CA2051533A1

CA2051533A1 - Procedure for monitoring an area of ground

Info

Publication number: CA2051533A1
Application number: CA002051533A
Authority: CA
Inventors: Ernst Geutebruck
Original assignee: Individual
Current assignee: Proterra Gesellschaft fur Umwelttechnik GmbH
Priority date: 1990-09-17
Filing date: 1991-09-17
Publication date: 1992-03-18
Also published as: IL99506A0; EP0477167A3; HUT58925A; JPH05126670A; HU208870B; HU912989D0; NO913645L; EP0477167A2; CS284091A3; NO913645D0

Abstract

ABSTRACT

A process and a system for monitoring an area, in which the potential is measured at several measurement points within the area by means of detectors and then converted into electrical signals, the signals being interrogated at specific time intervals by a central processing unit, processed in this, and then displayed and/or recorded; the measurement points are arranged at predetermined intervals along at least one line, preferably a continuous line, that is adjacent to the area, and at least some of the measurement points are arranged beneath the area and the potential differentials between each two adjacent measurement points are measured. Each detector has an interrogation stage and a data storage device that is controlled by a microprocessor.

(Figure 1)

Description

2 ~ 3 The present invention xelates to a procedure for monitoring an area of ground, in which the potential is measured at a plurality of points within the area, converted into digital eleatrical signals, these signals then being interrogated at specific time intervals, preferably periodically, from a central computer unit, processed within this unit, and then either displayed and/or recordad, the measurement points being arranged at specific intervals along at lea~t one line that defines the area and which is preferably continuous~

In addition, the present invention relates to a system for carrying out the process, this system incorporating alectr:ical detectors, eacil of which incorporates a transmitter for measured values and is connected through an analog-digital converter and through a transmission channel to an analysis point, the detectors being arranged at specific intervals along at least one line, which is preferably continuous, and which definesthe area in question; each detector is connPcted to an interrogator stage that is arranged in its vicinity and connected to the measured-value transmitters, the analysis point having a central computer unit and a central interrogator unit that is connected to the interrogator stages through the transmission channel.

A process and a system such as this, used for determining underground storage facilities that are filled with hydrocarbons are known from DE-Al-35 29 466.

Today, one problem is becoming increasingly important and this is connected with the prevention and identification of contamination of the ground and the initiation of appropriate counter-measures.
This problem occurs mainly in the case of depots, tank farms, sewexs, and abandoned sites. On the othar hand, there is also a need to identify the migration of non-contaminated liquids within the ground, for example, in order to establish the integrity of storage dams and the like.

It is the task of the present invention to solve this problem, or to satisfy this need, and to create a process as well as a systsm for monitoring the ground at such places and in such areas.

On the one hand, this task has been solved by means of a process of the type described in the introduction hereto, in that, according to the present invention, at least some of the measurement points are arranged beneath the area, and in that the potential differentlal between any two adjacent measurement points i5 measured.

On the other hand, this task has been solved by a system of the type described in the introduction hereto such that, according to the present invention, at least some of the detectors are arranged beneath the area and such that each detector, which is preferably connected to the interrogation stage through a filter, incorporates a data storage device, the analog-digital converter and the data-storage device being controlled by means of a microprocessor.

In this way, the present invention creates a process and a system with which the specified area, e.g., a depot, a sewer network, a storage dam, or the like, can be monitored constantly in order to permit the identi~ication of any liquids that escape and to permit the initiation of counter-measures. Thus, in the shortest possible time, details concerning the integrity of a depot or of a sewer network can be prepared and the necessary measures initiated. The clear subordination of the measured values to the measurement polnts can be ensured by way o~ interrogation ~rom the centxal computer unit. Thus, the present invention can be used both in existing dumps, sewer networks, storage dams, and the like~ as a retrofitted system, or can also be built in to dumps, sewer networks, storage dams, and the likP that are to be established.

