Apparatus and method for simultaneous measurement of soil water characteristic curve and hydraulic conductivity curve of a soil

Abstract

The application provides a device and a method for synchronously measuring soil-water characteristic curve and permeability coefficient curve of soil. The device comprises a water supply device, a soil sample device, soil sample blocks, a data acquisition device and a data processing device. The soil sample device comprises a soil sample cylinder with a water inlet and an exhaust port, and a plurality of soil sample blocks wrapped by a first filter paper are arranged in a longitudinal direction of the soil sample cylinder, and a first filter paper is arranged between two soil sample blocks. The data acquisition device measures the resistance of each first filter paper and records the time when the resistance changes and measures the water content of the first filter paper; the data processing device receives the collected data from the data acquisition device, and obtains the soil-water characteristic curve and the permeability coefficient curve through the collected data. The device and the method can quickly and accurately synchronously measure the soil-water characteristic curve and the permeability coefficient curve of unsaturated soil.

Description

Technical Field

[0001] This application relates to the measurement of the hydraulic properties of soil under unsaturated water, specifically to the measurement of soil-water characteristic curves and permeability coefficients of unsaturated soil. Background Technology

[0002] Unsaturated soils are widely found in nature, and most soils encountered in water and soil engineering are also unsaturated soils. Soil-water characteristic curves and permeability coefficients are important parameters for unsaturated soils, and they are of great significance for predicting and analyzing the water-holding capacity, permeability, deformation, and strength characteristics of unsaturated soils. Among them, the permeability coefficient of unsaturated soils is a key parameter for analyzing seepage problems in landfills, nuclear waste treatment facilities, and rain-induced landslides.

[0003] There are problems with the techniques for measuring the soil-water characteristic curves and permeability coefficients of unsaturated soils, including difficulties in simultaneously measuring these curves and coefficients, long measurement times, and challenges in sample preparation. Therefore, there is a need for a method to improve upon these problems for measuring the soil-water characteristic curves and permeability coefficients of unsaturated soils. Summary of the Invention

[0004] The purpose of this application is to provide a technical solution that can simultaneously measure the soil-water characteristic curve and permeability coefficient of soil, especially unsaturated soil. It can quickly and simultaneously measure the soil-water characteristic curve and permeability coefficient curve, and is easy to operate and simple to prepare soil samples.

[0005] To achieve the above objectives, a first aspect of this application provides an apparatus for simultaneously measuring the soil-water characteristic curve and permeability coefficient curve of soil, comprising:

[0006] Water supply equipment;

[0007] A soil sampling device includes: a soil sampling tube, which includes a water inlet connected to a water supply device and an exhaust port communicating with the outside of the soil sampling tube; and multiple soil sample blocks, which are stacked in the longitudinal direction of the soil sampling tube, each soil sample block being wrapped with a first filter paper and the first filter paper being arranged between two soil sample blocks.

[0008] A data acquisition device is connected to multiple soil sample blocks and a first filter paper to acquire data. The data acquisition device measures the resistance of the first filter paper at a predetermined frequency and records the time of resistance change, as well as measures the moisture content of the first filter paper.

[0009] A data processing device is connected to a data acquisition device to receive acquired data from the data acquisition device. It obtains the suction force of the first filter paper and the soil sample block and the water content of the soil sample block through the water content of the first filter paper. It establishes the relationship between the resistance of the first filter paper and the suction force of the soil sample block, as well as the relationship between the resistance of the first filter paper and the water content of the soil sample block, to obtain a soil-water characteristic curve. Furthermore, it uses the time of resistance change of the first filter paper, the suction force of the soil sample block, and the water content to obtain the permeability coefficient curve through Darcy's law.

[0010] Optionally, the data acquisition device includes: a resistance tester, which is connected to each first filter paper via test electrodes to measure the resistance of the first filter paper and record the time of resistance change of the first filter paper; and a moisture content measuring device, which measures the moisture content of the first filter paper.

