CN110865244B

CN110865244B - Single-hole monitoring system and method for fracture diffusion electric field intensity of intersection part of broken belt

Info

Publication number: CN110865244B
Application number: CN201910970098.6A
Authority: CN
Inventors: 陈国能; 曾强
Original assignee: Guangdong Zhongda Institute Of Geosciences Co ltd
Current assignee: Guangdong Zhongda Institute Of Geosciences Co ltd
Priority date: 2019-10-12
Filing date: 2019-10-12
Publication date: 2022-01-11
Anticipated expiration: 2039-10-12
Also published as: CN110865244A

Abstract

The invention relates to a single-hole monitoring system and a single-hole monitoring method for the electric field intensity of fracture diffusion at the intersection part of a fracture zone. The monitoring system comprises a reference electrode, a plurality of superficial electrodes, a monitoring instrument and a computing device, wherein the reference electrode and at least two superficial electrodes form at least one group of monitoring channels; the reference electrode is arranged in a fracture zone below the surface of the bedrock, the at least two superficial electrodes in a group of monitoring channels are jointly arranged in a superficial soil layer in a certain fracture disc, and the monitoring instrument detects the electro-physical quantity difference between the reference electrode and the electro-physical quantity detected by each superficial electrode and sends the difference to the computing equipment; and the computing equipment performs interpolation of the equal difference points of the electro-physical quantities on each group of monitoring measuring channels, and outlines equipotential lines of the fracture diffusion electric field in the superficial soil layer according to the equal difference points of the electro-physical quantities. The single-hole monitoring system for the strength of the fracture diffusion electric field at the fracture zone intersection part can accurately monitor the strength change of the fracture diffusion electric field at the fracture zone intersection part.

Description

Single-hole monitoring system and method for fracture diffusion electric field intensity of intersection part of broken belt

Technical Field

The invention relates to the field of ground electric field detection, in particular to a single-hole monitoring system and method for the electric field intensity of fracture diffusion at the intersection part of a broken zone.

Background

The fracture electric field refers to an electric field distributed in and near a fracture zone, and as shown in fig. 1, a prerequisite for the formation of the fracture electric field is the existence of compressive stress, and the compressive stress is the interaction force of two fractured disk blocks, which can be clarified from the origin of an earthquake. The stress concentration is used for explaining the pressure source in the piezoelectric effect forming the fracture electric field, and then the piezoelectric minerals which are orderly arranged are needed. The fact that the depth of the continental earthquake source is more than 5-25km in the so-called continental earthquake layer shows that the stress concentration point on the fracture surface mainly appears in the deep part of the crust 5-25km below the surface, and the depth is the distribution range of the granite layer. Therefore, when the fracture is cut to the depth range, orderly arranged quartz minerals are necessarily present, and the piezoelectric effect is naturally generated when stress concentration occurs on the two disks of the fracture, namely the source of an electric field in the fracture. According to the principle, the broken piezoelectric part is an obstruction part which is on the section and is used for preventing the two broken discs from moving relatively, and is a potential earthquake-generating source, namely a pregnant earthquake part. The intensity of the fracture electric field is therefore only related to the stress of this obstacle, while the size of the obstacle depends on the roughness of the fracture, independently of the mechanical and kinematic properties of the fracture.

As shown in fig. 2, the piezoelectric effect of the pregnant part can be regarded as a "power source", however, the power source may exist under the earth's surface for several kilometers or even tens of kilometers, and a human must have a "wire" for observing the power source on the earth's surface, and the "wire" is a fracture itself. According to the existing ultra-deep drilling data, the deep part of the land crust still has water, and the water can be used as a current carrier in the fracture of crack development, and the piezoelectric current generated in the deep part of the fracture can reach a shallow area due to the good conductivity of the current carrier, so that a fracture electric field is formed.

The strength of different parts of the fracture electric field is different, and the electric field strength is larger as the fracture electric field is closer to a power supply. Relative to the interior of the fractured zone, the upper and lower discs have a much lower water content than the fractured zone itself due to the failure of the fracture to develop, so that the two discs are substantially insulated. When the piezoelectric current in the fracture zone is conducted to the surface, it will contact with the superficial water to generate "leakage phenomenon". In other words, the pre-earthquake electrical anomaly measured by the above methods is essentially a "leakage electric field" (see fig. 2) formed by the radiation effect of the fracture electric field in the shallow aquifer, and the "leakage electric field" is essentially the extension of the fracture electric field at the surface region. We will refer to this as the shallow earth diffusion electric field of the fracture electric field, hereinafter referred to as the fracture diffusion electric field. The existing natural electric field method cannot accurately detect the strength change of the fracture diffusion electric field.

Disclosure of Invention

Accordingly, an object of the present invention is to provide a single-hole monitoring system and method for monitoring the strength of a fracture propagation electric field at a fracture zone intersection, which can monitor the strength change of the fracture propagation electric field at the fracture zone intersection relatively accurately.

In a first aspect, an embodiment of the present invention provides a single-hole monitoring system for fracture propagation electric field intensity at an intersection of fracture zones, including:

the device comprises a reference electrode, a plurality of superficial electrodes, a monitoring instrument and computing equipment, wherein the reference electrode and at least two different superficial electrodes in each fracture disc at the intersection part of fracture and fracture zones form at least one group of monitoring channels;

the reference electrode is installed in a fracture zone below the bedrock face through a probe borehole;

the at least two superficial electrodes in a group of monitoring measuring channels are jointly installed in a superficial soil layer in a certain fracture disc, the at least two superficial electrodes are not located on a curve consistent with the fracture and fracture carrying direction at the same time, or the magnitude of the electrical physical quantity difference between each superficial electrode and the reference electrode is different but the variation trend is consistent;

