Saturated water-containing rock resistivity measuring device

Abstract

The utility model discloses a saturated water-containing rock resistivity measuring device which comprises a base, two sides of the base are respectively provided with a conductive metal, one side of the base is provided with a sliding rail, the sliding rail is in sliding contact with the conductive metal on the side, and the conductive metal on the sliding rail side is provided with a sliding rod along one side of the sliding rail. The sliding rod penetrates through a locking limiting device at the end of the base and is in sliding connection with the locking limiting device, the conductive metal on the other side is fixedly connected with the base, the conductive metal on the two sides is provided with a rock contact pole plate used for making contact with and clamping the saturated water-containing rock to be detected, and the rock contact pole plate and the conductive metal are rotationally connected and make mutual conductive contact. The rock contact pole plate can be controlled to rotate, and the conductive metal is provided with a conductive bolt used for being connected with a wire. Graphite conductive adhesive is used as a contact material of an electrode and a rock surface, the electrical connectivity of the electrode and a rock sample is enhanced by utilizing the characteristics of good contact and strong conductivity of the conductive adhesive, and meanwhile, the conductive adhesive is more uniformly coated on the electrode by utilizing the characteristics of a rotating element, so that the measurement error is reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to engineering surveying technical field, especially a saturated water-bearing rock resistivity measuring device. BACKGROUND

[0002] The resistivity of rock is an important electrical parameter of rock, which can reflect the difference of different rocks from the angle of electricity, which plays an important role in identifying rock characteristics and judging reservoirs. For large hydropower stations, pumped storage power stations and other systems, when short-circuit current occurs, the rock under the reservoir is an important medium for the dispersion of the grounding grid, and this part of rock is soaked in water for a long time, which can be considered as saturated water-bearing. It is of great significance to study the grounding problem by analyzing the saturated water-bearing resistivity of rock.

[0003] Rock is a porous medium, and there are pores inside it. When saturated with water, the internal pore water pressure reaches a maximum. This pressure represents the pressure of pore water on rock particles. At this time, water will infiltrate under the action of gravity. As the saturation decreases, air exists inside, and the water in the pores and the air between them will have a capillary phenomenon, which will cause a matrix suction force, which represents the attraction of water by rock particles. When the matrix suction force and the pore water pressure are balanced, the rock is in a stable state, and the water is evenly distributed. At this time, it is in the capillary pressure balance stage.

[0004] Rock in a completely dry state can be considered as an insulator because it lacks a path for conductive medium. Water in water-bearing rock can form a small path in the internal pore structure of the rock, thus having certain electrical conductivity.

[0005] Rock resistivity parameter measurement can be divided into four-pole method and two-pole method. The basic principle is to divide the voltage flowing through the conductor by the current flowing through it.

[0006] The four-pole method measures resistance using two current poles and two voltage poles. The current is injected at two points on the rock, and the voltage at multiple points inside the rock is measured using a probe. The resistance is obtained by the ratio of voltage to current, and the resistivity is obtained by combining the effective measurement size of the rock. This method can overcome the influence of contact resistance and has high accuracy. However, it requires drilling on the surface of the rock, which damages the rock structure. In order to ensure good contact between the rock inside and the electrode, sometimes conductive medium needs to be filled, which increases the complexity of the operation. For saturated rock, the water content inside is high, and the water absorption of the rock is less than the pore water pressure of the rock. The infiltration of water leads to uneven distribution of water content. According to section 7.1 of SY / T5385-2007, when the rock can ensure capillary pressure balance, the four-pole method is used, otherwise the two-pole method is used.

[0007] The secondary method has poor measurement accuracy compared with the quadrupole method due to the voltage pole, current pole and contact resistance of the electrode surface, especially because the rock surface is granular and has poor contact with the electrode, and the rock resistivity will be larger when part of the conductive channel containing water is not in contact with the electrode, and the deviation can be more than 10 times. The commonly used method is to use non-polarized copper sulfate cotton sheet to ensure contact and avoid the influence of electrode polarization on the measurement result.