[0011] Optionally, the data processing device includes: a storage module that stores the resistance and moisture content of the first filter paper transmitted from the resistance tester and the moisture content measuring device; and a processing module that obtains the suction and moisture content of the soil sample block based on the moisture content of the first filter paper, establishes the relationship between the resistance of the first filter paper, the suction of the soil sample block, and the moisture content of the soil sample block to obtain a soil-water characteristic curve, obtains the wetting front advance velocity curve using the resistance change of the first filter paper, and obtains the permeability coefficient curve using the wetting front advance velocity curve, the suction of the soil sample block, and the moisture content of the soil sample block through Darcy's law.

[0012] Optionally, the soil sample tube further includes: a buffer layer disposed below the inlet, a porous plate disposed below the buffer layer and above the first soil sample block at the top, an annular member for receiving the soil sample block, a second filter paper disposed below the plurality of soil sample blocks, and a permeable plate disposed at the bottom of the soil sample tube below the second filter paper.

[0013] Optionally, the buffer layer is composed of quartz sand with different particle sizes, the porous plate is connected to the top soil sample block among multiple soil sample blocks by a fastening device, and the annular element is formed of transparent resin material.

[0014] Optionally, the water inlet and air outlet of the soil sample tube are arranged at the top of the soil sample tube, and soil sample blocks are made according to the set dry density and optimum moisture content, and the soil sample blocks are air-dried to the saturation corresponding to the dry density and optimum moisture content.

[0015] Optionally, the water supply device includes: a Marshall bottle connected to the water inlet of the soil sample tube via a connecting pipe, the connecting pipe being equipped with a switch valve; and an electronic scale, the Marshall bottle being arranged on the electronic scale, the electronic scale being connected to a data processing device for measuring the water input rate in the Marshall bottle at a predetermined frequency and transmitting the water input rate to the data processing device.

[0016] Optionally, the test electrode of the resistance tester is a titanium electrode, the predetermined frequency for measuring resistance is once every 10 seconds, and the measurement range is 0.1 to 10. 12 ohm.

[0017] Optionally, the joints of adjacent soil samples are sealed with waterproof tape.

[0018] According to a second aspect of this application, a method for simultaneously measuring soil-water characteristic curves and permeability coefficient curves of soil is provided, comprising:

[0019] Provide water supply equipment;

[0020] Provide soil sample blocks, prepare soil sample blocks according to the set dry density and optimum moisture content, and air-dry the soil sample blocks to the saturation corresponding to the dry density and optimum moisture content, and wrap each soil sample block with a first filter paper;

[0021] A soil sampling device is provided, in which multiple soil sample blocks are stacked in the soil sample tube along the longitudinal direction of the soil sample tube, wherein a first filter paper is arranged between adjacent soil sample blocks and the joint between adjacent soil sample blocks is sealed with waterproof tape.

[0022] Data collection begins when the water supply device is activated to supply water to the inside of the soil sample tube through the water inlet. Data collection begins when water overflows from the vent of the soil sample tube. The resistance of the first filter paper is measured at a predetermined frequency and the time of resistance change of the first filter paper is recorded. The moisture content of the first filter paper is also measured. Water supply is stopped when the second filter paper at the bottom of the soil sample tube is wetted.

[0023] Data processing involves obtaining the suction and moisture content of the soil sample block from the moisture content of the first filter paper, establishing the relationship between the resistance of the first filter paper, the suction of the soil sample block, and the moisture content of the soil sample block to obtain the soil-water characteristic curve, and using the time of resistance change of the first filter paper, the suction of the soil sample block, and the moisture content to obtain the permeability coefficient curve through Darcy's law.

