CN100483153C - Detecting method for bunching DC resistivity - Google Patents

Abstract

This invention discloses a detection method for the bunch DC resistivity, which uses a negative electrode, a measurement reference electrode, a primary electrode, two screening electrodes in the same supplying pole with the primary electrode, an electrode system composed of four mutual acted monitor electrodes to detect a certain sphere and thickness under the earth, in which, the primary and the screen electrodes are connected by leads to form a supply loop together with the negative electrode, the monitor electrodes are symmetrical in pair and connected in short circuit to constitute a measurement loop with the measurement reference electrode. Said method utilizes the repulsion effect of like electric fields underground to keep large current density distribution at a deep place, thus, the underground abnormal substances arise large field changes at the surface of the ground so as to increase the deepness and accuracy of the detection.

Description

Detecting method for bunching DC resistivity

Technical field: the present invention relates to a kind of geophysical probing technique, relate in particular to a kind of detecting method for bunching DC resistivity

Background technology: the dc resistivity exploration is an emerging geoscience, no matter aspect generaI investigation metal, nonmetallic minerals, still at aspects such as energy exploration, geologic mapping and the hydrology, engineering geological surveys, good geological effect is arranged all, bringing into play important effect.

The basic goal of dc resistivity exploration is to ask for formation apparent resistivity, by measuring face of land electric field change, judges the existence of the subsurface anomaly body of different depth; The metering system of present conventional dc resistivity depth measurement has multiple, and wherein the most conventional DC detecting deep method is symmetrical four-electrode method, and this method comprises the steps:

One, with point symmetry among four relative MN of configuration of electrodes of electrodes of A and B, monitor electrode M and N of measurement mechanism; The calculating formula of its electrode coefficient is as follows:

$K=\mathrm{\π}\·\frac{\mathrm{AM}\·\mathrm{AN}}{\mathrm{MN}}$

The MN mid point is measured point, and the calculation formula of apparent resistivity of the underground medium of measured point is:

$\mathrm{\ρ}=K\·\frac{\mathrm{\ΔU}}{I}$

Δ U is the potential difference (PD) between the MN, and I is the supply current of AB.

The corresponding degree of depth that it is generally acknowledged the apparent resistivity that measures is 1/2 of an AB distance, in measuring process, and fixedly M and N electrode, traveling electrode A and B, the AB distance is big more, and investigation depth is dark more.

Dc resistivity is used very extensive in engineer geological prospecting, but also exists intrinsic defective.The electrode power supply electric current is limited, and current density increases along with depth of stratum and reduces rapidly, and electric current can not flow toward darker stratum, causes depth of exploration limited; The horizontal and vertical resolution of geoelectric section is lower, also is the technical barrier of the conventional dc resistivity of puzzlement to the not ideal enough grade of complex geological condition exploration effects.

Summary of the invention:

Ask for the existing problem of formation apparent resistivity in order to solve above-mentioned symmetrical four-electrode method, the purpose of this invention is to provide the detecting method for bunching DC resistivity that a kind of investigation depth is big, certain limit and thickness and the banded interrupted bad ground that distributes had better Effect on Detecting:

Technical scheme of the present invention realizes in the following manner:

A kind of detecting method for bunching DC resistivity: it is that next decides scope and thickness is surveyed to ground for the electrode system that adopts transmitting electrode, guarded electrode, monitor electrode to interact to form, it is characterized in that: a negative electrode (B), a witness mark electrode (N), a central electrode (A ₀), two power polarity and central electrode (A ₀) identical guarded electrode (A ₁, A ₂); Four monitor electrode (M ₁, M ₁＇, M ₂, M ₂＇);

The arrangement mode of electrode system is: with central electrode (A ₀) be arranged on the ground of measured point, with central electrode (A ₀) be the center, with monitor electrode (M ₁, M ₁＇), monitor electrode (M ₂, M ₂＇), guarded electrode (A ₁, A ₂) three pairs of electrode orders are arranged in electrode A symmetrically ₀Both sides, be straight line, negative electrode (B) and witness mark electrode (N) are arranged in the both sides of straight line, A ₀B and A ₀N is all vertical with this rectilinear direction;

The connection mode of electrode system is: central electrode (A ₀), guarded electrode (A ₁, A ₂) connect with lead, the current potential on these three electrodes is identical, with negative electrode (B) be current supply circuit altogether, monitor electrode (M ₁, M ₁, ＇ M ₂, M ₂) symmetrical short-circuit connection in twos, these two pairs of electrodes all constitute with witness mark electrode (N) measures the loop;

