SlideShare a Scribd company logo
1 of 13
Download to read offline
87° Congresso della Società Geologica Italiana e
90° Congresso della Società Italiana di Mineralogia e Petrologia
10 - 12 Settembre 2014 - Milano
A new prototype system for MASW2D roadside survey
Mario Naldi, Emmanuele Duò – Techgea Srl (info@techgea.eu)
GROUND INVESTIGATION IN URBAN AREAS: A NEW FIELD FOR THE
NEAR SURFACE GEOPHYSICS
Urban areas represent some of the most challenging environments
for civil works:
•Metro lines
•Underground utilities (sewage, pipe lines, heating system)
•Underground parking
In such a context, the geophysical surveys can play an important
role for the assessment of the geology and soil mechanics
properties
Some “obstacles” should be considered in the
survey design :
1.Restricted space,
2.the necessity for traffic management,
3.high ambient noise (electrical and vibration),
4.underground utilities,
… all THESE issues help to complicate the design
and setting out of the geophysical profiles or
grids.
HOW TO SELECT THE RIGHT
METHODOLOGY
The conventional seismic
surveys (refraction or
reflection) can have many
limitations in urban areas:
•do not work well in noisy
areas
•take long time for data
acquisition (hard traffic
management)
•require high energy source
Among geophysical methods,
the seismic survey is the most
commonly applied
for civil engineering projects.
MASW 2D profiling has many advantages for surveys in urban areas:
•More energetic wavelets (less energy required)
•Short acquisition time with just one shot and fast move of the
geophone layout (no stop of the road traffic)
•Favorable ratio between the length of the seismic line and the soil
depth. MASW2D = 1:1  seismic refraction = 5:1
Seismic surveys in urban
areas
Among geophysical methods,
the seismic survey is the most
commonly applied
for civil engineering projects.
Seismic sources generate a continuous spectrum of surface wave frequencies.
Where there is vertical velocity variation, different frequency waves travel at different
phase velocities. This is dispersion. By examining dispersion curves (phase velocity vs.
frequency), we can determine material properties (e.g., layer thickness, depth, Vs) via Inversion
BASIC THEORY OF MASW
Lower frequency
 deeper strata
DISPERSION
INVERSION
Low density shallow soil
Gravel and sand (not cemented)
Gravel and sand (partially cemented)
Masw2D (Vs - m/s)
Seismic refraction (Vp – m/s)
Low density shallow soil
MASW2D HAS A HIGHER VERTICAL AND LATERAL RESOLUTION COMPARED WITH THE
REFRACTION METHOD
Velocity inversion in the subsurface is one of the most serious limitations of the
shallow seismic refraction method  GEOPHYSICAL IMAGING HAS A POOR
HIDDEN
HIDDEN
How to improve MASW 2D survey efficiency in urban areas?
1.Mobile system  continuous profiling (no traffic interruption)
2.High seismic energy  bypass of the urban noise
Slow motion
(low gear)
STOP: One shot and recording (20 seconds)
GO: Slow move to the next station (2 m)
String of geophones on
a land streamer
Source of energy
(ACCELERATED WEIGHT)
Seismograph on board
(DATA RECORDING)
The streamer is towed at low speed with
stop at every recording station
Winch
(powered by a 100 Ah/12 V
Battery)
Traction springs
Propelled mass
Uncoupling devices
Source of energy
(ACCELERATED
WEIGHT)
Lift
The prototype has
been designed and
produced for
Techgea by TREFFE
Land streamer
Sensors (4.5 hz geophones)
mounted on a metal plate)
String of geophones on a land
streamer
Source of energy
(ACCELERATED WEIGHT)Seismograph on board
(DATA RECORDING)
The streamer is towed at low speed with stop at every recording
station
Distance [m]
Küçükbakkalköy station
projection
COLOUR SCALE
Shear wave velocity [m/s]
Made ground and/or soft soil
[Vs: 0÷200 m/s]
Dense soil and/or overburden
[Vs: 200 – 370 m/s]
Very dense soil/soft
rock
[Vs: 370÷800 m/s]
Rock
[Vs: 800÷1200 m/s]
Hard rock
[Vs > 1200 m/s]
800
m/s
370
m/s
200
m/s
1200
m/s
Remark:
soil classification from ASCE table (7-2005),
(modified)
Fault zone
Solid rock (LIMESTONE)
Fractured rock
Fractured rock
Weathered rock
Top soil
Line M5-13 - Shear Wave section
Weathered rock
Küçükbakkalköy station
EXAMPLE 1 – ISTANBUL METRO LINE BOSTANCI – DUDULLU (TURKEY)
Masw2d SURVEY FOR THE GEOLOGICAL ASSESSMENT AND THE
SEISMIC SOIL CLASSIFICATION
Fault zone
THE MASW2D LINE IS POSITIONED ALONG A ROAD BETWEEN THE PROJECTION OF THE TWIN TUNNELS
OVERNIGHT SURVEY
EXAMPLE 2 – SEWER PIPE SETTLEMENT (MILAN AREA, ITALY)
ROAD SUBSIDENCE AFTER THE PIPELINE POSITIONING
CEMENTED ZONE (GROUTING BELOW THE
DEFORMED ROAD)
DENSE GRAVEL
VERY LOW DENSITY SAND-
GRAVEL/VOIDS
SUBSIDENCE AREA
SUBSIDENCE AREA
SUBSIDENCE AREA
EXAMPLE 3 – SLOPE FAILURES ASSOCIATED WITH ABANDONED
UNDERGROUND QUARRIES (Alessandria, Italy)
ROAD SUBSIDENCE AND DEFORMATION
BA
Siltstone (soft rock)
Highly weathered siltstone
(silt consistency)
Landslide projection (IFFI)
S1
Very low density zone
(collapsed tunnels)
Tunnel
Subsidence area
Subsidence area
87° Congresso della Società Geologica Italiana e
90° Congresso della Società Italiana di Mineralogia e Petrologia
10 - 12 Settembre 2014 - Milano
A new prototype system for MASW2D roadside survey
Mario Naldi, Emmanuele Duò – Techgea Srl
Thank you for the attention

