random multi-frequency current signal, the current is usually tens of amperes to more than one hundred amperes, and the transmitting waveform is a densely-frequency pseudo-random multi-frequency wave. The main frequency point is selected from 7 frequencies, 9 frequencies, 11 frequencies, 13 frequencies, 15 frequencies, and 19 frequencies according to actual conditions; measure and record the transmitting current information; set multiple measuring lines in the target detection area according to the detection mission, and the measuring line spacing is 50 meters to 100 meters; plan the flight mission plan according to certain principles.

[0073] Furthermore, step 2 specifically includes:

[0074] Step 2.1, using a magnetic receiver to record the potential difference between the two measuring electrodes and the distance between the measuring electrodes, using the ratio of the potential difference to the distance between the measuring electrodes to obtain a single frequency electromagnetic component, and using electromagnetic signals of different frequencies to record multi-frequency electromagnetic components of the measuring points in the measuring line;

[0075] Step 2.2, using multi-frequency electromagnetic components to combine adjacent frequency points, and using the first-order difference derivative approximation method to calculate the derivative of the electromagnetic field of the corresponding frequency combination with respect to the frequency point;

[0076] Step 2.3, use the derivative to convert the apparent resistivity to obtain the apparent resistivity of the landslide site.

[0077] Furthermore, the apparent resistivity of the landslide site is obtained as:

[0078]

[0079] Among them, μ is the magnetic permeability, r is the distance between the center of the dipole moment and the observation point, ω is the angular frequency, i is the emission current, dl is the length of the dipole emission source, represents the partial derivative, Ex represents the component of the electric field in the x direction, ρ i represents the apparent resistivity at the ith frequency point.

[0080] Furthermore, step 3 specifically includes:

[0081] Step 3.1, obtaining the topographic information of the landslide site, dividing the landslide site into three-dimensional grids based on the topographic information, and combining the apparent resistivity with the position information to obtain the resistivity in each grid.

[0082] Step 3.2, obtaining the location of the groundwater veins at the landslide site by inverting the resistivity within each grid.

[0083] Furthermore, obtaining the resistivity in each grid includes:

[0084] The smooth constrained least squares inversion algorithm is used to obtain the resistivity in each grid. The resistivity inversion objective function is:

[0085] (G T G+λC T C) Δm=G T Δd

[0086] Among them, Δd is the residual vector between the observed data d and the forward theoretical calculated value d; G is the coefficient matrix; Δm is the modification vector of the initial model m, C is the model smoothing matrix; λ is the smoothing damping factor.

[0087] Furthermore, step 4 specifically includes:

[0088] Step 4.1, after the heat source is powered on and generates heat, record the temperature change data detected by each temperature probe over time;

[0089] Step 4.2, according to the relationship between the temperature value detected by the temperature probe and time, the temperature detected by each temperature probe at the same time is taken as the vector size, and the direction from the linear heat source to each probe is taken as the vector direction, and the vector corresponding to each probe is determined;

[0090] Step 4.3, according to the principle of vector superposition, the direction obtained after superposition of each vector is determined as the groundwater flow direction. According to the relationship between the temperature change detected by each probe and time, the groundwater flow velocity is calculated. The groundwater flow velocity is determined by combining the flow velocity values ​​obtained by each probe.

[0091] More specifically, the principle of step 4.1 is:

[0092] A long straight resistance wire with a resistance of 20 ohms is set at the center position of one end of the probe, and both ends of the resistance wire are connected to a 25-volt regulated DC power supply; with the resistance wire as the center, 8 high-precision temperature sensors are evenly spaced on a circle with a radius of 2.5 cm, and the temperature sensors are connected to a multi-channel data acquisition system through a signal line, and the data acquisition system is connected to a microcomputer through a data transmission line; the power supply switch of the resistance wire is controlled by a microcomputer, and after the power is turned on, the multi-channel data acquisition system is controlled to detect the temperature value of each temperature sensor once at a certain interval, and the collected temperature data is transmitted to the microcomputer, and the control software is used to automatically save the data.

[0093] This embodiment also provides a landslide site groundwater vein detection system combining high-density electrical method and shallow low-temperature method, including:

[0094] The signal transmitting unit sets a transmitting source at the landslide site, arranges transmitting pole distances and multiple measuring lines, and transmits high-density pseudo-random multi-frequency current signals;

[0095] The signal receiving unit uses a drone equipped with a magnetic receiver to receive electromagnetic signals converted from pseudo-random multi-frequency current signals along the measuring line, and at the same time carries a locator to record position information;

[0096] The position detection unit obtains the apparent resistivity of the landslide site according to the electromagnetic signal, and obtains the location of the underground water vein of the landslide site by combining the apparent resistivity of the landslide site with the position information;

[0097] The flow velocity detection unit sets multiple shallow drill points of different depths at the location of the groundwater vein, sets a heat source in the shallow drill point, determines the groundwater flow velocity by the change of the temperature of the heat source over time, and obtains the groundwater detection result.

