GB2587892A

GB2587892A - Apparatus for non-destructively measuring water migration law of frozen soil and measurement method thereby

Info

Publication number: GB2587892A
Application number: GB2010910.4A
Authority: GB
Inventors: Teng Jidong; Luo Haoliang; Zhang Sheng; Sheng Daichao
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2019-07-19
Filing date: 2020-07-15
Publication date: 2021-04-14
Anticipated expiration: 2040-07-15
Also published as: CN110333269A; GB202010910D0; GB2587892B; CN110333269B

Abstract

An apparatus for non-destructively measuring a water migration law of frozen soil, comprises: a container 7 with openings at two ends, a controller 8, several electrode patches 5, several electrode connecting lines 6, a low-temperature circulator 4, an upper computer 10, an external measurement apparatus 9, and a water injection module 1. The low-temperature circulator is mounted at two ends of the container with openings at two ends, and controls temperature of a frozen soil sample placed in the container. The controller controls operation of the electrode patch, and obtains an electrical signal used for measurement. The electrode patch obtains an input power supply signal or output the electrical signal for measurement, and the water injection module is connected to a water injection hole of the low-temperature circulator, and injects water into the container. The external measurement apparatus supplies power to the controller, provides the input power supply signal, and obtains, by using the controller, the electrical signal used for measurement. The upper computer controls the electrode patch, and controls operation of the low-temperature circulator. Further disclosed is a method for non-destructively measuring a water migration law of frozen soil by using the measurement apparatus.

Description

APPARATUS FOR NON-DESTRUCTIVELY MEASURING WATER MIGRATION LAW OF FROZEN SOIL AND MEASUREMENT METHOD THEREBY

TECHNICAL FIELD

The present invention specifically relates to an apparatus for non-destructively measuring a water migration law of frozen soil, and a measurement method thereby.

BACKGROUND

Frozen soil is defined as rocks and soil containing ice crystals when temperature is below 0°C.

According to a freezing time, the frozen soil can be classified into permafrost (also referred to as permafrost, which is soil layers that are frozen and unmelted for two or more years), seasonal frozen soil (half to several months), and short-term frozen soil (hours/days to half a month). Permafrost in China accounts for more than 1/5 of the national territorial area, and has the third largest permafrost in the world, second only to Russia and Canada. The permafrost in China is mainly distributed in high-latitude and high-altitude regions such as Northeast China, Inner Mongolia, Xinjiang, and Tibet, and extremely cold and hot climate is often formed. Due to impact of climate, most frozen soil in China is seasonal frozen soil.

However, the biggest challenge facing construction of high-speed railways and airports in cold regions is how to deal with a problem of "frozen heave" of roadbeds. The so-called frost heave is a fact that water in the roadbeds is condensed into ice due to subzero temperature, thereby causing a volume to expand, and causing the roadbeds and road surfaces to bulge. Consequently, quality of projects is particularly seriously damaged. The two established high-speed railways in the cold regions of China, both the Harbin-Dalian high-speed railway and the Lanzhou-Wulumuqi highspeed railway, have the frost heave problem in different degrees. The frost heave of the Harbin-Dalian Line is 5mm on average, and up to 20 mm, which seriously affects operation safety. The frost heave problem has become a primary concern during construction in the cold regions, especially key projects such as high-speed railways and airports that have extremely high requirements for road surface smoothness. Essence of the frost heave is water migration. The Harbin-Dalian Line is used as an example. Since surface temperature of roadbeds in the cold regions is as low as -30°C, temperature in the roadbed soil is about 10°C. Current water migration in frozen soil is generally migration of liquid water, and unfrozen water in a freezing process is generally liquid water. Therefore, studying water migration is to study a content and change of the unfrozen water, and a content of the unfrozen water changes with temperature. A phase change of water affects hydraulic, thermal, and physical properties of frozen soil. Therefore, it is very important to measure the unfrozen water.

At present, a commonly used method for measuring water migration of unsaturated soil in a freezing process is an indoor experimental method. An apparatus for measuring water migration of unsaturated soil in a freezing process in China generally directly use a layer drying method, a method similar to a TDR, etc. However, although this type of method has a certain scope of application, the method still has the following limitations 1. By using the layer drying method, only a total amount of water in soil migrated in an entire process can be learned, but a water migration law in the process cannot be reflected, hi addition, the method takes a relatively long time and brings a large workload.

