CN1342891A - 4-electrode electric measuring method for measuring and calculating apparatus AC conductivity of ground - Google Patents

Abstract

A 4-electrodes method for electrically measuring and calculating the apparent AC conductivity of ground is disclosed. The horizontal and vertical coordinate axises of curve chart are AB/2 and Rhok. The Rhok values at two points at both sides of the lines in the curve chart and a line is linked to said two points. After it coincides with said curve chart. The line is crossed with said lines in curve chart. The readings on vertical axis for each crossed points are just the Rho k values.

Description

Four utmost point electrical measurements exchange the measurement computing method of apparent earth conductivity

The present invention relates to the measurement computing method that a kind of four utmost point electrical measurements exchange apparent earth conductivity, particularly measure the method for the conductance of a comprehensive equivalence of various electric conduction of rock in the distribution range of current field in the earth.

To aspect the influence of Telecommunication Lines electromagnetic induction, existing technology based on four utmost point resistivity soun dings has two kinds, i.e. " rad row " curve method and experimental formula method at the prediction line of electric force.

1, " rad row " curve method

Adopt four utmost point resistivity soun dings to measure electrical sounding curve, and explain ρ ₁, h ₁, the μ value, on this basis, utilize " rad row " opisometer to calculate the interchange apparent earth conductivity of demand again.The distinct issues that exist are to control depth measurement, and computation process is loaded down with trivial details, must come to home to explain by the geophysics professional.

2, experimental formula method

Adopt four utmost point resistivity soun dings to measure electrical sounding curve, utilize experimental formula to be painted on the straight line in the logarithmic coordinate and the intersection point of measured curve, calculate the interchange apparent earth conductivity.This technology existence fathoms incorrect, causes the inaccurate of measurement result.Under identical geologic condition, this method is compared with first kind of classic method and is had 30～60% difference.The former is the usual practice of recommending in the world, the current leading position that occupy on engineering; The latter is still immature because of experimental formula, still can not replace traditional " rad row " method, is in reference to the status on engineering is used.

Look into newly through the Searches of Patent Literature that China Intellectual Property Office carries out, find no the method for further improvement four-electrode method measurements and calculations ground conductivity, list of references is seen Appendix.

The purpose of this invention is to provide a kind of easier measurement computing method that more are applicable to the engineering survey design, promptly only survey the ρ of a certain polar distance of supplying power _kValue, and needn't measure a complete ρ _kCurve just can be obtained σ fast _kThe method of value.

Technical scheme of the present invention is achieved in that

Ground conductivity measuring and calculating curve map is at first arranged, survey ρ then _kValue and curve map contrast, calculating, ground conductivity measuring and calculating curve map of the present invention is that its horizontal ordinate is represented with logarithmic coordinate , ordinate is represented ρ _k, curve wherein draws four alignments according to following equation: $I_{50}:\frac{\mathrm{<figure-callout\; id="2"\; label="AB"\; filenames="A0011601200081.png"\; state="\{\{state\}\}">AB</figure-callout>}}{2}=30.5\&times;{\left({2.22\mathrm{\&rho;}}_k\right)}^{\frac{1}{2.25}}$ ${\mathrm{II}}_{50}:\frac{\mathrm{<figure-callout\; id="2"\; label="AB"\; filenames="A0011601200081.png"\; state="\{\{state\}\}">AB</figure-callout>}}{2}={10}^{[2.014\&times;{\left({\mathrm{Lg}}_{{\mathrm{\&rho;}}_k}\right)}^{0.17}+0.41]}$ ${\mathrm{III}}_{800}:\frac{\mathrm{<figure-callout\; id="2"\; label="AB"\; filenames="A0011601200081.png"\; state="\{\{state\}\}">AB</figure-callout>}}{2}=3.5\&times;{\left({10\mathrm{\&rho;}}_k\right)}^{\frac{1}{2.1}}$ ${\mathrm{IV}}_{800}:\frac{\mathrm{<figure-callout\; id="2"\; label="AB"\; filenames="A0011601200081.png"\; state="\{\{state\}\}">AB</figure-callout>}}{2}={10}^{[1.7299\&times;{\left({\mathrm{Lg}}_{{\mathrm{\&rho;}}_k}\right)}^{0.288}+0.099]}$

Following formula AB: the pole span of representing point-to-point transmission

ρ _k: represent ground resistivity

In engineering design, 6 of common demand 50Hz and 800Hz _kValue.σ when four-electrode method on-site measurement 50Hz electric current _kDuring value, only need measure 50H-z alignment I or near 2 ρ of II both sides among the figure _kValue.At this moment, the logarithmic coordinate of alignment diagram coordinate with the in-site measurement record are overlapped, as actual measurement ρ _k2 lines with the logarithmic coordinate of the identical modulus of alignment diagram in line when increasing from shallow to deep, find out the reading with the corresponding ordinate of intersection point of alignment I, be the σ that is asked _kValue; As the ρ that records _kWhen the value line reduces from shallow to deep, find out with the corresponding ordinate of alignment II intersection point reading get final product.When measuring 800Hz electric current σ _kThe time, method is the same, and institute's difference is found out the ρ with alignment III this moment _kBe worth when increasing or alignment IV ρ _kThe reading of the corresponding ordinate of the intersection point when value reduces gets final product.