More Related Content

What's hot

Geological mapping using satellite images.
Geological mapping using satellite images.Geological mapping using satellite images.
Geological mapping using satellite images.Diego Bedoya Gonzalez
 
11CCEE_23Jul2015_Final
11CCEE_23Jul2015_Final11CCEE_23Jul2015_Final
11CCEE_23Jul2015_FinalUpul Atukorala
 
20160602 Non-Invasive Geophysical Techniques
20160602 Non-Invasive Geophysical Techniques20160602 Non-Invasive Geophysical Techniques
20160602 Non-Invasive Geophysical TechniquesSam Setchell
 
DYNAMIC RESPONSE OF CONCRETE GRAVITY DAM ON RANDOM SOIL
  DYNAMIC RESPONSE OF CONCRETE GRAVITY DAM ON RANDOM SOIL  DYNAMIC RESPONSE OF CONCRETE GRAVITY DAM ON RANDOM SOIL
DYNAMIC RESPONSE OF CONCRETE GRAVITY DAM ON RANDOM SOILIAEME Publication
 
Evaluation of Structural Geology of Jabal Omar
Evaluation of Structural Geology of Jabal OmarEvaluation of Structural Geology of Jabal Omar
Evaluation of Structural Geology of Jabal OmarIJERD Editor
 
Tunnel Stability Factor Michalis_Konstantis
Tunnel Stability Factor Michalis_KonstantisTunnel Stability Factor Michalis_Konstantis
Tunnel Stability Factor Michalis_KonstantisILIAS MICHALIS
 
