Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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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.
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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.
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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.
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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.
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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.
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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.
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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
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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.
