Rock resistivity measurement method considering moisture content change and application

Abstract

The invention relates to the technical field of geological survey, and particularly discloses a rock resistivity measurement method considering water content change and application. The method comprises the following steps: firstly, synchronously acquiring initial mass and initial volume parameters of an on-site rock sample by using a weighing method and a drainage method, and further accurately calculating the initial density of the on-site rock sample; in the rock processing link, after the rock is processed into a regular geometrical shape, the rock volume is accurately measured, the theoretical mass is calculated by combining the initial density, meanwhile, the actual mass is obtained by adopting a weighing method, and the moisture content of the rock is accurately regulated and controlled by adopting a dehydration method or an infiltration method by comparing the difference between the theoretical mass and the actual mass. The deviation between the density of the processed rock and the initial density is controlled within an extremely small range, so that the initial physical state of the rock in the natural environment is effectively restored, and the measurement of the initial resistivity of the rock is realized. And the resistivity measurement result deviates from the true value of the natural state due to the significant change of the moisture content.

Description

Technical Field

[0001] The present application relates to the field of geological survey technology, and in particular to a rock resistivity measurement method and application taking into account changes in water content. Background Art

[0002] Amidst accelerating urbanization and the rapid development of energy infrastructure, land resources are becoming increasingly scarce, posing significant challenges in the site selection and acquisition of DC grounding electrodes. Traditional horizontal and vertical grounding electrodes, due to their large footprint and limited site selection, are unable to meet current project requirements. In contrast, deep-well grounding electrodes, with their significant advantages such as a small footprint, flexible site selection, scalable construction, and minimal impact on surrounding public facilities, present broad application prospects in DC transmission projects.

[0003] Deep-well grounding electrodes are buried up to 1 km deep, often operating in rock formations. As a key parameter characterizing rock conductivity, accurate measurement of rock resistivity directly impacts analysis of grounding electrode current dispersion characteristics, calculation of grounding resistance, and the reliability of grounding system optimization. Therefore, accurate rock resistivity measurement is crucial for the design, performance evaluation, and safe operation of deep-well grounding electrodes. However, due to rock geological characteristics and field measurement conditions, accurate rock resistivity measurement presents numerous technical challenges. For example, field-collected rock samples often lack regular cross-sections and require pre-processing such as cutting and polishing before resistivity testing. This process involves collaboration among multiple organizations and is lengthy, from sample collection and processing to testing. During this time, the rock's moisture content is susceptible to fluctuations. Furthermore, the significant heat generated during the cutting process can cause rock cracking. Therefore, to ensure sample integrity, water cooling and lubrication are required, significantly altering the rock's initial moisture content. According to Archie's law, the water content of rock is nonlinearly related to its resistivity. Significant fluctuations in the water content will cause a large deviation between the measured resistivity and the true resistivity of the rock in its natural state, which in turn affects the accuracy of the calculation of grounding electrode design parameters. This may lead to engineering risks such as errors in grounding system performance assessment and excessive grounding resistance, threatening the safe and stable operation of the DC transmission system.

[0004] Therefore, it is urgent to develop a resistivity measurement method that can effectively overcome the changes in rock moisture content to ensure that the test results truly reflect the electrical properties of rocks in the natural environment and provide reliable data support for the design and optimization of deep well grounding electrode engineering. Summary of the Invention

[0005] In view of this, the purpose of this application is to provide a rock resistivity measurement method and application that takes into account changes in water content, so as to solve the defect that the existing rock resistivity measurement technology cannot overcome the defect that the test accuracy is prone to deviation due to fluctuations in water content.

