Issue 192 by Hernán E. Martínez-Carvajal
The paper shows how axisymmetric finite element numerical models can be used to optimize the desi... more The paper shows how axisymmetric finite element numerical models can be used to optimize the design of friction piles foundations in an environment that is prone to regional subsidence. The study considers friction piles in typical Mexico City soft clays, that are subjected to external loads and soil consolidation due to variations in piezometric conditions. The constitutive models used to numerically simulate the behavior of the clays vary from a basic elastic perfectly-plastic model to a critical state model that is able to account for the anisotropic yielding behavior of Mexico City clay. The simulations consider the long term behavior of the internal piles within a large pile group.
Issue 194 by Hernán E. Martínez-Carvajal
A huge landslide took place at Alto Verde residential complex at the end of 2008 in the city of M... more A huge landslide took place at Alto Verde residential complex at the end of 2008 in the city of Medellin, Colombia, claiming the lives of
twelve people and destroying six houses. Landslides are characterized by large deformations in the soil mass. This study used the material
point method (MPM), a particle-based method that takes advantage of a double Lagrangian-Eulerian discretization. This approach provides
a robust framework that enables the numerical simulation of large strains, without mesh entanglement issues that are common with the
Finite Element Method. The numerical model proposed here assumes simplifications of the geotechnical, morphological and structural
buildings conditions on the site. Nevertheless, the final numerical deformed configuration described the geometric features observed in the
field successfully. The result allows applications such as the design of barriers, risk assessment or determination of a minimum safe distance
for a building from a slope susceptible to landslides.
Papers by Hernán E. Martínez-Carvajal
The surface and downhole accelerations records of "Central de Abasto Oficinas (CAO)" array at Mex... more The surface and downhole accelerations records of "Central de Abasto Oficinas (CAO)" array at Mexico City, have been analyzed to determine the soil stiffness as a function of shear strain amplitude. The 09/10/95 seismic event (NS component) has been used for this purpose. The shear stress-strain histories have been evaluated directly from the field downhole acceleration records, employing a technique of system identification, and used to obtain the variation of shear modulus with shear strain amplitude. A shear-beam model, calibrated by the identified properties, is found to represent the site dynamic response characteristics. The results have been compared with values obtained in previous investigations from field and laboratory tests.
A Brief Introduction to Nanoseismic Monitoring
Geociências, Jun 25, 2018
Introduction Methods Results and Discussions Conclusions and Recommendations for future work Ackn... more Introduction Methods Results and Discussions Conclusions and Recommendations for future work Acknowledgments References ABSTRACT-Ever increasing urbanization over the thick and less cohesive soil of the Federal District (DF)-Brazil, has increased area's vulnerability to natural hazards, especially the soil erosion and mass movement. This preliminarily study applied noise based geophysical techniques like power spectral density (PSD), horizontal to vertical spectral ratio (HVSR), multichannel analysis of surface waves (MASW) and noise interferometry to a mass movement in Brasilia for the understating of geodynamic processes working in the background of these hazards. Here obtained results show a uniform stratigraphic peak at 2 Hz observed on all HVSR curves, a four layered shear wave section was obtained by MASW. Dispersion curve (frequency vs phase velocity) shows first and second fundamental modes at frequencies of 5 and 25 Hz, respectively. Noise correlograms show time delay larger than +-0.5 sec on the waveforms of ZR (vertical-radial) component, mainly in acausal part. Relative velocity changes calculated by stretching technique show anomalous trends in response to rainfall events. Follow research will focus on the detection of possible changes in noise records within mass movement mainly related to natural triggering factors (rainfall and river erosion) under more controlled data conditions.
Time-Lapse Monitoring of an Engineering Scaled Excavation at Federal District, Brazil by Passive Ambient NoiseInterferometry
AGU Fall Meeting Abstracts, Dec 1, 2016
Análise De Ondas De Superfície Registradas Em Um Movimento De Massas Em Brasília, Brasil: Uma Implicação Na Mitigação De Riscos
Geociências (São Paulo), Mar 13, 2019
Ever increasing urbanization over the thick and less cohesive soil of the Federal District (DF) –... more Ever increasing urbanization over the thick and less cohesive soil of the Federal District (DF) – Brazil, has increased area's vulnerability to natural hazards, especially the soil erosion and mass movement. This preliminarily study applied noise based geophysical techniques like power spectral density (PSD), horizontal to vertical spectral ratio (HVSR), multichannel analysis of surface waves (MASW) and noise interferometry to a mass movement in Brasilia for the understating of geodynamic processes working in the background of these hazards. Here obtained results show a uniform stratigraphic peak at 2 Hz observed on all HVSR curves, a four layered shear wave section was obtained by MASW. Dispersion curve (frequency vs phase velocity) shows first and second fundamental modes at frequencies of 5 and 25 Hz, respectively. Noise correlograms show time delay larger than +- 0.5 sec on the waveforms of ZR (vertical-radial) component, mainly in acausal part. Relative velocity changes calculated by stretching technique show anomalous trends in response to rainfall events. Follow research will focus on the detection of possible changes in noise records within mass movement mainly related to natural triggering factors (rainfall and river erosion) under more controlled data conditions.
