scholarly journals Geotechnical characterization and seismic response of shallow geological formations in downtown Lisbon

2014 ◽  
Vol 57 (4) ◽  
Author(s):  
Paula Teves-Costa ◽  
Isabel M. Almeida ◽  
Isabel Rodrigues ◽  
Rita Matildes ◽  
Claudia Pinto
Keyword(s):  
Seismic Response ◽  
Fundamental Frequency ◽  
Linear Method ◽  
Ambient Vibration ◽  
Building Stock ◽  
Alluvial Deposits ◽  
Amplification Factors ◽  
Geotechnical Characterization ◽  
Geotechnical Database

<p> </p><p>The geological and geotechnical characterization of shallow formations is one of the main steps in performing a microzonation study. This paper presents an example of the usefulness of the information compiled in a geological and geotechnical database for the estimation of the seismic response of the shallower formations of the Lisbon downtown area of Baixa. The geotechnical characterization of this area was performed based on the analysis of Standard Penetration Test (SPT) data compiled in the geological and geotechnical database. This database, connected to a geoscientific information system (CGIS), allows, also, the definition of 2D geological profiles used for estimating the thickness of the shallower layers. The shear-wave velocities (V<span><sub>S </sub></span>) for each layer were estimated from empirical correlations using mean SPT values computed from the statistical evaluation of the compiled data. These V<span><sub>S</sub></span> values were further calibrated with ambient vibration recording analysis. The seismic response of Baixa’s superficial deposits was estimated by applying a 1D equivalent linear method to a set of soil profiles, regularly distributed across the area, and using synthetic accelerograms to simulate input motions associated with probable earthquake occurrences in Lisbon. The results are presented in terms of maps of predominant frequencies, with the corresponding amplification level, as well as spectral amplification factors for 1 Hz and 2.5 Hz. The results show that the fundamental frequency of the Baixa area is between 1.2 Hz and 2 Hz, for the whole central valley, reaching 3 Hz near the edges where anthroprogenic and alluvial deposits have less expression. Amplification factors up to 5 were obtained. These results were achieved regardless of the considered input motion. The similarity of the obtained fundamental frequency with the natural frequency of Baixa’s old building stock increases the probability of resonance effects in future earthquakes.</p><p><span style="font-size: medium;"><br /></span></p>

Characterization of unstable rock slopes using ambient vibration analysis

2020 ◽  
Author(s):  
Donat Fäh ◽  
Mauro Häusler ◽  
Franziska Glueer ◽  
Jan Burjanek ◽  
Ulrike Kleinbrod
Keyword(s):  
Seismic Response ◽  
Normal Mode ◽  
Wave Velocity ◽  
Ambient Vibration ◽  
Mode Analysis ◽  
Permafrost Degradation ◽  
Rock Slopes ◽  
Spectral Ratios ◽  
S Wave

&lt;p&gt;Earthquake-induced landslides can have serious social impacts, causing many casualties and significant damage to infrastructure. They are the most destructive secondary hazards related to earthquakes. The impact of strong seismic events is not limited just to triggering of catastrophic slope failures, it also involves weakening of intact rock masses and reactivation of dormant slides. Hazard mitigation of potentially catastrophic landslides requires a thorough understanding of the mechanisms driving slope movements and seismic response.&lt;/p&gt;&lt;p&gt;We present an overview of the investigations on more than 25 instabilities. The results show that ambient vibration measurements allow for a rapid and objective characterization of potential slope instabilities. It is possible to distinguish unstable from stable areas, to identify slope eigen-frequencies, local amplification levels due to weak excitation, local deformation directions and properties of the internal slope structure. The ambient vibration techniques include single-station H/V ratios and polarization analyses, site-to-reference spectral ratios, array methods to identify surface-wave dispersion curves, and/or normal mode analysis using enhanced frequency domain decomposition. We analyse the seismic response of the rock slopes in different frequency bands together with its spatial and azimuthal variability, which is a fingerprint of the slope&amp;#8217;s internal structure at different scales (tenth of meters to hundred meters). Normal mode behaviour is typically observed in structures with distinct sub-volumes, where the wave field at the resonance frequencies is oriented perpendicular to the deep persistent fractures. These structures show maximum amplification at their resonance frequency. Normal mode behaviour is also observed for rock towers, similar to what can be observed for buildings. In contrast, a highly fractured rock mass without dominant cracks is characterized by an S-wave velocity gradient with shear-wave velocity being significantly reduced close to the surface. Generally, normal modes do not develop, but surface waves propagate in such structures, which can be used for the determination of the S-wave profile. This is typical for large deep seated landslides with a layered structure. Without strong S-wave velocity contrast at depth, H/V spectral ratios show no clear peak and are not conclusive to characterize structures with highly fractured material. However, frequency-dependent ground-motion amplification from standard spectral ratios is directly related to the S-wave velocity profile and damping. Therefore, wave amplification can be a measure for the disintegration of the rock.&lt;/p&gt;&lt;p&gt;Repeated measurements on slopes allow for the detection of possible changes in their properties. Semi-permanent installations on instabilities of interest allow for a continuous assessment of the dynamic response in order to understand variations due to weather conditions and potential long-term changes. This includes the measurement of site-amplification during earthquakes derived from empirical spectral modelling. When measuring in the same season and weather condition, the seismic response of rock instabilities in general remains unchanged over years, as long a no external trigger affects the instability, including a strong earthquake, partial failure of the slope or permafrost degradation.&lt;/p&gt;