2. Although the method similar to the TDR method is relatively simple to operate with a relatively short time, such a method requires to insert a probe into soil. In this way, integrity of the soil is destroyed. When the TDR method is used to explore water migration, precision is relatively low, there are relatively many influence factors on experiments, and the TDR method is unstable.

SUMMARY

A first objective of the present invention is to provide a highly reliably, simple, and convenient apparatus for non-destructively measuring a water migration law of frozen soil.

A second objective of the present invention is to provide a method for non-destructively measuring a water migration law of frozen soil by the above measurement apparatus.

The apparatus for non-destructively measuring a water migration law of frozen soil provided in the present invention includes a container with openings at two ends, a controller, several electrode patches, several electrode connecting lines, a low-temperature circulator, an upper computer, an external measurement apparatus, and a water injection module, where the low-temperature circulator includes a first low-temperature circulating plate and a second low-temperature circulating plate that are mutually connected, the first low-temperature circulating plate is mounted at one end of the container with openings at two ends, the second low-temperature circulating plate is mounted at the other end of the container with openings at two ends, and the low-temperature circulator is configured to control temperature of a frozen soil sample placed in the container, one end of the controller is connected to the electrode connecting line, and is connected to the electrode patch by using the electrode connecting line, the other end of the controller is directly connected to the external measurement apparatus, the controller is configured to control operation of the electrode patch, arid obtain an electrical signal that is output by the electrode patch for measurement, the electrode patch is mounted on an inner wall of the container, is connected to the external measurement apparatus sequentially by using the electrode connecting line and the controller, and is configured to obtain a input power supply signal or output the electrical signal for measurement, the water injection module is connected to a water injection hole of the low-temperature circulator, and is configured to inject water into the container; the external measurement apparatus is configured to supply power to the controller, provide the input power supply signal, and obtain, by using the controller, the electrical signal that is output by the electrode patch for measurement; the upper computer is connected to the controller, and is configured to control operation of the electrode patch by using the controller, and control temperature of the low-temperature circulator.

The container with openings at two ends is a round organic glass cylinder with openings at two ends.

The water injection module includes a Markov bottle and a water injection hose; the lvfarkov bottle is connected to the water injection hole of the low-temperature circulator through the water injection hose and is configured to inject water into the container.

The electrode patch is mounted on the inner wall of the container, the container is divided into several layers, several electrode patches are mounted every other layer, and the electrode patch is connected to the external measurement apparatus by using the electrode connecting line and the controller, and is configured to obtain the input power supply signal or output the electrical signal for measurement; the electrode patch is configured to measure, by using the van der Pauw method, resistivity of a layer at which the electrode patch is located.

The electrode patch is mounted on the inner wall of the container, the container is specifically divided into 20 layers, four electrode patches are mounted every other layer, a connecting line between a first electrode patch and a third electrode patch passes through a circle center of a layer at which the first electrode patch and the third electrode patch are located, a connecting line between a second electrode patch and a fourth electrode patch passes through a circle center of a layer at which the second electrode patch and the fourth electrode patch are located, and a distance between the first electrode patch and the second electrode patch is equal to a distance between the third electrode patch and the fourth electrode patch.

The electrode patch is a thin-copper electrode patch.

The electrode patch is mounted on the inner wall of the container, and the electrode patch is specifically stuck to the inner wall of the container by using glue.

