CN101266271A - Electromagnetic wave test soil body dielectric coefficient test method and device - Google Patents

Abstract

The invention discloses a device and method for testing the dielectric constant of the soil with high conductivity. A sensor is connected with an electromatic radiation reflector by a coaxial cable and the electromatic radiation reflector is connected with the PC. The device and method can prevent the electromagnetic wave from dispersing due to high conductivity in the traditional electromagnetic wave technique and test the dielectric constant of the soil with high conductivity and is free from the effect of the alkalinity of the soil. The method can test the dielectric constant of the soil with high conductivity such as chemical reinforced soil, high organic soil, high water content and high plastic clay or the like and is a safe, quick, accurate method for testing the dielectric constant and provides basis for testing the water content of the soil of high conductivity.

Description

The method of testing of electromagnetic wave test soil body dielectric coefficient and device

Technical field

The present invention relates to utilize the pick-up unit of reflection of electromagnetic wave, especially relate to a kind of method of testing and device of electromagnetic wave test soil body dielectric coefficient.

Background technology

Can utilize electromagnetic wave method on-the-spot test soil body water cut on the engineering.The U.S. on-the-spot water cut testing standard ASTM6780 utilizes TDR (electromagnetic wave Time Domain Reflectometry method) test soil body water cut, needs to measure earlier the specific inductive capacity of the soil body earlier, obtains the water cut of the soil body then by the indoor standardization equation.The specific inductive capacity of traditional TDR method test soil body is to use the journey time method, is according to electromagnetic wave velocity of propagation difference in the soil body of differing dielectric constant, obtains the travel-time of electromagnetic wave at the test soil body earlier.And the travel-time is to determine according to first reflection spot and the end reflection point of electromagnetic wave in sensor.For the high conductivity soil body, electromagnetic wave has very big energy loss in the time of can propagating in the soil body, cause electromagnetic dissipation, is difficult to accurately determine the end reflection point in this case.So traditional TDR method is difficult to test the specific inductive capacity of the high conductivity soil body, thereby obtain its water cut.And in actual engineering, the water cut of the chemical consolidation soil of high conductivity is again a very important physical parameter, so the present invention has introduced a kind of proving installation and method of new test high conductivity dielectric constant of soil body, lays the first stone for testing its water cut.

Summary of the invention

The object of the present invention is to provide a kind of proving installation and method of electromagnetic wave test soil body dielectric coefficient, especially the test of high conductivity dielectric constant of soil body.

The technical solution used in the present invention is as follows:

One, a kind of method of testing of electromagnetic wave test soil body dielectric coefficient, the step of this method is as follows:

1) soil body that will test is hit the solid yardage method according to the soil test standard and in hitting real bucket, hit reality, make soil body height and to hit real bucket concordant, squeeze into the stainless steel probe at the center;

2) on hitting real bucket, put stainless steel ring, first screw rod is equipped with at the center of the piece of stainless steel lower end on the coaxial gauge head, on the same circumference of piece of stainless steel lower end five equilibrium be equipped with second and third, four screw rods, expose at four screw rods of piece of stainless steel lower end isometric, then four reference test bars are received on four screw rods, the coaxial gauge head that will connect reference test bar then is placed on the stainless steel ring, and the stainless steel probe contacts with first reference test bar, second and third, four reference test bars contact with stainless steel ring;

