Transcript 161130_CERN_investigations + SITUATIONx

geophysics
engineering
monitoring
CERN
Geneve
30/11/2016
our philosophy…
 constant theoretical study of applications
 critical analysis of used methodologies
(potential and limits)
 particular attention at the instruments to be
used on the field:
geophysics
non
destructive
testing
on site
testing
monitoring
 quality
 modularity and flexibility
 technological innovation
 engineering of hardware and software
 professional approach and reliability in
problem solving
Buildings
Tunnels
Bridges
HL-LHC project – on site investigations
target and metodologies
INVESTIGATIO
NS
METHODOLOGY
TARGET
Concrete’s strength
High frequency georadar
200/600+ 1.500MHz
Voids on the back of walls
Kind of renforcement (number and diameters of
bars)
STRUCTURAL
GEOTECHNICA
L
Evaluation of possible existing damage
Son.Reb (rebound hammer +
ultrasonic pulse velocity)
Concrete class and Rck distribution (NDT)
Coring + laboratory test
Concrete class (direct test)
Flat jacks
Stress/strain of the lining
Low frequency georadar 25MHz
Layers, fractured zones of the rock around lining
Seismic refraction tomography
Optical televiewer (inside
coring)
Main geotechnical parameters of the rock
layers, fractured zones
Video ispection of rock quality
Survey metodology


Non destructive testing

georadar

seismic refraction tomography

Son.Reb.

optical televiewer
Partially destructive (point survey)

coring

flat jack
First of all…
 Our technicians are able to work in..
 hard conditions
 very confined spaces
 particular situations (i.e. artistic and monumental sites)
 Our “clean” solution: the “White box”
White isolated box
a small (1.5x2.5m)“clean room”
 Protection
 mechanical
 water
 White box structure
 crosslinked aluminum frame anchored to the tunnel walls
 drop cloths (plastic film – water - and geotextile - dust)
 protection to the ground on two layers

fluffy towels

waterproof plastic film
 absorbent material for water on floor (sawdust)
White box
photo gallery
Georadar /1
 completely Non Destructive Test
 the ground-penetrating radar (GPR) uses electromagnetic energy to
obtain information about the subsurface
 the antenna produces a short pulse of high-frequency
electromagnetic energy, which is transmitted into the ground
 penetration depth is roughly inversely proportional to the first power of
the conductivity of the material and decreases with increasing
frequency
 the signal propagates perpendicularly to the surface.
 antenna receives reflections from subsurface boundary
Georadar /2
 Equipment
 DAD Control Unit: data acquisition unit and laptop
 Antenna



1.500 MHz
200-600 MHz
25 MHz
 The required space is that of a technician who walks along the
tunnel walls crawling the antenna (a glass fiber box) on the
same walls
Seismic refraction tomography /1
 completely Non Destructive Test
 the seismic refraction method, uses time travel of seismic
waves that are refracted from discontinuities in the subsurface
 a refraction tomography survey must provide a change from
classical methodology regarding the acquisition geometries.
 it will be defined a geometry such that the individual pixels of
the tomographic matrix are affected by at least a path of
seismic pulse
 for each line are provided a minimum number of 6 external
points and 3 internal once (in case of 48 channels lines)
Seismic refraction tomography /2
 equipment
 Data acquisition: 24/48 channels seismograph
 Receiver: geophones
 Seismic sources: 3/5kg hammer
 the geophones are installed on the walls by means of steel
plates (3x3cm) which are glued to concrete
 energizations are performed on the wall by means of a
hammer from 3kg
 The required space is that of a technician who walks along the
tunnel
Son.Reb.
 each method provides information about different properties
that affect the strength of concrete
 special sample preparation is not required
 tests are carried out quickly
 test methods provide strength estimations with good accuracy
 tests don’t affect the structural performance of the unit under
test
 Two combined non destructive test
 Ultrasonic pulse velocity
 Concrete hammer
Son.Reb.
Ultrasonic pulse velocity/1
INDIRECT TRANSMISSION
RECEIVER
 completely Non Destructive Test
TRANSMITTER
 Ultrasonic Pulse Velocity method
 indirect method: the probes are placed on the same face of the
element under investigation
 the test is performed by applying the transducers on the surface
of the element to be analyzed
 the pulse generator is activated and the Time Of Flight (TOF) is
measured (from trasnmitter to receiver probe)
 velocity is calculated from spacing and TOF
Son.Reb.
Ultrasonic pulse velocity/2
 Equipment
 data acquisition unit D1000 LF
 piezoelectric