[0006] To achieve the above technical objectives, the present application provides a rock resistivity measurement method that takes into account changes in water content, comprising the following steps:

[0007] Step S1: Collect rock samples at the construction site, obtain the initial mass and initial volume of the rock samples by weighing and water displacement methods within a preset time, and then calculate the initial density of the rock samples;

[0008] Step S2: Processing the rock sample into a regular shape, measuring the size of the regular-shaped rock and calculating the volume of the regular-shaped rock, and calculating the theoretical mass of the regular-shaped rock based on the initial density; and simultaneously measuring the actual mass of the regular-shaped rock using a weighing method;

[0009] In step S3, a dehydration method and / or an infiltration method are used to make the difference between the theoretical mass and the actual mass of the regular-shaped rock less than 5%. The regular-shaped rock is then wrapped, sealed, and left to stand until the moisture content inside the regular-shaped rock is evenly distributed, and the resistivity of the regular-shaped rock is measured.

[0010] Furthermore, the preset time is less than or equal to 1 hour.

[0011] Furthermore, the shape of the regularly shaped rock includes one of a cylinder and a rectangle.

[0012] Furthermore, the dehydration method includes one of a drying method and a vacuum dehydration method.

[0013] Furthermore, the infiltration method is as follows: immersing the rock in a soil simulating solution;

[0014] The soil simulating liquid is prepared according to the initial geological environment of the rock sample. The specific preparation method is: take the soil of the initial geological environment, mix it with water in a mass ratio of 1:1, stir, let it stand, and filter to obtain the soil simulating liquid.

[0015] Furthermore, when the actual mass is greater than the theoretical mass, the dehydration method is used to dehydrate the regular-shaped rock; when the actual mass is less than the theoretical mass, the infiltration method is used to soak the regular-shaped rock.

[0016] Furthermore, when the water displacement method is used to measure the initial volume of the rock sample, the measurement time is less than 5 minutes.

[0017] Furthermore, when the regularly shaped rocks are wrapped and sealed and then left to stand for a period of time greater than 48 hours.

[0018] The present application provides an application of a rock resistivity measurement method that takes into account changes in water content, which is applied to scenarios where on-site in-situ resistivity measurement cannot be performed.

[0019] Furthermore, application scenarios include: rock resistivity measurement in deep well grounding electrode projects, geological exploration in high-altitude or permafrost areas, and electrical property analysis of concealed rock masses in urban underground projects.

[0020] In summary, the present application provides a rock resistivity measurement method that takes into account changes in water content. The method first uses the weighing method and the drainage method to simultaneously obtain the initial mass and initial volume parameters of the on-site rock sample, and then accurately calculate its initial density. In the rock processing link, after the rock is processed into a regular geometric shape, its volume is accurately measured, and the theoretical mass is calculated in combination with the initial density; at the same time, the actual mass is obtained, and by comparing the difference between the two, a dehydration method (such as low-temperature vacuum drying) or an infiltration method is used to accurately control the water content of the rock, so that the deviation between the density of the treated rock and the initial density is controlled within an extremely small range, thereby effectively restoring the initial physical state of the rock in the natural environment. This method successfully overcomes the technical difficulty that the resistivity measurement results deviate from the true value of the natural state due to significant changes in water content during the collection and processing of rock samples. It can accurately restore the on-site conditions of rock samples and measure their initial resistivity.

[0021] Compared to traditional measurement techniques, this method overcomes the technical bottleneck of effectively controlling fluctuations in rock moisture content. By quantitatively controlling rock density parameters, which are strongly correlated with moisture content, it accurately restores the rock's initial state. Furthermore, through a standardized measurement process and scientific parameter control strategies, it eliminates interference from differences in the rock's geographical environment and its own morphological irregularities, significantly improving the accuracy and reliability of rock resistivity measurements and further broadening the application of this measurement method in various fields, including geological exploration and deep-well grounding electrode design. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0023] Figure 1 A schematic diagram of the rock resistivity measurement method provided in an embodiment of the present application;

[0024] Figure 2 Schematic diagram of a machine tool for processing rock samples provided in an embodiment of the present application;

[0025] Figure 3 A physical image of an intermediate rock form obtained when processing a rock sample provided in an embodiment of the present application;

[0026] Figure 4Actual image of the cylindrical rock sample provided in the examples of this application. DETAILED DESCRIPTION

[0027] The following will clearly and completely describe the technical solutions of the embodiments of this application in conjunction with the accompanying drawings. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this specification, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection requested by this application.

