Suction and time effects in rockfill deformation     

Eduardo E. Alonso  Mauricio A. Tapias 《国际地质力学数值与分析法杂志》2019,43(5):1032-1050

Ambient relative humidity controls the stress-strain-time behaviour of granular media exhibiting particle breakage. Breakage is the result of crack propagation inside loaded particles. The DEM model developed uses the results of subcritical crack propagation in brittle rock to predict breakage and the subsequent structural rearrangement. Two closed-form solutions at grain level, stress distribution under diametrically opposed forces and the mode I crack propagation velocity, were included in the DEM formulation. Crack propagation velocity depends explicitly on relative humidity. The resulting model incorporates comminution and splitting modes of particle breakage as well as arbitrary grain shapes by means of aggregation of spherical microparticles. The model was first validated against a large diameter suction-controlled oedometer test on hard limestone crushed gravel. Direct tests on contact properties (local stiffness and friction) helped to validate the model. The model was then used to predict the response of large diameter suction-controlled triaxial tests on gravels having different (uniform) initial sizes. Time delayed deformations and wetting-induced collapse deformations under maintained load are also a natural outcome of the model. They were shown to follow quite accurately the experimental results.  相似文献   

Widely linear denoising of multicomponent seismic data     

Breno Bahia  Mauricio D. Sacchi 《Geophysical Prospecting》2020,68(2):431-445

Seismic data processing is a challenging task, especially when dealing with vector-valued datasets. These data are characterized by correlated components, where different levels of uncorrelated random noise corrupt each one of the components. Mitigating such noise while preserving the signal of interest is a primary goal in the seismic-processing workflow. The frequency-space deconvolution is a well-known linear prediction technique, which is commonly used for random noise suppression. This paper represents vector-field seismic data through quaternion arrays and shows how to mitigate random noise by proposing the extension of the frequency-space deconvolution to its hypercomplex version, the quaternion frequency-space deconvolution. It also shows how a widely linear prediction model exploits the correlation between data components of improper signals. The widely linear scheme, named widely-linear quaternion frequency-space deconvolution, produces longer prediction filters, which have enhanced signal preservation capabilities shown through synthetic and field vector-valued data examples.  相似文献   

Effects of pre-orogenic tectonic structures on the Cenozoic evolution of Andean deformed belts: Evidence from the Salar de Punta Negra Basin in the Central Andes of Northern Chile     

Fernando Martínez  Cristopher López  Mauricio Parra 《Basin Research》2020,32(6):1441-1462

We integrated new field observations, two-dimensional (2-D) seismic profiles and new and previously reported chronological data to understand the effects of pre-orogenic structures on the tectonic evolution of the Salar de Punta Negra in the Central Andes. For first time a series of restored geological cross-sections are presented, thus showing the pre-orogenic tectonic architecture of the region and new ideas about the tectonic evolution of the inner forearc of the Central Andes. Our results show a series of east-dipping normal faults as the main pre-orogenic structures in the region, which resulted from lithospheric stretching of the western continental margin during the Paleozoic to Mesozoic (Triassic–Jurassic). These were later incorporated into the Andean orogen by tectonic inversion, forming west-verging inversion anticlines. The beginning of the tectonic inversion is constrained by the first on-lap of the Upper Cretaceous-Palaeocene syn-kinematic deposits on the top of the Mesozoic syn-rift successions, highlighting that inversion occurred during this period. These syn-kinematic deposits display zircons with older age peaks between ca. 200 and 300 Ma, thus indicating that some Carboniferous to Triassic sources of sediments were eroded during the uplift of the orogen. Other basement reverse faults affect the footwalls of normal inverted faults and the shoulders of ancient half-graben structures. These truncate and decapitate previous inverted faults and completely cut the infill of the basin, leading to exhumation of the pre-rift basement rocks. We propose that the propagation of these structures was favoured by the modified thermal-tectonic state of the lithosphere from the eastward migration of the volcanic arc, and not by the previous pre-orogenic structures. The structural and stratigraphic relationships recognized both in the field and 2-D seismic profiles indicate that many reverse faults originated after the initial tectonic inversion and continued to be active from the Eocene until the Pleistocene period.  相似文献   

Comparative review of data-driven landslide susceptibility models: case study in the Eastern Andes mountain range of Colombia     