3) connect concentric cable and TDR Test instrument, open PC, the PMTDR software collection waveform that utilizes the TDR instrument to carry, dielectric constant of soil body $\sqrt{K_{\mathrm{soil}}^{*}}=k\frac{1-{\mathrm{\ρ}}_3}{1+{\mathrm{\ρ}}_3},$ K is the demarcation constant relevant with instrument, and k gets 1 in the method, ρ in the formula ₃Be the soil body surface reflection coefficient, can try to achieve by following formula: ρ ₁=ρ _1f(1) ${\mathrm{\ρ}}_2=\frac{{\mathrm{\ρ}}_{2f}-{\mathrm{\ρ}}_{1f}}{(1-{{\mathrm{\ρ}}_1}^2)}$ (2) ${\mathrm{\ρ}}_3=\frac{{\mathrm{\ρ}}_{3f}-{\mathrm{\ρ}}_{2f}}{(1-{\mathrm{\ρ}}_1^2)(1-{{\mathrm{\ρ}}_2}^2)}$ (3), ρ wherein _1fBe the reflection coefficient of coaxial gauge head on the TDR Test waveform and concentric cable interface, ρ _2fBe the reflection coefficient of reference test bar on the test waveform and coaxial gauge head interface, ρ _3fReflection coefficient for soil body surface on the test waveform, their obtaining value method is as follows, utilize Svitzky and Golay described method of waveform being asked first order derivative in 1964, to the differentiate of TDR Test waveform, obtaining a horizontal ordinate is the time, ordinate is the waveform of the first order derivative of reflection coefficient, time t when the reflection that obtains coaxial gauge head, reference test bar, three interfaces of the soil body on waveform finishes ₁, t ₂And t ₃, find the value of ordinate on the corresponding TDR Test waveform then, be ρ _1f, ρ _2f, ρ _3fValue; Through type (1) is tried to achieve ρ ₁, with ρ ₁Substitution formula (2) is tried to achieve ρ ₂, again with ρ ₁, ρ ₂Substitution formula (3) is tried to achieve ρ ₃

Two, a kind of proving installation of electromagnetic wave test soil body dielectric coefficient:

Sensor is connected with electromagnetic wave transmitter through concentric cable by BNC connector, and electromagnetic wave transmitter is connected with PC; Described sensor comprises coaxial gauge head and coaxial test bucket, wherein:

1) coaxial gauge head: comprise piece of stainless steel, four reference test bars and four screw rods, have the shoulder hole that the upper end is little, the lower end is big at the piece of stainless steel center, BNC connector is housed in the aperture, potting resin piece and first screw rod is housed at the center in the macropore of piece of stainless steel lower end, on the same circumference of piece of stainless steel lower end five equilibrium be equipped with second and third, four screw rods, expose at four screw rods of piece of stainless steel lower end isometricly, under each root screw rod isometric reference test bar is housed respectively;

2) coaxial test bucket: comprise the real bucket of hitting of stainless steel probe, hollow, stainless steel ring and insulator foot, fill the real bucket of hitting of test soil body center and insert the stainless steel probe, the stainless steel probe is coaxial with first reference test bar at center, piece of stainless steel lower end, hit real bucket and be placed on the insulator foot location, hit stainless steel ring on the real bucket upper end cover.

The beneficial effect that the present invention has is:

Can avoid because the situation that the caused electromagnetic wave of the high conductivity of material dissipates in the traditional electrical magnetic wave method can be tested the specific inductive capacity of the high conductivity soil body, and is not subjected to the influence of soil body saline and alkaline.The present invention can realize the specific inductive capacity test to high conductivity soil bodys such as chemical consolidation soil, high organic soil, high-moisture highly plastic claies, be a kind of dielectric constant of soil body method of testing safely, fast and accurately, also lay the first stone for test high conductivity soil body water cut.

Description of drawings

Fig. 1 is a proving installation structural representation of the present invention.

Fig. 2 is the structural representation of coaxial gauge head and reference test bar.

Fig. 3 is the structural representation of coaxial test bucket.

Fig. 4 is the structural representation of probe jig.

Fig. 5 is to the figure after the differentiate of typical TDR Test waveform waveform ordinate.

Fig. 6 is typical TDR Test waveform waveform.

Fig. 7 is the calibration curve of proving installation k value.

Among the figure: 1, PC, 2, electromagnetic wave transmitter, 3, concentric cable, 4, BNC connector, 5, sensor, 6, coaxial gauge head, 7, reference test bar, 8, coaxial test bucket, 9, piece of stainless steel, 10, resin mass, 11, screw rod, 12, spring, 13, stainless steel probe, 14, hit real bucket, 15, stainless steel ring, 16, insulator foot, 17, soil surface, 18, the probe jig

Embodiment

As Fig. 1, Fig. 2, Fig. 3, shown in Figure 4, sensor 5 of the present invention is connected with electromagnetic wave transmitter 2 through concentric cable 3 by BNC connector 4, and electromagnetic wave transmitter 2 is connected with PC 1; Described sensor 5 comprises coaxial gauge head 6 and coaxial test bucket 8, wherein:

