CN110023769B - Resistivity measuring unit for measuring resistivity anisotropy of unsaturated soil - Google Patents

Resistivity measuring unit for measuring resistivity anisotropy of unsaturated soil Download PDF

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CN110023769B
CN110023769B CN201780069036.7A CN201780069036A CN110023769B CN 110023769 B CN110023769 B CN 110023769B CN 201780069036 A CN201780069036 A CN 201780069036A CN 110023769 B CN110023769 B CN 110023769B
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array
point
current source
point current
point potential
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CN110023769A (en
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牛起飞
伍玉鑫
王幼行
赵俊康
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Hong Kong University of Science and Technology HKUST
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G01N27/043—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a granular material
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/24—Earth materials
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/14—Measuring resistance by measuring current or voltage obtained from a reference source

Abstract

The resistance measuring unit comprises a first resistor, a second resistor and a resistorProbe array (M)1) Comprising, in a first direction, a first array of first point current sources (C)11) A first array of second point current sources (C)12) A first array of first potential electrodes (P)11) And a first array of second point potential electrodes (P)12) (ii) a And a second four-probe array (M)2) Comprising, in a second direction, a second array of first point current sources (C)21) A second array of second point current sources (C)22) A second array of first potential electrodes (P)21) And a second array of second point potential electrodes (P)22) Wherein, in a third direction, the first array of first point potential electrodes (P)11) And a first array of second point potential electrodes (P)12) Each of which is placed in contact with a first point potential electrode (P) of the second array21) And a second array of second point potential electrodes (P)22) At different planes from each of the trailing ends.

Description

Resistivity measuring unit for measuring resistivity anisotropy of unsaturated soil
Cross Reference to Related Applications
This application claims priority to U.S. provisional patent application No. 62/497,046, filed 2016, 11, 08, the disclosure of which is incorporated herein by reference in its entirety, including any figures, tables, or drawings.
Background
During the process of soil settlement or compaction, the texture anisotropy develops due to the influence of the tendency of the non-spherical particles to align. The texture anisotropy in turn leads to anisotropic responses of flow-related soil properties, such as resistivity (conductivity) anisotropy, thermal conductivity anisotropy, and permeability (water conductivity) anisotropy. Because all of these flow phenomena are similar processes, and resistivity is relatively easy to measure in the flow-related properties of these unsaturated soils, resistivity of the soil is often used to assist in predicting other flow characteristics, such as water conductivity and even related anisotropic responses. Existing methods for measuring anisotropic resistivity are expensive or difficult to measure for unsaturated soils. The traditional four-electrode method can only measure the apparent resistivity of soil and cannot measure the anisotropy of the resistivity.
Disclosure of Invention
Embodiments of the subject invention provide a novel and advantageous resistivity measuring cell that includes two probes to be inserted into a soil sample to simultaneously measure anisotropy of resistivity and soil moisture profile of unsaturated soil.
In an embodiment, the resistivity measurement cell may include a first measurement array arranged in a first direction; and a second measurement array arranged in a second direction, wherein the second measurement array comprises a first point current source, a second point current source, a first point potential electrode, and a second point potential electrode; and wherein, in the third direction, each of the first point potential electrode and the second point potential electrode is lower than each of the first point current source and the second point current source.
In another embodiment, the resistivity measurement unit may include a first four probe array including a first array of first point current sources, a first array of second point current sources, a first array of first point potential electrodes, and a first array of second point potential electrodes in a first direction; and a second fourth probe array comprising a second array of first point current sources, a second array of second point current sources, a second array of first point potential electrodes, and a second array of second point potential electrodes in a second direction; wherein, in a third direction, each trailing end of the first array of first point potential electrodes and the first array of second point potential electrodes is placed at a different plane than each trailing end of the second array of first point potential electrodes and the second array of second point potential electrodes.