[0024] The technical solutions provided by the embodiments of this application may include the following beneficial effects: providing improved soil samples and testing methods to simultaneously measure and obtain the variables required for soil-water characteristic curves and permeability coefficient curves; using improved data processing methods to simultaneously obtain soil-water characteristic curves and permeability coefficient curves, which can shorten the measurement time to several days; eliminating the need to use expensive moisture sensors and suction sensors, significantly saving costs; the testing process does not damage the soil sample, the measurement data is more accurate, there is no need to repeatedly disassemble and reassemble the soil sample, and the testing operation is simple; the measuring device has a simple structure, occupies less space, and simplifies the soil sample preparation method. Attached Figure Description

[0025] The accompanying drawings, which form part of this application, are used to provide a further understanding of the application and to make other features, objects, and advantages of the application more apparent. The illustrative embodiments and descriptions of this application are used to explain the application and do not constitute an undue limitation of the application. In the drawings:

[0026] Figure 1 This is a schematic diagram of an apparatus for simultaneously measuring soil-water characteristic curves and permeability coefficient curves of soil according to an embodiment of this application.

[0027] Figure 2 A schematic diagram of a soil sample block of a measuring device according to an embodiment of this application; and

[0028] Figure 3 This is a cross-sectional view of the top of the water supply device of the measuring apparatus according to an embodiment of this application. Detailed Implementation

[0029] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0030] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0031] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0032] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0033] Furthermore, the terms "installation," "setup," "equipped with," "connection," "linked," and "socketing" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0034] Reference Figures 1 to 3 This application describes an example implementation.

[0035] To better understand the advantages of this application, we will first briefly describe some of the problems existing in the current measurement methods.

[0036] First, it is difficult to accurately measure the soil-water characteristic curve and permeability coefficient of unsaturated soil simultaneously. Although there are existing methods for simultaneous measurement, these methods are not accurate enough and are complex. Please refer to CN202210877527, CN202123449685, and CN201911165944.

[0037] Second, the matrix suction present in unsaturated soil makes the measurement time of soil-water characteristic curves relatively long, and different measurement methods are only suitable for measuring soil-water characteristic curves within a specific measurement range.

[0038] Third, the matrix suction present in unsaturated soils makes conventional permeability coefficient testing methods for saturated soils unsuitable for measuring their permeability coefficients. Existing methods for measuring unsaturated soil permeability coefficients include indirect and direct methods. Indirect methods typically predict the permeability coefficient of unsaturated soils using soil-water characteristic curves, pore distribution curves, and particle size distribution curves, but their prediction accuracy is insufficient. Direct methods include steady-state methods, instantaneous profiling methods, and wetting front advance methods. Steady-state methods are complex to operate, time-consuming, and have a limited suction measurement range (0-100 kPa). Instantaneous profiling methods require controlling very low infiltration rates, are time-consuming, have large errors in measuring permeability coefficients in high suction ranges, and require more sensors to improve measurement accuracy. Wetting front advance methods can measure permeability coefficients over a wide suction range (high suction range) in about one week. However, the sensors used in wetting front advance methods are relatively large, thus requiring soil column tests; however, preparing soil samples that meet experimental requirements is difficult.

[0039] The measurement method provided in this application can solve the above problems.

[0040] Figure 1 An example diagram of an apparatus for simultaneously measuring soil-water characteristic curves and permeability coefficient curves of soil according to this application is shown. Figure 1 The measuring device includes: a water supply device 15, a soil sampling device 16, a data acquisition device 13, and a data processing device 14.

[0041] Water supply device 15 supplies water to soil sampling device 16 to provide measurement conditions similar to those of actual unsaturated soil.

[0042] The soil sampling device 16 provides soil conditions similar to those of actual unsaturated soil in natural or engineering environments, within which soil-water characteristic curves and permeability coefficient curves are measured. Figure 1 As shown, the soil sampling device 16 may include: a soil sampling cylinder 17, which includes an inlet 4 connected to a water supply device 15 and an exhaust port 5 communicating with the outside of the soil sampling cylinder 17; and a plurality of soil sample blocks 10, which are stacked below the inlet 4 in the longitudinal direction of the soil sampling cylinder 17, each soil sample block 10 being wrapped with a first filter paper 9, and the first filter paper 9 being arranged between two soil sample blocks 10.