the monitoring instrument is respectively connected with the reference electrode and each superficial electrode in each group of measuring channels, detects the electro-physical quantity difference between the reference electrode and the electro-physical quantity detected by each superficial electrode in each group of monitoring measuring channels, and sends the electro-physical quantity difference to the computing equipment;

the computing equipment performs interpolation of equal difference points of the electro-physical quantity on each group of monitoring measuring channels from the intersection position of the broken zone of the earth surface along the arrangement direction of the at least two superficial electrodes in each group of monitoring measuring channels by adopting an interpolation method according to the electro-physical quantity difference, and draws out an equipotential line of a fracture diffusion electric field in a superficial earth layer according to the equal difference points of the electro-physical quantity of each group of monitoring measuring channels;

in the same group of monitoring channels, the vertical projection of each superficial electrode on the ground and the vertical projection of the reference electrode on the ground are positioned on the same straight line;

the computing equipment computes the electrical physical quantity difference between every two adjacent superficial electrodes on the same straight line according to the physical quantity difference between the reference electrode and each superficial electrode in the monitoring channel; calculating a unit distance electro-physical quantity attenuation value between the vertical projections of the two superficial electrodes on the ground according to the electro-physical quantity difference between the two adjacent superficial electrodes and the distance between the vertical projections of the two superficial electrodes on the ground; and performing interpolation of equal difference points of the electro-physical quantities between the vertical projections of the two superficial electrodes on the ground according to the unit distance electro-physical quantity attenuation value;

the computing equipment also interpolates the equal difference point of the electric physical quantity between the intersection position of the broken zone of the ground surface and the nearest superficial electrode on the straight line according to the unit distance electric physical quantity attenuation value between the two superficial electrodes nearest to the intersection position of the broken zone, and interpolates the equal difference point of the electric physical quantity in the direction of the superficial electrode farthest from the intersection position of the broken zone away from the intersection position of the broken zone on the straight line according to the unit distance electric physical quantity attenuation value between the two superficial electrodes farthest from the intersection position of the broken zone.

Furthermore, the number of the monitoring measuring channels on a certain rupture disc is more than 1, and the computing equipment connects the electrical physical quantity equal difference points of different groups of monitoring measuring channels in the rupture disc, so that an equipotential line of a rupture diffusion electric field of a shallow soil layer of the rupture disc is drawn;

alternatively, the first and second electrodes may be,

the number of the monitoring measuring channels on a certain rupture disc is 1, and the computing equipment draws out an equipotential line of a rupture diffusion electric field located in a shallow soil layer of the rupture disc along a rupture breaking taking-away direction consistent with the direction of the rupture breaking taking-away direction adjacent to the rupture disc according to an electro-physical quantity equal difference point of the monitoring measuring channels.

Further, in the same group of monitoring channels, the vertical projection of each superficial electrode on the ground and the vertical projection of the reference electrode on the ground are not located on the same straight line simultaneously;

the computing equipment projects the vertical projections of the superficial electrodes in the monitoring channels on the ground to a straight line along the direction consistent with the direction of fracture and fragmentation; calculating the electro-physical quantity difference between every two adjacent superficial electrodes projected to the same straight line according to the electro-physical quantity difference between the reference electrode and each superficial electrode in the group of monitoring channels; calculating a unit distance electro-physical quantity attenuation value of the two superficial electrodes projected on the straight line according to the electro-physical quantity difference between every two adjacent superficial electrodes and the distance of the two superficial electrodes projected on the straight line, and interpolating an electro-physical quantity equal difference point between the two superficial electrodes projected on the straight line according to the unit distance electro-physical quantity attenuation value;

the computing equipment also performs interpolation of the equal difference point of the electric physical quantity between the intersection position of the broken belt on the ground surface and the nearest superficial electrode on the straight line according to the unit distance electric physical quantity attenuation value between the two superficial electrodes closest to the intersection position of the broken belt after projection, and performs interpolation of the equal difference point of the electric physical quantity on the straight line in the direction of the superficial electrode farthest from the intersection position of the broken belt away from the intersection position of the broken belt according to the unit distance electric physical quantity attenuation value between the two superficial electrodes farthest from the intersection position of the broken belt after projection.

In a second aspect, an embodiment of the present invention provides a single-hole monitoring method for fracture diffusion electric field intensity at an intersection of fracture zones, including the following steps:

acquiring an electro-physical quantity difference between a reference electrode and an electro-physical quantity detected by each superficial electrode in each group of monitoring channels from a monitoring instrument, wherein the reference electrode and at least two different superficial electrodes in each fracture disc at the intersection of fracture and fracture zones form at least one group of monitoring channels; the reference electrode is installed in a fracture zone below the bedrock face through a probe borehole; the at least two superficial electrodes in a group of monitoring measuring channels are jointly installed in a superficial soil layer in a certain fracture disc, the at least two superficial electrodes are not located on a curve consistent with the fracture and fracture carrying direction at the same time, or the magnitude of the electrical physical quantity difference between each superficial electrode and the reference electrode is different but the variation trend is consistent; the monitoring instrument is respectively connected with the reference electrode and each superficial electrode in each group of measuring channels and detects the electro-physical quantity difference between the reference electrode and the electro-physical quantity detected by each superficial electrode in each group of monitoring measuring channels;

performing interpolation of equal difference points of the electrical physical quantity on each group of monitoring measuring channels from the intersection position of the broken zone of the earth surface along the arrangement direction of the at least two superficial electrodes in each group of monitoring measuring channels by adopting an interpolation method according to the electrical physical quantity difference;

drawing an equipotential line of a fracture diffusion electric field in the shallow soil layer according to the electro-physical quantity equipotential points of each group of monitoring and measuring tracks;