[0028] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of this application and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0029] Unless otherwise specified or limited, the terms "mounted," "connected," and "connected" should be interpreted broadly. For example, they can refer to fixed, removable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; and internal communication between two components. Those skilled in the art will understand the specific meanings of these terms in this application.

[0030] The sources of all raw materials in the present invention are not particularly limited and can be purchased on the market or prepared according to conventional methods known to those skilled in the art.

[0031] See also Figure 1 The present invention provides a rock resistivity measurement method taking into account changes in water content, including the following steps:

[0032] Step S1: Collect rock samples at the construction site, obtain the initial mass and initial volume of the rock samples by weighing and water displacement methods within a preset time, and then calculate the initial density of the rock samples;

[0033] Step S2: Processing the rock sample into a regular shape, measuring the size of the regular-shaped rock and calculating the volume of the regular-shaped rock, and calculating the theoretical mass of the regular-shaped rock based on the initial density; and simultaneously measuring the actual mass of the regular-shaped rock using a weighing method;

[0034] In step S3, a dehydration method and / or an infiltration method are used to make the difference between the theoretical mass and the actual mass of the regular-shaped rock less than 5%. The regular-shaped rock is then wrapped, sealed, and left to stand until the moisture content inside the regular-shaped rock is evenly distributed, and the resistivity of the regular-shaped rock is measured.

[0035] It should be noted that the internal moisture content of rock samples collected at the construction site is prone to significant changes during the subsequent transportation and processing. For example, during transportation, the water exchange between the rock and the ambient humidity is affected by factors such as temperature and humidity gradients and transportation time, resulting in dynamic fluctuations in moisture content. Figure 2 As shown, to prevent thermal damage to the rock caused by heat generated during cutting, water cooling is typically used. This inevitably causes the rock to absorb water, thus changing its initial moisture content. Existing measurement techniques are generally limited and often fail to fully consider the potential impact of moisture changes during transportation and processing on rock resistivity measurements. This measurement method, based on an in-depth analysis of the dynamic evolution of rock moisture content, achieves high-precision restoration of the rock's initial state (initial moisture content) at the construction site through systematic parameter control and precise measurement strategies. This effectively eliminates interference from differences in transportation environments and cutting processes on initial resistivity measurements.

[0036] In some embodiments, the preset time is less than or equal to 1 hour.

[0037] It should be noted that if the sample is exposed for too long, the water inside the rock will continue to evaporate, resulting in mass loss, which will cause the initial mass and density data obtained from the measurement to deviate from the true value, ultimately affecting the accuracy of the rock resistivity measurement results.

[0038] In some embodiments, the shape of the regularly shaped rock includes one of a cylinder and a rectangle.

[0039] It should be noted that when the shape of the regular-shaped rock is a cylinder, V=πD can be used. 2 The volume is calculated using L / 4 (D is the diameter of the base and L is the height of the cylinder). If the cylinder is rectangular, use V=LDH (L, D, and H correspond to length, width, and height, respectively).

[0040] In some embodiments, the dehydration method includes a drying method and a vacuum dehydration method.

[0041] In some embodiments, the infiltration method is: soaking the rock in a soil simulating solution;

[0042] The soil simulating liquid is prepared according to the initial geological environment of the rock sample. The specific preparation method is: take the soil of the initial geological environment, mix it with water in a mass ratio of 1:1, stir, let it stand, and filter to obtain the soil simulating liquid.

[0043] In some embodiments, when the actual mass is greater than the theoretical mass, the dehydration method is used to dehydrate the regularly shaped rock; when the actual mass is less than the theoretical mass, the infiltration method is used to soak the regularly shaped rock.