[0043] The data acquisition device 13 is used to acquire the data required to obtain the soil-water characteristic curve and permeability coefficient curve. The data acquisition device 13 is connected to multiple soil sample blocks 10 and a first filter paper 9 to acquire data related to the soil sample blocks 10 and the first filter paper 9. The acquired data specifically includes measuring the resistance of the first filter paper 9 at a certain frequency and recording the time of resistance change, as well as measuring the moisture content of the first filter paper 9.

[0044] The data processing device 14 is connected to the data acquisition device 13 to receive data from the data acquisition device 13, and is used to process the acquired data and obtain soil-water characteristic curves and permeability coefficient curves accordingly. Figure 1 As shown, the data processing device 14 can be implemented as a computer. After receiving the transmitted data, the data processing device 14 obtains the suction force of the first filter paper 9 by measuring its moisture content. According to the principles of this application, the suction force and moisture content of the first filter paper 9 can be used as the suction force and moisture content of the soil sample block 10. Furthermore, the data processing device 14 establishes the relationship between the resistance of the first filter paper 9 and the suction force and moisture content of the soil sample block 10 to obtain the soil-water characteristic curve of the soil sample. It also uses the time of resistance change of the first filter paper 9, the suction force of the soil sample block 10, and the moisture content of the soil sample block 10 to obtain the permeability coefficient curve of the soil sample through Darcy's law.

[0045] In the above-mentioned measuring device of this application, the structure and arrangement of the soil sample block 10 are improved, thereby enabling the simultaneous measurement and acquisition of the practical data required for soil-water characteristic curves and permeability coefficient curves, namely, the suction and water content of the soil sample block 10, the resistance of the first filter paper 9, and the moment of resistance change of the first filter paper 9. Through the corresponding improved data processing method, the soil-water characteristic curves and permeability coefficient curves can be obtained quickly and accurately. At the same time, the structure of the soil sample block 10 is simple and suitable for small soil sample tubes, which can save the space occupied by experimental equipment.

[0046] Continue to refer to Figure 1 More specific aspects of the measuring apparatus according to this application are described below.

[0047] Figure 1 The data acquisition device 13 includes a resistance tester 13A and a moisture content measuring device 13B. The resistance tester 13A is connected to each first filter paper 9 via a test electrode 19 to measure the resistance of the first filter paper 9 and record the time of resistance change. The moisture content measuring device 13B is connected to each first filter paper 9 to measure the moisture content of the first filter paper 9. In one embodiment, the measuring electrode 19 connecting the resistance tester 13A and the first filter paper 9 can be a titanium electrode. The predetermined frequency for data acquisition by the resistance tester 13A is set to measure the resistance once every 10 seconds, with a measurement range of 0.1 to 10. 12 Ohms. In one embodiment, the resistance tester 13A uses the average resistance of the plurality of first filter papers 9 as the resistance value of the first filter paper 9, thereby obtaining more accurate and reliable experimental results.

[0048] Figure 1 The data processing device 14 includes a storage module 14A and a processing module 14B. The storage module 14A stores the resistance of the first filter paper 9 measured by the resistance tester 13A, the recorded time of resistance change, and the moisture content of the first filter paper 9 measured by the moisture content measuring device 13B. The processing module 14B processes the data in the storage module 14A, obtaining the suction force of the first filter paper 9 from its moisture content. Since the soil sample block 10 is wrapped by the first filter paper 9, in this application, the moisture content and suction force of the first filter paper 9 are used as the moisture content and suction force of the soil sample block 10. The processing module 14B then establishes the relationship between the resistance of the first filter paper 9 and the suction force of the soil sample block 10, as well as the relationship with the moisture content of the soil sample block 10, to obtain the soil-water characteristic curve of the soil sample. Meanwhile, the processing module 14B uses the resistance change of the first filter paper 9 to obtain the wet front advance distance curve according to the wet front advance method, and then uses the wet front advance distance curve to obtain the wet front advance speed curve. Then, it uses the advance speed curve, the suction and water content of the soil sample block 10 to obtain the permeability coefficient curve of the soil sample through Darcy's law.