in the same group of monitoring channels, the vertical projection of each superficial electrode on the ground and the vertical projection of the reference electrode on the ground are positioned on the same straight line; performing interpolation of equal difference points of the electrical physical quantity on each group of monitoring measuring channels from the intersection position of the broken zone of the earth surface along the arrangement direction of the at least two superficial electrodes in each group of monitoring measuring channels by adopting an interpolation method according to the electrical physical quantity difference, wherein the interpolation method comprises the following steps:

calculating the electrical physical quantity difference between every two adjacent superficial electrodes on the same straight line according to the physical quantity difference between the reference electrode and each superficial electrode in the group of monitoring channels;

calculating a unit distance electro-physical quantity attenuation value between the vertical projections of the two superficial electrodes on the ground according to the electro-physical quantity difference between the two adjacent superficial electrodes and the distance between the vertical projections of the two superficial electrodes on the ground;

and performing interpolation of equal difference points of the electric physical quantity between the vertical projections of the two superficial electrodes on the ground according to the unit distance electric physical quantity attenuation value.

Further, if the number of the monitoring traces in a certain fracture disc is greater than 1, the step of drawing out an equipotential line of a fracture diffusion electric field in a shallow soil layer according to the equal difference points of the electric physical quantities of each group of monitoring traces comprises the following steps:

connecting the equal difference points of the electro-physical quantities of each group of monitoring and measuring channels with each other, thereby outlining an equipotential line of a fracture diffusion electric field positioned in a shallow soil layer;

alternatively, the first and second electrodes may be,

if the number of the monitoring measuring channels on a certain fracture disc is 1, the process of drawing out the equipotential lines of the fracture diffusion electric field in the superficial soil layer according to the equal difference points of the electric physical quantity of each group of monitoring measuring channels comprises the following steps:

according to the electro-physical quantity equal difference points of the monitoring and measuring channels, an equipotential line of a fracture diffusion electric field positioned in a superficial soil layer is drawn along the direction in which fracture breaking and taking adjacent to the fracture plate are consistent.

Further, still include:

according to the unit distance electro-physical quantity attenuation value between two superficial electrodes closest to the intersection part of the broken zone, performing interpolation of the electro-physical quantity equal difference points between the intersection part of the broken zone of the earth surface and the superficial electrode closest to the intersection part on the straight line;

and performing interpolation of equal difference points of the electrical physical quantity on the direction of the superficial electrode farthest from the intersection position of the crushing zone away from the intersection position of the crushing zone on the straight line according to the attenuation value of the electrical physical quantity in the unit distance between the two superficial electrodes farthest from the intersection position of the crushing zone.

Further, in the same group of monitoring channels, the vertical projection of each superficial electrode on the ground and the vertical projection of the reference electrode on the ground are not located on the same straight line simultaneously; performing interpolation of equal difference points of the electrical physical quantity on each group of monitoring measuring channels from the intersection position of the broken zone of the earth surface along the arrangement direction of the at least two superficial electrodes in each group of monitoring measuring channels by adopting an interpolation method according to the electrical physical quantity difference, wherein the interpolation method comprises the following steps:

projecting the vertical projection of the superficial electrodes in the monitoring survey on the ground to a straight line along the direction consistent with the direction of fracture and breakage carrying away, wherein the straight line passes through the vertical projection of one of the superficial electrodes on the ground and the vertical projection of the reference electrode on the ground;

calculating the electro-physical quantity difference between every two adjacent superficial electrodes projected to the same straight line according to the electro-physical quantity difference between the reference electrode and each superficial electrode in the group of monitoring channels;

calculating the unit distance electro-physical quantity attenuation value of the two superficial electrodes projected on the straight line according to the electro-physical quantity difference between every two adjacent superficial electrodes and the distance of the two superficial electrodes projected on the straight line;

and interpolating equal difference points of the electric physical quantity between the projections of the two superficial electrodes on the straight line according to the unit distance electric physical quantity attenuation value.

Further, still include:

according to the unit distance electro-physical quantity attenuation value between two shallow electrodes which are nearest to the intersection part of the broken zone after projection, interpolation of the electro-physical quantity equal difference points is carried out between the intersection part of the broken zone of the ground surface and the shallow electrode which is nearest to the intersection part of the broken zone on the straight line;

and performing interpolation of equal difference points of the electro-physical quantity on the direction of the superficial electrode farthest from the intersection position of the crushing zone away from the intersection position of the crushing zone on the straight line according to the unit distance electro-physical quantity attenuation value between the two superficial electrodes farthest from the intersection position of the crushing zone after projection.

In the embodiment of the application, at least one group of monitoring channels are arranged on each fracture plate at the intersection of the fracture zone, a monitoring instrument detects the electro-physical quantity difference between a reference electrode and a plurality of superficial electrodes in the fracture zone, a computing device draws equipotential lines of a fracture diffusion electric field of a fracture upper plate or a fracture lower plate superficial soil layer by an interpolation method according to the electro-physical quantity difference, the equipotential lines are perpendicular to electric field lines, the density degree of the equipotential lines can reflect the speed of potential change in the electric field, and the denser the equipotential lines are, the electric potential in the electric field is reduced to the next level by a shorter distance, and the smaller the electric field strength is; the more sparse the equipotential lines are, the more the potential in the electric field is reduced to the next level through a longer distance, and the larger the electric field intensity is, so that the intensity change of the fracture diffusion electric field of the shallow soil layer of each fracture disc at the intersection part of the fracture zone can be monitored by monitoring the intensity of the equipotential lines in real time in the application of earthquake monitoring, the monitoring of the intensity of the fracture electric field generated by the piezoelectric effect of the pregnant and earthquake part is indirectly realized, and the accuracy of fracture stability evaluation of the intersection part of the fracture zone is improved.

For a better understanding and practice, the invention is described in detail below with reference to the accompanying drawings.