Measure: make central electrode (A ₀) and guarded electrode (A ₁, A ₂) supply with the identical electric current I of polarity respectively ₀And I ₁, and regulate I ₀, make two couples of monitor electrode (M ₁, M ₁＇ and M ₂, M ₂It is identical that current potential ＇) keeps, promptly $U_{M_1}={\mathrm{<figure-callout\; id="2"\; label="U\; M"\; filenames="C200610017562E00121.png,C200610017562E00131.png"\; state="\{\{state\}\}">U</figure-callout>}}_{M_{}}$ Or $U_{M_1^{\&prime;}}={\mathrm{<figure-callout\; id="2"\; label="U\; M"\; filenames="C200610017562E00121.png,C200610017562E00131.png"\; state="\{\{state\}\}">U</figure-callout>}}_{M_{}^{}};$

The apparent resistivity ρ that records _sBe calculated as follows:

ρ _s＝ρ _i-ρ _i-1?(1)

$\mathrm{\&rho;}=K\frac{U_{M_1}}{I_0}---\left(2\right)$

In the formula (2)

Be monitor electrode M ₁Current potential; I ₀Be central electrode (A ₀) electric current, K is that beam forming electrode is an electrode coefficient, value is 1, i is expressed as natural number.

Central electrode (A ₀) and negative electrode (B) between distance be 5～10 times of required maximum depth of exploration, central electrode (A ₀) and witness mark electrode (N) between distance be 5～8 times of required maximum depth of exploration.

When duplicate measurements, guarded electrode (A ₁And A ₂) move laterally simultaneously, the each mobile step pitch of guarded electrode is 0.2m～0.3m, regulates principal current and makes the electric field pack, continues to repeat the aforesaid operations process, measures end when the distance of guarded electrode and central electrode is 5m～8m, the degree of depth of corresponding sensing point is (l ₁+ (i-1) * s) * d; L in the formula ₁Be A ₀A ₁Initial distance, l ₁＜1m; S is mobile step pitch, and d is A ₀A ₁The multiple of distance, 2.8≤d≤3.2; At last, the apparent resistivity curve of the different depth that draws is judged the existence that anomalous body is arranged in this depth range unusually according to the apparent resistivity of a certain degree of depth.

Pack principle of the present invention is: because M ₁, M ₁Between ＇ two equipotential surfaces and M ₂, M ₂Can not there be electric current to flow between ＇ two equipotential surfaces, so the electric current that flows out from central electrode or guarded electrode is all at M ₁, M ₁＇ and M ₂, M ₂＇ turns round at the place, forces central electrode A ₀Supply current vertically flow into the stratum.The apparent resistivity ρ that records _sBe expressed as:

${\mathrm{\&rho;}}_s=K\frac{U_{M_1}}{I_0}$

In the formula Be illustrated in a M ₁The current potential at place.Measurement point M during exploration ₁And monitor electrode B is the potential difference (PD) between the reference electrode.Because the B utmost point is far away, think U approx _B=0, so some M ₁And epd in fact just equals M between the B utmost point ₁The current potential U at place _M1, K is that beam forming electrode is an electrode coefficient, value is 1.

This " detecting method for bunching DC resistivity " electric field of exciting has certain directivity underground, the shielding that can go beyond resistive formation, and reduce the influence of low resistivity zone shunting, so investigation depth is higher than conventional dc resistivity.Detecting method for bunching DC resistivity is wideless to scope, and thickness is little, and the banded interrupted bad ground that distributes has the better detection effect, and this method is applied to obtain success in the detection test of the Yellow River dykes and dams root stone.This method utilizes same sex electric field at underground repelling effect, makes electric current in darker place bigger electric current distribution be arranged, and makes the subsurface anomaly body cause bigger electric field change on the face of land, has improved investigation depth greatly, and detection accuracy is higher.

Description of drawings:

Fig. 1 is the electrode system distribution schematic diagram of symmetrical four-electrode method electric sounding.

Fig. 2 is an electrode system distribution schematic diagram of the present invention.

Fig. 3 is a pack principle schematic of the present invention.

Fig. 4 leads 134 dam measuring points, 1 resistivity sounding correlation curve for the control of the Yellow River, Zhongmou County.

Fig. 5 leads 134 dam measuring points, 2 resistivity sounding correlation curves for the control of the Yellow River, Zhongmou County.

The electrode system instrument principle of work block diagram of Fig. 6 for using among the present invention.

The microcomputer principle of work block scheme that Fig. 7 uses for the present invention.

Embodiment:

Below in conjunction with embodiment and accompanying drawing the present invention is described in further detail.