[0049] Figure 1The water supply device 15 generally includes a Marshall bottle 1 for storing water and an electronic scale 18 for measuring water volume. The Marshall bottle 1 is connected to the water inlet 4 of the soil sample cylinder 17 via a connecting pipe 3, such as a PTFE pipe, and a switch valve 2 is installed on the connecting pipe 3 to control the water flow. The Marshall bottle 1 is placed on the electronic scale 18, which is connected to a data processing device 14 to measure the water input rate in the Marshall bottle 1 at a predetermined frequency and transmit the water input rate to the data processing device 14. The predetermined frequency for the electronic scale 18 to collect data can be set to collect the water input rate once every 10 seconds.

[0050] like Figure 1 As shown, the water inlet 4 and the vent 5 of the soil sample tube 17 are both located at the top of the soil sample tube 17, specifically at the center and side of the top of the soil sample tube 17, respectively. In one embodiment, the distance between the vent 5 and the water inlet 4 is 15 mm. Specifically, the inner sides of the water inlet 4 and the vent 5 are threaded. Figure 3 (As shown in the image), for mounting the inlet port 4A with external threads and the vent port 5A, as... Figure 1 As shown in the image.

[0051] exist Figure 1 In the illustrated embodiment, a buffer layer 6 is disposed below the water inlet 4 of the soil sample tube 17, and a perforated plate 7 is arranged below the buffer layer 6, positioned above the top soil sample block 10. The buffer layer 6 and the perforated plate 7 serve to buffer the water injected from the water inlet 4, allowing the water to flow onto the soil sample block 10 below at a uniform and moderate speed. The buffer layer 6 buffers the water flow, and the perforated plate 7 distributes the water flow from the buffer layer 6 evenly and pours it onto the soil sample block 10. In one embodiment, the buffer layer 6 is composed of quartz sand with different particle sizes, and the gaps between the quartz sand allow water to pass through while buffering the rapidly poured water flow. The perforated plate 7 has evenly distributed 3mm diameter circular holes with external threads around its perimeter, screwed onto the internal threads inside the soil sample tube 17, such as... Figure 3 As shown. In addition, a fastening device such as screws or clips (not shown) is used to connect the perforated plate 7 to the uppermost soil sample block 10 among the plurality of soil sample blocks 10, so that the soil sample block 10 will not separate from the perforated plate 7 in the case of water supply.

[0052] refer to Figure 2The illustration shows the specific structure and arrangement of soil sample blocks 10. Each soil sample block 10 is surrounded by an annular member 8, which holds the soil sample block 10 and defines its boundaries. The annular member 8 is made of a transparent resin material, such as highly transparent acrylic, thus allowing observation of the soil sample block 10 from the outside. In one embodiment, the annular member 8 has a diameter of 61.8 mm and a height of 20 mm to produce soil sample blocks 10 of the same size. In one embodiment, a soil sample block 10 wrapped with a first filter paper 9 is placed inside the annular member 8 to form an independent soil sample block unit. Then, a layer of the first filter paper 9 is placed between two adjacent soil sample blocks 10 for measuring resistance and attraction. Multiple such soil sample blocks 10 are stacked to form a unit. Figure 2 The soil sample block device is shown in the figure. In one embodiment, the first filter paper 9 may be of the Whatman #42 type, but other suitable types of filter paper may also be used in the measuring device of this application. In addition, the joints of adjacent soil sample blocks 10 are sealed with waterproof tape to connect adjacent soil sample blocks 10 and to prevent water from leaking out from the joints of adjacent soil sample blocks 10.

