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Resistivity and Surface Wave Seismic Surveys in Geotechnical Site Investigations

Wisén, Roger LU (2005)
Abstract (Swedish)
Popular Abstract in Swedish

Anpassningen av geofysiska metoder till infrastrukturtillämpningar är en viktig del i utvecklingen av geoteknisk förundersökningsmetodik. Det som här benämns geotekniska förundersökningar hänvisar till alla undersökningar som görs före eller under konstruktion, alltså sådana som syftar till att stödja och förbättra en konceptuell geologisk modell så väl som sådana som syftar till att ta fram en modell av geotekniska designparametrar. I varje steg i förundersökningsprocessen tillhandahåller geofysiska metoder information som underlättar vid interpolering av geologiska, geotekniska och hydrogeologiska strukturer mellan punkter där detaljerade sonderingsundersökningar har utförts. Geofysiska metoder... (More)
Popular Abstract in Swedish

Anpassningen av geofysiska metoder till infrastrukturtillämpningar är en viktig del i utvecklingen av geoteknisk förundersökningsmetodik. Det som här benämns geotekniska förundersökningar hänvisar till alla undersökningar som görs före eller under konstruktion, alltså sådana som syftar till att stödja och förbättra en konceptuell geologisk modell så väl som sådana som syftar till att ta fram en modell av geotekniska designparametrar. I varje steg i förundersökningsprocessen tillhandahåller geofysiska metoder information som underlättar vid interpolering av geologiska, geotekniska och hydrogeologiska strukturer mellan punkter där detaljerade sonderingsundersökningar har utförts. Geofysiska metoder har potential att beskriva sektioner, ytor eller volymer. Detta är information som inte är lätt tillgänglig från någon annan undersökningsmetod.



Gemensamt för nästan alla geofysiska metoder är behovet av inversmodellering av observerade data. Resultaten från inversmodellering kan tolkas direkt med avseende på de fysikaliska egenskaper de beskriver.



DC-resistivitet och ytvågsseismik är två metoder som fungerar väl i geotekniska förundersökningar. Denna avhandling fokuserar på användandet av dessa två metoder och olika tillvägagångssätt för geofysisk inversmodellering samt diskuterar och belyser värdet av att tillämpa dessa tekniker, bl.a. genom fältstudier.



- Den vanligast använda tekniken för inversion av profilerande resistivitetsdata, 2D-inversion med en cellindelad modell, är robust även för komplicerade geologiska miljöer. Denna teknik är dock oförmögen att skapa modeller med skarpa lagergränser vilket ibland gör resultaten svårtolkade.



- 3D-inversion med cellindelad modell ger bättre resultat i geologiska miljöer med framträdande 3D strukturer.



- En nyligen utvecklad metod för lateralt bunden inversion använder lagerindelade modeller. Utöver en slutlig modell över markens resistivitetsfördelning erhålls från inversionen också en uppskattning av modellparametrarnas osäkerheter. Detta förbättrar möjligheterna till tolkning av resultaten.



- Lateralt bunden inversion av dispersionskurvor från profilerande ytvågsseismiska data resulterar i en skjuvvågshastighetsmodell. Metoden utvecklades inom ramarna för detta avhandlingsarbete. Denna metod stabiliserar inversionen av yvågsseismiska data vilket ger upphov till en förbättring av inversionsresultatet jämfört med separat inversion av enskilda dispersionskurvor.



- Gemensamt kopplad inversion av olika datatyper är ett nytt koncept som här tillämpas för första gången för samtidig inversion av resistivitets- och ytvågsseismiska data. Metoden ger en förbättring av de resulterande modellerna jämfört med separat inversion av de två datatyperna och tillåter geogeometriska skillnader mellan resistivitets- och skjuvvågshastighetsmodellerna.