[0098] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for detecting underground water veins in landslide sites by combining high-density electrical method and shallow low-temperature method, characterized in that: include: Step 1, setting up a transmitting source at the landslide site, laying out transmitting pole distances and multiple measuring lines, and transmitting a high-density pseudo-random multi-frequency current signal; Step 2, using a drone equipped with a magnetic receiver to receive electromagnetic signals converted from pseudo-random multi-frequency current signals along the survey line, and carrying a locator to record position information, and obtaining the apparent resistivity of the landslide site according to the electromagnetic signals; Step 3, obtaining the location of the groundwater vein of the landslide site by combining the apparent resistivity of the landslide site with the location information; Step 4, setting a plurality of shallow drilling points of different depths at the location of the groundwater vein, setting a heat source in the shallow drilling point, determining the groundwater flow rate by the change of the temperature of the heat source over time, and obtaining the groundwater detection result.

2. The method for detecting underground water veins in landslide sites by combining high-density electrical method and shallow low-temperature method according to claim 1 is characterized in that: The high-density pseudo-random multi-frequency current signal described in step 1 specifically includes: a pseudo-random multi-frequency current signal with 7-19 main frequency points.

3. The method for detecting underground water veins in landslide sites by combining high-density electrical method and shallow low-temperature method according to claim 1 is characterized in that: The step 2 specifically includes: Step 2.1, using a drone equipped with a magnetic receiver to receive the electromagnetic signal converted from the pseudo-random multi-frequency current signal along the measuring line, and carrying a locator to record position information, using the magnetic receiver to record the potential difference between two measuring electrodes, and at the same time recording the distance between the measuring electrodes, using the ratio of the potential difference to the distance between the measuring electrodes to obtain a single frequency electromagnetic component, and recording the multi-frequency electromagnetic components of the measuring points in the measuring line through electromagnetic signals of different frequencies; Step 2.2, using the multi-frequency electromagnetic components to combine adjacent frequency points, and using an approximate method of first-order difference derivation to calculate the derivative of the electromagnetic field of the corresponding frequency point combination with respect to the frequency point; Step 2.3, using the derivative to convert the apparent resistivity to obtain the apparent resistivity of the landslide site.

4. The method for detecting underground water veins in landslide sites by combining high-density electrical method and shallow low-temperature method according to claim 3 is characterized in that: The apparent resistivity of the landslide site is obtained as: Among them, μ is the magnetic permeability, r is the distance between the center of the dipole moment and the observation point, ω is the angular frequency, i is the emission current, dl is the length of the dipole emission source, represents the partial derivative, Ex represents the component of the electric field in the x direction, ρ i represents the apparent resistivity at the ith frequency point.

5. The method for detecting underground water veins in landslide sites by combining high-density electrical method and shallow low-temperature method according to claim 1, characterized in that: Obtaining the step 3 specifically includes: Step 3.1, obtaining the terrain information of the landslide site, dividing the landslide site into three-dimensional grids based on the terrain information, and combining the apparent resistivity with the location information to obtain the resistivity in each grid; Step 3.2, obtaining the location of the groundwater veins at the landslide site by inverting the resistivity within each grid.

6. The method for detecting underground water veins in landslide sites by combining high-density electrical method and shallow low-temperature method according to claim 5, characterized in that: Obtaining the resistivity within each grid includes: The smooth constrained least squares inversion algorithm is used to obtain the resistivity in each grid. The resistivity inversion objective function is: (G T G+λC T C)Δm=G T Δd Among them, Δd is the residual vector between the observed data d and the forward theoretical calculated value d; G is the coefficient matrix; Δm is the modification vector of the initial model m, C is the model smoothing matrix; λ is the smoothing damping factor.

7. The method for detecting underground water veins in landslide sites by combining high-density electrical method and shallow low-temperature method according to claim 1, characterized in that: The step 4 specifically includes: Step 4.1, after the heat source is powered on and generates heat, record the temperature change data detected by each temperature probe over time; Step 4.2, according to the relationship between the temperature value detected by the temperature probe and time, the temperature detected by each temperature probe at the same time is taken as the vector magnitude, and the direction from the linear heat source to each probe is taken as the vector direction, to determine the vector corresponding to each probe; Step 4.3, according to the principle of vector superposition, the direction obtained after superposition of each vector is determined as the groundwater flow direction. According to the relationship between the temperature change detected by each probe and time, the groundwater flow velocity is calculated. The groundwater flow velocity is determined by combining the flow velocity values ​​obtained by each probe.

8. A system for detecting underground water veins in landslide sites by combining high-density electrical method and shallow low-temperature method, characterized in that: include: The signal transmitting unit sets a transmitting source at the landslide site, arranges transmitting pole distances and multiple measuring lines, and transmits high-density pseudo-random multi-frequency current signals; A signal receiving unit, using a drone equipped with a magnetic receiver to receive the electromagnetic signal converted from the pseudo-random multi-frequency current signal along the measuring line, and carrying a locator to record position information; A position detection unit, which obtains the apparent resistivity of the landslide site according to the electromagnetic signal, and obtains the position of the underground water vein of the landslide site by combining the apparent resistivity of the landslide site with the position information; The flow velocity detection unit sets a plurality of shallow drilling points of different depths at the location of the groundwater vein, sets a heat source in the shallow drilling point, determines the groundwater flow velocity by the change of the temperature of the heat source over time, and obtains the groundwater detection result.

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