Thesis Proposal Simon Fraser University
Thesis Proposal Simon Fraser UniversityThesis Proposal Simon Fraser University
Thesis Proposal Simon Fraser UniversityDanilo Moretti
 
Rock mass classification or rock mass rating of rock materials in civil and m...
Rock mass classification or rock mass rating of rock materials in civil and m...Rock mass classification or rock mass rating of rock materials in civil and m...
Rock mass classification or rock mass rating of rock materials in civil and m...Ulimella Siva Sankar
 
Conference paper subgrade reaction
Conference paper subgrade reactionConference paper subgrade reaction
Conference paper subgrade reactionabdulhakim mawas
 
Vs30 measurements for Seismic Site Classification
Vs30 measurements for Seismic Site ClassificationVs30 measurements for Seismic Site Classification
Vs30 measurements for Seismic Site ClassificationAli Osman Öncel
 
Rock mechanics for engineering geology part 1
Rock mechanics for engineering geology part 1Rock mechanics for engineering geology part 1
Rock mechanics for engineering geology part 1Jyoti Khatiwada
 
Dr. Malek Smadi, Ph.D. thesis lateral deformation and associated settlement r...
Dr. Malek Smadi, Ph.D. thesis lateral deformation and associated settlement r...Dr. Malek Smadi, Ph.D. thesis lateral deformation and associated settlement r...
Dr. Malek Smadi, Ph.D. thesis lateral deformation and associated settlement r...Dr. Malek Smadi
 
Geophysics for Geotechnical Engineers
Geophysics for Geotechnical EngineersGeophysics for Geotechnical Engineers
Geophysics for Geotechnical EngineersRamanuja Chari Kannan
 

What's hot (17)

Geological mapping using satellite images.
Geological mapping using satellite images.Geological mapping using satellite images.
Geological mapping using satellite images.
 
11CCEE_23Jul2015_Final
11CCEE_23Jul2015_Final11CCEE_23Jul2015_Final
11CCEE_23Jul2015_Final
 
20160602 Non-Invasive Geophysical Techniques
20160602 Non-Invasive Geophysical Techniques20160602 Non-Invasive Geophysical Techniques
20160602 Non-Invasive Geophysical Techniques
 
DYNAMIC RESPONSE OF CONCRETE GRAVITY DAM ON RANDOM SOIL
  DYNAMIC RESPONSE OF CONCRETE GRAVITY DAM ON RANDOM SOIL  DYNAMIC RESPONSE OF CONCRETE GRAVITY DAM ON RANDOM SOIL
DYNAMIC RESPONSE OF CONCRETE GRAVITY DAM ON RANDOM SOIL
 
Evaluation of Structural Geology of Jabal Omar
Evaluation of Structural Geology of Jabal OmarEvaluation of Structural Geology of Jabal Omar
Evaluation of Structural Geology of Jabal Omar
 
Tunnel Stability Factor Michalis_Konstantis
Tunnel Stability Factor Michalis_KonstantisTunnel Stability Factor Michalis_Konstantis
Tunnel Stability Factor Michalis_Konstantis
 
Thesis Proposal Simon Fraser University
Thesis Proposal Simon Fraser UniversityThesis Proposal Simon Fraser University
Thesis Proposal Simon Fraser University
 
Brochure_PIEDRA_EN
Brochure_PIEDRA_ENBrochure_PIEDRA_EN
Brochure_PIEDRA_EN
 
Rock mass classification or rock mass rating of rock materials in civil and m...
Rock mass classification or rock mass rating of rock materials in civil and m...Rock mass classification or rock mass rating of rock materials in civil and m...
Rock mass classification or rock mass rating of rock materials in civil and m...
 