1) coaxial gauge head 6: comprise piece of stainless steel 9, four reference test bars 7 and four screw rods 11, have the shoulder hole that the upper end is little, the lower end is big at piece of stainless steel 9 centers, BNC connector 4 is housed in the aperture, potting resin piece 10 and first screw rod 11 is housed at the center in the macropore of piece of stainless steel 9 lower ends, on the same circumference of piece of stainless steel 9 lower ends five equilibrium be equipped with second and third, four screw rods 11, expose at four screw rods 11 of piece of stainless steel 8 lower ends isometricly, each root screw rod is equipped with isometric reference test bar 7 11 times respectively;

2) coaxial test bucket 8: comprise the real bucket 14 of hitting of stainless steel probe 13, hollow, stainless steel ring 15 and insulator foot 16, fill the real bucket of hitting of the test soil body 14 centers and insert stainless steel probe 13, stainless steel probe 13 is coaxial with first reference test bar 7 at center, piece of stainless steel 8 lower end, hit real bucket 14 and be placed on insulator foot 16 location, hit stainless steel ring 15 on real bucket 14 upper end covers.

Piece of stainless steel 9 diameters are 140～180mm in the described coaxial gauge head 6, highly be 50mm～80mm, resin mass 10 is the polyoxymethylene resin material, four isometric screw rod 11 length are 30～40mm, second and third, four screw rods are evenly distributed on the circumference that radius r is 60～70mm, second and third, any screw rod is connected with piece of stainless steel 9 elasticity by spring in four screw rods, can move down by in the vertical direction; Isometric reference test bar 7 length L are 200～300mm.

Hitting real bucket 13 height h in the described coaxial test bucket 8 is 110～120mm, and interior diameter D is 100～110mm; Stainless steel probe 13 diameter d are 8～10mm; Stainless steel ring 15 height c are 30～40mm, and insulator foot 16 is the polyoxymethylene resin material, will hit real bucket 14 by the support on the insulator foot 16 and fix;

As shown in Figure 1, sensor is connected with electromagnetic wave transmitter by BNC connector through concentric cable respectively, and electromagnetic wave transmitter is connected with PC; Described sensor comprises coaxial gauge head, coaxial test bucket; Wherein coaxial gauge head: comprise piece of stainless steel, four reference test bars and four screw rods, have the shoulder hole that the upper end is little, the lower end is big at the piece of stainless steel center, BNC connector is housed in the aperture, potting resin piece and first screw rod is housed at the center in the macropore of piece of stainless steel lower end, on the same circumference of piece of stainless steel lower end five equilibrium be equipped with second and third, four screw rods, expose at four screw rods of piece of stainless steel lower end isometricly, under each root screw rod isometric reference test bar is housed respectively; Coaxial test bucket: comprise the real bucket of hitting of stainless steel probe, hollow, stainless steel ring and insulator foot, fill the real bucket of hitting of test soil body center and insert the stainless steel probe, the stainless steel probe is coaxial with first reference test bar at center, piece of stainless steel lower end, hit real bucket and be placed on the insulator foot location, hit stainless steel ring on the real bucket upper end cover.

Described electromagnetic wave transmitter is the product TDR100 of U.S. Campbell Scientific company.

Described concentric cable is the concentric cable of model RG58A/U, and its length is 1～2 meter.

The PMTDR software of Campbell company exploitation is adopted in data acquisition and processing.