Drawings

FIGS. 1 and 2 are schematic diagrams illustrating the principle of the formation of the breaking electric field;

FIG. 3 is a schematic diagram of a single hole monitoring system for electric field strength of fracture propagation at the fracture zone intersection of the present invention in an exemplary embodiment;

FIG. 4 is a schematic illustration of the internal connections of a single hole monitoring system of the electric field strength of fracture propagation at the fracture zone intersection of the fracture zone of the present invention shown in one exemplary embodiment;

FIGS. 5A and 5B are schematic views of drill placement locations for monitoring a borehole shown in an exemplary embodiment;

FIG. 6 is a schematic illustration of interpolation of electrical physical quantity isodyne points in a fractured fracture zone shown in an exemplary embodiment;

FIG. 7 is a schematic diagram of a single hole monitoring system for electric field strength of fracture propagation at the fracture zone intersection of the subject invention in an exemplary embodiment;

FIG. 8 is a schematic illustration of interpolation of electrical physical quantity isodyne points in a fractured fracture zone shown in an exemplary embodiment;

FIG. 9 is a flow chart of a single hole monitoring method of fracture propagation electric field strength at fracture zone intersections of the present invention shown in an exemplary embodiment;

FIG. 10 is a schematic diagram of fracture diffusion electric field equipotential lines of a stable electric field region delineated according to the principles of an embodiment of the present application;

fig. 11 is a schematic diagram of fracture diffusion electric field equipotential lines of an unstable electric field region delineated according to the principles of an embodiment of the present application.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some but not all of the relevant aspects of the present invention are shown in the drawings.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

It is to be understood that although the terms first, second, third, etc. may be used herein to describe various information, these information should not be limited to these terms. These terms are only used to distinguish one type of information from another. For example, first information may also be referred to as second information, and similarly, second information may also be referred to as first information, without departing from the scope of the present invention. The word "if" as used herein may be interpreted as "at … …" or "when … …" or "in response to a determination", depending on the context.

The existing natural electric field method is essentially to observe the 'electric leakage phenomenon' which is a fracture diffusion electric field, when the measuring channel of the natural electric field method is obliquely cut or vertically fractured and spread, the electrical abnormity occurs, so that the careless arrangement of the earth electric channel on the earth surface is the root cause of unreliable earth electric observation.

Since the conductivity of the intact rock is very low, much smaller than the fracture zone rich in free water, the conductor of the current in the fracture zone can be considered as free water. From the basic principle of electricity and the model shown in fig. 2, it can be known that the fracture electric field has two main characteristics: firstly, in a fracture zone, the farther a place is away from a piezoelectric point in a space position, the smaller the field intensity is, the smaller the current value is, and the smaller the voltage is; secondly, in the ground surface fracture diffusion electric field, the intensity of the fracture electric field is attenuated from the fracture zone to the two disks, and the attenuation speed of the two disks in the fracture zone is greater than that in the fracture zone.

Based on the principle, when the stress of the pregnant earthquake area is accumulated, the power of the power supply is increased. Therefore, the power of the power supply, namely the stress accumulation condition, can be calculated back by observing the change amplitude (voltage difference or current difference) of the electric field in the fracture zone and on the disk and combining various geological physical quantities to compare the background electric field. However, this method can only do detection, and cannot do true monitoring.

The application provides a single hole monitoring system of broken scattered electric field intensity of position fracture in broken area, can monitor the broken scattered electric field intensity change of each fracture dish in the broken area intersection position.

Fig. 3 and 4 are schematic structural diagrams of a single-hole monitoring system for the electric field intensity of fracture propagation at the intersection of fracture zones in an embodiment of the present application, in which the fracture zone includes fracture zones F1 and F2 that intersect, and the two fracture zones divide the space into 4 parts, corresponding to an upper disc F1 and an upper disc F2, an upper disc F1 and a lower disc F2, a lower disc F1 and an upper disc F2, and a lower disc F1 and a lower disc F2, respectively.

The single-hole monitoring system for the fracture propagation electric field intensity at the fracture zone intersection comprises a reference electrode a, superficial electrodes c1 and c2 arranged on an upper disk of F1 and an upper disk of F2, superficial electrodes d1 and d2 arranged on an upper disk of F1 and a lower disk of F2, superficial electrodes b1 and b2 arranged on a lower disk of F1 and an upper disk of F2, superficial electrodes e1 and e2 arranged on a lower disk of F1 and a lower disk of F2, a monitoring instrument e and a calculating device F, wherein the reference electrode a is used for detecting the electric physical quantity at the fracture zone intersection, and the superficial electrodes b1, b2, c1, c2, d1, d2, e1 and e2 are respectively used for detecting the electric physical quantity in the superficial soil layer in the fracture zone where the fracture zone intersection is located.

In fig. 3 and the following drawings, the connection line between the two monitoring electrodes indicates that the two monitoring electrodes form a group of monitoring channels, and does not mean that the two monitoring electrodes are directly communicated through a wire.

The single-hole monitoring system for the fracture diffusion electric field intensity of the fracture zone at the intersection part in the embodiment is suitable for construction of a single monitoring station. The range of interest for a single monitoring station should be limited to the visual range of the naked eye in open space, such as a school, or a building.

The fracture zone corresponding to the single-hole monitoring system for the fracture diffusion electric field strength at the fracture zone intersection in the embodiment is not only a tensile fracture zone, but also the same for the reverse fracture zone and the slip fracture zone (corresponding to the compressive fracture zone and the torsional fracture zone), because the generation of the fracture electric field is unrelated to the mechanical property and the kinematic property of the fracture and only related to the roughness of the fracture surface (explained in the foregoing theory). The fracture zone is a regional deep fracture for controlling landform, old stratum dislocation can be seen by naked eyes, or small ore control fractures or filling dikes are not considered, because the fractures, fractures or faults can not cause large-scale tectonic earthquakes.