Conference paper subgrade reaction
Conference paper subgrade reactionConference paper subgrade reaction
Conference paper subgrade reaction
 
MASW_Love_Waves
MASW_Love_WavesMASW_Love_Waves
MASW_Love_Waves
 
Fundementals of MASW
Fundementals of MASWFundementals of MASW
Fundementals of MASW
 
Vs30 measurements for Seismic Site Classification
Vs30 measurements for Seismic Site ClassificationVs30 measurements for Seismic Site Classification
Vs30 measurements for Seismic Site Classification
 
Rock mechanics for engineering geology part 1
Rock mechanics for engineering geology part 1Rock mechanics for engineering geology part 1
Rock mechanics for engineering geology part 1
 
Dr. Malek Smadi, Ph.D. thesis lateral deformation and associated settlement r...
Dr. Malek Smadi, Ph.D. thesis lateral deformation and associated settlement r...Dr. Malek Smadi, Ph.D. thesis lateral deformation and associated settlement r...
Dr. Malek Smadi, Ph.D. thesis lateral deformation and associated settlement r...
 
slope stability and computers
 slope stability and computers slope stability and computers
slope stability and computers
 
Geophysics for Geotechnical Engineers
Geophysics for Geotechnical EngineersGeophysics for Geotechnical Engineers
Geophysics for Geotechnical Engineers
 

Similar to S24 naldi

Ground Geophysical Survey
Ground Geophysical SurveyGround Geophysical Survey
Ground Geophysical SurveyOmary Issa
 
Jim_Mitchell_Nottingham Centre for Geomechanics_talk.ppt
Jim_Mitchell_Nottingham Centre for Geomechanics_talk.pptJim_Mitchell_Nottingham Centre for Geomechanics_talk.ppt
Jim_Mitchell_Nottingham Centre for Geomechanics_talk.pptFiratPulat
 
Kent Odaklı Mikrobölgeleme: Sivas Örneği
Kent Odaklı Mikrobölgeleme: Sivas ÖrneğiKent Odaklı Mikrobölgeleme: Sivas Örneği
Kent Odaklı Mikrobölgeleme: Sivas ÖrneğiAli Osman Öncel
 
Earthquake Strong Motions.ppt
Earthquake Strong Motions.pptEarthquake Strong Motions.ppt
Earthquake Strong Motions.pptPreethiRVR
 
Geophysical survey for the risk management
Geophysical survey for the risk managementGeophysical survey for the risk management
Geophysical survey for the risk managementMario Naldi
 
FR01_01_GlezetalIGARSS2011.ppt
FR01_01_GlezetalIGARSS2011.pptFR01_01_GlezetalIGARSS2011.ppt
FR01_01_GlezetalIGARSS2011.pptgrssieee
 
FR01_01_GlezetalIGARSS2011.ppt
FR01_01_GlezetalIGARSS2011.pptFR01_01_GlezetalIGARSS2011.ppt
FR01_01_GlezetalIGARSS2011.pptgrssieee
 
SEISMIC FOR EXPLORING SEABED MINERALS AT THE MID-ATLANTIC RIDGE
SEISMIC FOR EXPLORING SEABED MINERALS AT THE MID-ATLANTIC RIDGESEISMIC FOR EXPLORING SEABED MINERALS AT THE MID-ATLANTIC RIDGE
SEISMIC FOR EXPLORING SEABED MINERALS AT THE MID-ATLANTIC RIDGEiQHub
 
A Comparison Between Shear Wave Velocities
A Comparison Between Shear Wave VelocitiesA Comparison Between Shear Wave Velocities
A Comparison Between Shear Wave VelocitiesAli Osman Öncel
 
TH1.T04.2_MULTI-FREQUENCY MICROWAVE EMISSION OF THE EAST ANTARCTIC PLATEAU_IG...
TH1.T04.2_MULTI-FREQUENCY MICROWAVE EMISSION OF THE EAST ANTARCTIC PLATEAU_IG...TH1.T04.2_MULTI-FREQUENCY MICROWAVE EMISSION OF THE EAST ANTARCTIC PLATEAU_IG...
TH1.T04.2_MULTI-FREQUENCY MICROWAVE EMISSION OF THE EAST ANTARCTIC PLATEAU_IG...grssieee
 