In another embodiment, the resistivity measurement unit may include a first array of first point current sources and a first array of second point current sources disposed in a first direction; a first array of first point potential electrodes and a first array of second point potential electrodes disposed between a first array of first point current sources and a first array of second point current sources in a first direction; a second array of first point current sources and a second array of second point current sources arranged in a second direction; a second array of first point potential electrodes and a second array of second point potential electrodes disposed between a second array of first point current sources and a second array of second point current sources in a second direction; wherein in the third direction, each tail end of the second array first point potential electrodes and the second array second point potential electrodes is positioned lower than each tail end of the second array first point current sources and the second array second point current sources, and wherein the first direction and the second direction are horizontal directions and the third direction is a vertical direction.
Drawings
Fig. 1(a) shows a schematic diagram of the potential over a semi-infinite space with respect to a single-point current source.
FIG. 1(b) shows a diagram of a semi-infinite space relative to a first four-probe array M1Schematic diagram of the potential of (a).
FIG. 1(c) shows a semi-infinite space relative to a second four-probe array M2Schematic diagram of the potential of (a).
FIG. 2 is a schematic diagram of a resistivity measurement cell in accordance with an embodiment of the subject invention.
FIG. 3 shows the correction factor α as a function of R1/R2 for the first and second four probe arrays1And alpha2。
FIG. 4(a) shows a first four probe array M according to an embodiment of the subject invention1Cross-sectional view of (a).
FIG. 4(b) shows a second four according to an embodiment of the subject inventionProbe array M2Cross-sectional view of (a).
FIG. 4(c) shows a perspective view and a photographic inset of a resistivity measurement cell in accordance with an embodiment of the subject invention.
FIG. 5 illustrates a soil moisture characteristic curve (SWCC) device incorporating a resistivity measurement cell in accordance with an embodiment of the subject invention.
Detailed Description
Embodiments of the subject invention provide a novel and advantageous resistivity measuring cell that includes two probes to be inserted into a soil sample to simultaneously measure anisotropy of resistivity and soil moisture profile of unsaturated soil.
Fig. 1(a) shows a schematic diagram of the potential over a semi-infinite space with respect to a single-point current source. Referring to fig. 1(a), the resistivity of the potential ψ at a point P caused by a point current source C located on a semi-infinite space surface is in the x and y directions (i.e., horizontal direction ρ)H) Having the same value but in the z-direction (i.e. the vertical direction p)V) Different. Further, the potential ψ at the point P can be as shown by the following equation:
Figure BDA0002052771860000031
where I is the magnitude of the applied current, pMIs the average resistivity: (
Figure BDA0002052771860000032
Usually pVRatio rhoHLarge), λ is the anisotropy coefficient
Figure BDA0002052771860000033
And r is the equivalent distance to the current source,
Figure BDA0002052771860000034
FIG. 1(b) shows a diagram of a semi-infinite space relative to a first four-probe array M1Schematic diagram of the potential of (a). Referring to FIG. 1(b), a first four-probe arrayM1(or first measuring array) comprises four electrodes for probing, in particular, a first array of first point current sources C11A first array of second point current sources C12A first array of first potential electrodes P11And a first array of second point potential electrodes P12. In a first direction (i.e., x-direction), a first dot potential electrode P11And a second point potential electrode P12At a first point a current source C11And a second point current source C12In the meantime. In a third direction (i.e., the z direction), all electrodes lie on the same plane of the ground surface, which may be the soil sample surface to be measured, with each electrode spaced from an adjacent electrode by a horizontal spacing a.
As shown in FIG. 1(b), the first point current source C of the first array11Providing a current and a first array of second point current sources C12Receiving the current, thereby forming a current line. When the current flows from the first point of the first array to the current source C11A current source C for flowing to the second point of the first array12While the first array of first potential point electrodes P11And a first array of second point potential electrodes P12The potential is measured.