The present invention further provides a method for non-destructively measuring a water migration law of frozen soil, including the following steps: Si. placing only one layer of soil sample with a known water content into the measurement apparatus, and skipping starting a low-temperature circulator and a water injection module; S2, measuring and obtaining resistivity of a single layer of soil sample by using the van der Pauw method; 53. filling the measurement apparatus up with a soil sample with a water content same as the water content in step Si, and skipping starting the low-temperature circulator and the water injection module; 54. measuring and obtaining, by using the van der Pauw method, resistivity of a soil sample of a layer at which an electrode patch is located; 55. calculating, based on the resistivity that is obtained in step S2 and that is of the single layer of soil sample and the resistivity that is obtained in step S4 and that is of the soil sample of the layer at which the electrode patch is located, a correction factor of a layer at which each electrode patch is located; SG, filling the measurement apparatus up with the soil sample with the water content same as the water content in step Si, setting temperature of the low-temperature circulator and a quantity of water injected by the water injection module, and starting the low-temperature circulator and the water injection module, to obtain a frozen soil sample; 57. measuring and obtaining, by using the van der Pauw method, resistivity of a test frozen soil sample of the layer at which the electrode patch is located; S8. correcting, based on the correction factor that is obtained in step 55 and that is of the layer at which each electrode patch is located, the resistivity that is obtained in step 57 and that is of the test frozen soil sample of the layer at which the electrode patch is located, so as to obtain actual resistivity of the frozen soil sample of the layer at which the electrode patch is located; S9. calculating, based on the actual resistivity that is obtained in step 58 and that is of the frozen soil sample of the layer at which the electrode patch is located, a content of unfrozen water of the frozen soil sample of the layer at which the electrode patch is located; S10, repeating steps S7 to S9 according to a specified measurement time point, to obtain a curve of the content that changes with time and that is of the unfrozen water of the frozen soil sample of the layer at which the electrode patch is located; and S11. analyzing a migration law of unfrozen water of frozen soil according to the curve, obtained in step S10, of the content that changes with time and that is of the unfrozen water of the frozen soil sample of the layer at which the electrode patch is located.

The resistivity is measured by using the van der Pauw method, and the resistivity is specifically measured by using the following steps: a. for four electrode patches connected to the frozen soil sample, injecting a constant current 1141-A2 between a first electrode patch and a second electrode patch, and measuring a voltage V-13-A4 between a third electrode patch and a fourth electrode patch, to obtain a first resistance VA3-A4 R1 Al A2 b. for the four electrode patches connected to the frozen soil sample, injecting a constant current '42 42 between the second electrode patch and the third electrode patch, and measuring a voltage T144-A1 between the fourth electrode patch and the first electrode patch, to obtain a second resistance V R -fA4 Al 1A2 Al; c, calculating the resistivity it) by using the following formula: (1121 7(112, e +e P =1 in the formula, R1 is the first resistance, R2 is the second resistance, and d is a diameter of a container.

The calculating a correction factor of a layer at which each electrode patch is located in step S5 is specifically calculating, by using the following equation, the correction factor of the layer at which each electrode patch is located: = in the formula, 111 is a correction factor of a layer at which an lth layer of electrode patch is located, 7; is resistivity of a soil sample of the layer at which the lth layer of electrode patch is located, and r is the resistivity of the single layer of soil sample.

The correcting, based on the correction factor that is obtained in step S5 and that is of the layer at which each electrode patch is located, the resistivity that is obtained in step S7 and that is of the test frozen soil sample of the layer at which the electrode patch is located in step S8 is specifically multiplying, by the resistivity that is obtained in step S7 and that is of the test frozen soil sample of the layer at which the electrode patch is located, the correction factor that is obtained in step S5 and that is of the layer at which each electrode patch is located, so as to obtain actual resistivity of the frozen soil sample of the layer at which the electrode patch is located.

The calculating a content of unfrozen water of the frozen soil sample of the layer at which the electrode patch is located in step S9 is specifically calculating, by using the following formula, the content of the unfrozen water of the frozen soil sample of the layer at which the electrode patch is located: P= 739 By in the formula, is the resistivity of the frozen soil sample of the layer at which the electrode patch is located, and ev is the content of the unfrozen water of the frozen soil sample of the layer at which the electrode patch is located.

Based on the apparatus for non-destructively measuring a water migration law of frozen soil and the measurement method that are provided in the present invention, the unfrozen water in the frozen soil is measured by using the designed measurement apparatus and measurement method, so as to provide basic data and measurement data for analyzing the migration law of the unfrozen water in the frozen soil. The method in the present invention is simple and reliable, and is convenient to

USC

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a measurement apparatus according to the present invention; FIG. 2 is a schematic diagram of arranging a single layer of electrode patch and a schematic diagram of the van der Pauw method according to the present invention; and FIG. 3 is a schematic method flowchart of a method according to the present invention.

