Project I M P A C T
WP6: Geophysical Monitoring
Vojtech Benes, Zuzana Boukalova,
Michal Tesar, Vojtech Zikmund
GEO Group a.s.
Objectives of WP6

Geophysical monitoring
•
testing the capabilities of geophysical methods for
the description of the condition of the dikes and
detection of the dike defects
•
incorporation of geophysical measurements into
the process of dike inspection and maintenance
•
planned application of geophysical methods in the
monitoring of large scale field tests of breach
formation
(unfortunately, this planned task due to late inclusion of WP6 activities
into IMPACT project has not been executed)
Steps taken in meeting the objectives
during IMPACT project
Deliverables
D6.1  • retrieval of information
D6.2  • testing measurement
D6.3  • optimizing of methodology of
measurement and processing of data
• consultation with end user
dam foot
Jilešovice location
Špluchov location
Velký Bělčický pond location
300
dam crown
3 test sites:
350
dam foot
river
The scope of testing geophysical
measurements performed within
IMPACT project
J1
J2
J3
JK270
250
JK225
200
P2
x (m)
1 : 2,3
JK150
150
JK135
JK125
3 stages of repeated measurements :
100
weir
Milestones
April 2003
 M6.2.1
September 2003  M6.2.2
March 2004
 M6.2.3
50
JK20
0
-50
-20
-10
y (m)
0
10
P1
3m
1 : 2,7
2,5 - 3 m
JK182,5
P3
Material:
sandy clay
Overview of applied geophysical methods:
Geoelectric methods
resistivity profiling (RP)
self potential method (SP)
multielectrode method (MEM)
electromagnetic frequency method (EFM)
Seismic methods
shallow seismic method (SSM)
seismic tomography (ST)
multi-channel analysis
of seismic waves (MASW)
Microgravimetric method
GPR method
Geomagnetic survey,
Gamma-ray spectrometric survey
During the testing measurement,
we focused on the following:

methodology of measurement (measurement spacing,
orientation of profiles, etc.)

methodology of processing (database of the measured
data, statistical evaluation)

weather effects on repeatability and errors of
measurement

effects of water level fluctuation in a dike and
underlying beds
Example of weather effect
corrected area
0
Difference of measured apparent resistivity
2nd - 1st stage
dam extent
0
-10
-15
60
80
100
120
140
160
180
200
220
240
260
280
300
x (m)
gravel in old river bed
2 nd stage
repeated measurement
-5
Difference of measured apparent resistivity
2nd - 1st stage
detailed measurement
0
0
-5
-5
difference of app. resist.
2nd - 1st stage (ohmm)
40
depth (m)
20
depth (m)
0
depth (m)
depth (m)
-5
dam extent
-10
-10
-10
80
-15
80
100
100
120
140
x (m)
-15
80
x (m)
160
120
180
100
120
140
140
x (m)
160
180
During the execution of IMPACT project
there arose 3 basic questions :

What tasks and problems can be dealt with
by geophysical methods in the process of
maintenance and keeping dike safety?

In this respect, what requirements are most
often laid by dike owners/managers?

What is the optimal methodology of
geophysical measurement which would be
able to tackle these typical tasks?
What tasks and problems can be dealt with
by geophysical methods in the process of
maintenance and keeping dike safety?
Geophysical Monitoring
Large-scale, laboratory
and mathematical simulation
P R E - Breach Formation
Dike structure defects
Overtopping
Piping
Actual dike condition
Repeated high water attacks
Slope deformation
Internal erosion
Seepages through or
below the dike
YEAR
MONTH
Time
DAY
HOUR
In this respect, what requirements are
most often laid by dike owners/managers?
……
we have approx. 10 – 100 km of old dikes with no
information available. We need to roughly know what materials
were used during construction, whether some parts were
subjected to repairs, and whether there occur major
construction defects or hidden defects in the dikes ……
pace, simplicity and productivity of measurement, acceptable costs
……
we have approx. a 200 m long questionable part of a dike
where there occur leakages, slope deformations, etc. We need
to know dike defect extent and location ……
resolution of measurement, accuracy
……
in some parts of a dike we need to approximately know
geomechanical properties of dike material, and whether there
occur changes in such properties in time (for example, in the
cases of new repairs where we check the work quality and
gradual consolidation of the used material) ……
geotechnical intepretation of measured data
What is the optimal methodology of
geophysical measurement which would be
able to tackle these typical tasks?
Geophysical Monitoring System = GMS
Geophysical Monitoring
System = GMS
What do we mean by the term monitoring – a long-term
observation of the condition of the dikes by means of repeated
measurements
What is the advantage – we acquire a new type of information, we
are able to differentiate in time the stable and unstable anomalies
What has to be eliminated in the interpretation – weather effects,
instrumentation, etc.
Geophysical Monitoring
System
newly included in inspection and maintenance of the dikes
(together with airborne photographs analyses,
visual inspection, etc.)
Quick testing
measurement
Plan of repairs
Measurement of
geotechnical condition
Diagnostic
measurements
Quick testing measurement:
Basic methods:
electromagnetic frequency method
(with multi-frequency and GPS navigation system)
GPR method
Output:
basic description of the dike structure and material, delimitation of quasihomogeneous
blocks
app. resitivity (???)
Block C
Block B
Block A
300
200
100
0
0
20
40
60
80
100
120
Problematic
segment
140
160
x (m)
180
200
220
240
260
280
300
Diagnostics measurents of problematic
segments
Basic methods:
Outputs:
- detailed identification of problematic segments
- multielectrode resistivity method
- self potential method
- thermovision, thermometry
- microgravimetry
- seismic method
(seepages, slope deformations, etc.)
- analysis of reasons for a defect occurrence
- grounds for the repair project
le
ob
Pr
-2
m
-4
0
5
ic
-5
at
0
se
x (m)
gm
-2
en
-5
-2
-4
0
5
x (m)
0
-8
-2
-6
-4
-2
0
2
4
6
8
x (m)
-4
-8 0
-6
-4
-2
0
2
4
6
8
x (m)
depth (m)
depth (m)
0
depth (m)
-4
t
depth (m)
depth (m)
0
-2
-4
-8
-6
-4
-2
0
x (m)
2
4
6
8
An overview of common dike defects
and geophysical methods appropriate
for the detection of such defects
METHOD
PARAMETERS/
DEFECTS
GPR
Seismic
method
Gravity
measure
ment
Thermo
metry
Magneto
metry
X-ray
measur
ement
In frame
IMPACT
O
O
++
++
-
O
O
Yes
Dike Structure and
Homogeneity
++
++
+
+
-
O
O
Yes
Contact Dike vs.
Subsoil
++
+
++
+
O
O
-
Yes
Seepage
++
+
O
O
+
-
-
Yes
Piping
+
+
O
+
+
-
-
No
Fissuring
+
+
+
O
-
-
-
Yes
Slope Deformation
+
+
+
+
O
-
-
No
Overtopping (*)
-
-
-
-
-
-
-
No
Geoelectric
method
Geomechanical
Parameters
Legend:
++ Most suitable method
O Conditionally appropriate method
+ Appropriate method
- Mostly inappropriate method
(*) Remark: In some cases, geophysical methods allow us to detect reasons for dike surface subsidence at
the point of overtopping.
Contact Dike vs. Subsoil
GPR cross-section
0
depth (m)
-2
-4
-6
-8
110
120
130
140
150
160
x (m)
170
180
190
200
METHOD
PARAMETERS/
DEFECTS
GPR
Seismic
method
Gravity
measure
ment
Thermo
metry
Magneto
metry
X-ray
measur
ement
In frame
IMPACT
O
O
++
++
-
O
O
Yes
Dike Structure and
Homogeneity
++
++
+
+
-
O
O
Yes
Contact Dike vs.
Subsoil
++
+
++
+
O
O
-
Yes
Seepage
++
+
O
O
+
-
-
Yes
Piping
+
+
O
+
+
-
-
No
Fissuring
+
+
+
O
-
-
-
Yes
Slope Deformation
+
+
+
+
O
-
-
No
Overtopping (*)
-
-
-
-
-
-
-
No
Geoelectric
method
Geomechanical
Parameters
Legend:
++
Most suitable method
+
Appropriate method
O
Conditionally appropriate method
Mostly inappropriate method
(*) Remark: In some cases, geophysical methods allow us to detect reasons for dike surface
subsidence at the point of overtopping.
Seepage detection
300
apparatus CM031 - September 2003
apparatus CM031 - December 2003
relative resistivity anomaly (%)
250
apparatus GEM2 - (frequency 16475 Hz)
April 2004
200
150
100
50
anomalous area
0
0
20
40
60
80
x (m)
100
120
140
Seepage detection
Map of resistivity differences
stage 2 minus stage 1
Resistivity cross-section stage 1
0
0
depth (m)
depth (m)
0
-2
load bench
-4
-5
-6
90
95
100
105
110
-10
Resistivity cross-section stage 2
-5
0
40
60
80
100
120
140
x (m)
Map of resistivity differences
stage 3 minus stage 1
!!!
0
depth (m)
depth (m)
x (m)
-2
load bench
-4
-6
90
95
100
105
110
115
x (m)
-10
Resistivity cross-section stage 3