When equation (1) is applied to a first arrangement of four probe measurements, as illustrated in FIG. 1(b), it is referred to herein as a first four probe array M1Potential electrode P11And potential electrode P12With a measured potential difference V between1As shown in the following equation (2)
Figure BDA0002052771860000041
Wherein psi11And psi12Are respectively an electrode P11And P12The electrode potential of (a); i is1Is the magnitude of the applied current; a is the spacing between the electrodes, as also indicated in FIG. 1 (b). For convenience of the following discussion, equation (2) may be written as equation (3) below,
Figure BDA0002052771860000042
FIG. 1(c) shows a semi-infinite space relative to a second four-probe array M2Schematic diagram of the potential of (a). Referring to FIG. 1(c), a second four-probe array M2And a first four-probe array M1Similarly, except for the position of the point potential electrodes. In particular, a second four-probe array M2(or second measurement array) comprises four electrodes: second array first point current source C21A second array of second point current sources C22A second array of first potential electrodes P21And a second array of second point potential electrodes P22. In the second direction (i.e., y direction), the first dot potential electrode P21And a second point potential electrode P22At a first point a current source C21And a second point current source C22And each electrode is spaced apart from an adjacent electrode by a horizontal spacing a. In the third direction (i.e., z direction), the first dot potential electrode P21And a second point potential electrode P22Current source C lower than the first point21And a second point current source C22Is disposed so that the first potential electrode P21And a second point potential electrode P22Is inserted into the soil sample and placed at a position that is a vertical distance b below the surface of the soil sample.
And a first four-probe array M1Point current source C of11And C12Similarly, the second array first point current source C21Providing current and a second array of second point current sources C22A current is received. However, the second array of first potential electrodes P21And a second array of second point potential electrodes P22Measuring current source C21And C22The potential at a location below the formed current line.
Similarly, as shown in FIG. 1(c), the second arrangement for four probe measurements is referred to as a second four probe array M2Potential electrode P21And potential electrode P22With a measured potential difference V between2As shown in the following equation (4)
Figure BDA0002052771860000051
It can also be expressed by the following equation (5)
Figure BDA0002052771860000052
Wherein is psi21And psi22Are respectively an electrode P21And P22The electrode potential of (a); i is2Is the magnitude of the applied current; a is the horizontal spacing between the electrodes; and b is the vertical spacing between the potential and current electrodes.
With respect to the schematic diagrams of fig. 1(a), 1(b) and 1(c), the assumption of semi-infinite space, point current source and point potential electrodes used to derive equations (3) and (5) theoretically cannot be applied to laboratory test conditions due to boundary effects brought about by samples and electrodes of fixed size and shape, especially finite size samples. Therefore, in order to compensate for the deviation caused by the ideal assumption, equations (3) and (5) need to be corrected and a correction coefficient is introduced into the following two equations:
Figure BDA0002052771860000053
Figure BDA0002052771860000054
wherein
Figure BDA0002052771860000055
And
Figure BDA0002052771860000056
are respectively a measurement array M1And M2The correlation correction coefficient of (1). According to equations (6) and (7), two correction coefficients, i.e., α, are determined as follows1And alpha2Thereafter, by using the array M1And M2Can be accurately obtained by two independent measurementsAnisotropic resistivity of soil, i.e. pMAnd λ (or ρ)HAnd ρV)。
In equations (6) and (7), R1And R2Can be determined experimentally from the applied current I and the measured voltage V, while λ and ρMAre unknown parameters that need to be determined. Thus, R is established1/R2And correction factors to facilitate measurement correction is an intuitive approach. Furthermore, based on equations (6) and (7), the ratio R is maintained while the other parameters are maintained1/R2With average resistivity pMIrrespective, this indicates that R is being investigated1/R2And the correction coefficient, ρ can be ignoredMThe influence of (c).
