On soil-structure interaction in large non-slender partially buried structures     

J. Vega  J. J. Aznárez  A. Santana  E. Alarcón  L. A. Padrón  J. J. Pérez  O. Maeso 《Bulletin of Earthquake Engineering》2013,11(5):1403-1421

This paper addresses the seismic analysis of a deeply embedded non-slender structure hosting the pumping unit of a reservoir. The dynamic response in this type of problems is usually studied under the assumption of a perfectly rigid structure using a sub-structuring procedure (three-step solution) proposed specifically for this hypothesis. Such an approach enables a relatively simple assessment of the importance of some key factors influencing the structural response. In this work, the problem is also solved in a single step using a direct approach in which the structure and surrounding soil are modelled as a coupled system with its actual geometry and flexibility. Results indicate that, quite surprisingly, there are significant differences among prediction using both methods. Furthermore, neglecting the flexibility of the structure leads to a significant underestimation of the spectral accelerations at certain points of the structure.  相似文献   

Modeling Fate and Transport of Volatile Organic Compounds (VOCs) Inside Sewer Systems     

Mohammadyousef Roghani Ph.D.  Ying Li Ph.D.  Nader Rezaei Ph.D.  Ariel Robinson  Elham Shirazi Ph.D.  Kelly G. Pennell Ph.D. 《Ground Water Monitoring & Remediation》2021,41(2):112-121

Hazardous waste site investigations have shown that volatile organic compounds (VOCs) can be transported via sewer pipes and migrate into indoor spaces. Despite field data confirming the presence of this exposure pathway, there is lack of context-based numerical models that provide guidance to characterize and predict VOCs concentration in sewer gas at vapor intrusion sites. Particularly, this poses a challenge when assessing and mitigating risks associated with these exposure pathways. Therefore, a numerical model has been developed to simulate the concentration of VOCs in sewer gas in different stages throughout the sewer lines. The developed model considers various input parameters, including temperature, sewer liquid depth, groundwater depth, and sewer construction characteristics to incorporate local and operational conditions. The model's output is verified using field data from a sewer system constructed near a Superfund site. Moreover, a sensitivity analysis was conducted to evaluate the model's response to variation of the external input parameters. To the best of our knowledge, this study is the first attempt to model VOCs concentration in sewer gas, particularly to address vapor intrusion. The developed model can be used as a numerical tool to support the development of sewer assessment guidelines, risk assessment studies, and mitigation strategies.  相似文献   

The rate of water loss from olivine-hosted melt inclusions   总被引：1，自引：1，他引：0  

Yang Chen  Ariel Provost  Pierre Schiano  Nicolas Cluzel 《Contributions to Mineralogy and Petrology》2011,162(3):625-636

Diffusive water loss from olivine-hosted melt inclusions has been reported previously. This process must be considered when interpreting melt inclusion data. This study measured the rate of water loss from olivine-hosted melt inclusions during heating-stage experiments to test a previous diffusive reequilibration model and the hydrogen diffusion mechanism that controls the rate. Olivine-hosted melt inclusions were heated to a constant temperature in reduced Ar gas in a heating stage for a few hours, and unpolarized Fourier transform infrared spectra were repeatedly measured through the inclusions. Water loss occurred rapidly in the experiments. Within a few hours, the water absorbance at 3,500 cm⁻¹ wavenumber decreased by half. The observed water loss rate can be explained by the diffusive reequilibration model and hydrogen diffusion in olivine coupled with metal vacancy. The beginning of water loss was different in the low- and high-temperature experiments. At low temperatures (1,423 and 1,437 K), water loss did not occur in the initial 1 or 2 h. At high temperatures (1,471–1,561 K), water loss began immediately. The initial time period without water loss at low temperatures may be explained by a hydrogen fugacity barrier in the host olivine. At low temperatures, the internal pressure may be lower than the equilibrium pressure of melt inclusion and olivine, causing lower hydrogen fugacity in the melt inclusion than in the olivine, which will delay the water loss from the melt inclusion. The tested model and diffusivity were used to estimate the rate of water loss during homogenization experiments and magma eruption and cooling. For 1-h homogenization experiment, the model shows that large inclusions (50 μm radius) in large olivines (500 μm radius) are robust against water loss, while large or small inclusions (50–10 μm radius) in small olivines (150 μm radius) may suffer 30–100% water loss. For natural samples, the correlation between water concentration and melt inclusion and olivine sizes may be helpful to infer the initial water concentration, degree of diffusive reequilibration, and magma cooling rate.  相似文献   