The vertical projection of the reference electrode a on the ground is positioned on the same straight line as the vertical projections of the superficial electrodes b1 and b2 on the ground, and a group of monitoring traces ab1b2 is formed, and the group of monitoring traces specifically comprises a trace ab1 formed by the reference electrode a and the superficial electrode b1 and a trace ab2 formed by the reference electrode a and the superficial electrode b 2; the vertical projection of the reference electrode a on the ground is positioned on the same straight line as the vertical projections of the superficial electrodes b1 and b2 on the ground, and a group of monitoring traces ac1c2 is formed, wherein the group of monitoring traces specifically comprises a trace ac1 formed by the reference electrode a and the superficial electrode c1 and a trace ac2 formed by the reference electrode a and the superficial electrode c 2; the vertical projection of the reference electrode a on the ground and the vertical projections of the superficial electrodes d1 and d2 on the ground are positioned on the same straight line, and form a group of monitoring traces ad1d2, and the group of monitoring traces specifically comprises a trace ad1 formed by the reference electrode a and the superficial electrode d1 and a trace ad2 formed by the reference electrode a and the superficial electrode d 2; the vertical projection of the reference electrode a on the ground is positioned on the same straight line as the vertical projections of the superficial electrodes e1 and e2 on the ground, and a group of monitoring traces ae1e2 is formed, and the group of monitoring traces specifically comprises a trace ae1 formed by the reference electrode a and the superficial electrode e1 and a trace ae2 formed by the reference electrode a and the superficial electrode e 2.

In other examples, the monitoring traces in each fracture disk may also be a plurality of groups, the number of the superficial electrodes in each group of monitoring traces may also be a plurality of more than two, the vertical projection of the superficial electrodes in each group of monitoring traces on the ground may also be different from the vertical projection of the reference electrode on the ground, as long as it is ensured that each superficial electrode is not simultaneously located on a straight line consistent with the fracture zone direction or the value of the electrical physical quantity difference between each superficial electrode and the reference electrode is different, but the variation trend is consistent.

As shown in fig. 3, the reference electrode a is installed in the intersection of fractured and fractured zones below the bedrock surface by a probe borehole. In order to prevent the collapse of the fourth system layer and weathered bed layer and the influence of the change of the shallow water layer on the detection drill hole A, the detection drill hole A is provided with a casing for preventing the collapse and water-resisting in the corresponding hole section of the fourth system layer and weathered bed layer.

In some examples, the sleeve includes a steel layer and a PVC layer, the steel layer being wrapped around the PVC layer. As shown in fig. 5A and 5B, the drill placement position of the monitor drill hole depends on the shape of the fractured zone, and the higher the fracture shape, the closer the opening position is to the fractured zone.

In this embodiment, the shallow electrodes are installed in the shallow soil layer in the corresponding rupture discs, and the shallow electrodes have no installation depth requirement, and in some cases, the electrodes are simply buried in the soil layer, but the electrodes should be prevented from being exposed on the ground surface, and the isolation of artificial electromagnetic radiation is better if possible.

As shown in fig. 5, the monitoring instrument e is respectively connected to the reference electrode and each superficial electrode through a cable, and a voltage or current detection circuit is disposed in the monitoring instrument e, and is configured to detect an electrophysical quantity difference between an electrophysical quantity detected by the reference electrode a in a fracture zone and an electrophysical quantity detected by each superficial electrode in a superficial soil layer in real time, and send the electrophysical quantity difference to the computing device f.

And the computing equipment f interpolates the equal difference points of the electric physical quantity of each group of monitoring measuring channels from the intersection part of the fracture zone on the earth surface along the arrangement direction of the at least two superficial electrodes in each group of monitoring measuring channels by adopting an interpolation method according to the electric physical quantity difference, namely, the equal difference points of the electric physical quantity are interpolated along the directions of the superficial electrodes b1 and b2, the directions of the superficial electrodes c1 and c2, the directions of the superficial electrodes d1 and d2 and the directions of the superficial electrodes e1 and e2 respectively, and an equipotential line of the fracture diffusion electric field in the superficial soil layer is drawn according to the equal difference points of the electric physical quantity of each group of monitoring measuring channels. The dotted lines along the fracture zone in fig. 3 are equipotential lines of the fracture diffusion electric field outlined in the embodiment of the present application.

The computing equipment f can be a computer or a server or special experimental equipment, analysis software is installed in the computer, and interpolation of the electro-physical quantity and drawing of the fracture diffusion electric field equipotential lines of the superficial soil layer can be completed.

The electrophysical quantity equipoise points can be points with the same electrophysical quantity difference between the crossing positions of the broken zones in each group of monitoring measuring channels, if the number of the monitoring measuring channels in a certain broken disc is larger than 1, the computing equipment f connects the electrophysical quantity equipoise points of a plurality of groups of monitoring measuring channels with each other, so that equipotential lines of the broken diffusion electric field in the superficial soil layer can be drawn out, and in the area outside the connection range of the connected electrophysical quantity equipoise points, the equipotential lines of the broken diffusion electric field in the superficial soil layer can be drawn out in a direction consistent with the broken and broken zone adjacent to the broken disc. If the distances of the different equal difference points of the electro-physical quantities are far, when the equal difference points of the electro-physical quantities are connected, the equipotential lines of the fracture diffusion electric field positioned in the shallow soil layer between the two equal difference points of the electro-physical quantities can be additionally drawn along the direction consistent with the fracture breaking taking direction, namely, the computing equipment f connects the equal difference points of the electro-physical quantities of the multiple groups of monitoring and measuring channels with each other along the fracture breaking taking direction adjacent to the fracture plate.