Considering that electrodes with small contact areas have high interfacial impedance between the soil and the electrode and that high impedance affects measurement accuracy, electrodes with a diameter of 2mm may be selected in the designed device, and the method of the subject invention and the designed device may be simulated using FEM (finite element method), as shown in fig. 2. FIG. 2 shows a schematic of a resistivity measurement cell in accordance with an embodiment of the subject invention and used for simulations using FEM. Referring to FIG. 2, a first measurement array M1Arranged in a first direction x and a second measurement array M2Is placed in the second direction y. A soil sample configured to be measured was placed in a cylindrical container having a diameter of 60mm and a height of 30 mm. First measurement array M1All electrodes of and the second measuring array M2Point current source C of21And C22Placed on the top surface of the soil sample, and a second measurement array M2Point potential electrode P of21And P22Inserted into a soil sample. First measurement array M1And a second measurement array M2All electrodes of (a) include silver electrodes at their respective ends for contact with the soil sample. Due to the second measurement array M2Point potential electrode P of21And P22In a soil sample, a point potential electrode P21And P22Also included is a cable jacket located in the soil sample.
Model construction based on FEM simulation of FIG. 2, howeverPost-correction factor alpha1And alpha2Can be obtained by using FEMs according to their definition and equations (6) and (7), i.e. based on the difference between theoretical predictions based on point electrodes and semi-infinite space and FEM simulation results that take into account the influence of boundaries and electrode size. Can be derived as R1/R2A of a function of1And alpha2And is presented in fig. 3, fig. 3 shows as R1/R2Correction coefficient alpha of the first and second four-probe arrays of the function of1And alpha2. Thus, in a measurement, R is determined from the two measurement arrays1And R2Thereafter, α can be determined by using fig. 31And alpha2To correct for measurement drift.
FIG. 4(a) shows a first four probe array M according to an embodiment of the subject invention1And fig. 4(b) shows a second four-probe array M according to an embodiment of the subject invention2Cross-sectional view of (a). Additionally, FIG. 4(c) shows a perspective view of a resistivity measurement cell in accordance with an embodiment of the subject invention. Referring to fig. 4(a), 4(b) and 4(c), the resistivity measurement cell apparatus of the subject invention includes a first array M1And a second array M2Wherein the first array M1Aligned in a first direction x and a second array M2Aligned in a second direction y, and wherein the first array M1And a second array M2Comprises four electrodes, two of which serve as current sources and two of which serve as potential electrodes.
Referring to fig. 4(a), the first array M1Comprising a first array of first point current sources C11A first array of second point current sources C12A first array of first potential electrodes P11And a first array of second point potential electrodes P12. In a first direction x, a first potential electrode P11And a second point potential electrode P12At a first point a current source C11And a second point current source C12In the meantime. In the third direction z, all electrodes are located in the same plane. I.e. in the third direction z, four electrodes C11、C12、P11And P12Are all located at the same position.
Referring to FIG. 4(b), the second array M2Comprising a second array of first point current sources C21A second array of second point current sources C22A second array of first potential electrodes P21And a second array of second point potential electrodes P22. In the second direction y, the first potential electrode P21And a second point potential electrode P22At a first point a current source C21And a second point current source C22In the meantime. In a third direction z, a first potential electrode P21And a second point potential electrode P22Is lower than the first point current source C21And a second point current source C22To the tail end of the cell. I.e. the first potential electrode P21And a second point potential electrode P22Spaced from the cross frame.
Referring to fig. 4(a), 4(b) and 4(c), the first array M1And a second array M2Is supported by the cross frame to be fixed at a predetermined position, and the cross frame is attached to the container. The container has a cylindrical shape with an outer diameter D1Is 70mm, inner diameter D260mm and an outer height H of 40 mm. The cross frame is fixed to the top of the container so that the inner space of the container has an inner height h of 30 mm. Thus, a soil sample to be measured can be placed in an inner space whose volume is defined by a diameter of 60mm and a height of 30 mm. The container and cross frame may be manufactured using three-dimensional printing.
First array M1And a second array M2Comprises a silver electrode at each electrode tail end, a cable sheath passing through the cross frame and a copper rod connected to the silver electrode. The silver electrode has a diameter of 2mm and a height of 2mm, and is made of silver-silver chloride (Ag-AgCl). First potential electrode P21And a second point potential electrode P22Further extends into the inner space of the container to reach the first point potential electrode P21And a second point potential electrode P22The cable sheaths of the other six electrodes do not extend into the interior space.