[0044] It should be noted that in actual operation, when the actual mass of a regularly shaped rock is greater than the theoretical mass, it indicates that its water content is too high and needs to be dried by dehydration; conversely, if the actual mass is less than the theoretical mass, water is added through infiltration to ensure that the water content of the rock returns to its initial state.

[0045] In some embodiments, when the initial volume of a rock sample is measured using the water displacement method, the measurement time is less than 5 minutes.

[0046] It should be noted that this is because during the drainage measurement process, the contact between rock and water will cause water penetration. If the measurement time is too long, the water absorption of the rock will increase, which will cause the drainage volume measurement value to deviate from the true value.

[0047] In some embodiments, when the regularly shaped rocks are wrapped and sealed and then left to stand for a period of time, the standing time is greater than 48 hours.

[0048] It should be noted that, in addition, the step of leaving the regularly shaped rocks to stand after wrapping and sealing is helpful to redistribute and balance the water inside the rock, making the water content uniform, thereby restoring the original state of the rock in the natural environment to the maximum extent, effectively reducing the resistivity measurement error caused by uneven water content, and improving the accuracy and reliability of the measurement results.

[0049] An embodiment of the present application provides an application of a rock resistivity measurement method that takes into account changes in water content, which is applied to scenarios where on-site in-situ resistivity measurement cannot be performed.

[0050] In some embodiments, application scenarios include: rock resistivity measurement in deep well grounding electrode projects, geological exploration in high altitude or permafrost areas, and electrical property analysis of concealed rock masses in urban underground projects.

[0051] The applicant further provides the following reference specific embodiments to describe the present invention. It should be noted that these embodiments are merely illustrative and do not limit the present invention in any way.

[0052] Example 1

[0053] This embodiment provides a rock resistivity measurement method that takes into account changes in water content. The specific steps are as follows:

[0054] Step S1: Drilling operations are performed at the deep well ground electrode site. Within 1 hour, three rocks (corresponding to numbers 1, 2, and 3 in Table 1) near the deepest ground electrode from the surface are taken as rock samples. The soil attached to the surface of the rock samples is removed, and their initial weight M0 and initial volume V0 are measured using the weighing method and the water displacement method. The initial density of the rock samples is calculated according to ρ0=M0 / V0. When measuring the initial volume using the water displacement method, the measurement time should be controlled within 5 minutes to avoid a large amount of water infiltration into the rock sample.

[0055] Step S2: Use a cutting machine to cut the rock sample into cylindrical rock samples with smooth cross-section and regular shape (see Figures 3 and 4 , Figure 3 It is the intermediate form of rock sample during processing. Figure 4 The length L and diameter D of the cylindrical rock sample are measured with a vernier caliper, and V=πD 2 L / 4 is used to calculate the volume V1 of the cylindrical rock sample, and combined with ρ0, the theoretical mass M1 of the cylindrical rock sample is calculated according to M1=ρ0V1;

[0056] Step S3: Measure the actual mass M2 of the cylindrical rock sample using a weighing method, compare the actual mass M2 of the cylindrical rock sample with the theoretical mass M1, and perform the following operations according to the comparison results:

[0057] When M2>M1, the cylindrical rock sample is dehydrated in a constant temperature drying oven at 115°C. During the dehydration period, the cylindrical rock sample is weighed every 2 hours until the difference between M2 and M1 is less than 5%. The cylindrical rock sample is then sealed with a sealing film.

[0058] When M2 is less than M1, immerse the cylindrical rock sample in the soil simulating liquid and weigh the cylindrical rock sample every 2 hours until the difference between M2 and M1 is less than 5%. Then, seal the cylindrical rock sample with a sealing film. The soil simulating liquid is prepared by taking soil from the initial geological environment, mixing it with water in a mass ratio of 1:1, stirring it thoroughly, letting it stand, and filtering it to obtain the soil simulating liquid.