[0053] Continue to refer to Figure 1 A permeable plate 12 is arranged at the bottom of the soil sample tube 17, and a second filter paper 11 is arranged above the permeable plate 12. The permeable plate 12 is used to collect water flowing out from the bottom of the soil sample tube 17 and to guide the water to a water storage container (not shown). The second filter paper 11 has an area equivalent to the upper surface of the permeable plate 12 and is laid on the permeable plate 12 to prevent water from overflowing to the outside of the permeable plate 12. In one embodiment, the second filter paper 11 can be commercially available ordinary filter paper, and the permeable plate 12 can be made of commonly used permeable stone.

[0054] The above describes the construction method of the unsaturated soil water characteristic curve and permeability coefficient curve measuring device according to this application. This measuring device can provide the following beneficial effects:

[0055] (1) The present invention can accurately measure the soil-water characteristic curve and the permeability coefficient curve simultaneously, reducing the measurement time required for measuring the soil-water characteristic curve and the permeability coefficient curve from several months to a few days.

[0056] (2) This invention does not require the use of expensive moisture sensors and suction sensors, saving a lot of costs. In addition, the traditional filter paper measurement method does not involve the operation of repeatedly disassembling and reassembling soil samples. The measurement process is simple and does not damage the soil sample, making the measured data more accurate.

[0057] (3) The measuring device of the present invention has a simple structure, is easy to operate, has a small soil sample block, is easy to prepare, and occupies little test space.

[0058] Furthermore, based on the principles of this application, a method for simultaneously measuring the soil-water characteristic curve and permeability coefficient curve of soil is also provided, comprising the following steps:

[0059] Provide water supply device 15;

[0060] Prepare soil sample blocks 10 according to the set dry density and optimum moisture content. Air dry the soil sample blocks 10 to the saturation corresponding to the above dry density and optimum moisture content. Wrap each soil sample block 10 with first filter paper 9 (e.g., Whatman #42).

[0061] A soil sampling device 16 is provided, in which a plurality of soil sample blocks 10 are stacked in the soil sample tube 17 of the soil sampling device 16 along the longitudinal direction of the soil sample tube 17, wherein a first filter paper 9 is arranged between adjacent soil sample blocks 10 and the joint between adjacent soil sample blocks 10 is sealed with waterproof tape.

[0062] Data is collected by starting the water supply device 15 to supply water to the inside of the soil sample tube 17 through the water inlet 4. Data collection begins when water overflows from the vent 5 of the soil sample tube 17. The resistance of the first filter paper 9 is measured at a predetermined frequency and the time of resistance change of the first filter paper 9 is recorded. The moisture content of the first filter paper 9 is also measured. Water supply is stopped when the second filter paper 11 at the bottom of the soil sample tube 17 is wetted.

[0063] Data processing involves obtaining the suction of the first filter paper 9 and the soil sample block 10, as well as the water content of the soil sample block 10, through the water content of the first filter paper 9. The relationship between the resistance of the first filter paper 9 and the suction and water content of the soil sample block 10 is established to obtain the soil-water characteristic curve of the soil sample. Furthermore, the permeability coefficient curve of the soil sample is obtained by using Darcy's law through the recorded time of resistance change of the first filter paper 9, the suction and water content of the soil sample block.

[0064] Specifically, based on the principles of this application:

[0065] During the soil sample preparation process, after wrapping the soil sample block 10 with the first filter paper 9, the resistance and moisture content of the first filter paper 9 and the moisture content of the soil sample block 10 are measured after the moisture content of the first filter paper 9 and the soil sample block 10 are balanced. The suction force of the first filter paper 9 is obtained based on the moisture content of the first filter paper 9. Then, the original relationship curves between the suction force of the first filter paper 9 and the resistance of the first filter paper 9, and between the moisture content of the soil sample block 10 and the resistance of the first filter paper 9 are established as a reference for establishing the same relationship in subsequent experiments.

[0066] During data collection, the Marshall bottle 1 of the water supply device 15 is activated and valve 2 is opened to supply water to the soil sampling device 16 through the inlet 4. The experiment begins when water overflows from the vent 5, and data collection starts simultaneously. The experiment ends when the second filter paper 11 at the bottom of the soil sampling device 16 is moistened by the water passing through the soil sample block 10. The valve 2 of the Marshall bottle 1 is then closed to stop the water supply to the soil sampling device 16.