DETAILED DESCRIPTION

FIG. 1 is a schematic diagram of a measurement apparatus according to the present invention. The apparatus for non-destructively measuring a water migration law of frozen soil provided in the present invention includes a container with openings at two ends, a controller, several electrode patches, several electrode connecting lines, a low-temperature circulator, an upper computer, an external measurement apparatus, and a water injection module. The low-temperature circulator includes a first low-temperature circulating plate and a second low-temperature circulating plate that are mutually connected, the first low-temperature circulating plate is mounted at one end of the container with openings at two ends, the second low-temperature circulating plate is mounted at the other end of the container with openings at two ends, and the low-temperature circulator is configured to control temperature of a frozen soil sample placed in the container. One end of the controller is connected to the electrode connecting line, and is connected to the electrode patch by using the electrode connecting line. The other end of the controller is directly connected to the external measurement apparatus. The controller is configured to control operation of the electrode patch, and obtain an electrical signal that is output by the electrode patch for measurement. The electrode patch is mounted on an inner wall of the container, is connected to the external measurement apparatus sequentially by using the electrode connecting line and the controller, and is configured to obtain an input power supply signal or output the electrical signal for measurement.

The water injection module is connected to a water injection hole of the low-temperature circulator, and is configured to inject water into the container. The external measurement apparatus is configured to supply power to the controller, provide the input power supply signal, and obtain, by using the controller, the electrical signal that is output by the electrode patch for measurement. The upper computer is connected to the controller, and is configured to control operation of the electrode patch by using the controller, and control temperature of the low-temperature circulator.

During specific implementation, the apparatus for non-destructively measuring a water migration law of frozen soil provided in the present invention includes a container 7 with openings at two ends, a controller 8 (a programmable logic controller (PLC) may be configured during the specific implementation), an external measurement apparatus 9, an upper computer 10 (a computer may be configured during the specific implementation), several electrode patches 5, several electrode connecting lines 6, a low-temperature circulator 4, and water injection modules (1 and 2). The low-temperature circulator includes a first low-temperature circulating plate and a second low-temperature circulating plate that are mutually connected, the first low-temperature circulating plate is mounted at one end of the container with openings at two ends, the second low-temperature circulating plate is mounted at the other end of the container with openings at two ends, and the low-temperature circulator is configured to control temperature of a frozen soil sample placed in the container. The PLC can implement combined measurement between any two electrodes by using a dedicated system. The electrode patch is mounted on an inner wall of the container, is connected to the external measurement apparatus by using the electrode connecting line and the PLC, and is configured to obtain an input power supply signal or output the electrical signal for measurement.

A water injection module is connected to a water injection hole of the low-temperature circulator, and is configured to inject water into the container. 3 in the figure is an air pressure balance tube that is used to balance air pressure in a sample cylinder, so that water in a Markov bottle can flow into a water tank.

During specific implementation, the container with openings at two ends is a round organic glass cylinder with openings at two ends. The water injection module includes a Markov bottle 1 and a water injection hose 2. The Markov bottle is connected to the water injection hole of the low-temperature circulator through the water injection hose, and is configured to inject water into the container based on the communicating vessel principle (Purpose and function of water injection: to inject water into the sample cylinder and the water tank can replenish water in the water tank in real time, and keep a water level of the water tank unchanged, to conveniently manufacture a frozen soil sample. Water injection principle: the communicating vessel principle, where injection is performed based on a height difference). The electrode patch is a thin-copper electrode patch, and is stuck on the inner wall of the container by using glue. When the sample frozen soil is placed, a side of the electrode patch in contact with the sample is coated with a conductive adhesive, to enhance electrical connectivity between the electrode patch and the sample frozen soil, to reduce resistance of a contact surface.

The electrode patch is mounted on the inner wall of the container, the container is divided into several layers, several electrode patches are mounted every other layer, and the electrode patch is connected to the external measurement apparatus by using the electrode connecting line and the PLC, and is configured to obtain the input power supply signal or output the electrical signal for measurement. The electrode patch is configured to measure, by using the van der Pauw method, resistivity of a layer at which the electrode patch is located. For example, as shown in FIG.1 and FIG. 2, the electrode patch is mounted on the inner wall of the container, the container is divided into 20 layers, four electrode patches are mounted every other layer (FIG. 2 is a schematic diagram of mounting electrode patches at a layer), a connecting line between a first electrode patch Al and a third electrode patch A3 passes through a circle center of a layer at which the first electrode patch Al and the third electrode patch A3 are located, a connecting line between a second electrode patch A2 and a fourth electrode patch A4 passes through a circle center of a layer at which the second electrode patch A2 and the fourth electrode patch A4 are located, and a distance between the first electrode patch and the second electrode patch is equal to a distance between the third electrode patch and the fourth electrode patch.