The measurement computing method of above-mentioned interchange apparent earth conductivity, it surveys ρ _kBe worth 2 lines and abscissa axis to angle β＜45 °, can make relative error be limited in ± 10% in.

Four above-mentioned utmost point electrical measurements exchange the measurement computing method of apparent earth conductivity, and it surveys ρ _kThe distance of 2 lines of value is less than 100 meters.Theoretically, the distance of 2 lines is the smaller the better, but practical operation has any problem, if too senior general influences accuracy of measurement.

Advantage of the present invention is:

1, the control survey degree of depth more objectively, raising is measured, the accuracy of result of calculation.Make it to be limited in about 10% with measurement, the result of calculation maximum difference of traditional " rad row " curve method.

2, need not measure a complete ρ in the open air _kCurve has removed needing to explain ρ from ₁, h ₁, the μ value trouble, thereby obviously reduced the measurements and calculations workload, can significantly improve work efficiency.

3, easy to use, calculate rapidly, easily popularize.

Implement the present invention, only need duplicate Figure of description and on transparent film, make template and get final product, must be noted that the logarithmic coordinate modulus of template of the present invention equals the modulus of the recording log-log coordinate of field survey.

Below accompanying drawing is described, Fig. 1 is ground conductivity measurement, a calculated curve in nonhomogeneous media, and AB represents the pole span between transmitting electrode, ρ among the figure _kRepresent resistivity, I ₅₀Curve when curve increases progressively for the 50Hz conductance, II ₅₀Be the curve of 50Hz conductance when successively decreasing, III ₈₀₀Be the curve of 800Hz conductance when increasing progressively, IV ₈₀₀Be the curve of 800Hz conductance when successively decreasing.

Further specify principle of the present invention and embodiment below:

The solution that the present invention adopts is: according to the apparent resistivity notion in geophysics's resistivity prospecting theory, proposed to measure line of electric force first the ground conductivity in the influence of Telecommunication Lines electromagnetic induction is only depended on the measured ρ of a certain polar distance of supplying power of four-electrode method (AB) _kValue, and complete electric sounding ρ of unnecessary measurement _kCurve.

In view of the above, further propose fathoming of four utmost point electrical measuring methods and should depend on the buried depth of equivalent current line in the ground, and derived in uniform earth medium AB pole span and ground resistivity (ρ theoretically _k) and the mathematic(al) representation of power frequency (f): $\mathrm{AB}=788\sqrt{\frac{\mathrm{Pk}}{f}}$ On the basis of the above, according to the reference value and four utmost point electric sounding ρ of two layers of geologic structure ground conductivity of known parameters _kCurve, through a large amount of computational analysiss, inductive statistics goes out σ _kWith

Corresponding relation, and Corresponding relation is depicted in the transparent log-log coordinate, thereby is developed into σ in the non-homogeneous earth medium _kMeasure and calculated curve figure template.

In actual applications, the σ of common demand 50Hz or 800Hz electric current _kValue.As the σ that measures the 50Hz electric current _kThe time, only need measure alignment I or near the ρ in II both sides in the template _kGet final product,, at this moment, in-site measurement is write down 2 lines With ρ _kLogarithmic coordinate overlap with the coordinate of template, as the ρ that measures _kLine when increasing from shallow to deep, is found out the reading with the corresponding axis of ordinates of intersection point of alignment I, is the σ of demand _kValue; As the ρ that records _kWhen the value line reduces from shallow to deep, find out with the reading of the corresponding ordinate of alignment II intersection point and get final product.When measuring 800Hz electric current σ _kThe time, method is the same, and institute's difference is found out ρ this moment _kLine and alignment III (ρ _kDuring increase) or IV (ρ _kWhen reducing) the corresponding σ of intersection point _kThe reading of coordinate gets final product.The scope of application: the ρ that the field records _kLine with

Angle β＜45 of change in coordinate axis direction °, the distance of 2 lines is less than 100 meters.Implement the present invention, only need duplicate Figure of description and on transparent film, make template and get final product.Must be noted that the logarithmic coordinate modulus of template of the present invention equals the modulus of the recording log-log coordinate of field survey.

Through test of layer model digitally and the check of open-air field data, the result proves that template method of the present invention is feasible technically, is consistent with traditional " rad row " curve calculation result, and under identical geologic condition, its calculated difference is not more than 10%.So curve template method can replace traditional " rad row " curve method.Subordinate list 1 and subordinate list 2 are the contrasts with method of the present invention and mutual inductance method results of measuring.Be not difficult to find out that under identical geologic structure and power frequency condition, the measurement and the result of calculation of method of the present invention and objective and accurate digital model mutual inductance method are coincide, results of measuring is correct.