In another example, if the number of monitoring traces of a certain rupture disc is 1, since the rupture diffusion electric field is substantially the extension of the rupture electric field at the earth surface portion, the rupture diffusion electric field strength at the earth surface portion at the same vertical distance as the rupture zone is theoretically the same, and the computing device may draw the equipotential lines of the rupture diffusion electric field at the shallow soil layer in the direction in which the rupture zone adjacent to the rupture disc is aligned according to the electrical physical quantity equipotential points of the monitoring traces.

The equipotential lines are vertical to the electric field lines, the density degree of the equipotential lines can reflect the speed degree of potential change in the electric field, and the denser the equipotential lines are, the potential in the electric field is reduced to the next level by a shorter distance, which indicates that the electric field intensity is smaller; the more sparse the equipotential lines, the more the potential in the electric field decreases over a longer distance to the next level, indicating a greater electric field strength.

The electrical physical quantity in the present application may be a current and/or a voltage, and the following description will be made with reference to the voltage, that is, the electrical physical quantity difference is a voltage difference between the reference electrode and each superficial electrode, and the difference point of the electrical physical quantity is a difference point of the voltage.

In this embodiment, the intersections of the fractured zones form 4 fractured disks, in other examples, different fractured zone intersections may include other numbers of fractured disks, for example, 3 or more, and in order to monitor the fracture propagation electric field of the superficial soil layer of each fractured disk, at least one set of monitoring traces formed together with the reference electrode is also provided in each fractured disk.

As shown in fig. 6, fig. 6 is a schematic diagram of an embodiment of the present application, according to the principle that interpolation is performed on an electro-physical quantity difference between an electro-physical quantity detected by a reference electrode in a fractured fracture zone and an electro-physical quantity detected by each shallow electrode in a shallow soil layer by using an interpolation method, the shallow electrodes b1, b2 and the reference electrode a are projected in a straight line in a vertical direction on the ground, a voltage difference Δ Uab1 and Δ Uab2 between a measured trace ab1 and a measured trace ab2 can be obtained by a monitoring instrument, and a difference between the two values can obtain Δ Uab 1b2, that is, a voltage difference between the shallow electrodes b1 and b2, since distances (l1, l2) between the shallow electrodes b1 and b2 and the vertical projection of the reference electrode a on the ground are known, then the distance between the electrode b1 and the vertical projection of the electrode b2 on the ground is also known and is denoted as l 3; in an ideal situation, if the voltage is varied at regular intervals, the variable can be represented by Δ Ub1b2/l3, and the attenuation variable dU of the voltage difference, which is the attenuation value of the electrical physical quantity at a unit distance, is obtained in millivolts/meter (mV/m). Since Δ Ub1b2 is a vector, all voltage changes in the fracture boundary, i.e. the intersection of the fracture zones of the earth's surface, in the direction (b1b2) can be determined by the product of dU and l from the fracture boundary. Therefore, the interpolation is not a direct potential line of the electric field, but a difference point of the electric physical quantity, that is, a difference point of the voltage.

The interpolation can be interpolation of set voltage difference, namely, the voltage difference between two adjacent interpolation points is the set voltage difference, interpolation is carried out in a sequence that the voltage difference between each interpolation point and the intersection part of the crushing zone is increased, if a plurality of groups of monitoring channels exist, the interpolation points in each group of monitoring channels, which have the same voltage difference with the intersection part of the crushing zone, are connected, and equipotential lines of the fracture diffusion electric field in the superficial soil layer can be drawn.

In other examples, the interpolation may also be set distance interpolation, that is, the set distance between two adjacent interpolation points is the same, and interpolation is performed in an order that the set distance between each interpolation point and the intersection of the fragmentation zone increases, if there are multiple groups of monitoring channels, after interpolation is performed between the intersection of each group of monitoring channels and the fragmentation zone by the set distance, the interpolation points with the same voltage difference are connected to draw the equipotential lines of the fracture diffusion electric field in the shallow soil layer.

In fig. 6, interpolation is possible between the superficial electrodes b1b2 by setting the interpolation distance l, and since the interpolation distance l is controllable, the magnitude of each segment voltage contour depends directly on the measured values of Δ Ub1b2, i.e., Δ Uab1 and Δ Uab 2. dU-573 mV-422 mV)/10 m-15.1 mV/m; and (6) interpolation. Taking the interpolation at intervals of 2m as an example, the voltage difference of the first interpolation point between the superficial electrodes b1 and b2 is 422mV +15.1mV/m × 2m — 452.2 mV.

b1b2, using extrapolation, for example, the voltage difference at the first interpolation point between the intersection of superficial electrode b1 and the fragmentation zone is 422mV-15.1mV/m 2m 391.8 mV; the voltage difference of the superficial electrode b2 far from the first interpolation point of the intersection of the fracture and fragmentation zones is 573mV +15.1mV/m 2m 603.2 mV.

In other examples, there may be other superficial electrodes between the superficial electrode b1 with the smallest voltage difference with the reference electrode a and the superficial electrode b2 with the largest voltage difference with the reference electrode a, so that the computing device calculates the voltage difference between every two adjacent superficial electrodes on the same line according to the voltage difference between the reference electrode and each superficial electrode in the monitoring channel set; calculating a unit distance electro-physical quantity attenuation value between the vertical projections of the two superficial electrodes on the ground according to the voltage difference between the two adjacent superficial electrodes and the distance between the vertical projections of the two superficial electrodes on the ground; and interpolating equal difference points of the electric physical quantity between the vertical projections of the two superficial electrodes on the ground according to the unit distance electric physical quantity attenuation value.

The computing equipment also interpolates voltage equal difference points between the intersection position of the broken zone of the ground surface and the nearest superficial electrode on the straight line according to the unit distance electric physical quantity attenuation value between the two superficial electrodes nearest to the intersection position of the broken zone, and interpolates the voltage equal difference points in the direction of the superficial electrode farthest from the intersection position of the broken zone away from the intersection position of the broken zone on the straight line according to the unit distance electric physical quantity attenuation value between the two superficial electrodes farthest from the intersection position of the broken zone.