At first, arrange electrode system: with central electrode (A according to shown in Figure 2 ₀) be arranged on the ground of measured point, with central electrode (A ₀) be the center, with monitor electrode (M ₁, M ₁＇), monitor electrode (M ₂, M ₂＇), guarded electrode (A ₁, A ₂) three pairs of electrode orders are arranged in electrode A symmetrically ₀Both sides, be straight line, negative electrode (B) and witness mark electrode (N) are arranged in the both sides of straight line, A ₀B and A ₀N is all vertical with this rectilinear direction;

Be it can also be seen that by Fig. 2: the connection mode of electrode system is: central electrode (A ₀), guarded electrode (A ₁, A ₂) connect with lead, the current potential on these three electrodes is identical, with negative electrode B be current supply circuit altogether, monitor electrode (M ₁, M ₁, ＇ M ₂, M ₂) symmetrical short-circuit connection in twos, these two pairs of electrodes all constitute with witness mark electrode N measures the loop;

During measurement, regulate principal current A ₀Size, make M ₁With M ₂Between potential difference (PD) be zero, M at this moment ₁＇ and M ₂Potential difference (PD) between the ＇ also is zero, like this at M ₂And M ₂Form the pack electric field between the ＇, measure guarded electrode M ₁Magnitude of voltage and central electrode A ₀Current value, instrument automatically records, and calculates apparent resistivity value by formula (2), mobile simultaneously then guarded electrode A ₁And A ₂, moving direction is pressed shown in Fig. 2, and each mobile 0.2m～0.3m regulates principal current and makes the electric field pack, continues to repeat the aforesaid operations process.When the distance of guarded electrode and central electrode is 5m～8m, measure and finish.

By Fig. 6, Fig. 7 as can be seen: pack electrical resistivity survey instrument is made up of microcomputer, two group of received passages, three groups of feed circuit, balancing circuit, balance indicating circuit, filtering circuit, 24 A/D change-over circuits and data processing software etc., wherein, the microcomputer part constitutes microcomputer by 51 serial monolithics and ROM, RAM etc., receives control command from keyboard.Show various states and measurement result by dot lcd.The order that control interface sends power supply, constant current, precedingly puts, filtering etc. needs, and obtain desired data from A/D.Communication port is to be used in after measurement finishes the data in the instrument to be delivered to outer computer; Two group of received passages are used for receiving M ₁N, M ₂The voltage signal of N receiving electrode compares at balancing stage two groups of voltage signals, and the M1N voltage signal is recorded as receiving data after the balance; Three groups of feed circuit are launched same polarity current signal, A to the earth respectively by transmitting electrode ₀Be principal current, A ₁, A ₂Be bucking current, A after the balance ₀Becoming bunched current is recorded; The balancing circuit is used for regulating A ₀Or A ₁, A ₂Electric current makes M ₁N, M ₂The voltage signal balance of N receiving electrode or equal, at this moment, A ₀Just the bunched current that has formed vertical ground is powered downwards; The balance indicating circuit is used for monitoring M ₁N, M ₂The comparison equilibrium state of the voltage signal of N receiving electrode; Filtering circuit is used for eliminating the power frequency interference of alternating current and the interference of other high-frequency signal; 24 A/D change-over circuits are used for M ₁N, M ₂The analog voltage signal of N receiving electrode converts that digital signal stores or record to; Data processing software is analyzed the A/D data converted, handle and is calculated, and draws corresponding parameters such as apparent resistivity and also can show in real time.

The key technical indexes of pack electrical resistivity survey instrument:

Voltage channel: minimum sampled signal 1 μ V, maximum sampled signal 6000mV, error 1%, resolution 1 μ V

Main current channel: minimum sampled signal 1 μ A, maximum sampled signal 30mA, error 1%, resolution 1 μ A

Bucking current passage: minimum sampled signal 1mA, maximum sampled signal 2000mA, error 1%, resolution 1mA

Input impedance: 〉=30M Ω is from electric benefit scope: 1000mV

50Hz power frequency compacting: 〉=60dB

Maximum supply voltage: 600V

Maximum supply current: 4000mA

RS-232 interface

The chargeable source of built-in 12V, complete machine electric current 80mA, Overall Power Consumption 1W

Working temperature :-10 ℃～+ 50 ℃

Storage temperature :-20 ℃～+ 60 ℃

Complete machine weight: 10kg

Volume: 490mm * 380mm * 200mm

As seen from Figure 3: central electrode A ₀Supply current at guarded electrode A ₁, A ₂The shielding action of electric current under vertical current go into the stratum.