Seismic landstreamers and rapid Vs imaging
Seismic landstreamers and rapid Vs imagingSeismic landstreamers and rapid Vs imaging
Seismic landstreamers and rapid Vs imagingAdam O'Neill
 
Engineering geophysical study of unconsolidated top soil using shallow seismi...
Engineering geophysical study of unconsolidated top soil using shallow seismi...Engineering geophysical study of unconsolidated top soil using shallow seismi...
Engineering geophysical study of unconsolidated top soil using shallow seismi...Alexander Decker
 
Seismic Reflection for Engineering Problems
Seismic Reflection for Engineering ProblemsSeismic Reflection for Engineering Problems
Seismic Reflection for Engineering ProblemsAli Osman Öncel
 
Research Inventy : International Journal of Engineering and Science
Research Inventy : International Journal of Engineering and ScienceResearch Inventy : International Journal of Engineering and Science
Research Inventy : International Journal of Engineering and Scienceinventy
 
Subsurface Determination Of Cavities In Limestone Rock Area By Geoelectric Me...
Subsurface Determination Of Cavities In Limestone Rock Area By Geoelectric Me...Subsurface Determination Of Cavities In Limestone Rock Area By Geoelectric Me...
Subsurface Determination Of Cavities In Limestone Rock Area By Geoelectric Me...IJERA Editor
 
Geostatistical approach to the estimation of the uncertainty and spatial vari...
Geostatistical approach to the estimation of the uncertainty and spatial vari...Geostatistical approach to the estimation of the uncertainty and spatial vari...
Geostatistical approach to the estimation of the uncertainty and spatial vari...IOSR Journals
 
Geophysics of overburden moving geophysics gtom exploration to application
Geophysics of overburden  moving geophysics gtom exploration to application Geophysics of overburden  moving geophysics gtom exploration to application
Geophysics of overburden moving geophysics gtom exploration to application Dr Lendy Spires
 

Similar to S24 naldi (20)

20200727 IEM WEBINAR .pdf
20200727 IEM WEBINAR .pdf20200727 IEM WEBINAR .pdf
20200727 IEM WEBINAR .pdf
 
Ground Geophysical Survey
Ground Geophysical SurveyGround Geophysical Survey
Ground Geophysical Survey
 
Jim_Mitchell_Nottingham Centre for Geomechanics_talk.ppt
Jim_Mitchell_Nottingham Centre for Geomechanics_talk.pptJim_Mitchell_Nottingham Centre for Geomechanics_talk.ppt
Jim_Mitchell_Nottingham Centre for Geomechanics_talk.ppt
 
Kent Odaklı Mikrobölgeleme: Sivas Örneği
Kent Odaklı Mikrobölgeleme: Sivas ÖrneğiKent Odaklı Mikrobölgeleme: Sivas Örneği
Kent Odaklı Mikrobölgeleme: Sivas Örneği
 
Earthquake Strong Motions.ppt
Earthquake Strong Motions.pptEarthquake Strong Motions.ppt
Earthquake Strong Motions.ppt
 
Geophysical survey for the risk management
Geophysical survey for the risk managementGeophysical survey for the risk management
Geophysical survey for the risk management
 
FR01_01_GlezetalIGARSS2011.ppt
FR01_01_GlezetalIGARSS2011.pptFR01_01_GlezetalIGARSS2011.ppt
FR01_01_GlezetalIGARSS2011.ppt
 
FR01_01_GlezetalIGARSS2011.ppt
FR01_01_GlezetalIGARSS2011.pptFR01_01_GlezetalIGARSS2011.ppt
FR01_01_GlezetalIGARSS2011.ppt
 