[0008] Because the pore water pressure of the saturated water-bearing rock is large, the water infiltration causes uneven distribution of water content, at this time the quadrupole method is no longer applicable, and the secondary method also causes uneven distribution of rock water due to water infiltration and surface water evaporation of the rock, at this time the water in part of the rock conductive channel is displaced and affects its conductivity, so the measurement accuracy decreases. SUMMARY

[0009] The technical problem to be solved by the utility model is to provide a saturated water-bearing rock resistivity measuring device, which is used for overcoming the influence of uneven water distribution caused by gravity on the resistivity measurement accuracy in the process of measuring the resistivity of the saturated water-bearing rock, overcoming the uneven distribution of water content caused by water infiltration of the rock sample in the process of measurement, and ensuring good contact between the rock sample and the electrode to reduce the influence of the contact resistance.

[0010] To solve the above technical problems, the utility model adopts the technical scheme of:

[0011] A saturated water-bearing rock resistivity measuring device, including base, the both sides of base are equipped with a conductive metal, one side of base is equipped with slide rail, the conductive metal of this side is in sliding contact with slide rail, the conductive metal of slide rail side is equipped with slide bar along one side of slide rail, slide bar penetrates the locking position device of base end and is in sliding connection with it, the conductive metal of the other side is fixedly connected with base, the conductive metal of both sides is equipped with rock contact electrode plate for being in contact with the saturated water-bearing rock to be measured and clamping, rock contact electrode plate is rotatably connected with conductive metal and is in conductive contact with each other, rock contact electrode plate can be controlled to rotate, and the conductive bolt for connecting the wire is arranged on the conductive metal.

[0012] The rock contact electrode plate and the conductive metal rotatable connection structure are that a rotatable conductive connection bearing is arranged between the rock contact electrode plate and the conductive metal, and the rock contact electrode plate penetrates the rotatable conductive connection bearing and is in contact with the cylindrical roller at the center of the rotatable conductive connection bearing.

[0013] The rock contact electrode plate is used to clamp the side of the saturated water-bearing rock to be measured protruding from the surface of the conductive metal.

[0014] The conductive metal on the non-clamping side of the rock contact electrode plate is rotatably controlled by the structure that the conductive metal on the non-clamping side is equipped with a fixedly connected rocker.

[0015] The conductive metal controlled rotation structure fixedly connected with the base is provided with a transmission rod on the non-clamping side of the conductive metal, and the transmission rod is connected with the rotary motor.

[0016] The two conductive metals are provided with insulating bottom plates, and the insulating bottom plates are used for insulation with the base.

[0017] The conductive bolt is provided with an insulating nut.

[0018] The locking and limiting device limits the sliding position of the conductive metal by the boss on the sliding rod.

[0019] The saturated water-bearing rock resistivity measuring device has the following beneficial effects:

[0020] 1) The water distribution in the saturated water-bearing rock is uniform through the rotating element, and the measurement error is reduced.

[0021] 2) The conductive medium graphite conductive adhesive is uniformly brushed on the electrode by the rotating element, and the electrode and the rock are in good contact, so that the problem of poor contact between the electrode and the rock due to the rough surface of the rock is effectively solved, and the resistivity measurement accuracy is improved. BRIEF DESCRIPTION OF DRAWINGS

[0022] The utility model will be further described below in combination with the drawings and examples:

[0023] Figure 1 It is a structure schematic view of the saturated water-bearing rock resistivity measuring device of the utility model;

[0024] Figure 2 It is a sectional view of the rotating conductive connecting bearing;

[0025] Figure 3 It is a stress condition of rock pore water in the rotating process.

[0026] In the drawing: conductive metal 1, rock contact electrode plate 2, rotating conductive connecting bearing 3, insulating nut 4, conductive bolt 5, rocker 6, sliding rod 7, sliding rail 8, base 9, insulating bottom plate 10, transmission rod 11, rotary motor 12, cylindrical roller 13, locking and limiting device 14. DETAILED DESCRIPTION

[0027] Example 1:

[0028] For example Figure 1 And 2As shown in the middle, a saturated water-bearing rock resistivity measuring device, including the base 9, both sides of the base 9 are provided with a conductive metal 1, the base 9 is provided with a slide rail 8 on one side, the slide rail 8 is in sliding contact with the conductive metal 1 on this side, the conductive metal 1 on the side of the slide rail is provided with a slide rod 7 along one side of the slide rail, the slide rod 7 penetrates the locking limiting device 14 at the end of the base 9 and is in sliding connection with it, the conductive metal 1 on the other side is fixedly connected with the base 9, the conductive metal 1 on both sides is provided with a rock contact plate 2 for contacting and clamping the saturated water-bearing rock to be measured, the rock contact plate 2 is rotatably connected with the conductive metal 1 and is in conductive contact with each other, the rock contact plate 2 can be controlled to rotate, and the conductive metal 1 is provided with a conductive bolt 5 for connecting a wire.