Fix earlier during test and hit real bucket, the soil body that test is hit the solid yardage method according to the soil test standard hit actual arrival and hit real bucket, and hit the soil body of real bucket with the scraper leveling, make soil body height with hit in fact barrel concordant; Put probe jig 18 (shown in Fig. 4 (a) and (b)) then, make the mould lower surface be close to native face 17, squeeze into stainless steel probe 13 with hand hammer then; Mold removal is put stainless steel ring 15; Guarantee stainless steel ring 15 on hit real bucket 14 and with its tight contact, the coaxial gauge head 6 that connects four reference test bars 7 is placed on above the stainless steel ring 15, guarantee first reference test bar in stainless steel probe upper end and closely contact, second and third, four reference test bars closely contact with stainless steel ring; Connect concentric cable and TDR Test instrument, open PC, sharp PCTDR software collection waveform, the connection of proving installation structure as shown in Figure 1, typical test waveform as shown in Figure 6, test waveform is asked the method for first order derivative according to Svitzky and Golay (1964) are described to waveform, and obtaining a transverse axis is the time, the longitudinal axis be reflection coefficient first order derivative waveform as shown in Figure 5.Waveform in the analysis chart 5 finds three the obvious crests of waveform in 20～30ns, and wherein first crest appears near the 24ns, and the direction of crest projection upwards; Second crest appears near the 25ns, and the direction of crest projection upwards; The 3rd crest appears near the 27ns, and being directed downwards of crest projection.The end point of three crests (as shown in Figure 5) is TDR pulse time t when first reflection, reflection for the second time and reflection end for the third time ₁, t ₂And t ₃, find then that horizontal ordinate is t on the corresponding TDR Test waveform ₁, t ₂And t ₃The value of the pairing ordinate of point, be ρ _1f, ρ _2f, ρ _3fValue.ρ ₃Can try to achieve by following formula: ρ ₁=ρ _1f(1) ${\mathrm{\ρ}}_2=\frac{{\mathrm{\ρ}}_{2f}-{\mathrm{\ρ}}_{1f}}{(1-{{\mathrm{\ρ}}_1}^2)}$ (2) ${\mathrm{\ρ}}_3=\frac{{\mathrm{\ρ}}_{3f}-{\mathrm{\ρ}}_{2f}}{(1-{\mathrm{\ρ}}_1^2)(1-{{\mathrm{\ρ}}_2}^2)}$ (3)。Dielectric constant of soil body can be tried to achieve by following formula: $\sqrt{K_{\mathrm{soil}}^{*}}=k\frac{1-{\mathrm{\ρ}}_3}{1+{\mathrm{\ρ}}_3},$ K is the demarcation constant relevant with instrument, k can be similar to and get 1, also can adopt scaling method to obtain, scaling method is as follows, utilize the known solution of specific inductive capacity (deionized water is 79.90, and absolute ethyl alcohol 17.70, butanols are 25.20), test its TDR waveform according to method of testing as herein described, and try to achieve the surface reflectance ρ of solution separately ₃, utilize function (y=kx) right then $\sqrt{K^{*}}~\frac{1-{\mathrm{\ρ}}_3}{1+{\mathrm{\ρ}}_3}$ Carry out linearity and fit, obtain slope k, as shown in Figure 7.Then k is the demarcation constant of instrument.

Claims (4)

1, a kind of method of testing of electromagnetic wave test soil body dielectric coefficient is characterized in that the step of this method is as follows:

1) soil body that will test is hit the solid yardage method according to the soil test standard and in hitting real bucket, hit reality, make soil body height and to hit real bucket concordant, squeeze into the stainless steel probe at the center;

2) on hitting real bucket, put stainless steel ring, first screw rod is equipped with at the center of the piece of stainless steel lower end on the coaxial gauge head, on the same circumference of piece of stainless steel lower end five equilibrium be equipped with second and third, four screw rods, expose at four screw rods of piece of stainless steel lower end isometric, then four reference test bars are received on four screw rods, the coaxial gauge head that will connect reference test bar then is placed on the stainless steel ring, and the stainless steel probe contacts with first reference test bar, second and third, four reference test bars contact with stainless steel ring;