Table 1 mutual inductance method digital model test findings and nomography contrast table G type curve (ρ _l＜ρ _z)

F (Hz)	h 1(m)	μ	ρ 1(Ω m)	σ Mutually(10 -3S/m)	σ Row(10 -3S/m)	Remarks
							50	30	3	10	44.3	45.4	σ Row: the ground conductivity of expression nomography measuring and calculating.σ Mutually: the test findings of expression digital model mutual inductance method.
????20	????21.6	????20.0
			????40	????10	????9.52
????100	????3.9	????3.58
			????200	????2.03	????1.77
????10	????10	????20.7				????21.2
			????20	????8.6	????8.5
	????40	????3.8				????3.64
			????30	????10	????11.7				????13.0
????20	????4.38	????4.40
				????40	????1.95	????1.80
?800	?100	????3							????10	????100	????100
			????20	????52.5	????50.0
						????40	????24.3	????25.0
			????100	????8.27	????9.26
						????200	????3.55	????4.00
			????10	????10	????104				????100
		????20				????53.6	????50.0
				????40	????23.8			????24.0
		????100				????7.2	????8.2
				????30	????10			????105	????100
		????20	????54.3			????48.8
					????40		????23.8	????23.8

Table 2 mutual inductance method digital model test findings and nomography contrast table D type curve (ρ ₁＞ρ ₂)

F (Hz)	h 1(m)	μ		ρ 1(Ω m)	σ Mutually(10 -3S/m)	σ With(10 -3S/m)	Remarks
								50	10	1/3		20	140	1.50 *	*: extend the numerical value that alignment reads.
????40	????71	????74.63
			????100	????28.5	????29.76
????200	????14.2	????14.88
			????400	????7	????7.41
??1/10		????100				????90	????99.0
			????200	????46	????49.0
		????400				????21.3	????24.5
			?800	????10	????1/3					????20	????120	????130 *
????40	????66	????71.02
							????100	????27	????28.90
????200	????13.8	????14.60
							????400	????7	????7.25
????1000	????2.9	????2.95
							??1/10		????40	????176	??＞100
????100	????78.4	????90.5
					????200	????42.3			????47.39
????400	????22.0	????24.0
					????1000	????9.0			????9.8

Claims (3)

1, a kind of four utmost point electrical measurements exchange the measurement computing method of apparent earth conductivity, and four utmost point electrical measurement ground conductivity calculated curve figure are at first arranged, and survey ρ then _kValue and curve map contrast, calculating, ground conductivity measuring and calculating curve map is that its horizontal ordinate is represented with logarithmic coordinate

, ordinate is represented ρ _k, it is characterized in that the curve in the coordinate system draws four alignments according to following equation: $I_{50}:\frac{\mathrm{AB}}{2}=30.5\&times;{\left({2.22\mathrm{\&rho;}}_k\right)}^{\frac{1}{2.25}}$ ${\mathrm{II}}_{50}:\frac{\mathrm{AB}}{2}={10}^{[2.014\&times;{\left({\mathrm{Lg}}_{{\mathrm{\&rho;}}_k}\right)}^{0.17}+0.41]}$ ${\mathrm{III}}_{800}:\frac{\mathrm{AB}}{2}=3.5\&times;{\left(10{\mathrm{\&rho;}}_k\right)}^{\frac{1}{2.1}}$ ${\mathrm{IV}}_{800}:\frac{\mathrm{AB}}{2}={10}^{[1.7299\&times;{\left({\mathrm{Lg}}_{{\mathrm{\&rho;}}_k}\right)}^{0.228}+0.099]}$

Following formula AB: represent the spacing between transmitting electrode

ρ _k: represent ground resistivity in engineering design, 6 of common demand 50Hz and 800Hz _kValue is as the σ of four-electrode method on-site measurement 50Hz electric current _kDuring value, only need measure 50Hz alignment I or near 2 ρ of II both sides among the figure _kValue overlaps the logarithmic coordinate of alignment diagram coordinate with the in-site measurement record, then as actual measurement ρ _k2 lines with the logarithmic coordinate of the identical modulus of alignment diagram in line when increasing from shallow to deep, find out the reading with the corresponding ordinate of intersection point of alignment I, be the σ that is asked _kValue is as the ρ that records _kWhen the value line reduces from shallow to deep, find out with the reading of the corresponding ordinate of alignment II intersection point and get final product, when measuring 800Hz electric current σ k, method is the same, and institute's difference need be found out with the reading of the corresponding ordinate of intersection point of alignment III or IV get final product this moment.

2, four utmost point electrical measurements according to claim 1 exchange the measurement computing method of apparent earth conductivity, it is characterized in that surveying ρ _kBe worth 2 lines and abscissa axis to angle β＜45 °.

3, four utmost point electrical measurements according to claim 1 and 2 exchange the measurement computing method of apparent earth conductivity, it is characterized in that surveying ρ _kThe distance of 2 lines of value is less than 100 meters.

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