In other examples, the attenuation variable dU may also be a function of the distance l, i.e. a non-uniform variation. Then dU can be calculated more accurately by differentiation, which is basically consistent with the concept of acceleration differentiation, except that the latter is the change in velocity over time.

In some application scenarios, it may not be necessary to arrange all the vertical projections of the superficial electrodes in a group of monitoring channels to be on the same straight line with the vertical projection of the reference electrode due to terrain limitation and the like, and in order to solve the problem that the reference electrode and the superficial electrode cannot be arranged in a straight line due to terrain limitation, the present application also proposes another solution, as shown in fig. 7, in another embodiment, the single-hole monitoring system for a fractured diffusion electric field of the present application comprises a reference electrode a and three superficial electrodes b1, b2, b 3. The three superficial electrodes b1, b2 and b3 and the reference electrode a form a group of monitoring channels, the three superficial electrodes b1, b2 and b3 are not located on a straight line consistent with the direction of the fracture and fragmentation belt at the same time, and the magnitude of the electro-physical quantity difference between each superficial electrode and the reference electrode is different.

When the voltage equal difference point in this embodiment is interpolated, as shown in fig. 8, the computing device projects the vertical projections of the superficial electrodes in the group of monitoring channels on the ground in the same direction along the fracture and fracture zone to a straight line, where the straight line passes through the vertical projection of one of the superficial electrodes on the ground and the vertical projection of the reference electrode on the ground; for example, in fig. 8, superficial electrode b1 is projected onto a line on which reference electrode a and superficial electrode b2 lie, forming a virtual electrode b 1', and based on the same principle, the computing device also projects superficial electrode b3 onto a line on which reference electrode a and superficial electrode b2 lie.

The computing equipment computes the electro-physical quantity difference between every two adjacent superficial electrodes projected to the same straight line according to the electro-physical quantity difference between the reference electrode a and each superficial electrode in the monitoring channels; and calculating the unit distance electro-physical quantity attenuation value of the two superficial electrodes projected on the straight line according to the electro-physical quantity difference between every two adjacent superficial electrodes and the distance of the two superficial electrodes projected on the straight line, and interpolating the equal difference point of the electro-physical quantities between the two superficial electrodes projected on the straight line according to the unit distance electro-physical quantity attenuation value.

Based on the same principle as the single-hole monitoring system of fracture propagation electric field strength of the fracture zone intersection in the above embodiment, the present invention further provides a single-hole monitoring method of fracture propagation electric field strength of the fracture zone intersection, as shown in fig. 9, the method is executed by the computing device in the above embodiment, and includes the following steps:

step S101: acquiring an electro-physical quantity difference between the electro-physical quantities detected by the reference electrode and each superficial electrode in each group of monitoring channels from a monitoring instrument;

wherein the reference electrode and at least two different superficial electrodes in each fracture disk at the intersection of the fracture zone form at least one group of monitoring traces; the reference electrode is installed in a fracture zone below the bedrock face through a probe borehole; the at least two superficial electrodes in a group of monitoring measuring channels are jointly installed in a superficial soil layer in a certain fracture disc, the at least two superficial electrodes are not located on a curve consistent with the fracture and fracture carrying direction at the same time, or the magnitude of the electrical physical quantity difference between each superficial electrode and the reference electrode is different but the variation trend is consistent; the monitoring instrument is respectively connected with the reference electrode and each superficial electrode in each group of measuring channels and detects the electro-physical quantity difference between the reference electrode and the electro-physical quantity detected by each superficial electrode in each group of monitoring measuring channels;

step S102: performing interpolation of equal difference points of the electrical physical quantity on each group of monitoring measuring channels from the intersection position of the broken zone of the earth surface along the arrangement direction of the at least two superficial electrodes in each group of monitoring measuring channels by adopting an interpolation method according to the electrical physical quantity difference;

step S103: and drawing an equipotential line of a fracture diffusion electric field in the shallow soil layer according to the electro-physical quantity equipotential points of each group of monitoring and measuring channels.

In an alternative embodiment, if the number of the monitoring traces in a certain fracture disk is greater than 1, the step of drawing an equipotential line of a fracture diffusion electric field in the shallow soil layer according to the equal difference points of the electric physical quantities of each group of monitoring traces includes:

alternatively, the first and second electrodes may be,

In an alternative embodiment, within the same group of monitoring traces, the vertical projection of each superficial electrode on the ground is located on the same straight line as the vertical projection of the reference electrode on the ground; performing interpolation of equal difference points of the electrical physical quantity on each group of monitoring measuring channels from the intersection position of the broken zone of the earth surface along the arrangement direction of the at least two superficial electrodes in each group of monitoring measuring channels by adopting an interpolation method according to the electrical physical quantity difference, wherein the interpolation method comprises the following steps:

In an optional embodiment, further comprising:

In an alternative embodiment, within the same group of monitoring traces, the vertical projection of each superficial electrode on the ground is not located on the same straight line as the vertical projection of the reference electrode on the ground; performing interpolation of equal difference points of the electrical physical quantity on each group of monitoring measuring channels from the intersection position of the broken zone of the earth surface along the arrangement direction of the at least two superficial electrodes in each group of monitoring measuring channels by adopting an interpolation method according to the electrical physical quantity difference, wherein the interpolation method comprises the following steps:

In an optional embodiment, further comprising:

As for the method embodiment, since it is basically similar to the system embodiment described above, the description is simple, and the relevant points can be referred to the partial description of the system embodiment.