Proposal for an International Molybdenum Isotope Measurement Standard and Data Representation     

Thomas F. Nägler  Ariel D. Anbar  Corey Archer  Tatiana Goldberg  Gwyneth W. Gordon  Nicolas D. Greber  Christopher Siebert  Yoshiki Sohrin  Derek Vance 《Geostandards and Geoanalytical Research》2014,38(2):149-151

Molybdenum isotopes are increasingly widely applied in Earth Sciences. They are primarily used to investigate the oxygenation of Earth's ocean and atmosphere. However, more and more fields of application are being developed, such as magmatic and hydrothermal processes, planetary sciences or the tracking of environmental pollution. Here, we present a proposal for a unifying presentation of Mo isotope ratios in the studies of mass‐dependent isotope fractionation. We suggest that the δ^98/95Mo of the NIST SRM 3134 be defined as +0.25‰. The rationale is that the vast majority of published data are presented relative to reference materials that are similar, but not identical, and that are all slightly lighter than NIST SRM 3134. Our proposed data presentation allows a direct first‐order comparison of almost all old data with future work while referring to an international measurement standard. In particular, canonical δ^98/95Mo values such as +2.3‰ for seawater and ?0.7‰ for marine Fe–Mn precipitates can be kept for discussion. As recent publications show that the ocean molybdenum isotope signature is homogeneous, the IAPSO ocean water standard or any other open ocean water sample is suggested as a secondary measurement standard, with a defined δ^98/95Mo value of +2.34 ± 0.10‰ (2s).  相似文献   

Selection and scaling of earthquake records in assessment of structures in low-to-moderate seismicity zones     

Ariel Catalán  Amadeo Benavent-Climent  Xavier Cahís 《Soil Dynamics and Earthquake Engineering》2010,30(1-2):40-49

The behaviour of a building during an earthquake depends on many factors including the characteristics of the ground motion, the configuration and dynamic characteristics of the structure, the hysteretic behaviour of the structural components, the building's non-structural parts, and the local soil behaviour. When conducting seismic assessment studies, controlling the first factor involves selecting and scaling appropriate earthquake records. It is a common practice to scale the records to fit a target acceleration response S_a determined from a pre-determined spectrum or attenuation law. In doing so, two key-problems must be faced: (i) the value adopted for the “effective” period T₁,which lengthens as the structure enters the non-linear range, and (ii) the reliability of the reference value adopted for S_a(T₁). In this work, the influence of selecting appropriate values for these two parameters—T₁ and S_a(T₁)—on the response of the building is investigated from the study of two structures, of 4 and 8 stories. The study does not focus on evaluating a particular seismic code; rather, it uses a European attenuation model as the target spectrum. Non-linear dynamic response analyses are carried out to investigate the Collapse Prevention State of these structures subjected to records representative of a Performance-based Earthquake Engineering level characterized by 2% exceedence in 50 years with 2475 years of return time. The records are selected from a database of European earthquakes, and the failure of the structures is evaluated by statistical means. From the results of the analyses, it is proposed that in seismic assessment studies the reference period for scaling should be 1.1 times the fundamental period of the structure, and at least 30 records should be used to guarantee reliable results.  相似文献   

High CO2 Levels in Boreholes at El Teide Volcano Complex (Tenerife, Canary Islands): Implications for Volcanic Activity Monitoring     

V. Soler  J. A. Castro-Almazán  R. T. Viñas  A. Eff-Darwich  S. Sánchez-Moral  C. Hillaire-Marcel  I. Farrujia  J. Coello  J. de la Nuez  M. C. Martín  M. L. Quesada  E. Santana 《Pure and Applied Geophysics》2004,161(7):1519-1532