First array M1And a second array M2Are different from each other and may be perpendicular to each other in the same horizontal plane. In addition, the first array M1And a second array M2May be placed in different planes to avoid interference with each other.
Can be prepared by using two different four-probe arrays M as shown in FIGS. 4(a) and 4(b)1And M2Performing two independent resistivity measurements to perform a pair R1And R2And p is measured according to equations (6) and (7)MAnd calculation of λ. Furthermore, it is preferable to place the two arrays in different planes to avoid interference with each other. FIGS. 4(a), 4(b) and 4(c) show a sample container having an outer diameter D1Is 70mm, inner diameter D260mm, an outer height H of 40mm and an inner height H of 30 mm; and the entire container can be placed into a SWCC device (to be shown later). Furthermore, there is a cross frame for mounting the electrode array. A multi-material three-dimensional printer may be used to print the sample containers and frames. Silver-silver chloride (Ag-AgCl) electrodes, 2mm in diameter and 2mm in height, can be used to inhibit corrosion during long-term testing. Copper rods of various lengths, 2mm in diameter, were used as bridges to connect the electrodes to the resistivity meter.
The subject invention includes, but is not limited to, the following exemplary embodiments.
Embodiment 1.a resistivity measurement cell comprising:
a first measurement array arranged in a first direction; and
a second measurement array arranged in a second direction,
wherein the second measurement array comprises a first point current source, a second point current source, a first point potential electrode, and a second point potential electrode; and is
Wherein, in the third direction, each of the first and second point potential electrodes is placed at a measurement depth different from a measurement depth of each of the first and second point current sources (e.g., in the third direction, the measurement depth of the first and second point potential electrodes may be lower than the measurement depth of the first and second point current sources).
Embodiment 2. the resistivity measurement unit according to embodiment 1, wherein the first point current source, the first point potential electrode, the second point potential electrode and the second point current source are arranged in any type of array (e.g., in series).
Embodiment 3. the resistivity measurement unit according to any one of embodiments 1 to 2, wherein a horizontal interval between the first point current source and the first point potential electrode in the second direction is the same as a vertical interval between the first point current source and the first point potential electrode in the third direction.
Embodiment 4. the resistivity measurement cell of any of embodiments 1-3, wherein the first direction and the second direction are different from each other, and the third direction is perpendicular to the first direction and the second direction.
Embodiment 5. the resistivity measurement cell of any one of embodiments 1-4, wherein each of the first point current source, the second point current source, the first point potential electrode, and the second point potential electrode comprises a silver electrode, a copper rod electrically connected to the silver electrode, and a cable jacket surrounding the copper rod.
Embodiment 6. the resistivity measurement cell of any of embodiments 1-5, wherein the first measurement array comprises two first array point current sources and two first array point potential electrodes; and the two first array point current sources and the two first array point potential electrodes are positioned on the same plane in a third direction.
Embodiment 7. the resistivity measurement cell of any of embodiments 1-6, further comprising a cross frame supporting the first measurement array and the second measurement array.
Embodiment 8. a soil moisture characteristic curve (SWCC) apparatus, comprising:
the resistivity measurement cell of any one of embodiments 1-7; and
a chamber surrounding the resistivity measurement cell,
wherein the chamber comprises a plurality of apertures through which a plurality of wires are connected to the first measurement array and the second measurement array.
Embodiment 9. a resistivity measurement cell, comprising:
a first fourth probe array comprising a first array of first point current sources, a first array of second point current sources, a first array of first point potential electrodes, and a first array of second point potential electrodes in a first direction; and
a second fourth probe array comprising a second array of first point current sources, a second array of second point current sources, a second array of first point potential electrodes, and a second array of second point potential electrodes in a second direction;
wherein, in the third direction, each trailing end of the first array of first point potential electrodes and the first array of second point potential electrodes is placed at a different plane than each trailing end of the second array of first point potential electrodes and the second array of second point potential electrodes.