- Genom att styra modellgeometrin med a priori-information mildras effekterna av problem med dolda eller undertryckta lager, icke-unika lösningar eller ekvivalens vid inversion av geofysiska data. Lateralt bunden inversion tillåter denna typ av a priori information i inversionen vilket leder till en förbättring av den slutliga geofysiska modellen.



Dessa metoder är kostnadseffektiva, snabba och robusta verktyg för att beskriva geologiska enheter. Om de används som komplement till de traditionella geotekniska undersökningsmetoderna kan en förbättrad materialmodell erhållas vilket i sin tur leder till säkrare design och slutligen sannolikt till en reducerad konstruktionskostnad. (Less)
Abstract
The adaptation of geophysical methods for civil engineering purposes represents an important contribution to the development of geotechnical site investigation methodology. The term geotechnical site investigation here refers to all investigations performed prior to or during construction; i.e. investigations to support and refine a conceptual geological model as well as to provide a model of geotechnical design parameters. At any stage in the site investigation process, geophysical methods provide information to facilitate the interpolation of geological, geotechnical and hydro-geological structures between positions where detailed information, e.g. from drilling, are available. Geophysical methods have the potential to provide... (More)
The adaptation of geophysical methods for civil engineering purposes represents an important contribution to the development of geotechnical site investigation methodology. The term geotechnical site investigation here refers to all investigations performed prior to or during construction; i.e. investigations to support and refine a conceptual geological model as well as to provide a model of geotechnical design parameters. At any stage in the site investigation process, geophysical methods provide information to facilitate the interpolation of geological, geotechnical and hydro-geological structures between positions where detailed information, e.g. from drilling, are available. Geophysical methods have the potential to provide information that describes sections, areas or volumes; such information that would not be readily available from any other investigation method.



Common to almost all geophysical methods is the need for inverse modelling of the observed data. The modelling result can be interpreted directly in terms of the physical properties that it describes.



DC resistivity and surface wave seismics are two methods that perform well in geotechnical site investigations. This thesis focuses on the use of these two methods and different approaches for inverse modelling; the thesis illustrates and comments on the value of these approaches, e.g. through field studies.



- 2D smooth inversion, the commonly used technique for inversion of profiling resistivity data, is a robust technique also for data from complicated geological environments. However, this method is unable to produce sharp layer interfaces, which sometimes makes the resulting models difficult to interpret.



- 3D smooth inversion of resistivity data results in improved models in environments with prominent three-dimensional structures.



- The recently developed laterally constrained inversion of resistivity data provides a few-layer model together with estimates of the uncertainty of model parameters. When this technique is used together with 2D smooth inversion the interpretability of the results is improved.



- The laterally constrained inversion of dispersion curves from surface wave seismic data for a layered shear wave velocity model was developed within this thesis work. It provides a more stable inversion process compared to individual inversion of the dispersion curves.



- The new concept of mutually constrained inversion is implemented for the first time for combined inversion of resistivity and surface wave seismic data. It produces a better model estimate than separate inversion of the two data types and still allows for differences in geometry between the shear wave velocity and the resistivity models.



- By constraining the model geometry with a priori information, the effects from problems with hidden or suppressed layers, non-uniqueness and equivalence in the inversion can be reduced. The laterally constrained inversion allows the inclusion of a priori information on the model so that the uncertainties of the geophysical model parameters are reduced and the final geophysical model is improved.