In the search for ore and crude-oil deposits, both geophysical trial procedures, so-called geoelectrical processes, are known;
using these, an understanding of the underground structure can be derived from the measured distribution of electric currents flowing in the ground. These geoelectrical processes can be divided into electro magnetic and potential processes, and these once again can be subdivided into processes using artificial and natural current feeds.

In all of these proce~ses, as a rule, measurements are made between a fixed base detector and a so-callecl mobile detector.
In addition, it is also known that some detectors can be arranged along a line that is essentially rectilinear~ with each being connected by a cable to the base detector. The measured values picked up by the detectors are passed in analog form to an analysis point where they are processed and analysed.

Disadvantageous in this regard are the facts that only very few measured values can be picked up, and dthat the transmission of the measured values in analog form is vulnerable to noise and cross-talk, which can lead to falsifi~d results. In addition, in the event that a plurality of detectors is each connected by its own dedicated cable to the analy~is point, the cabling costs can be considexable.

The conduct of measurements at relatively few measurement points or detector locations is not particularly important during the devslopment of ore or crude-oil deposits, for the deposits are relatively large and are of a composition that is essentially homogenous.

2 ~3 ~ 3 The present invention is also useful for the processes and systems used in the mining sector but which, in their existing form, are neither suitable nor useable for identifying leaking dumps or sewers, for very often, the toxic substances that leak from a drum in liquid form, for example, contaminate only a very small area of the underground structure.

In an adva~tageous deveIopment of the present process, at least some o~ the measurement points can be arranged beneath the groundwater table.

More advantageously, the electrical signals are stored at tha measurement points.

~f, in this process, at least one reference measurement point is used, it is an advantage if every referPnce measurement point is arranged on the far 8ide of the line with reference to the area.

When this is done, the reference measurement points can be arranged in the groundwater in-flow area and, if necessary, in the groundwater out-flow area.

In order to reduce errors or interference, the measurement points and the reference measurement points can be exchanged with respect to locationt each of the two measured potentials that are a~sociated to each other can be subtracted one from the other, and then the differences subjected to further procsssing.

In order to enhanae the reliability of the monitoring, it is preferred that the measured values be stored and then compared to previous measured values at the predet~rmined time intervals.

In addition, an alarm can be triggered in the event that the measured or the comparative results exceed a predetermined limiting value.

When this is done, the alarm signal can also be. used as a control signal for an automatic control system, such as is used, for example, for a pump.

It is a ~urther advantage if the interrogation o~ the alectrical signals at the central computer unit is effected by radio.

In order to achieve clear monitoring, provision can be made such that graduated ~cales of magnitude ca~ be assigned to the electrical signals, these scales of magnitude, together with the remaining signals being displayed and/or recorded.

In an advantageous development o~ the system, at least some of the detectors can be arranged beneath the ground-water table.

~ 2 ~

More expediently, the transmission channel can be in the for~ of a radio link.

In a system with at least one reference detector, it i~
advantageous if the reference detector is arranged on the far side of the line with reference to the area.

In this connection, each reference detector can be arranged either in the ground-water out-flow area or in the ground-water in-flow area.

It is also an advantage i~ the detectors incorporate a built-in source of electrical energy.

It is also favourable if a control apparatus, e.g., for a pump, i5 connected to the central processing unit.

The present invention will be described in greater detail below on the basis of a preferred embodiment of the system that i5 shown diagramatically in the drawings appended hereto; these drawings show the following:

igure 1: a cross section through a dump with a system according to the present invention;
Figure 2: a block schematic diagram of the system;
Figure 3: a block circuit diagram for a detector.

~ 0 3 ~ ~ ~, 3 Figure 1 shows a cross section thro~gh a dump in which there are detectors 3 spaced at speci~ic equal intervals along a straight line adjacent to the dump, beneath, for example, a three-layer sealing bed 2 that is applied to the ~round; these detectors 3 are connected to a central processinq unit CPU, a modem, and a monitor by way of a transmission channel 4.