The external measurement apparatus includes a power supply module, a voltage measurement module, and a current measurement module. The power supply module is configured to supply power to an electrode patch of the apparatus. The voltage measurement module is configured to measure a voltage signal of the electrode patch. The current measurement module is configured to measure a current signal of the electrode patch. The PLC is an electronic apparatus of a Digital operation operation dedicatedly designed for industrial production, uses a type of programmable memory, and is configured to internally store a program, execute logical operation, and perform sequential control. Before experiments, a measurement module and an electrode line of the external measurement apparatus are respectively connected to two ends of the PLC, and then program control is performed on the PLC by using the upper computer, so that circuits at the two ends of the PLC can automatically communicate based on program settings, and respectively supply power to the apparatus and measure a voltage signal and a current signal between corresponding electrode patches of the apparatus.

FIG. 3 is a schematic flowchart of a method for non-destructively measuring a water migration law of frozen soil by using the measurement apparatus according to the present invention. The measurement method provided in the present invention includes the following steps: Si. place only one layer of soil sample with a known water content into the measurement apparatus, and skip starting a low-temperature circulator and a water injection module; S2, measure and obtain resistivity of a single layer of soil sample by using the van der Pauw method Si fill the measurement apparatus up with a soil sample with a water content same as the water content in step Si, and skip starting the low-temperature circulator and the water injection module; 54. measure and obtain, by using the van der Pauw method, resistivity of a soil sample of a layer at which an electrode patch is located; S5, calculate, based on the resistivity that is obtained in step 52 and that is of the single layer of soil sample and the resistivity that is obtained in step S4 and that is of the soil sample of the layer at which the electrode patch is located, a correction factor of a layer at which each electrode patch is located, where specifically, the correction factor of the layer at which each electrode patch is located is calculated by using the following equation: r, r in the formula, 11/ is a correction factor of a layer at which an i layer of electrode patch is located, 7; is resistivity of a soil sample of the layer at which the in' layer of electrode patch is located, and r is the resistivity of the single layer of soil sample; So, fill the measurement apparatus up with the soil sample with the water content same as the water content in step Sl, set temperature of the low-temperature circulator and a quantity of water injected by the water injection module, and start the low-temperature circulator and the water injection module, to obtain a frozen soil sample; S7. measure and obtain, by using the van der Pauw method, resistivity of a test frozen soil sample of the layer at which the electrode patch is located; S8. correct, based on the correction factor that is obtained in step S5 and that is of the layer at which each electrode patch is located, the resistivity that is obtained in step S7 and that is of the test frozen soil sample of the layer at which the electrode patch is located, to obtain actual resistivity of the frozen soil sample of the layer at which the electrode patch is located is specifically multiplying, by the resistivity that is obtained in step S7 and that is of the test frozen soil sample of the layer at which the electrode patch is located, the correction factor that is obtained in step S5 and that is of the layer at which each electrode patch is located, so as to obtain the actual resistivity of the frozen soil sample of the layer at which the electrode patch is located.

S9. calculate, based on the actual resistivity that is obtained in step S8 and that is of the frozen soil sample of the layer at which the electrode patch is located, a content of unfrozen water of the frozen soil sample of the layer at which the electrode patch is located, where specifically, the content of the unfrozen water of the frozen soil sample of the layer at which the electrode patch is located is calculated by using the following formula: in the formula, is the resistivity of the frozen soil sample of the layer at which the electrode patch is located, and er is the content of the unfrozen water of the frozen soil sample of the layer at which the electrode patch is located.

510, repeat steps S7 to S9 according to a specified measurement time point, to obtain a curve of the content that changes with time and that is of the unfrozen water of the frozen soil sample of the layer at which the electrode patch is located; and Si I. analyze a migration law of unfrozen water of frozen soil according to the curve of the content that changes with time and that is of the unfrozen water of the frozen soil sample of the layer at which the electrode patch is located.