[0029] The rotating connection structure of the rock contact plate 2 and the conductive metal 1 is that a rotating conductive connection bearing 3 is arranged between the rock contact plate 2 and the conductive metal 1, and the rock contact plate 2 penetrates the rotating conductive connection bearing 3 and is in contact with the cylindrical roller 13 at the center of the rotating conductive connection bearing 3.

[0030] The rock contact plate 2 is used for clamping the saturated water-bearing rock to be measured on one side of the surface of the conductive metal 1.

[0031] The controlled rotating structure of the conductive metal 1 on one side of the slide rail 8 is that a fixedly connected rocker 6 is arranged on the non-clamping side of the conductive metal 1.

[0032] The controlled rotating structure of the conductive metal 1 fixedly connected with the base 9 is that a transmission rod 11 is arranged on the non-clamping side of the conductive metal 1, and the transmission rod 11 is connected with a rotating motor 12.

[0033] The bottom of the two conductive metals 1 is provided with an insulating bottom plate 10, and the insulating bottom plate 10 is used for insulating the base 9, and the insulating bottom plate 10 of the conductive metal 1 on one side of the slide rail 8 is in sliding contact with the slide rail 8.

[0034] The conductive bolt 5 is provided with an insulating nut 4.

[0035] Embodiment 2:

[0036] The utility model adopts two-stage method as resistivity measuring method, through measuring cylindrical rock sample both ends voltage and current, get rock resistance, through formula resistance = resistivity x length ÷ surface area, conversion get resistivity.

[0037] Saturated water causes the pore water pressure in the rock to be greater than the water absorption of the rock, and the water infiltration causes uneven distribution of water, which reduces the accuracy of the resistivity measurement in the rock measurement process. In view of this problem, the method proposed in this patent is to rotate the rock sample, which ensures that the water does not fly out under the action of centrifugal force, so that the water is evenly distributed.

[0038] For the secondary method measurement process due to excessive contact resistance leads to the problem of insufficient measurement accuracy, the utility provides graphite conductive adhesive as the electrode and rock surface contact material, using the characteristics of good contact and strong conductivity of conductive adhesive to enhance the electrical connection of the electrode and rock sample, and using the characteristics of rotating elements to make the conductive adhesive more evenly brushed on the electrode, reducing measurement error.

[0039] The device can rotate the electrode by the principle of bearing rotation, which can uniformly rotate the rock during rock resistivity measurement, overcome the uneven problem of less on the top and more on the bottom due to water infiltration, and improve the measurement accuracy. At the same time, the characteristics of the electrode can be rotated, so that the conductive medium is evenly brushed on the electrode, and the electrode and rock sample are in good contact.

[0040] Rock is a kind of porous medium with less porosity, and its rock permeability coefficient is often low. When it is saturated with water, its permeability can be represented by saturated permeability coefficient. At this time, the rock is rotated, and the water in the rock is subjected to force, as shown in Figure 3 When the gravity and centrifugal force are in the same direction, the maximum force is applied, and when the centrifugal force and pore water pressure act on the water, the water infiltrates. At this time, it is assumed that a microelement Δm in the rock is saturated and infiltrated. At this time, the seepage velocity can be calculated.

[0041] At this time, the water pressure is equal to the pore water pressure, which is equal to the sum of the gravity and centrifugal force, as shown in equation 1:

[0042] ;

[0043] Where, ρ is the density of water, g is the acceleration of gravity, m is the mass of microelement, ω is the angular velocity, and r is the radius of rotation.

[0044] The relationship between the saturated medium permeation velocity and the water head can be expressed by the following Darcy law:

[0045] ;

[0046] Where, k is the permeability coefficient, Δh is the water head difference, and L is the seepage length.

[0047] The linear velocity and angular velocity are as follows: the angular velocity is multiplied by the radius of rotation:

[0048] ;

[0049] Let the microelement be a sphere, and the diameter 2R is regarded as the seepage length, which is:

[0050] ;

[0051] Where, m The mass is pWater density, V Volume.

[0052] With all the above formula, the water infiltration rate is:

[0053] ;

[0054] Take , r =0.025m, , m =1g, the calculated infiltration rate is v =4.45×10 -5 m / s, assuming the radius of rotation is 0.015m (in the middle of the rock), converted into angular velocity =3×10 -3 rad / s, which is much smaller than the rotation speed = rad / s, and considering the maximum centrifugal force at the outside when the infiltration rate, the actual infiltration angular velocity is smaller.