Does GPM-based multi-satellite precipitation enhance rainfall estimates over Pakistan and Bolivia arid regions?
AGUFM, Dec 1, 2016
Earth Sciences Research Journal, 2020
Rainfall-induced landslides pose a significant risk to communities and infrastructures. To improv... more Rainfall-induced landslides pose a significant risk to communities and infrastructures. To improve the prediction of such events, it is imperative to adequately investigate the rainfall-dependent dynamics (leading to fluidization) and any associated internal sliding along shear planes within clayey slopes. Therefore, the present study adopted ambient noise analysis based on the Horizontal to Vertical Spectral Ratio (HVSR) method, to measure the seasonal variation of Rayleigh wave ellipticity as an indicator for the internal deformation and transition in the material state. The methodology was applied to an existing landslide, where variations in soil stiffness and internal sliding were expected to occur in response to rainfall. To improve the interpretation of the HVSR results (and hence the prediction of landslide’ reactivation by rainfall), HVSR measurements were also conducted on a field-scale pile load test. The pile test allowed a comparison of the seismic data generated by the...
International Journal of Economic and Environmental Geology, Jan 8, 2019
The present study provides a brief description of the ambient noise recorded at a slow moving mas... more The present study provides a brief description of the ambient noise recorded at a slow moving mass movement in Ribeirão Contagem Basin. The area is an interesting natural laboratory as river detachment processes in a number of different stages can be identified and are easily accessible. We investigate the site dynamic characteristics of the study area by recording ambient noise time-series at nine points, using portable nine three-component short period seismometers. The time-series are processed to give both horizontal to vertical spectral ratio (HVSR) curves as well as time-frequency plots of noise power spectral density (SPD). The HVSR curves illustrate and quantify aspects of site resonance effects due to the local geological setting. Probability density function (PDF) shows that noise level lies well between new high noise model (NHNM) and new lower noise model (NLNM) and their probabilities are higher above 2 Hz. HVSR curves present a uniform lithologically controlled peak at...
Sustainability, 2019
Geophysical methods have a varying degree of potential for detailed characterization of landslide... more Geophysical methods have a varying degree of potential for detailed characterization of landslides and their dynamics. In this study, the application of four well-established seismic-based geophysical techniques, namely Ambient Noise Interferometry (ANI), Horizontal to Vertical Spectral Ratio (HVSR), Multi-Channel Analysis of Surface Waves (MASW) and Nanoseismic Monitoring (NM), were considered to examine their suitability for landslide characterization and monitoring the effect of seasonal variation on slope mass. Furthermore, other methods such as Ground Penetrating Radar (GPR) and DC Resistivity through Electrical Resistivity Tomography (ERT) were also used for comparison purpose. The advantages and limitations of these multiple techniques were exemplified by a case study conducted on Sobradinho landslide in Brazil. The study revealed that the geophysical characterization of the landslide using traditional techniques (i.e., GPR, ERT and MASW) were successful in (i) the differenti...
Geosciences = Geociências, 2018
Ever increasing urbanization over the thick and less cohesive soil of the Federal District (DF), ... more Ever increasing urbanization over the thick and less cohesive soil of the Federal District (DF), Brazil has increased area's vulnerability to natural hazards, especially the soil erosion and mass movement. This preliminarily study applied noise based geophysical techniques like power spectral density (PSD), horizontal to vertical spectral ratio (HVSR), multichannel analysis of surface waves (MASW) and noise interferometry to a mass movement in Brasilia for the understating of geodynamic processes working in the background of these hazards. Here obtained results show a uniform stratigraphic peak at 2 Hz observed on all HVSR curves, a four layered shear wave section was obtained by MASW. Dispersion curve (frequency vs phase velocity) shows first and second fundamental modes at frequencies of 5 and 25 Hz, respectively. Noise correlograms show time delay larger than +- 0.5 sec on the waveforms of ZR (vertical-radial) component, mainly in acausal part. Relative velocity changes calcu...