Embodiment 10 the resistivity measurement unit of embodiment 9, wherein, in the third direction, the tail ends of the second array of first point potential electrodes and the tail ends of the second array of second point potential electrodes are positioned lower than the tail ends of the first array of first point potential electrodes and the tail ends of the first array of second point potential electrodes.
Embodiment 11 the resistivity measurement unit of any one of embodiments 9 to 10, wherein the tail end of the first array of first point potential electrodes and the tail end of the first array of second point potential electrodes are positioned in the same plane as the tail end of the first array of first point current sources, the tail end of the first array of second point current sources, the tail end of the second array of first point current sources, and the tail end of the second array of second point current sources.
Embodiment 12. the resistivity measurement cell of any of embodiments 9-11, wherein the first array of first point current sources, the first array of first point potential electrodes, the first array of second point potential electrodes, and the first array of second point current sources are arranged in series and spaced apart at a horizontal pitch; and the second array of first point current sources, the second array of first point potential electrodes, the second array of second point potential electrodes, and the second array of second point current sources are arranged in series and spaced apart at a horizontal pitch.
Embodiment 13. the resistivity measurement unit of any of embodiments 9-12, further comprising a cross frame supporting the first and second four probe arrays, and a container connected to the cross frame and surrounding the cross frame and the first and second four probe arrays.
Embodiment 14 the resistivity measurement cell of any one of embodiments 9-13, wherein each of the first array of first point current sources, the first array of second point current sources, the first array of first point potential electrodes, the first array of second point potential electrodes, the second array of first point current sources, the second array of second point current sources, the second array of first point potential electrodes, and the second array of second point potential electrodes comprises a cable sheath passing through the cross frame.
Embodiment 15 the resistivity measurement cell of any one of embodiments 9-14, wherein each of the first array of first point current sources, the first array of second point current sources, the first array of first point potential electrodes, the first array of second point potential electrodes, the second array of first point current sources, the second array of second point current sources, the second array of first point potential electrodes, and the second array of second point potential electrodes further comprises an electrode disposed in the container.
Embodiment 16 the resistivity measurement cell of any one of embodiments 9-15, wherein each cable jacket of the second array of first point potential electrodes and the second array of second point potential electrodes extends to each of the second array of first point potential electrodes and the second array of second point potential electrodes in the vessel.
Embodiment 17. a soil moisture characteristic curve (SWCC) apparatus, comprising: a plate;
a resistivity measurement unit according to any one of embodiments 9-16 disposed on the board;
a chamber surrounding the resistivity measurement cell and the plate; and
a plurality of wires passing through the chamber and connected to the first and second four-probe arrays.
Embodiment 18. a resistivity measurement cell, comprising:
a first array of first point current sources and a first array of second point current sources arranged in a first direction;
a first array of first point potential electrodes and a first array of second point potential electrodes disposed between a first array of first point current sources and a first array of second point current sources in a first direction;
a second array of first point current sources and a second array of second point current sources arranged in a second direction;
a second array of first point potential electrodes and a second array of second point potential electrodes disposed between a second array of first point current sources and a second array of second point current sources in a second direction;
wherein each tail end of the second array first point potential electrodes and the second array second point potential electrodes is positioned lower than each tail end of the second array first point current sources and the second array second point current sources in the third direction, and
wherein the first and second directions are horizontal directions and the third direction is a vertical direction.
Embodiment 19. a soil moisture characteristic curve (SWCC) apparatus, comprising:
the resistivity measurement cell of embodiment 18; and
a chamber surrounding the resistivity measurement cell.
The invention will be better understood and many advantages will be obtained from the following examples, which are given by way of illustration. The following examples illustrate some of the methods, applications, embodiments and variations of the present invention. They should not, of course, be construed as limiting the invention. Many variations and modifications may be made to the present invention.