[0055] According to the above calculation structure, the water in the rock can be regarded as non-displacement during rotation, so that the water in the rock is uniformly distributed.

[0056] The saturated water-bearing rock resistivity measuring device of the utility model, the structure is as shown in Figure 1 The specific steps of measurement are:

[0057] 1) Dip the brush with graphite conductive glue on the rock contact plate 2, start the rotating motor 12 to evenly brush the graphite conductive glue on the rock contact plate 2, for the other side without motor plate, use the rocker 6 to manually rotate the plate, realize the uniform brushing of graphite conductive glue;

[0058] 2) Stop the rotating motor 12, put the rock sample between the two rock contact plates 2, use the slide rail 8 to clamp the rock sample, use the slide rod 7 to control the slide rail position, use the locking limiting device 14 to lock;

[0059] 3) Wrap two voltage wires and two current wires on the two pairs of conductive bolts 5 respectively, tighten the insulating nuts 4, connect the power supply, voltmeter, ammeter and other equipment to form a two-pole measurement circuit;

[0060] 4) Start the rotating motor 12, use the transmission rod 11 connected rock contact plate 2 to drive the rock and the opposite rock contact plate 2, at this time the rock realizes uniform rotation;

[0061] 5) Record the voltage and current values, divide the voltage by the current to get the resistance, and use the formula to get the resistivity;

[0062] 6) Repeat 1-5 for other saturated water-bearing rock samples.

Claims

1. A saturated water-bearing rock resistivity measuring device, characterized in that, The base (9) is provided with a conductive metal (1) on each side, a slide rail (8) is arranged on one side of the base (9), the slide rail (8) is in sliding contact with the conductive metal (1) on this side, the conductive metal (1) on the side of the slide rail (8) is provided with a slide rod (7) on one side, the slide rod (7) penetrates through the locking and limiting device (14) at the end of the base (9) and is in sliding connection with the locking and limiting device (14), the conductive metal (1) on the other side is fixedly connected with the base (9), the conductive metals (1) on the two sides are provided with rock contact plates (2) for contacting and clamping the saturated water-bearing rock to be measured, the rock contact plates (2) are in rotating connection with the conductive metals (1) and are in conductive contact with each other, the rock contact plates (2) can be controlled to rotate, and the conductive metals (1) are provided with conductive bolts (5) for connecting wires.

2. A saturated water-bearing rock resistivity measuring device according to claim 1, characterized in that, The rotating and conductive connection structure of the rock contact plate (2) and the conductive metal (1) is that a rotating and conductive connection bearing (3) is arranged between the rock contact plate (2) and the conductive metal (1), and the rock contact plate (2) penetrates through the rotating and conductive connection bearing (3) and is in contact with a cylindrical roller (13) at the center of the rotating and conductive connection bearing (3).

3. A saturated water-bearing rock resistivity measuring device according to claim 2, characterized in that, The rock contact plate (2) is used for clamping the saturated water-bearing rock to be measured on one side of the surface of the protruding conductive metal (1).

4. A saturated water-bearing rock resistivity measuring device according to claim 3, characterized in that, The controlled rotating structure of the conductive metal (1) on one side of the slide rail (8) is that a fixedly connected rocker (6) is arranged on the non-clamping side of the conductive metal (1).

5. A saturated water-bearing rock resistivity measuring device according to claim 4, characterized in that, The controlled rotating structure of the conductive metal (1) fixedly connected with the base (9) is that a transmission rod (11) is arranged on the non-clamping side of the conductive metal (1), and the transmission rod (11) is connected with a rotating motor (12).

6. A saturated water-bearing rock resistivity measuring device according to claim 5, characterized in that, The two conductive metals (1) are provided with insulating bottom plates (10) at the bottom, the insulating bottom plates (10) are used for insulating the base (9), and the insulating bottom plate (10) of the conductive metal (1) on one side of the slide rail (8) is in sliding contact with the slide rail (8).

7. A saturated water-bearing rock resistivity measuring device according to claim 6, characterized in that, The conductive bolt (5) is provided with an insulating nut (4).

8. A saturated water-bearing rock resistivity measuring device according to claim 7, characterized in that, The locking and limiting device (14) limits the sliding position of the conductive metal (1) by using the boss on the slide rod (7).

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