SEISMIC FOR EXPLORING SEABED MINERALS AT THE MID-ATLANTIC RIDGE
SEISMIC FOR EXPLORING SEABED MINERALS AT THE MID-ATLANTIC RIDGESEISMIC FOR EXPLORING SEABED MINERALS AT THE MID-ATLANTIC RIDGE
SEISMIC FOR EXPLORING SEABED MINERALS AT THE MID-ATLANTIC RIDGE
 
A Comparison Between Shear Wave Velocities
A Comparison Between Shear Wave VelocitiesA Comparison Between Shear Wave Velocities
A Comparison Between Shear Wave Velocities
 
TH1.T04.2_MULTI-FREQUENCY MICROWAVE EMISSION OF THE EAST ANTARCTIC PLATEAU_IG...
TH1.T04.2_MULTI-FREQUENCY MICROWAVE EMISSION OF THE EAST ANTARCTIC PLATEAU_IG...TH1.T04.2_MULTI-FREQUENCY MICROWAVE EMISSION OF THE EAST ANTARCTIC PLATEAU_IG...
TH1.T04.2_MULTI-FREQUENCY MICROWAVE EMISSION OF THE EAST ANTARCTIC PLATEAU_IG...
 
Seismic landstreamers and rapid Vs imaging
Seismic landstreamers and rapid Vs imagingSeismic landstreamers and rapid Vs imaging
Seismic landstreamers and rapid Vs imaging
 
Engineering geophysical study of unconsolidated top soil using shallow seismi...
Engineering geophysical study of unconsolidated top soil using shallow seismi...Engineering geophysical study of unconsolidated top soil using shallow seismi...
Engineering geophysical study of unconsolidated top soil using shallow seismi...
 
Seismic Reflection for Engineering Problems
Seismic Reflection for Engineering ProblemsSeismic Reflection for Engineering Problems
Seismic Reflection for Engineering Problems
 
Methods
MethodsMethods
Methods
 
Research Inventy : International Journal of Engineering and Science
Research Inventy : International Journal of Engineering and ScienceResearch Inventy : International Journal of Engineering and Science
Research Inventy : International Journal of Engineering and Science
 
Subsurface Determination Of Cavities In Limestone Rock Area By Geoelectric Me...
Subsurface Determination Of Cavities In Limestone Rock Area By Geoelectric Me...Subsurface Determination Of Cavities In Limestone Rock Area By Geoelectric Me...
Subsurface Determination Of Cavities In Limestone Rock Area By Geoelectric Me...
 
Identification of Groundwater Prospective Zones Using Geoelectrical and Elec...
Identification of Groundwater Prospective Zones Using  Geoelectrical and Elec...Identification of Groundwater Prospective Zones Using  Geoelectrical and Elec...
Identification of Groundwater Prospective Zones Using Geoelectrical and Elec...
 
Geostatistical approach to the estimation of the uncertainty and spatial vari...
Geostatistical approach to the estimation of the uncertainty and spatial vari...Geostatistical approach to the estimation of the uncertainty and spatial vari...
Geostatistical approach to the estimation of the uncertainty and spatial vari...
 
Geophysics of overburden moving geophysics gtom exploration to application
Geophysics of overburden  moving geophysics gtom exploration to application Geophysics of overburden  moving geophysics gtom exploration to application
Geophysics of overburden moving geophysics gtom exploration to application
 

More from Mario Naldi

Geoelettrica 2D e 3D per siti contaminati
Geoelettrica 2D e 3D per siti contaminatiGeoelettrica 2D e 3D per siti contaminati
Geoelettrica 2D e 3D per siti contaminatiMario Naldi
 
Indagini geofisiche per la diagnostica di beni culturali
Indagini geofisiche per la diagnostica di beni culturaliIndagini geofisiche per la diagnostica di beni culturali
Indagini geofisiche per la diagnostica di beni culturaliMario Naldi
 
Combined use of geophysical methods
Combined use of geophysical methodsCombined use of geophysical methods
Combined use of geophysical methodsMario Naldi
 