In the single-hole monitoring system and the single-hole monitoring method for the electric field intensity of the fracture diffusion at the intersection part of the fracture zone, at least one group of monitoring channels is arranged on each fracture disc at the intersection part of the fracture zone, a monitoring instrument detects the electro-physical quantity difference between a reference electrode and a plurality of superficial electrodes in the fracture zone, a computing device draws out equipotential lines of a fracture diffusion electric field of an upper fracture disc or a lower fracture disc superficial soil layer by adopting an interpolation method according to the electro-physical quantity difference, the equipotential lines are perpendicular to electric field lines, the density degree of the equipotential lines can reflect the speed degree of electric potential change in the electric field, and the denser the equipotential lines are more, so that the electric potential in the electric field is reduced to the next level by a shorter distance, and the electric field intensity is smaller; the more sparse the equipotential lines are, the more the potential in the electric field is reduced to the next level through a longer distance, and the larger the electric field intensity is, so that the intensity change of the fracture diffusion electric field of the shallow soil layer of each fracture disc at the intersection part of the fracture zone can be monitored by monitoring the intensity of the equipotential lines in real time in the application of earthquake monitoring, the monitoring of the intensity of the fracture electric field generated by the piezoelectric effect of the pregnant and earthquake part is indirectly realized, and the accuracy of fracture stability evaluation of the intersection part of the fracture zone is improved.

Fig. 10 and 11 are schematic diagrams of fracture propagation electric field equipotential lines drawn in a monitoring region by a fracture propagation electric field strength monitoring system and method at a fracture zone intersection according to an embodiment of the present application and a fracture propagation electric field strength monitoring system, i.e., a method, in a normal fracture zone. The fracture electric field and the diffusion electric field are different in size between the fractures in the monitored area, depending on the geological background. However, if the fracture electric field or the diffusion electric field of each fracture in the monitored region does not continuously increase the electric indexes (electric field intensity, electric potential intensity, current magnitude, etc.) such as the field intensity for a certain period of time, we can judge that the region is basically stable as far as now. In FIG. 10, the fracture electric field and the fracture propagation electric field are referred to as normal electric fields. As shown in fig. 11, when the monitored value of a certain fracture in a certain area is continuously strengthened in duration and non-human disturbance is confirmed, it can be said that the fracture has activity as far as present and the activity is continuously increased with the time. According to the principle of formation of the fracture electric field and the fracture diffusion electric field, the activity is mainly shown in that when the electrical indexes (electric field intensity, electric potential intensity, current magnitude and the like) for monitoring the fracture diffusion electric field are used, the magnitude of the electrical indexes is increased or the electric field range is increased (the potential line in the electric field in fig. 11 is enlarged or the value is increased continuously). This phenomenon in which the intensity of the breaking electric field increases with time is called an abnormal electric field. Second, the anomalous electric field of a fracture may only occur in one segment of a certain fracture, since the fractures in the region are cut from each other.

According to the principle, the fracture electric field monitoring station comprising a plurality of real-time monitoring electrodes can be arranged at different fracture positions in the intersection region of different fracture and fracture zones. A monitoring network is formed by a large number of monitoring stations, a fracture diffusion electric field of each fracture zone intersection in a monitoring area is obtained, equipotential lines of the fracture diffusion electric field are drawn on a fracture layout in a monitoring system in real time, and therefore the fracture diffusion electric field of the fracture zone intersection in the area is stronger, which is weaker, and the real-time change of the field intensity is known. The activity of the fracture in the zone is thus evaluated and the stability of the crust of the zone is obtained.

Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

It will be understood that the invention is not limited to the precise arrangements described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.

Claims

1. A single-hole monitoring system for the electric field intensity of fracture diffusion at the intersection of fracture zones is characterized by comprising the following components:

2. The single-hole monitoring system for the electric field intensity of fracture propagation at the intersection of fracture zones of claim 1, wherein:

the number of the monitoring measuring channels on a certain rupture disc is more than 1, and the computing equipment connects the equal difference points of the electric physical quantities of different groups of monitoring measuring channels in the rupture disc, so that the equipotential lines of a rupture diffusion electric field positioned in a shallow soil layer of the rupture disc are outlined;

alternatively, the first and second electrodes may be,

3. The single-hole monitoring system for the electric field intensity of fracture propagation at the intersection of fracture zones of claim 1, wherein:

in the same group of monitoring channels, the vertical projection of each superficial electrode on the ground and the vertical projection of the reference electrode on the ground are not on the same straight line simultaneously;

4. A single-hole monitoring method for the electric field intensity of fracture diffusion at the intersection part of a fracture zone is characterized by comprising the following steps:

5. The method for monitoring the electric field intensity of fracture propagation at the intersection of fracture zones as claimed in claim 4, wherein:

if the number of the monitoring measuring channels on a certain fracture disc is larger than 1, the equipotential lines of the fracture diffusion electric field in the superficial soil layer are drawn according to the equal difference points of the electric physical quantity of each group of monitoring measuring channels, and the equipotential lines comprise:

alternatively, the first and second electrodes may be,

6. The method for monitoring the electric field intensity of fracture propagation at the intersection of fracture zones as claimed in claim 4, further comprising:

7. The single-hole monitoring method for the electric field intensity of the fracture propagation at the intersection part of the fracture zone is characterized in that the vertical projection of each superficial electrode on the ground and the vertical projection of the reference electrode on the ground are not located on the same straight line simultaneously in the same monitoring trace; performing interpolation of equal difference points of the electrical physical quantity on each group of monitoring measuring channels from the intersection position of the broken zone of the earth surface along the arrangement direction of the at least two superficial electrodes in each group of monitoring measuring channels by adopting an interpolation method according to the electrical physical quantity difference, wherein the interpolation method comprises the following steps:

8. The method for monitoring the electric field intensity of fracture propagation at the intersection of fracture zones as claimed in claim 7, further comprising: