seismic cross-hole survey

SEISMIC CROSS-HOLE SURVEY
SOLGEO WAS FOUNDED IN 2001 AS A SPIN-OFF COMPANY FROM ISMES SPA
(ENEL GROUP, LEADER IN THE ITALIAN AND INTERNATIONAL ENERGY MARKET)
INHERING ITS GEOPHYSICAL EXPERIENCE.
SOLGEO CAN RELIES ON A TEAM OF TECHNICIANS (MADE BY ELECTRONICS
ENGINEERS, GEOPHYSICISTS, COMPUTER SCIENTISTS AND OTHER EXPERTS) WITH
MORE THAN 25 YEARS’ EXPERIENCE IN THE PLANNING AND EXECUTION OF
GEOPHYSICAL SURVEYS PANORAMA.
SOLGEO CARRIES OUT DEVELOPMENT OF DEVICES FOR DYNAMIC MONITORING OF
LAND, BUILDINGS AND PRODUCTION OF INSTRUMENTS FOR GEOPHYSICAL
RESEARCH.
Via Pastrengo 9, 24068 Seriate (BG)
Tel. +39 035 4520075
Web site: www.solgeo.it
E-mail:
info@solgeo.it
- INTRODUCTION SOLGEO performs all activities within their own company's Quality System,
certified by CSQ/IQNET, and all the operations related to cross hole surveys
provide for checks and calibration of equipment and instruments used,
before any investigation.
The geophysical survey called “Cross-Hole” consists in the determination of
horizontally travelling compression (P) and shear (S) seismic waves at test
sites, using two or three boreholes. (ASTM D4428/D4428M-07).
SOLGEO utilizes a set of instruments of its own design and construction
allowing to perform measurements quickly and very reliable.
In order to obtain share waves S and compressional waves P velocity soil
profile two steps of measurement are performed, using in different step an
electrodynamic waves S generator, GEOS-H™, and a three dimensional
receiver, that are clamped to the hole housing with a pneumatic system,
and an energy source SPARKER™ and an hydrophone receiver for the
wave P.
The new P&S receiver configuration developed by Solgeo to perform
cross-hole tests in a fast way (a unique cable for hydrophone and
vertical geophone available) and ensuring highly quality results
SOLGEO | - Introduction -
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Via Pastrengo 9, 24068 Seriate (BG)
Tel. +39 035 4520075
Web site: www.solgeo.it
E-mail:
info@solgeo.it
- COMPRESSIONAL P WAVES To generate P waves an automatic energy source, SOLGEO SPARKER™
is used; it can work at many different levels of power (from 100J to 1000J,
normally 300J) and it must be used in boreholes filled with water , up to 200
m depth.
Figure 1, 2: Electrodynamics power supply EG&G (from 100 to 1000 J), for P and
S waves generation (sx) and new Solgeo Hydrophone
An hydrophone is used as receiver of P waves in a borehole filled with
water.
Figure 3: P waves transmitter, SPARKER™ (sx) and its frequency signature (dx)
obtained in a sand-lime sequence
SOLGEO | - Compressional P waves -
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Via Pastrengo 9, 24068 Seriate (BG)
Tel. +39 035 4520075
Web site: www.solgeo.it
E-mail:
info@solgeo.it
- SHEAR S WAVES The energy source SOLGEO GEOS-H™ generates automatically polarized
waves and it has the possibility to work in boreholes up to 200 m of depth
also filled of water. The energy source substantially is composed from two
parts; a central section, that contains the pneumatic clamping assembly and
second part that contains the electrodynamics waves generator. The device
allows to generate alternatively upwards and downwards signals in a simple
way, in order to obtain an inversion of the shear waves polarization,. The
shear waves arrival can be determinate in a more reliable and precise way.
Figure 4, 5: Electrodynamics transmitter for S waves GEOS-H™ (sx) Geophone
receiver ATG-14 (dx) and its relating pneumatic clamping system
A three dimensional receiver, SOLGEO ATG-14™ (Amplified Triaxial
Geophone), containing three geophones 14 Hz (one vertical and two
horizontal) , with an electronics preamplifier and the possibility of many step
of gain is used to receive seismic signals. The clamping to the borehole
housing is obtained with a pneumatic device and it is possible to make
surveys in boreholes till to 200 m of depth.
SOLGEO | - Shear S waves -
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Via Pastrengo 9, 24068 Seriate (BG)
Tel. +39 035 4520075
Web site: www.solgeo.it
E-mail:
info@solgeo.it
- ACQUISITION UNIT & SOFTWARE The data are recorded with a digital acquisition system by SOLGEO with
high sample rate and dynamic more than 110 dB, managed from dedicated
software WinCrossHole™. The system allows to complete operations of
“averaging” of signal in order to obtain, when necessary, an improvement of
the ratio signal/noise. This is possible because the trigger system is perfectly
synchronized.
Figure 6, 7: Acquisition unit MiniRec™ and its power supply Battey Box™,
designed and produced by Solgeo.
In fact both S and P SOLGEO waves sources have a triggering system
electronically controlled, this means that the trigger signal is perfectly
constant and delays are always measurable and controllable. For this
reason, the equipment used allows you to perform measurements using only
two boreholes, thus avoiding the costs of a third hole, while maintaining the
reliability of the results in full compliance with ASTM recommendations.
Figure 8, 9: WinCrossHole™ software, by Solgeo, permits to acquire and pick P
wave (sx) and S wave first arrival (dx) acquired during acquisition.
