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Near Surface Geoscience Conference & Exhibition 2022 Workshop Programme
- Conference date: September 18-22, 2022
- Location: Belgrade, Serbia
- Published: 18 September 2022
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Examples for the application of “unusual” seismic methods to answer “special” questions in geotechnical engineering
By D. OrlowskySummaryIn geotechnical engineering questions are asked, which not always can be answered applying standard geophysical techniques. Physical properties of the underground sometimes do not show needed characteristics for the application of a geophysical method. Often, the accessibility of the area under investigation is limited, such that a required measurement geometry cannot be realized. This paper shows examples where seismic methods needed to be adjusted to answer “special” questions in geotechnical engineering. Usual applied techniques like reflection seismic, standard refraction seismic, refraction tomography, surface wave seismic, seismic cross-hole tomogra-phy, etc. had to be modified to meet “unusual” field conditions as well as to answer the ge-otechnical requests.
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Use of geophysical survey in geotechnical engineering practice – From one of geotechnical engineers’ perspective
By J. SugawaraSummaryIn geotechnical engineering practice, geotechnical investigation is one of the indispensable steps to identify the “fact” of the subsurface ground conditions. These days, geophysical survey is often used as a part of geotechnical investigation to gain additional subsurface ground information that will contribute to the geotechnical analysis and design. There are many useful correlations between geophysical outputs and geotechnical items.
In this paper, typical situations where geotechnical engineers consider using geophysical survey will be described from geotechnical engineering perspective. Advantages of using geophysical survey and key points that need to be paid attention to will be also discussed. It is noted that contents of this paper are purely based on the author’s opinion and experience and may differ from other geotechnical practitioners.
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The Need for Geophysicists and Engineers to Understand Each Other to Tackle Environmental and Civil Issues
Authors P. Martínez-Pagán, S. Sandoval-Castaño, E. Aracil-Ávila and U. MaruriSummaryNear-surface geophysics is employed to study the very outermost part of the earth’s crust. Indeed, the shallow subsurface is extremely important since it yields much of our water resources, support our agriculture and ecosystems, and influences our climate. Consequently, near-surface geophysics investigations are numerous and varied according to their applications: engineering, geotechnical, environmental, groundwater, mining, archaeological, etc. Also, it is needed to define users of near-surface geophysics as those professionals, formally trained in another discipline, who receives support of geophysics to tackle with near-surface problems. Among these users are those who propose applications of geophysics, contract for geophysical services, etc. Despite the educational background and experience, the near-surface geophysicist must deal with different approaches and conceptual understanding by the various types of users of near-surface geophysics that conducts to different perceptions of the results depending on the type of users (e.g., an engineer, a geologist, and/or a regulator). Therefore, this presentation attempts to help potential users to understand the true potentialities of near-surface geophysics as a crucial tool to address many problems on environment, engineering, earthquake risk studies, etc. Some successful case studies will be examined to provide actual knowledge of near-surface geophysics potentialities for those final users or decision-makers.
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Application of 1D, 2D and 3D passive surface wave methods to geotechnical site investigations
By K. HayashiSummaryS-wave velocity (Vs) is one of the most important physical property representing the stiffness of soil. Active and passive surface wave methods have been widely used to non-invasively estimate Vs profile from ground surface. The passive surface wave methods are particularly attractive since the methods can penetrate deeper than active methods without any sources. Conventional passive surface wave methods were usually one-dimensional (1D) investigation only using 5~10 receivers since traditional standalone seismograph required in array measurements were quite expensive, large and difficult to use. Considering the demand for non-invasively investigating two- or three-dimensional (2D or 3D) complicated underground structure is increasing, the passive surface wave methods will play important role in such investigations. We developed a passive surface wave method that delineates 2D/3D near-surface Vs structures from seismic ambient noise obtained from dozens of receivers on the ground surface. The method uses a sufficiently small receiver spacing to avoid spatial aliasing and calculates phase velocity locally using CMP-SPAC method to delineate horizontal velocity change. This abstract introduces the equipment, methodology and application of the passive surface wave methods to 1D, 2D and 3D geotechnical site investigations.
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Pseudo-N-value from S-wave velocity: A consideration for geotechnical application
By K. SutoSummaryThe SPT N-value is commonly used by engineers as an indicator of hardness of the ground. The load-bearing capacity derived from the N-value is used as a basis of subsequent engineering design. Among geophysicists, hardness of the ground is expressed by seismic velocity. The multichannel analysis of surface waves (MASW) delivers S-wave velocity structure with a high data density which is hard to achieve by the SPT surveys. Many authors attempted to relate these two parameters from the empirical correlation. Any proposed equations, albeit with great precisions, inevitably contain some error. Accepting the error range, the pseudo-N-value was proposed in 2011 to estimate N-value from S-wave velocity with simple conversion parameters. The pseudo-N-value does not reference to a particular site and it can be used where actual SPT data is not available. It is displayed as a seismic section in terms of N-value. This conversion provides the engineers with trend of distribution of ground hardness with high data density. This presentation includes an example of practical use of pseudo-N-value in a geotechnical site.
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Geotechnical and Geophysical Tests for the Study of Soils in Granada (Spain) Focused on Seismic Risk
SummaryThe research project of the Spanish Ministry of Science and Innovation that is going to be carried out is presented. The subsidy for this project has been obtained in a competitive call at the national level.
One of the main aims of this project is to study the optimal and affordable use of seismic methods, active and passive, to characterize the subsoil from a geotechnical point of view with a suitable detail that would let us properly predict induced seismic phenomena, such as liquefaction, unexpected soil settling, and failures.
It is planned to conduct improved passive seismic methods, in conjunction with up-to-date active seismic methods and traditional geotechnical techniques in the 32 municipalities that constitute the Granada Metropolitan Area (972 km2) in Spain. This important area is located in the most dangerous region of Spain in terms of seismicity and seismic risk. Moreover, this region presents clear evidence of significant seismic amplification and susceptibility to induced phenomena.
In this way, obtaining a microzonation of this area will enable to precisely quantify and pinpoint these effects and to establish empirical relationships between important parameters such as the corrected SPT-N, the liquefaction potential index, the Poisson’s coefficient, densification phenomena.
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GPR and NDT Surveys on a Proposed UK Spaceport Runway
By J. EasonSummaryA combined GPR and NDT survey mapping the structural capacity of existing surveys and mapping defects for future upgrades
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Fault detection in the area of a mini hydropower plant in Kotor Varoš by seismic reflection
By S. ArsenovićSummaryGeophysical surveys, in the area of MHP (Mini Hydropower Plant) ‘‘Kotor Varoš’’, were carried out by meaning of reflective seismics. The goal of the geophysical survey, as a part of the geotechnical study, was to identify the presence of a fault system in the area of MHP at machine room position and provide useful data for geotechnical engineers to determine geotechnical conditions. Identification of tectonized – crushed zones in fault areas was one of the geophysical survey goals.
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MASW-Refraction on railway embankments correlated with CPT
By A. VerweerdSummaryCorrelation of MASW and Seismic Refraction Data with CPT to generate full mode density girds to calculate elastic soilparameters
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Geophysical Methods and their applications - To reduce geological uncertainty in geotechnical projects -
More LessSummaryGeophysical survey is a scaled-down version of geophysical prospecting which used for resource exploration, and is applied to geotechnical engineering based on various innovations. When geophysical surveys are used in geotechnical engineering, it is necessary to select a geophysical survey method that meets the objective and plan the survey method, taking into account the purpose of the survey, the geological structure to be surveyed, surface topographic conditions, survey accuracy, and the depth to be covered.
Construction risk based on ground uncertainty is recognized as geo-risk, and efforts are being made to minimize the risk as much as possible at each stage of planning, investigation, and design in Japan. If the heterogeneity of the ground could not be fully recognized, the ground uncertainty becomes geo-risk. In this paper, we show that a combination of borehole survey and geophysical survey is effective for understanding the ground composition by case studies of levee and embankment investigations regarding the understanding of ground structure. The application of geophysical survey to geotechnical engineering is expected to be effective in understanding the heterogeneity of the ground and to reduce geo-risk.
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Closing the gaps between geophysics and ground/geotechnical engineering. Accelerating cloud driven collaboration of geoscience data projects
Authors M. Butcher, O. Ward, S. Goodman, B. Bodger and F. GiovacchiniSummaryToday’s geoscientists have access to more data than ever before. Accuracy and confidence in this data is as important as ever and the ability to filter through libraries of datasets and find the current versions can be the key in timely decision making. This is a particular challenge in Geophysics with it being integrated in the geotechnical engineering sector. ‘Seequent, the Bentley subsurface company,’ sits at the centre of the web of these collisions, converting complexity to clarity.
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