These methods for measurement and inversion of geophysical data provide cost-effective, fast and robust tools for describing geological units. If they are used to complement the traditional geotechnical methods, an improved material model is achieved. This in turn leads to a safer design and at the end most probably a reduction of the construction costs. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Professor Jongmans, Denis, Université J. Fourier, Grenoble, France
organization
publishing date
type
Thesis
publication status
published
subject
keywords
teknisk geografi, Hydrogeologi, teknisk geologi, Hydrogeology, geographical and geological engineering, resistivity method, surface wave seismic method, inverse modelling, site investigation, geophysics
pages
88 pages
publisher
Engineering Geology, Lund University
defense location
Room V:B, V-building, John Ericssons väg 1, Lund Institute of Technology
defense date
2005-12-02 10:15
external identifiers
  • Other:ISRN:LUTVDG/TVTG-1016-SE
ISBN
91-973406-5-0
language
English
LU publication?
yes
id
92c2ce7f-6942-4ae1-83cb-6855eb080799 (old id 545735)
date added to LUP
2007-09-10 15:58:54
date last changed
2016-09-19 08:45:05
@misc{92c2ce7f-6942-4ae1-83cb-6855eb080799,
  abstract     = {The adaptation of geophysical methods for civil engineering purposes represents an important contribution to the development of geotechnical site investigation methodology. The term geotechnical site investigation here refers to all investigations performed prior to or during construction; i.e. investigations to support and refine a conceptual geological model as well as to provide a model of geotechnical design parameters. At any stage in the site investigation process, geophysical methods provide information to facilitate the interpolation of geological, geotechnical and hydro-geological structures between positions where detailed information, e.g. from drilling, are available. Geophysical methods have the potential to provide information that describes sections, areas or volumes; such information that would not be readily available from any other investigation method.<br/><br>
<br/><br>
Common to almost all geophysical methods is the need for inverse modelling of the observed data. The modelling result can be interpreted directly in terms of the physical properties that it describes.<br/><br>
<br/><br>
DC resistivity and surface wave seismics are two methods that perform well in geotechnical site investigations. This thesis focuses on the use of these two methods and different approaches for inverse modelling; the thesis illustrates and comments on the value of these approaches, e.g. through field studies.<br/><br>
<br/><br>
- 2D smooth inversion, the commonly used technique for inversion of profiling resistivity data, is a robust technique also for data from complicated geological environments. However, this method is unable to produce sharp layer interfaces, which sometimes makes the resulting models difficult to interpret.<br/><br>
<br/><br>
- 3D smooth inversion of resistivity data results in improved models in environments with prominent three-dimensional structures.<br/><br>
<br/><br>
- The recently developed laterally constrained inversion of resistivity data provides a few-layer model together with estimates of the uncertainty of model parameters. When this technique is used together with 2D smooth inversion the interpretability of the results is improved.<br/><br>
<br/><br>
- The laterally constrained inversion of dispersion curves from surface wave seismic data for a layered shear wave velocity model was developed within this thesis work. It provides a more stable inversion process compared to individual inversion of the dispersion curves.<br/><br>
<br/><br>
- The new concept of mutually constrained inversion is implemented for the first time for combined inversion of resistivity and surface wave seismic data. It produces a better model estimate than separate inversion of the two data types and still allows for differences in geometry between the shear wave velocity and the resistivity models.<br/><br>
<br/><br>
- By constraining the model geometry with a priori information, the effects from problems with hidden or suppressed layers, non-uniqueness and equivalence in the inversion can be reduced. The laterally constrained inversion allows the inclusion of a priori information on the model so that the uncertainties of the geophysical model parameters are reduced and the final geophysical model is improved.<br/><br>
<br/><br>
These methods for measurement and inversion of geophysical data provide cost-effective, fast and robust tools for describing geological units. If they are used to complement the traditional geotechnical methods, an improved material model is achieved. This in turn leads to a safer design and at the end most probably a reduction of the construction costs.},
  author       = {Wisén, Roger},
  isbn         = {91-973406-5-0},
  keyword      = {teknisk geografi,Hydrogeologi,teknisk geologi,Hydrogeology,geographical and geological engineering,resistivity method,surface wave seismic method,inverse modelling,site investigation,geophysics},
  language     = {eng},
  pages        = {88},
  publisher    = {ARRAY(0x8e90a08)},
  title        = {Resistivity and Surface Wave Seismic Surveys in Geotechnical Site Investigations},
  year         = {2005},
}