Geotechnical characterization of the quaternary alluvial deposits in Tunis City (Tunisia)

2015 ◽  
Vol 108 ◽  
pp. 89-100 ◽  
Author(s):  
Moufida El May ◽  
Dhekra Souissi ◽  
Hela Ben Said ◽  
Mahmoud Dlala
Keyword(s):  
Alluvial Deposits ◽  
Geotechnical Characterization

Geotechnical characterization of the upper Pleistocene–Holocene alluvial deposits of Roma (Italy) by means of multivariate geostatistics: Cross-validation results

2008 ◽  
Vol 101 (3-4) ◽  
pp. 251-268 ◽  
Author(s):  
Giuseppe Raspa ◽  
Massimiliano Moscatelli ◽  
Francesco Stigliano ◽  
Antonio Patera ◽  
Fabrizio Marconi ◽  
...  
Keyword(s):  
Cross Validation ◽  
Multivariate Geostatistics ◽  
Alluvial Deposits ◽  
Upper Pleistocene ◽  
Geotechnical Characterization

The dynamic amplification factors for continuous beam bridges along high-speed railways

2021 ◽  
pp. 136943322110032
Author(s):  
Lin Ma ◽  
Wei Zhang ◽  
Steve C.S. Cai ◽  
Shaofan Li
Keyword(s):  
Fundamental Frequency ◽  
High Speed ◽  
Continuous Beam ◽  
Empirical Formulas ◽  
High Speed Railway ◽  
Amplification Factors ◽  
Girder Bridges ◽  
Continuous Beam Bridge ◽  
Train Speed ◽  
Dynamic Amplification

In this paper, the dynamic amplification factors (DAFs) of high-speed railway continuous girder bridges are studied. The vehicle-bridge interactions (VBIs) of 13 concrete continuous girder bridges with spans ranging from 48 to 130 m are analyzed, the influences of the train speed, the train marshalling and the bridge fundamental frequency on the DAF are investigated, and the DAF design standard for high-speed railway bridges is discussed. The results indicate that for the continuous beam bridge whose fundamental frequency is less than 3.0 Hz, the maximum DAF is no more than 1.15; while for the bridge examples with a fundamental frequency larger than 3.0 Hz, the maximum DAF reaches 1.25 because the resonance occurs at high train speed. The empirical formulas of the DAFs in the Japan Railway Technical Research Institute (JRTRI) code could provide a conservative estimation of the DAFs of high-speed railway continuous bridges.

scholarly journals Geotechnical characterization of Norwegian peat: database

2021 ◽  
Vol 710 (1) ◽  
pp. 012016
Author(s):  
P Paniagua ◽  
M Long ◽  
J-S L’Heureux
Keyword(s):  
Geotechnical Characterization

Geotechnical Characterization Of Rio Caribe Soils

1995 ◽  
Author(s):  
J.P. ullya ◽  
J. Sgambatti ◽  
J.S. Templetonb ◽  
Fugro McClelland ◽  
F. Perez ◽  
...  
Keyword(s):  
Geotechnical Characterization

Fieldwork on local-site seismic response in the Po Plain: examples from ambient vibration array and single station analyses

2016 ◽  
Vol 15 (6) ◽  
pp. 2349-2366 ◽  
Author(s):  
M. Massa ◽  
C. Mascandola ◽  
C. Ladina ◽  
S. Lovati ◽  
S. Barani
Keyword(s):  
Seismic Response ◽  
Ambient Vibration ◽  
Po Plain ◽  
Local Site ◽  
Single Station

The Influence of Support Hardware and Piping System Seismic Response on Snubber Support Damping

1997 ◽  
Vol 119 (4) ◽  
pp. 451-456 ◽  
Author(s):  
C. Lay ◽  
O. A. Abu-Yasein ◽  
M. A. Pickett ◽  
J. Madia ◽  
S. K. Sinha
Keyword(s):  
Seismic Response ◽  
Fundamental Frequency ◽  
Damping Ratio ◽  
Damping Coefficient ◽  
Piping System ◽  
Nodal Displacement ◽  
Damping Coefficients ◽  
Fundamental Frequencies ◽  
Piping Systems

The damping coefficients and ratios of piping system snubber supports were found to vary logarithmically with pipe support nodal displacement. For piping systems with fundamental frequencies in the range of 0.6 to 6.6 Hz, the support damping ratio for snubber supports was found to increase with increasing fundamental frequency. For 3-kip snubbers, damping coefficient and damping ratio decreased logarithmically with nodal displacement, indicating that the 3-kip snubbers studied behaved essentially as coulomb dampers; while for the 10-kip snubbers studied, damping coefficient and damping ratio increased logarithmically with nodal displacement.

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