Calderón-Guevara  Wilmar  Sánchez-Silva  Mauricio  Nitescu  Bogdan  Villarraga  Daniel F. 《Natural Hazards》2022,113(2):1105-1132

Natural Hazards - Estimating the likelihood of landslides has proven to be critical for development and protection of infrastructure (e.g. pipelines, roads) and urban settlements. Currently, for...  相似文献   

Ground- and space-based GPS data ingestion into the NeQuick model     

C. Brunini  F. Azpilicueta  M. Gende  E. Camilion  A. Aragón Ángel  M. Hernandez-Pajares  M. Juan  J. Sanz  Dagoberto Salazar 《Journal of Geodesy》2011,85(12):931-939

This paper presents a technique for ingesting ground- and space-based dual-frequency GPS observations into a semi-empirical global electron density model. The NeQuick-2 model is used as the basis for describing the global electron density distribution. This model is mainly driven by the F2 ionosphere layer parameters (i.e. the electron density, N _m F2, and the height, h _m F2 of the F2 peak), which, in the absence of directly measured values, are computed from the ITU-R database (ITU-R 1997). This database was established using observations collected from 1954 to 1958 by a network of around 150 ionospheric sounders with uneven global coverage. It allows computing monthly median values of N _m F2 and h _m F2 (intra-month variations are averaged), for low and high solar activity. For intermediate solar activity a linear interpolation must be performed. Ground-based GNSS observations from a global network of ~350 receivers are pre-processed in order to retrieve slant total electron content (sTEC) information, and space-based GPS observations (radio occultation data from the FORMOSAT-3/COSMIC constellation) are pre-processed to retrieve electron density (ED) information. Both, sTEC and ED are ingested into the NeQuick-2 model in order to adapt N _m F2 and h _m F2, and reduce simultaneously both, the observed minus computed sTEC and ED differences. The first experimental results presented in this paper suggest that the data ingestion technique is self consistent and able to reduce the observed minus computed sTEC and ED differences to ~25–30% of the values computed from the ITU-R database. Although sTEC and ED are both derived from GPS observations, independent algorithm and models are used to compute their values from ground-based GPS observations and space-based FORMOSAT-3/COSMIC radio occultations. This fact encourages us to pursue this research with the aim to improve the results presented here and assess their accuracy in a reliable way.  相似文献   

Anthropogenic heat in the city of S?o Paulo, Brazil     

Mauricio Jonas Ferreira  Amauri Pereira de Oliveira  Jacyra Soares 《Theoretical and Applied Climatology》2011,104(1-2):43-56

The main goal of this work is to describe the anthropogenic energy flux (Q _F) in the city of S?o Paulo, Brazil. The hourly, monthly, and annual values of the anthropogenic energy flux are estimated using the inventory method, and the contributions of vehicular, stationary, and human metabolism sources from 2004 to 2007 are considered. The vehicular and stationary sources are evaluated using the primary consumption of energy based on fossil fuel, bio fuel, and electricity usage by the population. The diurnal evolution of the anthropogenic energy flux shows three relative maxima, with the largest maxima occurring early in the morning (??19.9 Wm^?2) and in the late afternoon (??20.3 Wm^?2). The relative maximum that occurs around noontime (??19.6 Wm^?2) reflects the diurnal pattern of vehicle traffic that seems to be specific to S?o Paulo. With respect to diurnal evolution, the energy flux released by vehicular sources (Q _FV) contributes approximately 50% of the total anthropogenic energy flux. Stationary sources (Q _FS) and human metabolism (Q _FM) represent about 41% and 9% of the anthropogenic energy flux, respectively. For 2007, the monthly values of Q _FV, Q _FS, Q _FM, and Q _F are, respectively, 16.8?±?0.25, 14.3?±?0.16, 3.5?±?0.03, and 34.6?±?0.41?MJ?m^?2?month^?1. The seasonal evolution monthly values of Q _FV, Q _FS, Q _FM, and Q _F show a relative minimum during the summer and winter vacations and a systematic and progressive increase associated with the seasonal evolution of the economic activity in S?o Paulo. The annual evolution of Q _F indicates that the city of S?o Paulo released 355.2?MJ?m^?2?year^?1 in 2004 and 415.5?MJ?m^?2?year^?1 in 2007 in association with an annual rate of increase of 19.6?MJ?m^?2?year^?1 (from 2004 to 2006) and 30.5?MJ?m^?2?year^?1 (from 2006 to 2007). The anthropogenic energy flux corresponds to about 9% of the net radiation at the surface in the summer and 15% in the winter. The amplitude of seasonal variation of the maximum hourly value of the diurnal variation increases exponentially with latitude.  相似文献   