SOLGEO | - Acquisition Unit & Software -
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Via Pastrengo 9, 24068 Seriate (BG)
Tel. +39 035 4520075
Web site: www.solgeo.it
E-mail:
info@solgeo.it
- INCLINOMETER SURVEY In order to obtain the actual S and P waves soil velocity it is necessary to
measure the actual distance between the holes at any measurement depth.
The deviation logs that measures direction and inclination of the holes in the
3D space, are executed employing the probe INCLIS™, designed and
constructed by the SOLGEO, that allow to perform a three-dimensional
survey of the verticality of boreholes, being carried out simultaneously an
inclination relief and one of orientation.
PROBE CHARACTERISTICS
DIAMETER
LENGTH
WEIGHT
max 44 mm
1500 mm;
6.9 kg
RANGE OF MEASUREMENTS
AZIMUTH (LATITUDINE +/-55 GRADI)
INCLINATION
ROTATION
OPERATING TEMPERATURE
MAXIMUM WORK PRESSURE
+/- 0.3 gradi
+/- 0.1 gradi
+/- 0.1 gradi
0-125°C
20 bar
Figure 10, 11 – Inclinometer Probe A15 (sx) and its Acquisition Unit (dx)
The probe contains a triaxial magnetometer (giving the angle of azimuth
relative to the measured earth magnetic field) and a set of three
accelerometers, that are used to measure of the tilt and the spin relatively to
the measured force of gravity,.
For each borehole two series of measurements are performed: one on the
way down and one in the way up, at constant intervals of 3 meters. The
obtained values are then interpolated to intervals of 1.0 m and used to
calculate the distance between generation and receiving points in the
boreholes.
SOLGEO | - Inclinometer Survey -
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Via Pastrengo 9, 24068 Seriate (BG)
Tel. +39 035 4520075
Web site: www.solgeo.it
E-mail:
info@solgeo.it
- SONIC LOG SURVEY To check if the quality of contact between the holes casing and the soil is
good, SOLGEO performs a continuous sonic log into each hole. Signals are
reproduced as sonic variable density diagrams (with conventional name of
“diagraphy”), which represent the sequence of the sonic signals as a
function of time (horizontal axis) and depth (vertical axis).
When the grouting quality between soil and casing is constant, the
diagraphies show uniform characteristics; presence of voids or bad contact
is readily shown by variations of the recorded signal characteristics.
Figure 12: Sonic logging results (sonic diagraphies); on the left chart in blue line,
velocity profile along borehole. In yellow: grouting failure. Sonic probe made by a
transmitter and a receiver separated by 1m acoustic isolating material (dx).
SOLGEO | - Sonic Log Survey -
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Via Pastrengo 9, 24068 Seriate (BG)
Tel. +39 035 4520075
Web site: www.solgeo.it
E-mail:
info@solgeo.it
Figure 13 – Cross Hole intermediate results. Waterfall plot of recorded seismic
traces: signals on the left and P signals on the right.
SOLGEO | - Sonic Log Survey -
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Via Pastrengo 9, 24068 Seriate (BG)
Tel. +39 035 4520075
Web site: www.solgeo.it
E-mail:
info@solgeo.it
Figure 14 – Finale Cross Hole results: velocity profile for S waves (sx) and P waves
(dx). For each velocity its uncertainty is associated.
SOLGEO | - Sonic Log Survey -
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Via Pastrengo 9, 24068 Seriate (BG)
Tel. +39 035 4520075
Web site: www.solgeo.it
E-mail:
info@solgeo.it
MAIN CROSS HOLE SURVEYS CARRIED OUT BY SOLGEO (yrs 2006-2011)
YEAR
SITE
CLIENT
ABUDHABI – SHOWER TOWER - EAU
2006
Cross-Hole test in n. 1 couples of boreholes (total of 80 m) to determinate the
soil characteristics of the SHOWER TOWER foundation.
CROSS-HOLE VALENCIA – SPAIN
2007
N. 4 cross-hole test in n. 4 locations
BAYNUNAH
LABORATOR
IES
BUZZI
UNICEM
NEW METRO C ROMA - ITALY
2009-2010
Cross-Hole test in n. 23 couples of boreholes (total of 950 m) to evaluate the
soil characteristics along the new metro line tunnels.
METROC
CAMPOTOSTO DAM – ITALY
2010
Cross-Hole test in n. 4 couples of boreholes at the bottom of dam to
determinate the soil characteristics of foundation.
CESI
PROJECT OF THE NEW BRIDGE “STRETTO DI MESSINA” - ITALY
2010-2011
RCT
Cross.Hole test in n. 13 couples of boreholes, at 100m depth
GIOIOSA JONICA – SS106 – ITALY
2010
Cross hole test in n.4 couples of boreholes from 30 to 60 m depth to evaluate
the characteristic of the soil for tunnelling
AR.GI
GARIGLIANO NPP – ITALY
2010
SGI
Cross hole test in a couple of boreholes down to 65 m depth.
TUNGABHADRA DAM – INDIA
2011
n. 8 cross-hole tomography test wave P in velocity and attenuation (about
3200 measures) to determinate the homogeneity of the concrete.
AARVEE
ZELAZNY MOST – POLAND
2011-2012
Signed contract to perform n. 10 cross-hole test (530 m total) by means of the
ASTM optional method (couples of boreholes). To be executed in OctoberNovember 2011.
MERCUS
SOLGEO | - Sonic Log Survey -
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