The waste material 7 that is stored on the sealing bed 2 which is covered with a plastic foil 5, a non-woven textile layer 6 and a drainage bed 6 is covered over in th~ usual way wlth a levelling layer 8 on which thare is a sealing bed 9, on which lies the drainage bed 10 with its imbedded drainage pipes 11 lies, and which is finally covered with a layPr of humus 12 or the like.

Because of the ~act that the integrity of the plastic foil 5 can be destroyed in time, mostly because of the effects of aggressive substances in the waste material 7, it is highly desirable to be able to monitor the ground 1 that is located beneath the waste dump. This is done with the help of the detectors 3 whichl as can be seen in figure 2, are arranged not only beneath the waste material D, but also in the ground-water in-flow area Z and in the ground-water out-flow area A, the direction of flow of which is indicated by the arrow.

Figure 3 shows the configuration of one of the detectors 3 or a combination of such detactor with a special circuit arrangement B. The circuit arrangement B incorporates an analog-digital converter 14 that is connected through an amplifier and filter 15 to the measured value transmitter of the detector and is controlled by means of a microprocessor 16. The output ~rom the analog-digital converter 14 is connected to an interrogator stage 17, 18 that is controlled from an interxogator point of the central processing unit, and which controls the microproce.ssor 16. In addition, the circuit B incorporates a data-storage device 19 in the form of a buffer to which the digital data issued from the analog-digital converter 14 i5 transmitted through the transmittar 17 of the interrogator stage 17, 18 anA
which is connected to the recsiver 18 ~f the interrogator stage 17, 18.

It ls more advantageous if the circuit B be provided with a built-in dedicated source of electrical energy 20.

The detectors 3 are connected to each other in such a manner that their receivers 18 are connacted to the transmit line of the transmission channel 4, their transmitters 17 each being connected to the transmitters 17 of the adjacent detector 3 that is closer to the central processing unit CPU with the receiver line of the central processing unit CPV.

2~5~5~

The measured values that are picked up by the measured value transmitters of the detectors 3, such as ground current or ground potential, are thus amplified and filtered and converted to digital data within the analog-digital converter 14; this data is then stored in the data-storage device 19 and at predetermined times is interrogated from the interrogation point of the CPU.
Within the CPU, the data are preferably stored on diskettes, subjected to further processing and then displayed and/or recorded. To this end, a peripheral apparatus 23 is connected to the CPU, and this can be either a printer or a display. In particular, predetermined scales of magnitude are assigned to the data so that the display can be made clearer, put up in colour, and can indicate when a specific threshhold value is either exceeded or not reached, and can also be shown in three dimensions.

In addition, at least one reference detector Sref is arranged outside the waste-dump area, and a modem MODEM as well as a radio transmitter RADIO for remote monitoring (figure 2) are connected to the CPU. In addition, a control apparatus for a pump (not shown herein~ or anothar auxilliary apparatus can be connected to the central processing unit, if necessary through the modem, this then being controlled with the help of control signals issued from the central processing unit.

In the first place, the present invention is intended to detect anomalies in the electrical parameters within the ground that are caused by toxic substances, to identify their exact location as well as the locations of the "flags" that always occur, which is to say the long and narrow zones of contamination and leakage from the waste dump which could bP caused, perhaps, by cracks in the plastic foil 5.

But even underground sewers that hava begun to leak can be identified immediately with the help of the present invention.
The locations of leaks are displayed on the monitor or on a plotter printout as areas with elevated values of the electrical parameters, in contrast to which, for example, diver~ing or crossing sewers appear simply as narrowly defined points or lines. If the image is two-dimensional, the leak locations will be almost trapezoidal, although the sewers will appear as zig-zags.

Additional areas of application for the present invention are to be found in storage dams, tank farms, refineries, and underground water and crude oil pipelines.