-5
-2
60
!!!
80
100
-10
x (m)
40
60
80
x (m)
100
depth (m)
depth (m)
0
load bench
-4
120
-6
-8
120
140
95
100
105
x (m)
110
115
METHOD
PARAMETERS/
DEFECTS
GPR
Seismic
method
Gravity
measure
ment
Thermo
metry
Magneto
metry
X-ray
measur
ement
In frame
IMPACT
O
O
++
++
-
O
O
Yes
Dike Structure and
Homogeneity
++
++
+
+
-
O
O
Yes
Contact Dike vs.
Subsoil
++
+
++
+
O
O
-
Yes
Seepage
++
+
O
O
+
-
-
Yes
Piping
+
+
O
+
+
-
-
No
Fissuring
+
+
+
O
-
-
-
Yes
Slope Deformation
+
+
+
+
O
-
-
No
Overtopping (*)
-
-
-
-
-
-
-
No
Geoelectric
method
Geomechanical
Parameters
Legend:
++
+
O
-
Most suitable method
Appropriate method
Conditionally appropriate method
Mostly inappropriate method
(*) Remark: In some cases, geophysical methods allow us to detect reasons for dike surface subsidence at the point of overtopping.
Fissuring
Resistivity cross-section on base MEM method
0
-1
depth (m)
-2
-3
-4
-5
-6
90
95
100
105
x (m)
110
115
120
METHOD
PARAMETERS/
DEFECTS
GPR
Seismic
method
Gravity
measure
ment
Thermo
metry
Magneto
metry
X-ray
measur
ement
In frame
IMPACT
O
O
++
++
-
O
O
Yes
Dike Structure and
Homogeneity
++
++
+
+
-
O
O
Yes
Contact Dike vs.
Subsoil
++
+
++
+
O
O
-
Yes
Seepage
++
+
O
O
+
-
-
Yes
Piping
+
+
O
+
+
-
-
No
Fissuring
+
+
+
O
-
-
-
Yes
Slope Deformation
+
+
+
+
O
-
-
No
Overtopping (*)
-
-
-
-
-
-
-
No
Geoelectric
method
Geomechanical
Parameters
Legend:
++
Most suitable method
+
Appropriate method
O
Conditionally appropriate method
Mostly inappropriate method
(*) Remark: In some cases, geophysical methods allow us to detect reasons for dike surface
subsidence at the point of overtopping.
Slope Deformation
Density model on base gravimetric measurement
4
LEGENDE:
 gB res(m/s 2 )
Bouguer`s anomaly
2
Gravity effect
of density model
0
-2
71000 +900
71000 +940
71000 +980
71000 +1020
71000 +1060
71000 +1100
71000 +1140
71000 +1180
x (m)
Difference Density ( kg/m3 )
550
-200
-250
540
up 600
rock
101 to 599
disturbed rock
-200
-200
-85
-200
-200
0 to 100
damm material
-100 to -1
damm material with
lower compaction
altitude (m)
600
530
disturbed damm
0
-200 to -101 material
-500 to -201 strongly disturbed
520
damm material
less -1000
510
500
71900
71920
71940
71960
71980
72000
72020
72040
72060
x (m)
72080
72100
72120
72140
72160
72180
72200
strongly disturbed
damm material with
open cracks
Measurement of geotechnical condition
Change of gravity potential
Basic methods:
detailed seismic measurement
(MASW)
microgravimetry
Bouguer`s anomaly difference
0.15
repaired area
0.1
0.05
out of repaired area
0
-0.05
2003
2003.2
2003.4
2003.6
2003.8
2004
2004.2
2004.4
time (year)
Outputs:
150
density difference (kg/m 3 )
description of geomechanical
properties: bulk density,
modulus of elasticity, porosity,
long-term changes of properties
after the floods
(ageing of earth structures)
Change of bulk density
100
50
0
-50
2003
2003.2
2003.4
2003.6
2003.8
time (year)
2004
2004.2
2004.4
Organization of geophysical measurements
within the framework of GMS
A)
Initial stage
1)
2)
3)
4)
5)
6)
fast starting measurement in a selected part of a
catchment area
analysis of starting measurements and grounds
received from dike owners/managers (results of
visual inspection, airborne photographs)
selection of questionable dike parts for detailed
diagnostic measurement
interpretation of diagnostic measurements –
proposal of repairs and potential fixed monitoring
points for observation of geomechanical properties
preparation of monitoring points in the field
establishment of GMS database for the purpose of
keeping files of all types of measurements
performed within GMS
Organization of geophysical measurements
within the framework of GMS
B)
Check stages
1)
2)
3)
4)
5)
after approx. 3 years or in the case of a flood, repeated
fast testing and monitoring measurement will be
performed
the results will be compared on the basis of relative
changes of the measured parameters (elimination of
weather effects)
in the case of detection of new anomalies or impaired
dike condition, diagnostic measurement for selected dike
parts will be recommended
ditto A4
inclusion of newly acquired data into GMS database
Possibility of implication GMS information to the dike breach
modelling in the catchment
Summary

Definition of the objectives of measurement in
communication with end user. Example: diagnostic
measurement cannot be mistaken for quick testing
measurement – both types of measurement provide us
with different levels and quality of information.

Monitoring (repeated measurement) brings a new type
of information. Example: detection of seepages at a dike
base at high water level

Geophysical Monitoring System (GMS) newly
incorporated in dike inspection and maintenance system
Summary
Geophysical Monitoring System (GMS) newly
incorporated in dike inspection and maintenance system


Qick testing measurement of long dike segments
•
•

Diagnostic measurement
•
•

sufficient capacity of measurement is required
the basic method is EFM, GPR
sufficiently detailed grid of measurement and penetration
depth is required
the basic methods here are geoelectric methods
Measurement of geotechnical condition
•
•
correlation between geotechnical parameters determined by
geophysical methods and in laboratory
the basic methods here are seismic methods and
microgravimetry
Next planned activities

to prepare for a new grant covering establishment of
GMS demonstration database for a selected
catchment area
Thanks for your attention!
benes@gimpuls.cz