Examples of the invention
FIG. 5 illustrates a soil moisture characteristic curve (SWCC) device incorporating a resistivity measurement cell in accordance with an embodiment of the subject invention. Referring to fig. 5, the entire sample container is placed into the chamber of a Fredlund SWCC device (GCTS test system, arizona, usa) along with an electrode array. The resistivity measurement unit is disposed on the ceramic plate and surrounded by the chamber. Eight additional holes are drilled through the top wall of the chamber to allow wires to pass through to connect the electrodes to the resistivity meter; each hole is well sealed to ensure that no air and steam leaks in or out. The resistivity meter used in this measurement was SYSCAL JUNIOR SWITCH 48.
It is understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof are suggested to persons skilled in the art and are to be included within the spirit and purview of this application.
All patents, patent applications, provisional applications, and publications (including those in the "references" section) mentioned or cited herein are incorporated by reference in their entirety, including all figures and tables, so long as they are not inconsistent with the explicit teachings of this specification.
Reference to the literature
Amidu.S.A., and Dimbar, J.A.,2007, "Geoelectric students of social welting and drying of a Texas Vertisol". J.A. (Vadose Zone Journal),6(3), 511-.
Telford, W., Geldart, L., and Sheri, R.,1990, "Resistity methods" Cambridge university Press, UK.

Claims (19)

1. An anisotropic resistivity measurement unit for measuring resistivity of unsaturated soil, comprising:
a first measurement array arranged in a first direction; and
a second measurement array arranged in a second direction,
wherein the second measurement array comprises a first point current source, a second point current source, a first point potential electrode, and a second point potential electrode;
wherein, in a third direction, each of the first point potential electrode and the second point potential electrode is placed at a measurement depth different from a measurement depth of each of the first point current source and the second point current source,
wherein the first measurement array comprises a first array first point current source, a first array second point current source, a first array first point potential electrode and a first array second point potential electrode on the same plane in the third direction, and
wherein the first array first point current source and the first point current source provide current, the first array second point current source and the second point current source receive current,
wherein the anisotropy of resistivity of the soil is obtained by two independent measurements using the first measurement array and the second measurement array.
2. The resistivity measurement cell of claim 1, wherein the first point current source, the first point potential electrode, the second point potential electrode, and the second point current source are arranged in any type of array.
3. The resistivity measurement cell of claim 2, wherein a horizontal spacing between the first point current source and the first point potential electrode in the second direction is the same as a vertical spacing between the first point current source and the first point potential electrode in the third direction.
4. The resistivity measurement cell of claim 2, wherein the first and second directions are different from each other and the third direction is perpendicular to the first and second directions.
5. The resistivity measurement cell of claim 2, wherein each of the first point current source, the second point current source, the first point potential electrode, and the second point potential electrode includes a silver electrode, a copper rod electrically connected to the silver electrode, and a cable jacket surrounding the copper rod.
6. The resistivity measurement cell of claim 2, further comprising a cross frame supporting the first measurement array and the second measurement array.
7. A soil moisture characteristic curve (SWCC) apparatus comprising:
the resistivity measurement unit of claim 6; and
a chamber surrounding the resistivity measurement cell,
wherein the chamber comprises a plurality of apertures through which a plurality of wires are connected to the first measurement array and the second measurement array.
8. An anisotropic resistivity measurement unit for measuring resistivity of unsaturated soil, comprising:
a first fourth probe array comprising a first array of first point current sources, a first array of second point current sources, a first array of first point potential electrodes, and a first array of second point potential electrodes in a first direction; and
a second fourth probe array comprising a second array of first point current sources, a second array of second point current sources, a second array of first point potential electrodes, and a second array of second point potential electrodes in a second direction;
wherein, in a third direction, each trailing end of the first array of first point potential electrodes and the first array of second point potential electrodes is placed at a different plane than each trailing end of the second array of first point potential electrodes and the second array of second point potential electrodes,
wherein the first array first point current source, the first array second point current source, the first array first point potential electrode, and the first array second point potential electrode are located on the same plane in the third direction, and
wherein the first array first point current source and the second array first point current source provide current, the first array second point current source and the second array second point current source receive current,
wherein the anisotropy of resistivity of the soil is obtained by two independent measurements using the first and second four-probe arrays.