Anuário do Instituto de Geociências - UFRJ, 2018
Os movimentos de massa são um dos fenômenos naturais que mais tem causado prejuízos, no mundo. O ... more Os movimentos de massa são um dos fenômenos naturais que mais tem causado prejuízos, no mundo. O material transportado e depositado nas encostas em consequência de um movimento de massa pode ser reconhecido por um número de características granulométricas, morfométricas e micromorfológicas, da encosta. A área de estudo localiza-se no Distrito Federal na Região Administrativa da Fercal, dentro da bacia hidrográfica do Ribeirão Contagem. O objetivo da pesquisa consiste em caracterizar os diferentes materiais que constituem as encostas e fundos de vale com a finalidade de verificar a correlação entre o relevo do Planalto Central e as rampas do Sudeste Brasileiro. Três encostas com morfologias distintas (concavidade fechada, concavidade aberta, e convexo-retilínea) foram escolhidas e traçadas sua topossequência, utilizando trado manual. Foram recolhidas 78 amostras deformadas de solos para análise granulométricas/ morfoscópicas e 6 amostras indeformadas em porções distintas das encostas para realização dos testes de cisalhamento. A análise granulométrica revelou textura similar entre as encostas, sendo para a E1 (predominantemente argilosa, franco argilosa e silto argilosa), E2 (variação entre argilosa e arenosa) e E3 (entre argilosa, franco argilosa e silto argilosa). Análises morfoscópica corroboraram para distinguir o topo e média encosta típica de depósitos coluvionares (grãos irregulares, angulares e sub angulares com superfície rugosa) de amostras da baixa encosta típica depósitos aluvionares (grãos sub arredondados e arredondados com superfícies onduladas e alisadas). Os testes de cisalhamento revelaram altos valores para todas as porções das encostas, sendo que a convexo-retilínea apresentou a maior (68,11kPa). A porção média da encosta E2 é a única a apresentar fator de estabilidade crítico, devido principalmente a alta declividade. A estabilidade dos materiais averiguada por esta pesquisa admite dizer que a ocorrência de fenômenos de deslizamento na bacia do Ribeirão Contagem não estão predominantemente ligadas às características mecânicas dos materiais que as compõe. As análises geomorfológicas por sua vez indicam a existência pretérita da condição de eventos mais intensos que geraram as cicatrizes e grandes deposições, observadas atualmente. Palavras-chave: geomorfologia de encostas; resistência ao cisalhamento; movimentos de massa
Brazilian Journal of Geology, 2019
The application of geophysical monitoring technologies may offer an opportunity to understand the... more The application of geophysical monitoring technologies may offer an opportunity to understand the dynamic of slopes in response to factors triggering their instability. In this study, Ambient Noise Interferometry was used as a monitoring approach on a man-made reduced-scale vertical slope and on a natural-scale landslide in Sobradinho (Brazil), under the influence of mechanical stress and rainfall, respectively. For both experiments, we adopted similar data acquisition system and processing workflow. After preprocessing of ambient seismic noise, the time-lapse changes were determined in terms of relative velocity changes using the moving window cross spectral technique. For the vertical slope, terrestrial laser scanning was also performed to detect crack or fissure generation. The prototype experiment results showed a decreasing trend of relative velocity changes and reached a minimum value of-0.6% at the end of the experiment. No change was detected on the digital elevation model that was computed from terrestrial laser scanning images, due to the absence of centimeter scale superficial fissures. At natural scale (Sobradinho landslide), no significant variation in relative velocity changes was detected for the rainy and non-rainy days, mainly because of the inadequate change in the degree of saturation, which was found within a relatively short period of data acquisition.
Anuário do Instituto de Geociências - UFRJ, 2019
Brazilian landslides are characterized as shallow, clay rich and are commonly triggered by the su... more Brazilian landslides are characterized as shallow, clay rich and are commonly triggered by the summer rainfalls. Therefore, the landslide geological information, such as shear surface location, has a paramount importance in their mechanism comprehension. The most adapted methods for the estimation of shear wave velocity profile are borehole stratigraphic logs or Standard Penetration Test (SPT) and Cone Penetration Test (CPT). However, the present study applied shear wave velocity estimation of Sobradinho landslide (SLS) by a joint inversion of horizontal to vertical spectral ratio (HVSR) curve and dispersion curve (DC) extracted from frequency-wavenumber (f-k) analysis of ambient noise records. HVSR curves at all the stations in the area exhibit the ubiquitous resonance frequency peak at 2 Hz indicates that at these stations the substratum is common. The f-k results for E-W component let us obtain an acceptable DC between 5 and 7 Hz range. Finally, joint inversion was interpreted based on the diffuse field assumption. The initial model was proposed to be a three-layered over a half-space. Results of joint inversion indicate that the substratum is at 24 m depth, with Vs values close to 1500 m/s. DC defines two layers overlaying the substratum: superficial layer with velocities near to 200 m/s (7m thick), and the second layer with Vs value of 1000 m/s. We think that abrupt rheology (stiffness) change between the first and the second layer could provide an evidence of the landslide re-activation during moderate to strong rainfall events. The proposed methodology will prove a reconnaissance survey for the detailed geotechnical investigations that will confirm the obtained results.