Combined use of geophysical methods
Combined use of geophysical methodsCombined use of geophysical methods
Combined use of geophysical methodsMario Naldi
 
Geofluid 2014 - geophysical methods for groundwater research
Geofluid 2014 - geophysical methods for groundwater researchGeofluid 2014 - geophysical methods for groundwater research
Geofluid 2014 - geophysical methods for groundwater researchMario Naldi
 
Presentazione techgea baggio rovereto 2014
Presentazione techgea baggio rovereto 2014Presentazione techgea baggio rovereto 2014
Presentazione techgea baggio rovereto 2014Mario Naldi
 

More from Mario Naldi (8)

Geoelettrica 2D e 3D per siti contaminati
Geoelettrica 2D e 3D per siti contaminatiGeoelettrica 2D e 3D per siti contaminati
Geoelettrica 2D e 3D per siti contaminati
 
Indagini geofisiche per la diagnostica di beni culturali
Indagini geofisiche per la diagnostica di beni culturaliIndagini geofisiche per la diagnostica di beni culturali
Indagini geofisiche per la diagnostica di beni culturali
 
Combined use of geophysical methods
Combined use of geophysical methodsCombined use of geophysical methods
Combined use of geophysical methods
 
Combined use of geophysical methods
Combined use of geophysical methodsCombined use of geophysical methods
Combined use of geophysical methods
 
Geofluid 2014 - geophysical methods for groundwater research
Geofluid 2014 - geophysical methods for groundwater researchGeofluid 2014 - geophysical methods for groundwater research
Geofluid 2014 - geophysical methods for groundwater research
 
Presentazione techgea baggio rovereto 2014
Presentazione techgea baggio rovereto 2014Presentazione techgea baggio rovereto 2014
Presentazione techgea baggio rovereto 2014
 