The field test example:

Utilizing the present invention to be positioned at the control of the Yellow River, Zhongmou County at measuring point 1 by expression among Fig. 4 leads 134 Ba Chu, is 4 meters survey records that carry out from measuring point 1 distance.The symmetrical four-pole sounding curve that is illustrated by the broken lines is not obvious to the root stone layer reaction of 6.3m～8.5m; And the pack resistivity sounding curve of being represented by solid line is to the root stone layer significant reaction of 6.3m～8.5m.General symmetrical four-pole sounding curve has been described to the not obviously reflection of root stone, pack resistivity sounding curve is bigger unusually root stone layer, and apparent in view to the reflection of root stone, this shows that the Effect on Detecting of pack resistivity is better than general symmetrical level Four electrical method.Pack resistivity sounding curve judges that measuring point subsurface 6.3m～8.5m is a root stone layer.Show that according to on-the-spot borehole data underground 6.5m～8.3m is a root stone layer, comparative illustration pack dc resistivity is surveyed anomalous body reflection effect obvious.

Expression utilizes the present invention to be positioned at the control of the Yellow River, Zhongmou County at measuring point 2 and leads 134 Ba Chu among Fig. 5, is 4 meters survey records that carry out from measuring point 1 distance.The symmetrical four-pole sounding curve that is illustrated by the broken lines is not obvious to the root stone layer reaction of 5.4m～8m; And the pack resistivity sounding curve of being represented by solid line is to the root stone layer significant reaction of 5.4m～8m, and pack resistivity sounding curve judges that measuring point subsurface 5.4m～8m is a root stone layer.Borehole data shows that underground 4.8m～7m is a root stone layer.The validity that has shown pack resistivity detection root stone.

Claims (1)

1, a kind of detecting method for bunching DC resistivity: it is that next decides scope and thickness is surveyed to ground for the electrode system that adopts transmitting electrode, guarded electrode, monitor electrode to interact to form, it is characterized in that: a negative electrode (B), a witness mark electrode (N), a central electrode (A ₀), two power polarity and central electrode (A ₀) identical guarded electrode (A ₁, A ₂); Four monitor electrode (M ₁, M ₁', M ₂, M ₂');

The arrangement mode of electrode system is: with central electrode (A ₀) be arranged on the ground of measured point, with central electrode (A ₀) be the center, with monitor electrode (M ₁, M ₁'), monitor electrode (M ₂, M ₂'), guarded electrode (A ₁, A ₂) three pairs of electrode orders are arranged in electrode A symmetrically ₀Both sides, be straight line, negative electrode (B) and witness mark electrode (N) are arranged in the both sides of straight line, A ₀B and A ₀N is all vertical with this rectilinear direction;

The connection mode of electrode system is: central electrode (A ₀), guarded electrode (A ₁, A ₂) connect with lead, the current potential on these three electrodes is identical, with negative electrode (B) be current supply circuit altogether, monitor electrode (M ₁, M ₁, ' M ₂, M ₂) symmetrical short-circuit connection in twos, these two pairs of electrodes all constitute with witness mark electrode (N) measures the loop;

Measure: make central electrode (A ₀) and guarded electrode (A ₁, A ₂) supply with the identical electric current I of polarity respectively ₀And I ₁, and regulate I ₀, make two couples of monitor electrode (M ₁, M ₁' and M ₂, M ₂') on current potential keep identical, i.e. U _M1=U _M2Or $U_{M_1^{\&prime;}}=U_{M_2^{\&prime;}};$

The apparent resistivity ρ that records _sBe calculated as follows:

ρ _s＝ρ _i-ρ _i-1 (1)

$\mathrm{\&rho;}=K\frac{U_{M_1}}{I_0}---\left(2\right)$

In the formula (2)

Be monitor electrode M ₁Current potential; I ₀Be central electrode (A ₀) electric current, K is that beam forming electrode is an electrode coefficient, value is 1, i is a natural number;

Central electrode (A ₀) and negative electrode (B) between distance be 5～10 times of required maximum depth of exploration, central electrode (A ₀) and witness mark electrode (N) between distance be 5～8 times of required maximum depth of exploration;

When duplicate measurements, guarded electrode (A ₁And A ₂) move laterally simultaneously, the each mobile step pitch of guarded electrode is 0.2m～0.3m, regulates principal current and makes the electric field pack, continues to repeat the aforesaid operations process, measures end when the distance of guarded electrode and central electrode is 5m～8m, the degree of depth of corresponding sensing point is (l ₁+ (i-1) * s) * d; L in the formula ₁Be A ₀A ₁Initial distance, l ₁＜1m; S is mobile step pitch, and d is A ₀A ₁The multiple of distance, 2.8≤d≤3.2; At last, the apparent resistivity curve of the different depth that draws is judged the existence that anomalous body is arranged in this depth range unusually according to the apparent resistivity of a certain degree of depth.

Images