[0059] Step S4: After the sealed cylindrical rock sample is left to stand for 48 hours or more, the sealing film is removed and the resistivity of the cylindrical rock sample is tested using the two-pole method. Before the test, the surface of the cylindrical rock sample should be wiped dry to prevent moisture attached to the surface of the cylindrical rock sample from affecting the test results. During the test, a DC constant current power supply is used to generate voltages (U) of different amplitudes at two cross-sections of the cylindrical rock sample, and the current (I) flowing through the cylindrical rock sample is tested at the same time. The entire test process lasts for 5 seconds. After the test, the rock resistivity is calculated using the following formula: ρ (resistivity) (D is the diameter of the cylindrical rock sample, and L is the axial height of the cylindrical rock sample). To reduce measurement errors, three resistivity tests were performed on the cylindrical rock sample at different voltages, and the average of the three test results was used as the final test result. The test parameters and results involved in this embodiment are shown in Table 1.

[0060] Table 1. Test parameters and effect data

[0061]

[0062] The above are only preferred embodiments of the present application and are not intended to limit the present invention. Although the present application has been described in detail with reference to examples, those skilled in the art can still modify the technical solutions described in the aforementioned examples or make equivalent replacements for some of the technical features therein. However, any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A rock resistivity measurement method taking into account changes in water content, characterized in that: The following steps are involved: Step S1: Collect rock samples at the construction site, obtain the initial mass and initial volume of the rock samples by weighing and water displacement methods within a preset time, and then calculate the initial density of the rock samples; Step S2, processing the rock sample into a regular shape, measuring the size of the regular-shaped rock and calculating the volume of the regular-shaped rock, calculating the theoretical mass of the regular-shaped rock based on the initial density, and measuring the actual mass of the regular-shaped rock by weighing; In step S3, a dehydration method and / or an infiltration method are used to make the difference between the theoretical mass and the actual mass of the regular-shaped rock less than 5%. The regular-shaped rock is then wrapped, sealed, and left to stand until the moisture content inside the regular-shaped rock is evenly distributed, and the resistivity of the regular-shaped rock is measured.

2. The rock resistivity measurement method considering water content change according to claim 1, characterized in that: The preset time is less than or equal to 1 hour.

3. The rock resistivity measurement method considering water content variation according to claim 1, characterized in that: The shape of the regularly shaped rock includes one of a cylinder and a rectangle.

4. The rock resistivity measurement method considering water content variation according to claim 1, characterized in that: The dehydration method includes a drying method and a vacuum dehydration method.

5. The rock resistivity measurement method considering water content variation according to claim 1, characterized in that: The infiltration method is as follows: immersing the rock in a soil simulation liquid; The soil simulating liquid is prepared according to the initial geological environment of the rock sample. The specific preparation method is: take the soil of the initial geological environment, mix it with water in a mass ratio of 1:1, stir, let it stand, and filter to obtain the soil simulating liquid.

6. The rock resistivity measurement method considering water content variation according to claim 1, characterized in that: When the actual mass is greater than the theoretical mass, the dehydration method is used to dehydrate the regular-shaped rock; When the actual mass is less than the theoretical mass, the infiltration method is used to soak the regular-shaped rock.

7. The rock resistivity measurement method considering water content variation according to claim 1, characterized in that: When the drainage method is used to measure the initial volume of rock samples, the measurement time is less than 5 minutes.

8. The rock resistivity measurement method considering water content variation according to claim 1, characterized in that: When the regularly shaped rocks are wrapped and sealed and then left to stand for a period of time, the standing period of time is greater than 48 hours.

9. An application of a rock resistivity measurement method taking into account changes in water content, characterized in that: It is used in scenarios where on-site resistivity measurement is not possible.

10. The use according to claim 9, characterized in that The application scenarios include: rock resistivity measurement in deep well grounding electrode projects, geological exploration in high altitude or permafrost areas, and electrical property analysis of concealed rock masses in urban underground projects.

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