Revista Brasileira de Geomorfologia, 2019
O presente estudo tem por objetivo fazer uso de tecnologia GPR (Ground Penetration Radar), também... more O presente estudo tem por objetivo fazer uso de tecnologia GPR (Ground Penetration Radar), também conhecido como Georadar, para distinguir os materiais aluvionares, coluvionares e eluvionares depositados nas encostas e planícies da fazenda Vão do Buraco, calha do Contagem, porção leste do Planalto Central, na região do Distrito Federal. Foram definidas três encostas: côncava fechada (E1), côncava aberta (E2) e convexa (E3), para a aquisição de dados dos perfis de GPR, onde já se tinham descrições prévias dos materiais depositados, apresentando elúvio no topo, colúvio na média encosta e colúvio/aluvião na planície com formação de um leque aluvial. Fez-se uso de uma antena de 400 MHz para a sondagem, resultando em radargramas com informações de refletância. Devido às diferenças de composição entre o aluvião e o coluvião, seus contatos são abruptos. O alúvio, por apresentar cascalhos em sua composição, é definido por um número maior de alvos e alta refletância. Já o colúvio é constituí...
Remote Sensing, 2018
Launched in 2014, the Global Precipitation Measurement (GPM) mission aimed at ensuring the contin... more Launched in 2014, the Global Precipitation Measurement (GPM) mission aimed at ensuring the continuity with the Tropical Rainfall Measuring Mission (TRMM) launched in 1997 that has provided unprecedented accuracy in Satellite Precipitation Estimates (SPEs) on the near-global scale. Since then, various SPE versions have been successively made available from the GPM mission. The present study assesses the potential benefits of the successive GPM based SPEs product versions that include the Integrated Multi–Satellite Retrievals for GPM (IMERG) version 3 to 5 (–v03, –v04, –v05) and the Global Satellite Mapping of Precipitation (GSMaP) version 6 to 7 (–v06, –v07). Additionally, the most effective TRMM based SPEs products are also considered to provide a first insight into the GPM effectiveness in ensuring TRMM continuity. The analysis is conducted over different geomorphic and meteorological regions of Pakistan while using 88 precipitations gauges as the reference. Results show a clear en...
Modeling Earth Systems and Environment, 2017
respectively. The vulnerability of Tehcil Kot Addu is related positively to the recharge rates an... more respectively. The vulnerability of Tehcil Kot Addu is related positively to the recharge rates and agricultural landuse. Results of this study can be used for sustainable agriculture in the study area and other regions having silmilar hydrogeological characteristics.
Environmental Earth Sciences, 2017
The area of Thal Doab is located in the Indus Basin and is underlain by a thick alluvial aquifer ... more The area of Thal Doab is located in the Indus Basin and is underlain by a thick alluvial aquifer called the Thal Doab aquifer (TDA). The TDA is undergone intense hydrological stress owing to rapid population growth and excessive groundwater use for livestock and irrigated agricultural land uses. The potential impact of these land uses on groundwater quality was assessed using a DRASTIC model in a Geographic Information System environment. Seven DRASTIC thematic maps were developed at fixed scale and then combined into a groundwater vulnerability map. The resultant vulnerability index values were grouped into four zones as low, moderate, high and very high. The study has established that 76% of the land area that is underlain by the TDA has a high to very high vulnerability to groundwater contamination mainly because of a thin soil profile, a shallow water table and the presence of soils and sediments with high hydraulic conductivity values. In addition, only 2 and 22% of the total area lie in low and moderate vulnerability zones, respectively. The outcomes of this study can be used to improve the sustainability of the groundwater resource through proper land-use management.
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Issue 192 by Hernán E. Martínez-Carvajal
Issue 194 by Hernán E. Martínez-Carvajal
twelve people and destroying six houses. Landslides are characterized by large deformations in the soil mass. This study used the material
point method (MPM), a particle-based method that takes advantage of a double Lagrangian-Eulerian discretization. This approach provides
a robust framework that enables the numerical simulation of large strains, without mesh entanglement issues that are common with the
Finite Element Method. The numerical model proposed here assumes simplifications of the geotechnical, morphological and structural
buildings conditions on the site. Nevertheless, the final numerical deformed configuration described the geometric features observed in the
field successfully. The result allows applications such as the design of barriers, risk assessment or determination of a minimum safe distance
for a building from a slope susceptible to landslides.
Papers by Hernán E. Martínez-Carvajal