The present invention offers the advantages that the area beneath a waste dump can be constantly monitored, with external and disruptive influences being precluded, for all practical purposes. When an area is being monitored, because of the 2 ~ 3 measurements, the location of any damage can be roughly localized a~ter which additional detectors can be installed at shorter intervals in the ground adjacent to the dump in order to permit more accurate localization. The structure of the system makes it possible to use lighter and shorter cables, also permits precise association of the detectors to their locations and their measured values, and permits the repeated interrogation o~ these measured values and their comparison with previous measurements, when the constant presence o~ operating personnel is made unnecessary. On the other hand, remote monitoring is al50 possible, be it by way of cable or radio, and an alarm can be triggered and counter-measures can be initiated automatically.

Claims

1. A process for monitoring an area of ground, in which the potential is measured at several measurement points within the area and converted into digital-electrical signals, these signals being interrogated at predetermined time intervals, preferably periodically, from a central processing unit, processed within this, and then displayed and/or recorded, said measurement points being arranged at predetermined intervals along at least one preferably continuous line that is adjacent to the area, characterized in that at least some of the measurement points are arranged beneath the area; and in that the potential differentials between each two adjacent measurement points is measured.

2. A process as defined in claim 1, characterized in that at least some of the measurement points are arranged beneath the ground-water table.

3. A process as defined in claim 1 or claim 2, characterized in that the electrical signals are stored at the measurement points.

4. A process as defined in claims 1 to 3, in which at least one reference measurement point is used, characterized in that each reference measurement point is arranged on the far side of the line with reference to the area.

5. A process as defined in claim 4, characterized in that the reference measurement points are arranged in the ground-water in-flow area and, if necessary, in the ground-water out-flow area.

6. A process as defined in claim 4 or claim 5, characterized in that the locations of the reference points and the reference measurement points can be exchanged, in each instance the two measured potentials that are associated with each other being subtracted one from the other, and these differences then being subjected to further processing.

7. A process as defined in claims 1 to 6, characterized in that the measured values are stored and then compared with the preceding measured values at predetermined intervals of time.

8. A process as defined in claims 1 to 7, characterized in that an alarm signal is triggered if the measured or comparative values fail to reach or exceed a predetermined threshold value.

9. A process as defined in claim 8, characterized in that the alarm signal is used as a control signal for automatic control, e.g., for an automatic control system for a pump.

10. A process as defined in claims 1 to 9, characterized in that the interrogation of the electrical signals to the central processing unit is effected by radio.

11. A process as defined in claims 1 to 10, characterized in that the graduated scales of magnitude are assigned to the electrical signals; and in that these scales of magnitude, are displayed and/or recorded together with the remaining signals.

12. A system for carrying out the process as defined in claims 1 to 11, with electrical detectors, which each incorporate a measured value transmitter, and which are connected to the analysis point by way of an analog-digital converter and a transmission channel, the detectors being arranged at predetermined intervals along at least one line, preferably a continuous line, that is adjacent to the area, each detector being connected with an interrogator stage that is arranged in its vicinity and connected to the measured value transmitter, the analysis point incorporating a central processing unit and a central interrogation point that is connected to the interrogation stages by way of a transmission channel, characterized in that at least some of the detectors (3) are arranged beneath the area; and in that each detector (3) that is preferably connected through a filter to the interrogation stage (17, 18) incorporates a data storage device (19), the analog-digital converter (14) and the data storage device (19) being controlled by a microprocessor (16).

13. A system as defined in claim 12, characterized in that at least some of the detectors (3) are arranged below the ground-water table.

14. A system as defined in claim 12 or claim 13, characterized in that the transmission channel is in the form of a radio link.

15. A system as defined in claims 12 to 14, with at least one reference detector, characterized in that the reference detector (Sref) is arranged on the far side of the line with reference to the area.

16. A system as defined in claim 15, characterized in that each reference detector is arranged in the ground-water in-flow area or the ground-water out-flow area.

17. A system as defined in claims 12 to 16, characterized in that the detectors (3) are fitted with a built-in source of electrical energy (20).

18. A system as defined in claims 12 to 17, characterized in that a control apparatus, e.g., for a pump, is connected to the central processing unit.