[0067] During data processing, by utilizing the relationship between the resistance of the first filter paper 9 and the suction of the soil sample block 10, and the relationship between the resistance of the first filter paper 9 and the moisture content of the soil sample block 10, the relationship between the suction and moisture content of the soil sample block 10 can be obtained, i.e., the soil-water characteristic curve. Using the recorded changes in the resistance of the first filter paper 10, the wetting front advance distance curve of the soil sampling device 16 can be obtained. From the wetting front advance distance curve, the wetting front advance speed curve, i.e., the wetting front advance rate, can be obtained. Substituting the moisture content, suction, and wetting front advance rate of the soil sample at different times into Darcy's law formula, the permeability coefficient curve of the soil sample can be determined using the wetting front advance method.

[0068] The specific methods of execution of each unit in the above embodiments have been described in detail in the embodiments of the method, and will not be elaborated here.

[0069] In summary, this application provides an improved apparatus and method for measuring the soil-water characteristic curve and permeability coefficient of unsaturated soil, effectively solving the problems existing in the prior art. Specifically, it uses an improved soil sample block device and a simplified test method to quickly and synchronously measure the soil-water characteristic curve and permeability coefficient curve of unsaturated soil, improving the accuracy of the measurement results; the measuring device has a simplified structure, does not require expensive sensors, occupies little space, and significantly saves costs; soil sample preparation is simple, the arrangement method is improved, the soil sample is not damaged during the measurement process, there is no need to repeatedly disassemble and reassemble the soil sample, the test operation is simple, and the test accuracy is improved.

[0070] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A device for simultaneously measuring the soil water characteristic curve and the hydraulic conductivity curve of a soil, characterized in that, include: Water supply device (15); A soil sampling device (16) includes: a soil sampling tube (17), the soil sampling tube including an inlet (4) connected to the water supply device and an exhaust port (5) communicating with the outside of the soil sampling tube; a plurality of soil sampling blocks (10), the plurality of soil sampling blocks being stacked in the longitudinal direction of the soil sampling tube, each of the soil sampling blocks being wrapped with a first filter paper, and the first filter paper (9) being arranged between two soil sampling blocks; A data acquisition device (13) is connected to the plurality of soil sample blocks and the first filter paper to acquire data. The data acquisition device measures the resistance of the first filter paper at a predetermined frequency and records the time of resistance change, and measures the moisture content of the first filter paper. A data processing device (14) is connected to the data acquisition device to receive acquired data from the data acquisition device. It obtains the suction force and the moisture content of the soil sample block through the moisture content of the first filter paper, establishes the relationship between the resistance of the first filter paper and the suction force of the soil sample block, and the relationship between the resistance of the first filter paper and the moisture content of the soil sample block to obtain the soil-water characteristic curve, and obtains the permeability coefficient curve by using the resistance change time of the first filter paper, the suction force of the soil sample block, and the moisture content through Darcy's law.

2. The apparatus for simultaneous measurement of soil water characteristic curve and hydraulic conductivity curve of a soil body as claimed in claim 1, wherein, The data acquisition device includes: a resistance tester (13A), which is connected to each of the first filter papers via test electrodes (19) to measure the resistance of the first filter paper and record the time when the resistance of the first filter paper changes; and a moisture content measuring device (13B) for measuring the moisture content of the first filter paper.

3. The apparatus for simultaneously measuring the soil water characteristic curve and the hydraulic conductivity curve of a soil body of claim 1, wherein, The data processing device includes: a storage module (14A) for storing the resistance and moisture content of the first filter paper transmitted from the resistance tester and the moisture content measuring device; and a processing module (14B) for obtaining the suction and moisture content of the soil sample block based on the moisture content of the first filter paper, establishing the relationship between the resistance of the first filter paper, the suction of the soil sample block, and the moisture content of the soil sample block to obtain the soil-water characteristic curve, obtaining the wetting front advance velocity curve using the resistance change time of the first filter paper, and obtaining the permeability coefficient curve using the wetting front advance velocity curve, the suction of the soil sample block, and the moisture content through Darcy's law.