S24 naldi
S24 naldiS24 naldi
S24 naldi
 
S24 naldi
S24 naldiS24 naldi
S24 naldi
 

S24 naldi

  • 1. 87° Congresso della Società Geologica Italiana e 90° Congresso della Società Italiana di Mineralogia e Petrologia 10 - 12 Settembre 2014 - Milano A new prototype system for MASW2D roadside survey Mario Naldi, Emmanuele Duò – Techgea Srl (info@techgea.eu)
  • 2. GROUND INVESTIGATION IN URBAN AREAS: A NEW FIELD FOR THE NEAR SURFACE GEOPHYSICS Urban areas represent some of the most challenging environments for civil works: •Metro lines •Underground utilities (sewage, pipe lines, heating system) •Underground parking In such a context, the geophysical surveys can play an important role for the assessment of the geology and soil mechanics properties
  • 3. Some “obstacles” should be considered in the survey design : 1.Restricted space, 2.the necessity for traffic management, 3.high ambient noise (electrical and vibration), 4.underground utilities, … all THESE issues help to complicate the design and setting out of the geophysical profiles or grids. HOW TO SELECT THE RIGHT METHODOLOGY
  • 4. The conventional seismic surveys (refraction or reflection) can have many limitations in urban areas: •do not work well in noisy areas •take long time for data acquisition (hard traffic management) •require high energy source Among geophysical methods, the seismic survey is the most commonly applied for civil engineering projects. MASW 2D profiling has many advantages for surveys in urban areas: •More energetic wavelets (less energy required) •Short acquisition time with just one shot and fast move of the geophone layout (no stop of the road traffic) •Favorable ratio between the length of the seismic line and the soil depth. MASW2D = 1:1  seismic refraction = 5:1 Seismic surveys in urban areas
  • 5. Among geophysical methods, the seismic survey is the most commonly applied for civil engineering projects. Seismic sources generate a continuous spectrum of surface wave frequencies. Where there is vertical velocity variation, different frequency waves travel at different phase velocities. This is dispersion. By examining dispersion curves (phase velocity vs. frequency), we can determine material properties (e.g., layer thickness, depth, Vs) via Inversion BASIC THEORY OF MASW Lower frequency  deeper strata DISPERSION INVERSION
  • 6. Low density shallow soil Gravel and sand (not cemented) Gravel and sand (partially cemented) Masw2D (Vs - m/s) Seismic refraction (Vp – m/s) Low density shallow soil MASW2D HAS A HIGHER VERTICAL AND LATERAL RESOLUTION COMPARED WITH THE REFRACTION METHOD Velocity inversion in the subsurface is one of the most serious limitations of the shallow seismic refraction method  GEOPHYSICAL IMAGING HAS A POOR HIDDEN HIDDEN
  • 7. How to improve MASW 2D survey efficiency in urban areas? 1.Mobile system  continuous profiling (no traffic interruption) 2.High seismic energy  bypass of the urban noise Slow motion (low gear) STOP: One shot and recording (20 seconds) GO: Slow move to the next station (2 m) String of geophones on a land streamer Source of energy (ACCELERATED WEIGHT) Seismograph on board (DATA RECORDING) The streamer is towed at low speed with stop at every recording station
  • 8. Winch (powered by a 100 Ah/12 V Battery) Traction springs Propelled mass Uncoupling devices Source of energy (ACCELERATED WEIGHT) Lift The prototype has been designed and produced for Techgea by TREFFE
  • 9. Land streamer Sensors (4.5 hz geophones) mounted on a metal plate) String of geophones on a land streamer Source of energy (ACCELERATED WEIGHT)Seismograph on board (DATA RECORDING) The streamer is towed at low speed with stop at every recording station
  • 10. Distance [m] Küçükbakkalköy station projection COLOUR SCALE Shear wave velocity [m/s] Made ground and/or soft soil [Vs: 0÷200 m/s] Dense soil and/or overburden [Vs: 200 – 370 m/s] Very dense soil/soft rock [Vs: 370÷800 m/s] Rock [Vs: 800÷1200 m/s] Hard rock [Vs > 1200 m/s] 800 m/s 370 m/s 200 m/s 1200 m/s Remark: soil classification from ASCE table (7-2005), (modified) Fault zone Solid rock (LIMESTONE) Fractured rock Fractured rock Weathered rock Top soil Line M5-13 - Shear Wave section Weathered rock Küçükbakkalköy station EXAMPLE 1 – ISTANBUL METRO LINE BOSTANCI – DUDULLU (TURKEY) Masw2d SURVEY FOR THE GEOLOGICAL ASSESSMENT AND THE SEISMIC SOIL CLASSIFICATION Fault zone THE MASW2D LINE IS POSITIONED ALONG A ROAD BETWEEN THE PROJECTION OF THE TWIN TUNNELS OVERNIGHT SURVEY
  • 11. EXAMPLE 2 – SEWER PIPE SETTLEMENT (MILAN AREA, ITALY) ROAD SUBSIDENCE AFTER THE PIPELINE POSITIONING CEMENTED ZONE (GROUTING BELOW THE DEFORMED ROAD) DENSE GRAVEL VERY LOW DENSITY SAND- GRAVEL/VOIDS SUBSIDENCE AREA SUBSIDENCE AREA SUBSIDENCE AREA
  • 12. EXAMPLE 3 – SLOPE FAILURES ASSOCIATED WITH ABANDONED UNDERGROUND QUARRIES (Alessandria, Italy) ROAD SUBSIDENCE AND DEFORMATION BA Siltstone (soft rock) Highly weathered siltstone (silt consistency) Landslide projection (IFFI) S1 Very low density zone (collapsed tunnels) Tunnel Subsidence area Subsidence area
  • 13. 87° Congresso della Società Geologica Italiana e 90° Congresso della Società Italiana di Mineralogia e Petrologia 10 - 12 Settembre 2014 - Milano A new prototype system for MASW2D roadside survey Mario Naldi, Emmanuele Duò – Techgea Srl Thank you for the attention