The resistivity is measured by using the van der Pauw method, and the resistivity is specifically measured by using the following steps: a. for four electrode patches connected to the frozen soil sample, injecting a constant current 1*41-.42 between a first electrode patch and a second electrode patch, and measuring a voltage T113-214 between a third electrode patch and a fourth electrode patch, to obtain a first resistance R V.13-A I _ A1-A2; b. for the four electrode patches connected to the frozen soil sample, injecting a constant current 1212--23 between the second electrode patch and the third electrode patch, and measuring a voltage ;V ;A 4-Al between the fourth electrode patch and the first electrode patch, to obtain a second resistance ;V ;R2 A4-Al 42-A3 * c. calculating the resistivity by using the following formula: c1R1 e " +e P =1 in the formula, R1 is the first resistance, R2 is the second resistance, and d is a diameter of a container.

Claims

What is claimed is: 1. An apparatus for non-destructively measuring a water migration law of frozen soil, comprising a container with openings at two ends, a controller, several electrode patches, several electrode connecting lines, a low-temperature circulator, an upper computer, an external measurement apparatus, and a water injection module, wherein the low-temperature circulator comprises a first low-temperature circulating plate and a second low-temperature circulating plate that are mutually connected, the first low-temperature circulating plate is mounted at one end of the container with openings at two ends, the second low-temperature circulating plate is mounted at the other end of the container with openings at two ends, and the low-temperature circulator is configured to control temperature of a frozen soil sample placed in the container; one end of the controller is connected to the electrode connecting line, and is connected to the electrode patch by using the electrode connecting line, the other end of the controller is directly connected to the external measurement apparatus; the controller is configured to control operation of the electrode patch, and obtain an electrical signal that is output by the electrode patch for measurement; the electrode patch is mounted on an inner wall of the container, is connected to the external measurement apparatus sequentially by using the electrode connecting line and the controller, and is configured to obtain an input power supply signal or output the electrical signal for measurement; the water injection module is connected to a water injection hole of the low-temperature circulator, and is configured to inject water into the container; the external measurement apparatus is configured to supply power to the controller, provide the input power supply signal, and obtain, by using the controller, the electrical signal that is output by the electrode patch for measurement, the upper computer is connected to the controller, and is configured to control operation of the electrode patch by using the controller, and control temperature of the low-temperature circulator.
2. The apparatus for non-destructively measuring a water migration law of frozen soil according to claim 1, wherein the water injection module comprises a Markov bottle and a water injection hose; the Nlarkov bottle is connected to the water injection hole of the low-temperature circulator through the water injection hose and is configured to inject water into the container.
3. The apparatus for non-destructively measuring a water migration law of frozen soil according to claim 1 or 2, wherein the container with openings at two ends is a round organic glass cylinder with openings at two ends; the electrode patch is mounted on the inner wall of the container, and specifically the container is divided into several layers, several electrode patches are mounted every other layer, and the electrode patch is connected to the external measurement apparatus by using the electrode connecting line and the controller, and is configured to obtain the input power supply signal or output the electrical signal for measurement; the electrode patch is configured to measure, by using the van der Pauw method, resistivity of a layer at which the electrode patch is located.
4. The apparatus for non-destructively measuring a water migration law of frozen soil according to any ones of claims Ito 3, wherein the electrode patch is mounted on the inner wall of the container, the container is specifically divided into 20 layers, four electrode patches are mounted every other layer, a connecting line between a first electrode patch and a third electrode patch passes through a circle center of a layer at which the first electrode patch and the third electrode patch are located, a connecting line between a second electrode patch and a fourth electrode patch passes through a circle center of a layer at which the second electrode patch and the fourth electrode patch are located, and a distance between the first electrode patch and the second electrode patch is equal to a distance between the third electrode patch and the fourth electrode patch.
5. The apparatus for non-destructively measuring a water migration law of frozen soil according to any one of claims I to 4, wherein the electrode patch is a thin-copper electrode patch, and is mounted on the inner wall of the container, and the electrode patch is specifically stuck to the inner wall of the container by using glue.
