scholarly journals On the seismic response of instable rock slopes based on ambient vibration recordings

2017 ◽  
Vol 69 (1) ◽  
Author(s):  
Ulrike Kleinbrod ◽  
Jan Burjánek ◽  
Donat Fäh
Keyword(s):  
Seismic Response ◽  
Ambient Vibration ◽  
Rock Slopes

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

<p>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.</p><p>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’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.</p><p>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.</p>

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

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>

Reconstruction of a Reference Subsoil Model for the Seismic Microzonation of Gori (Georgia): A Procedure Based on Principal Component Analysis (PCA)

2021 ◽  
Author(s):  
Silvia Giallini ◽  
Enrico Paolucci ◽  
Pietro Sirianni ◽  
Dario Albarello ◽  
Iolanda Gaudiosi ◽  
...  
Keyword(s):  
Principal Component Analysis ◽  
Seismic Response ◽  
Principal Component ◽  
Component Analysis ◽  
Vibration Monitoring ◽  
Ambient Vibration ◽  
Geological Evidence ◽  
Local Seismic Response ◽  
Geophysical Surveys ◽  
Single Station

ABSTRACT This article focuses on the full exploitation of geological and economically viable geophysical surveys for the seismic characterization of the shallow subsoil in the frame of microzonation studies in urban areas where economic resources for detailed seismic response analyses are scarce. In these conditions, the outcomes of inexpensive geophysical surveys (e.g., based on ambient vibration monitoring or surface-wave prospecting) must be fully exploited. To reduce the uncertainties related to these kinds of procedures, their joint interpretation in the light of geological evidence is mandatory. To this purpose, we propose the application of principal component analysis to combine the results of distributed single-station ambient vibration measurements (horizontal-to-vertical spectral ratio [HVSR] technique) to provide a preliminary zonation of the study area. The zones identified in this way are then characterized by considering the available geognostic boreholes, VS profiles deduced by the joint inversion of HVSR curves, and available Rayleigh-wave dispersion curves deduced from active seismic prospecting (multichannel analysis of surface-waves technique). The final outcome allows the definition of a preliminary seismic model of the study area, which is also constrained by the available geological data deduced from on-purpose surveys. The proposed approach has been applied to the city of Gori (Georgia). The proposed approach allowed a reliable assessment of buried geometries, geological domains, and the distribution of lithofacies, which can control the local seismic response. In detail, the major role of paleovalley infills and interfluve domains has been enlightened by adding in evidence concerning the peculiar stratigraphic relationships and buried morphologies, which may determine 1D and 2D resonance effects.

scholarly journals Influence of Ground Motion Parameters on the Seismic Response of an Anchored Rock Slope

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Ningbo Peng ◽  
Yun Dong ◽  
Ye Zhu ◽  
Jie Hong
Keyword(s):  
Seismic Response ◽  
Axial Force ◽  
Seismic Waves ◽  
Rock Slope ◽  
Dominant Role ◽  
Dynamic Responses ◽  
Seismic Action ◽  
Rock Slopes ◽  
Permanent Displacement ◽  
Structural Plane

The seismic response of rock slopes is closely related to the dynamic characteristics of earthquakes. In this study, based on a numerical model of rock slopes with bolt support, the seismic responses of both anchored and unanchored rock slopes under different seismic waves are calculated. The results show that a “cumulative effect” of the relative permanent displacement of the slope is generated during seismic action, and it is found that the permanent displacement of the slope is caused by larger earthquake accelerations. The dynamic responses of an anchored slope are analyzed in terms of the wave type, frequency, amplitude, and duration and are compared with those of an unanchored rock slope. This comparison suggests that the nominal shear strain increases with the amplitude and duration, which decreases as frequency increases. The axial force is directly related to the surrounding rock strain. The maximum axial force of the bolt is near the rock interface, which shows that the structural plane of the slope plays a dominant role in the seismic response. The seismic waves are random, whereas the structural plane of the rock slope is certain. The seismic response characteristics of the slope under different earthquake conditions are similar, and the dynamic stability of the slope can be attributed to the structural analysis of the rock slope.

scholarly journals Study of the Seismic Response on the Infill Masonry Walls of a 15-Storey Reinforced Concrete Structure in Nepal

Buildings ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 39 ◽  
Author(s):  
André Furtado ◽  
Nelson Vila-Pouca ◽  
Humberto Varum ◽  
António Arêde
Keyword(s):  
Reinforced Concrete ◽  
Seismic Response ◽  
Concrete Structure ◽  
Numerical Study ◽  
Numerical Models ◽  
Ambient Vibration ◽  
Reinforced Concrete Structure ◽  
Infill Walls ◽  
Ambient Vibration Tests ◽  
Vibration Tests

Following the strong earthquake on April 25, 2015 in Nepal, a team from the University of Porto, in collaboration with other international institutions, made a field study on some of the most affected areas in the capital region of Kathmandu. One of the tasks was the study of a high-rise settle of buildings that were damaged following the earthquake sequence. A survey damage assessment was performed to a 15-storey infilled reinforced concrete structure, which will be detailed in the manuscript. Moreover, ambient vibration tests were carried out to determine the natural frequencies and corresponding vibration modes of the structure. The main aim of this manuscript is to present a numerical study concerning the influence of the masonry infill walls in the structure seismic response. For this, three numerical models were built discriminating the situations with and without damage and nondamaged infill walls. Validation and calibration of the numerical model was ensured by comparing the numerical frequencies with those obtained from ambient vibration tests. In addition, linear elastic analyses were carried out, using real accelerograms from the Gorkha earthquake to assess and quantify the major differences between the models in terms of inter-storey drifts ratios, inter-storey shear forces and seismic loadings.

Investigation of the Seismic Response of a Byzantine Church and Evaluation of the Effectiveness of Proposed Interventions

2010 ◽  
Vol 26 (2) ◽  
pp. 473-497 ◽  
Author(s):  
Ioannis N. Psycharis ◽  
Harris P. Mouzakis ◽  
Androniki Miltiadou ◽  
Evangelia P. Pavlopoulou ◽  
Ioannis M. Taflampas
Keyword(s):  
Seismic Response ◽  
Time History ◽  
Ambient Vibration ◽  
Seismic Events ◽  
Elastic Analysis ◽  
Severe Damage ◽  
Linear Elastic ◽  
Large Size ◽  
Byzantine Church ◽  
Ambient Vibration Measurements

The seismic response of the twelfth-century Byzantine church of Panhagia Krina in Chios, Greece, is investigated in this paper. The numerical model implements all the details of the geometry of the structure and is validated by comparison of the dynamic characteristics with ambient vibration measurements. Time-history elastic analyses are performed for selective seismic motions, chosen to comply with the expected ground motion in the area. The results show that the linear elastic approach can predict the existing damage quite accurately and explain the collapses that occurred during the 1881 earthquake. The effectiveness of several interventions is also examined; in some cases, cracks were introduced in the model to overcome the limitations of the elastic analysis. The proposed interventions enhance the structure but they cannot eliminate the possibility of severe damage or even local collapses during future seismic events. This is because there are inherent problems in the structure, e.g., the large size of the dome of the main church compared with the overall size of the structure and the structurally weak system of support of this dome.

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