transmitter:
unipolar square wave - burst;
emission frequency: 10Hz - 20 KHz;
energy 75-275 V;
 receiver:

wavelength 10KHz - 10MHz -3 db
 coupling material: plastiline
 The required space is that of a technician along the tunnel
walls
Son.Reb.
Concrete test hammer
 completely Non Destructive Test
 The hammer measures the hardness of the surface releasing a
spring loaded firing pin that impacts against the concrete
 The rebound index allows to calculate the compressive
strength through an experimental calibration curve
 Equipment characteristics
 Measurement range: 0-100;
 Resolution: 2.00;
 Accuracy: +/- 2.00
 the required space is that of a
technician along the tunnel walls
Coring /1
 Coring will be executed in accordance with the UNI EN 12504-1.
 The concrete will be cored by a diamond ring (100 mm outer
diameter); water cooled uses a special manual pump
 The sampled microcores will have a diameter of 94 mm; length will
be longer than 2.5 times the diameter
 The samples will be subjected to laboratory tests, which will issue
certificates with values of Rck
Coring /2
 Coring testing is a partial destructive test
 Coring will be performed by electric equipment. During the coring
operations water is used for cooling
 The workplace is strongly protected (white box)
 All sampling points (100mm diameter hole in tunnel walls) will be
restored by controlled shrinkage mortar, fiber-reinforced, rapid setting
and hardening
 The required space is about 1.50m from the tunnel walls.
 Equipment main features (Hilti core drill DD-350 model):
 rated power: 3600 W;
 no-load speed: 780-2600 rev / min
 weight of the system (complete with frame): 14.4 Kg
 drill rail
 manual water pump: capacity 10 l
Flat jack /1
 flat jack test is used to determine the axial stress level
(perpendicular to the plane of the cut) on the surface portion
of a concrete wall
 Procedure
 The trial involves the execution of a slotted floor, by a diamond
core saw, perpendicular to the wall
 the resulting partial closure of the cut is detected by convergence
measurements between pairs of points placed in a symmetrical
position with respect to the cut itself
 a flat jack (dimensions 350x260x3.5mm) is inserted into the slot
 the internal pressure of the jack is increased to bring the
measurement bases to the same measured distance before the
cut
 in these conditions the pressure inside the jack is equal to the pre-
existing stress in the structure investigated
Flat jack /2
 Flat jack testing is a partial destructive test
 The workplace is adequately protected (white box)
 the cutting operations on walls will produce a temporary 35x0.5cm
horizontal cut in concrete.
 all sampling points will be restored by controlled shrinkage mortar,
fiber-reinforced, rapid setting and hardening
 the required space is about 1.50m from the tunnel walls
 equipment
 circular saw with diamond blade
 flat jack
 the thickness of the jack (cut) will be between 4 mm
 the shape will be semicircular (with dimensions of 350 x 260 mm);
 hydraulic pump for pressurizing the jack (Hand Pump Glotzl)
 invar measurement bases
 digital deformometer (model DGEI250 - Mitutoyo), with an accuracy of
0.01mm
Summing up…
 Structural investigations
 Georadar
 Son.reb.
 Coring
 Flat jack
 Geotechnical investigations
 Seismic refraction tomography
 Georadar
 All tests will be performed in confined spaces
 Partially destructive test is expected
 the complete restoration of structures
 the use of a small protection room (white room) for water (small
and limited splashes) and material recovery
 the test operations can be performed in confined spaces
without affecting the surrounding environment
“Measure what is measurable,
and make measurable what is not "
Galileo Galilei
thanks for your attention …
Gianluca Ascari
[email protected]
mob. +39 335 5626227
geophysics
engineering
monitoring