3) connect concentric cable and TDR Test instrument, open PC, the PMTDR software collection waveform that utilizes the TDR instrument to carry, dielectric constant of soil body $\sqrt{K_{\mathrm{soil}}^{*}}=k\frac{1-{\mathrm{\ρ}}_3}{1+{\mathrm{\ρ}}_3},$ K is the demarcation constant relevant with instrument, and k gets 1 in the method, ρ in the formula ₃Be the soil body surface reflection coefficient, can try to achieve by following formula: ρ ₁=ρ _1f(1) ${\mathrm{\ρ}}_2=\frac{{\mathrm{\ρ}}_{2f}-{\mathrm{\ρ}}_{1f}}{(1-{{\mathrm{\ρ}}_1}^2)}$ (2) ${\mathrm{\ρ}}_3=\frac{{\mathrm{\ρ}}_{3f}-{\mathrm{\ρ}}_{2f}}{(1-{\mathrm{\ρ}}_1^2)(1-{{\mathrm{\ρ}}_2}^2)}$ (3), ρ wherein _1fBe the reflection coefficient of coaxial gauge head on the TDR Test waveform and concentric cable interface, ρ _2fBe the reflection coefficient of reference test bar on the test waveform and coaxial gauge head interface, ρ _3fReflection coefficient for soil body surface on the test waveform, their obtaining value method is as follows, utilize Svitzky and Golay described method of waveform being asked first order derivative in 1964, to the differentiate of TDR Test waveform, obtaining a horizontal ordinate is the time, ordinate is the waveform of the first order derivative of reflection coefficient, time t when the reflection that obtains coaxial gauge head, reference test bar, three interfaces of the soil body on waveform finishes ₁, t ₂And t ₃, find the value of ordinate on the corresponding TDR Test waveform then, be ρ _1f, ρ _2f, ρ _3fValue; Through type (1) is tried to achieve ρ ₁, with ρ ₁Substitution formula (2) is tried to achieve ρ ₂, again with ρ ₁, ρ ₂Substitution formula (3) is tried to achieve ρ ₃

2, the device that is used for the method for testing of the described a kind of electromagnetic wave test soil body dielectric coefficient of claim 1, it is characterized in that: sensor (5) is connected with electromagnetic wave transmitter (2) through concentric cable (3) by BNC connector (4), and electromagnetic wave transmitter (2) is connected with PC (1); Described sensor (5) comprises coaxial gauge head (6) and coaxial test bucket (8); Wherein:

1) coaxial gauge head (6): comprise piece of stainless steel (9), four reference test bars (7) and four screw rods (11), have the upper end at piece of stainless steel (9) center little, the shoulder hole that the lower end is big, BNC connector (4) is housed in the aperture, potting resin piece (10) and first screw rod (11) is housed at the center in the macropore of piece of stainless steel (9) lower end, five equilibrium is equipped with second on the same circumference of piece of stainless steel (9) lower end, three, four screw rods (11), expose at four screw rods (11) of piece of stainless steel (8) lower end isometricly, under each root screw rod (11) isometric reference test bar (7) is housed respectively;

2) coaxial test bucket (8): comprise the real bucket of hitting of stainless steel probe (13), hollow (14), stainless steel ring (15) and insulator foot (16), fill the real bucket of hitting of the test soil body (14) center and insert stainless steel probe (13), stainless steel probe (13) is coaxial with first reference test bar (7) at piece of stainless steel (8) center, lower end, hit real bucket (14) and be placed on insulator foot (16) location, hit stainless steel ring (15) on real bucket (14) upper end cover.

3, the device of the method for testing of a kind of electromagnetic wave test soil body dielectric coefficient according to claim 2, it is characterized in that: piece of stainless steel (9) diameter is 140～180mm in the described coaxial gauge head (6), highly be 50mm～80mm, resin mass (10) is the polyoxymethylene resin material, isometric four screw rods (11) length is 30～40mm, second, three, four screw rods are evenly distributed on the circumference that radius r is 60～70mm, second, three, any screw rod is connected with piece of stainless steel (9) elasticity by spring in four screw rods, can move down by in the vertical direction; Isometric reference test bar (7) length L is 200～300mm.

4, the device of the method for testing of a kind of electromagnetic wave test soil body dielectric coefficient according to claim 2, it is characterized in that: hitting real bucket (13) height h in the described coaxial test bucket (8) is 110～120mm, and interior diameter D is that 100～110mm stainless steel probe (13) diameter d is 8～10mm; Stainless steel ring (15) height c is 30～40mm, and insulator foot (16) is the polyoxymethylene resin material, and it is fixing to hit real bucket (14) by the support on the insulator foot (16).

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