Bloom of the Yessotoxin producing dinoflagellate Protoceratium reticulatum (Dinophyceae) in Northern Chile     

Gonzalo Álvarez  Eduardo Uribe  Rosario Díaz  Mauricio Braun  Carmen Mariño  Juan Blanco 《Journal of Sea Research》2011,65(4):427-434

Potential spawning habitat is defined as the area where environmental conditions are suitable for spawning to occur. Spawning adult data from the first quarter (January–March) of the International Bottom Trawl Survey have been used to study the inter-annual variability of the potential spawning habitat of North Sea plaice from 1980 to 2007. Generalised additive models (GAM) were used to create a model that related five environmental variables (depth, bottom temperature and salinity, seabed stress and sediment type) to presence–absence and abundance of spawning adults. Then, the habitat model was applied each year from 1970 to 2007 to predict inter-annual variability of the potential spawning habitat. Predicted responses obtained by GAM for each year were mapped using kriging. A hierarchical classification associated with a correspondence analysis was performed to cluster spawning suitable areas and to determine how they evolved across years. The potential spawning habitat was consistent with historical spawning ground locations described in the literature from eggs surveys. It was also found that the potential spawning habitat varied across years. Suitable areas were located in the southern part of the North Sea and along the eastern coast of England and Scotland in the eighties; they expanded further north from the nineties. Annual survey distributions did not show such northward expansion and remained located in the southern North Sea. This suggests that this species' actual spatial distribution remains stable against changing environmental conditions, and that the potential spawning habitat is not fully occupied. Changes in environmental conditions appear to remain within plaice environmental ranges, meaning that other factors may control the spatial distribution of plaice spawning habitat.  相似文献   

Evolution of the deep Atlantic water masses since the last glacial maximum based on a transient run of NCAR-CCSM3     

Juliana M. Marson  Lawrence A. Mysak  Mauricio M. Mata  Ilana Wainer 《Climate Dynamics》2016,46(3-4):865-877

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Ra and Rn isotopes as natural tracers of submarine groundwater discharge in the patagonian coastal zone (Argentina): an initial assessment     

Américo I. Torres  Carlos F. Andrade  Willard S. Moore  Mauricio Faleschini  José L. Esteves  Luis F. H. Niencheski  Pedro J. Depetris 《Environmental Earth Sciences》2018,77(4):145

Submarine groundwater discharge (SGD) is herein recognized as a significant pathway of material transport from land to the coastal SW Atlantic Ocean and thus, it can be a relevant factor affecting the marine biogeochemical cycles in the region. This paper focuses on the initial measurements of ²²⁶Ra, ²²⁸Ra and ²²²Rn made in Patagonia’s coastal zone of Chubut and Santa Cruz provinces (42°S–48°S, Argentina). ²²⁶Ra activity ranged from 2.9 to 73.5 dpm 100 L^?1, and ²²⁸Ra activity ranged from 11.9 to 311.0 dpm 100 L^?1 in groundwater wells. The radium activities found in Patagonia’s marine coastal regions and adjacent shelf indicate significant enrichment throughout the coastal waters. Groundwater samples presented the largest ²²²Rn activity and ranged from 2.66 to 1083 dpm L^?1. Conversely, in the coastal marine environment, the ²²²Rn activity ranged from 1.03 to 6.23 dpm L^?1. The Patagonian coastal aquifer showed a larger enrichment in ²²⁸Ra than in ²²⁶Ra, which is a typical feature for sites where SGD is dominant, probably playing a significant role in the biogeochemistry of these coastal waters.  相似文献   

The opening of the Magellan Strait and its geodynamic implications     

Matías C. Ghiglione  Angela Teresa Navarrete‐Rodríguez  Mauricio González‐Guillot  Gustavo Bujalesky 《地学学报》2013,25(1):13-20

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