6. A method for non-destructively measuring a water migration law of frozen soil by using the measurement apparatus according to any one of claims 1 to 5, comprising the following steps: Si. placing only one layer of soil sample with a known water content into the measurement apparatus, and skipping starting a low-temperature circulator and a water injection module; 52. measuring and obtaining resistivity of a single layer of soil sample by using the van der Pauw method; S3. filling the measurement apparatus up with a soil sample with a water content same as the water content in step Sl, and skipping starting the low-temperature circulator and the water injection module; 54. measuring and obtaining, by using the van der Pauw method, resistivity of a soil sample of a layer at which an electrode patch is located; 55. calculating, based on the resistivity that is obtained in step S2 and that is of the single layer of soil sample and the resistivity that is obtained in step S4 and that is of the soil sample of the layer at which the electrode patch is located, a correction factor of a layer at which each electrode patch is located; S6, filling the measurement apparatus up with the soil sample with the water content same as the water content in step S I, setting temperature of the low-temperature circulator and a quantity of water injected by the water injection module, and starting the low-temperature circulator and the water injection module, to obtain a frozen soil sample; S7, measuring and obtaining, by using the van der Pauw method, resistivity of a test frozen soil sample of the layer at which the electrode patch is located; 88. correcting, based on the correction factor that is obtained in step 55 and that is of the layer at which each electrode patch is located, the resistivity that is obtained in step 57 and that is of the test frozen soil sample of the layer at which the electrode patch is located, so as to obtain actual resistivity of the frozen soil sample of the layer at which the electrode patch is located; S9. calculating, based on the actual resistivity that is obtained in step 58 and that is of the frozen soil sample of the layer at which the electrode patch is located, a content of unfrozen water of the frozen soil sample of the layer at which the electrode patch is located; S10. repeating steps 57 to 59 according to a specified measurement time point, to obtain a curve of the content that changes with time and that is of the unfrozen water of the frozen soil sample of the layer at which the electrode patch is located; and S11. analyzing a migration law of unfrozen water of frozen soil according to the curve of the content that changes with time and that is of the unfrozen water of the frozen soil sample of the layer at which the electrode patch is located.
7. The measurement method according to claim 6, wherein the resistivity is measured by using the van der Pauw method, and the resistivity is specifically measured by using the following steps: a. for four electrode patches connected to the frozen soil sample, injecting a constant current 41-A2 between a first electrode patch and a second electrode patch, and measuring a voltage 12-14 between a third electrode patch and a fourth electrode patch, to obtain a first resistance _ V.13-A4 -I Al-A2; b. for the four electrode patches connected to the frozen soil sample, injecting a constant current '.12-13 between the second electrode patch and the third electrode patch, and measuring a voltage I/A 4-'1] between the fourth electrode patch and the first electrode patch, to obtain a second resistance V R2 42-A3 * c. calculating the resistivity by using the following formula: Julk, C 1-1 +e 1-1 =1 in the formula, RI is the first resistance, R2 is the second resistance, and d is a diameter of a container.
8. The measurement method according to claim 6 or 7, wherein the calculating a correction factor of a layer at which each electrode patch is located in step S5 is specifically calculating, by using the following equation, the correction factor of the layer at which each electrode patch is located: Pi = -r in the formula, Pi is a correction factor of a layer at which an VI' layer of electrode patch is located, 1; is resistivity of a soil sample of the layer at which the layer of electrode patch is located, and r is the resistivity of the single layer of soil sample.
9. The measurement method according to any one of claims 6 to 8, wherein the correcting, based on the correction factor that is obtained in step S5 and that is of the layer at which each electrode patch is located, the resistivity that is obtained in step S7 and that is of the test frozen soil sample of the layer at which the electrode patch is located in step S8 is specifically multiplying, by the resistivity that is obtained in step S7 and that is of the test frozen soil sample of the layer at which the electrode patch is located, the correction factor that is obtained in step S5 and that is of the layer at which each electrode patch is located, so as to obtain the actual resistivity of the frozen soil sample of the layer at which the electrode patch is located.
10. The measurement method according to any one of claims 6 to 9, wherein the calculating a content of unfrozen water of the frozen soil sample of the layer at which the electrode patch is located in step S9 is specifically calculating, by using the following formula, the content of the unfrozen water of the frozen soil sample of the layer at which the electrode patch is located: 6172 739 A, in the formula, is the resistivity of the frozen soil sample of the layer at which the electrode patch is located, and ev is the content of the unfrozen water of the frozen soil sample of the layer at which the electrode patch is located.