4. The apparatus for simultaneous measurement of soil water characteristic curve and hydraulic conductivity curve of a soil body according to any one of claims 1 to 3, characterized in that, The soil sample tube further includes: a buffer layer (6) arranged below the water inlet, a porous plate (7) arranged below the buffer layer and above the first soil sample block located at the top, an annular member (8) for accommodating the soil sample block, a second filter paper (11) arranged below the plurality of soil sample blocks, and a permeable plate (12) arranged at the bottom of the soil sample tube located below the second filter paper.

5. The apparatus for simultaneous measurement of soil water characteristic curve and hydraulic conductivity curve of a soil body as claimed in claim 4, wherein, The buffer layer is composed of quartz sand with different particle sizes, the porous plate is connected to the top soil sample block in the soil sample block by a fastening device, and the annular member is formed of transparent resin material.

6. The apparatus for simultaneously measuring the soil water characteristic curve and the hydraulic conductivity curve of a soil body of claim 4, wherein, Soil samples are prepared according to a set dry density and optimum moisture content, and the soil samples are air-dried to a saturation level corresponding to the dry density and optimum moisture content.

7. The apparatus for simultaneous measurement of soil water characteristic curve and hydraulic conductivity curve of a soil body according to any one of claims 1 to 3, characterized in that, The water supply device includes: a Marshall bottle (1), which is connected to the water inlet of the soil sample tube via a connecting pipe (3), and a switch valve (2) is provided on the connecting pipe; and an electronic scale (18), on which the Marshall bottle is arranged, and the electronic scale is connected to the data processing device for measuring the water input rate in the Marshall bottle at a predetermined frequency and transmitting the water input rate to the data processing device.

8. The apparatus for simultaneously measuring the soil water characteristic curve and the hydraulic conductivity curve of a soil body of claim 2, wherein, The test electrode of the resistance tester is a titanium electrode, the predetermined frequency for measuring the resistance is 10s measurement of resistance once, and the measurement range is 0.1-10 12 ohms.

9. The apparatus for simultaneous measurement of soil water characteristic curve and hydraulic conductivity curve of a soil body according to any one of claims 1 to 3, characterized in that, The joints of adjacent soil sample blocks are sealed with waterproof tape.

10. A method for simultaneously measuring soil-water characteristic curves and permeability coefficient curves of soil, characterized in that, include: Provide water supply equipment (15); Provide soil sample blocks (10), prepare the soil sample blocks according to the set dry density and optimal moisture content, and air-dry the soil sample blocks to a saturation level corresponding to the dry density and optimal moisture content, and wrap each soil sample block with a first filter paper; A soil sampling device (16) is provided, in which a plurality of soil sample blocks are stacked in the soil sample tube along the longitudinal direction of the soil sample tube, wherein the first filter paper is arranged between adjacent soil sample blocks and the joint between adjacent soil sample blocks is sealed with waterproof tape. Data is collected by starting the water supply device to supply water to the inside of the soil sample tube through the water inlet of the soil sample tube. Data collection begins when water overflows from the vent of the soil sample tube. The resistance of the first filter paper is measured at a predetermined frequency and the time of resistance change of the first filter paper is recorded. The moisture content of the first filter paper is also measured. Water supply is stopped when the second filter paper at the bottom of the soil sample tube is wetted. Data processing involves obtaining the suction force and moisture content of the soil sample block from the moisture content of the first filter paper, establishing the relationship between the resistance of the first filter paper, the suction force of the soil sample block, and the moisture content of the soil sample block to obtain the soil-water characteristic curve, and using the resistance change time of the first filter paper, the suction force of the soil sample block, and the moisture content to obtain the permeability coefficient curve through Darcy's law.

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