Emissions of CO₂ have been known for more than a hundred years as fumarolic activity at the terminal crater of El Teide volcano and as diffuse emissions at numerous water prospection drillings in the volcanic island of Tenerife. Large concentrations of CO₂ (>10% in volume) have been found inside galleries, long horizontal tunnels excavated for water mining. However, CO₂ concentrations of only 2900 ppm have been observed at the surface of the central region of the island (Las Cañadas del Teide caldera). In this work we analysed CO₂ concentrations in the subsurface of Las Cañadas caldera, in an attempt to study the vertical distribution of carbon dioxide and, in particular, the low emissions at the surface. This has been done through a series of 17 vertical profiles in two deep boreholes excavated in the Caldera. We found high levels of CO₂, varying in time from 13 vol% up to 40 vol% in different profiles directly above the water table, while no significant concentrations were detected above the thermal inversion that takes places in both boreholes at approximately 100 m from the water table. Water analyses also showed high dissolved CO₂ levels in equilibrium with the air, and an average 13C value in DIC of +4.7 (PDB), apparently induced by fast CO₂ degassing in the bicarbonated water.  相似文献   

Continuous Monitoring Reveals Drivers of Dissolved Oxygen Variability in a Small California Estuary     

Rafael Santana  Guilherme C. Lessa  John Haskins  Kerstin Wasson 《Estuaries and Coasts》2018,41(1):99-113

Estuarine ecosystem diversity and function can be degraded by low oxygen concentrations. Understanding the spatial and temporal patterns of dissolved oxygen (DO) variation and the factors that predict decreases in DO is thus essential to inform estuarine management. We investigated DO variability and its drivers in Elkhorn Slough, a shallow, well-mixed estuary affected by high nutrient loading and with serious eutrophication problems. Long-term (2001–2012), high-resolution (15 min) time series of DO, water level, winds, and solar radiation from two fully tidal sites in the estuary showed that hypoxia events close to the bottom are common in the summer at the more upstream estuarine station. These events can occur in any lunar phase (spring to neap), at any time of the day, and both on sunny or cloudy days. They are, however, short-lived (lasting in average 40 min) and mainly driven by momentary low turbulent diffusion around slack tides (both at high and low water). Tidal advective transport explains up to 52.1% of the daily DO variability, and the water volume (or DO reservoir) contained in the estuary was not sufficient to avoid hypoxia in the estuary. Solar radiation was responsible for a positively correlated DO daily cycle but caused a decreased in the averaged DO in the summer at the inner station. Wind-driven upwelling reduced the average DO at the more oceanic station during spring. The approach we employed, using robust techniques to remove suspect data due to sensor drift combined with an array of statistical techniques, including spectral, harmonic, and coherence spectrum analysis, can serve as a model for analyses of long-term water quality datasets in other systems. Investigations such as ours can inform coastal management by identifying key drivers of hypoxia in estuaries.  相似文献   

Effect of Void Ratio on <Emphasis Type="Italic">K</Emphasis><Subscript>0</Subscript> of a Sand by Means of Triaxial Stress-Path Testing     

Teresa Santana  Mariline Candeias 《Geotechnical and Geological Engineering》2018,36(1):257-266

This paper presents an experimental technique using a computer controlled triaxial test to evaluate K ₀, not requiring the use of any radial measurement transducers. It uses commercial software that applies a ramp of radial stress with back volume measurement and control. The method is applicable only to saturated specimens in drained conditions. The equipment used is briefly described, as well as the testing procedures. Results of laboratory tests on Toyoura sand specimens, with four different initial void ratios, are presented. For the preparation of all specimens tested, a dry funnel deposition method with undercompaction was used. It was concluded that, for the initial void ratios tested and for the stress level induced, stress-strain behavior fell in a narrow range the \(K_{0}^{NC}\) values were slightly higher for looser specimens, although lower than predicted by Jaky’s equation.  相似文献   

A BEM–FEM model for the dynamic analysis of building structures founded on viscoelastic or poroelastic soils     

A. Santana  J. J. Aznárez  L. A. Padrón  O. Maeso 《Bulletin of Earthquake Engineering》2016,14(1):115-138

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Impact of Biocides on Hydrogen Sulfide Production and Growth of Desulfovibrio vulgaris          下载免费PDF全文

Eitan Ben‐Dov  Ofir Zisman  Asher Brenner  Ariel Kushmaro 《洁净——土壤、空气、水》2016,44(10):1423-1427

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