9. The resistivity measurement unit of claim 8, wherein, in the third direction, the tail ends of the second array of first point potential electrodes and the tail ends of the second array of second point potential electrodes are positioned lower than the tail ends of the first array of first point potential electrodes and the tail ends of the first array of second point potential electrodes.
10. The resistivity measurement cell of claim 8, wherein the tail ends of the first array of first point potential electrodes and the tail ends of the first array of second point potential electrodes are positioned in a same plane as the tail ends of the first array of first point current sources, the tail ends of the first array of second point current sources, the tail ends of the second array of first point current sources, and the tail ends of the second array of second point current sources.
11. The resistivity measurement cell of claim 10, wherein the first array first point current source, the first array first point potential electrode, the first array second point potential electrode, and the first array second point current source are arranged in series and spaced apart at a horizontal pitch; and the second array first point current source, the second array first point potential electrode, the second array second point potential electrode, and the second array second point current source are arranged in series and spaced apart at the horizontal pitch.
12. The resistivity measurement cell of claim 8, further comprising a cross frame supporting the first and second quad probe arrays, and a container connected to the cross frame and surrounding the cross frame and the first and second quad probe arrays.
13. The resistivity measurement cell of claim 12, wherein each of the first array first point current source, the first array second point current source, the first array first point potential electrode, the first array second point potential electrode, the second array first point current source, the second array second point current source, the second array first point potential electrode, and the second array second point potential electrode comprises a cable sheath passing through the cross-frame.
14. The resistivity measurement cell of claim 13, wherein each of the first array first point current source, the first array second point current source, the first array first point potential electrode, the first array second point potential electrode, the second array first point current source, the second array second point current source, the second array first point potential electrode, and the second array second point potential electrode further comprises an electrode disposed in the container.
15. The resistivity measurement unit of claim 14, wherein each cable jacket of the second array of first point potential electrodes and the second array of second point potential electrodes extends to each of the second array of first point potential electrodes and the second array of second point potential electrodes in the vessel.
16. A soil moisture characteristic curve (SWCC) apparatus comprising:
a plate;
a resistivity measurement cell according to claim 15 disposed on the plate;
a chamber surrounding the resistivity measurement cell and the plate; and
a plurality of wires passing through the chamber and connected to the first and second four-probe arrays.
17. An anisotropic resistivity measurement unit for measuring resistivity of unsaturated soil, comprising:
a first array of first point current sources and a first array of second point current sources arranged in a first direction;
a first array of first point potential electrodes and a first array of second point potential electrodes disposed between the first array of first point current sources and the first array of second point current sources in the first direction;
a second array of first point current sources and a second array of second point current sources arranged in a second direction;
a second array of first point potential electrodes and a second array of second point potential electrodes disposed between the second array of first point current sources and the second array of second point current sources in the second direction;
wherein in a third direction, each tail end of the second array first point potential electrodes and the second array second point potential electrodes is positioned lower than each tail end of the second array first point current sources and the second array second point current sources,
wherein the first direction and the second direction are horizontal directions and the third direction is a vertical direction,
wherein the first array first point current source, the first array second point current source, the first array first point potential electrode, and the first array second point potential electrode are located on the same plane in the third direction, and
wherein the first array first point current source and the second array first point current source provide current, the first array second point current source and the second array second point current source receive current,
wherein the first array of first point current sources, the first array of second point current sources, the first array of first point potential electrodes and the first array of second point potential electrodes constitute a first measurement array, the second array of first point current sources, the second array of second point current sources, the second array of first point potential electrodes and the second array of second point potential electrodes constitute a second measurement array, and the anisotropy of the resistivity of the soil is obtained by two independent measurements using the first measurement array and the second measurement array.
18. A soil moisture characteristic curve (SWCC) apparatus comprising:
the resistivity measurement cell of claim 17; and
a chamber surrounding the resistivity measurement cell.
19. The soil moisture profile apparatus of claim 18, further comprising a ceramic plate, said resistivity measurement unit being disposed on said ceramic plate.
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