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1.
Different phenomena such as soil consolidation, erosion, and scour beneath an embedded footing supported on piles may lead to loss of contact between soil and the pile cap underside. The importance of this separation on the dynamic stiffness and damping of the foundation is assessed in this work. To this end, a numerical parametric analysis in the frequency domain is performed using a rigorous three‐dimensional elastodynamic boundary element–finite element coupling scheme. Dimensionless plots relating dynamic stiffness functions computed with and without separation effects are presented for different pile–soil configurations. Vertical, horizontal and rocking modes of oscillation are analyzed for a wide range of dimensionless frequencies. It is shown that the importance of separation is negligible for frequencies below those for which dynamic pile group effects start to become apparent. Redistribution of stiffness contributions between piles and footing is also addressed. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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FTIR spectroscopy of Ti-chondrodite,Ti-clinohumite,and olivine in deeply subducted serpentinites and implications for the deep water cycle 总被引：1，自引：0，他引：1
Tingting Shen Jőrg Hermann Lifei Zhang José Alberto Padrón-Navarta Jing Chen 《Contributions to Mineralogy and Petrology》2014,167(4):1-15
Separated olivine grains from a deeply subducted serpentinized wehrlite (Changawuzi in the western Tianshan ultrahigh-pressure belt, China) were analysed with unpolarized transmission FTIR and the Ti contents were determined using LA-ICP-MS. The major bands in the olivine spectra display striking similarities to Ti-clinohumite and are interpreted as OH in lamellae. The quantification of the water content in lamellae requires calibration of the IR-absorption for such bands. We have obtained a new absorption coefficient for Ti-clinohumite of 0.125+/?0.017 ppm cm2 based on polarized FTIR measurements on three orthogonal sections through a large single crystal of Ti-clinohumite from Val Malenco, which has a known water content of 1.53 wt%. The resulting water content in olivine using this calibration factor ranges from 440 to 2,600 ppm and correlates positively with the Ti content that ranges from 130 to 1,400 ppm. For the quantification of the water content in Ti-chondrodite and Ti-clinohumite that are associated with olivine, we developed a new method using attenuated total reflectance FTIR spectroscopy. Ti-chondrodite and Ti-clinohumite display similar IR bands at ~3,562, 3,525 and ~3,583–3,586 cm?1. As in olivine, the water content and Ti content correlate in both Ti-clinohumite and Ti-chondrodite, indicating an intergrowth of these minerals, which has been confirmed by TEM analyses. Our results confirm previous suggestions that there is a strong correlation between the Ti content of ultramafic rocks and their capacity to transport water to the deeper mantle in subduction zones beyond conditions where hydrous phases are stable. 相似文献
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Cristina Medina Luis A. Padrón Juan J. Aznárez Ariel Santana Orlando Maeso 《地震工程与结构动力学》2014,43(13):2035-2050
The beneficial or detrimental role of battered piles on the dynamic response of piled foundations has not been yet fully elucidated. In order to shed more light on this aspect, kinematic interaction factors of deep foundations with inclined piles, are provided for single‐battered piles, as well as for 2 × 2 and 3 × 3 groups of piles subjected to vertically incident plane shear S waves. Piles are modelled as linear‐elastic Bernoulli beams, whereas soil is assumed to be a linear, isotropic, homogeneous viscoelastic half‐space. Different pile group configurations, pile‐soil stiffness ratios, and rake angles are considered. The relevance and main trends observed in the influence of the rake angle on the kinematic interaction factors of the analysed foundations are inferred from the presented results. An important dependence of the kinematic interaction factors on the rake angle is observed together with the existence of an inclination angle at which cap rotation and excitation become out of phase in the low‐to‐mid frequency range. The existence of a small batter angle that provides minimum cap rotation is also shown. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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J.?MauriceEmail author N.?Bolfan-Casanova J.?A.?Padrón-Navarta G.?Manthilake T.?Hammouda J.?M.?Hénot D.?Andrault 《Contributions to Mineralogy and Petrology》2018,173(10):86
Phase relations for a natural serpentinite containing 5 wt% of magnetite have been investigated using a multi-anvil apparatus between 6.5 and 11 GPa and 400–850 °C. Post-antigorite hydrous phase assemblages comprise the dense hydrous magnesium silicates (DHMSs) phase A (11.3 wt% H2O) and the aluminous phase E (Al-PhE, 11.9 wt% H2O). In addition, a ferromagnesian hydrous silicate (11.1 wt% H2O) identified as balangeroite (Mg,Fe)42Si16O54(OH)40, typically described in low pressure natural serpentinite, was found coexisting with Al-PhE between 650 and 700 °C at 8 GPa. In the natural antigorite system, phase E stability is extended to lower pressures (8 GPa) than previously reported in simple chemical systems. The reaction Al-phase E?=?garnet?+?olivine?+?H2O is constrained between 750 and 800 °C between 8 and 11 GPa as the terminal boundary between hydrous mineral assemblages and nominally anhydrous assemblages, hence restricting water transfer into the deep mantle to the coldest slabs. The water storage capacity of the assemblage Al-PhE?+?enstatite (high-clinoenstatite)?+?olivine, relevant for realistic hydrated slab composition along a relatively cold temperature path is estimated to be ca. 2 wt% H2O. Attempts to mass balance run products emphasizes the role of magnetite in phase equilibria, and suggests the importance of ferric iron in the stabilization of hydrous phases such as balangeroite and aluminous phase E. 相似文献
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Eleazar Padrón Gladys Melián Rayco Marrero Dácil Nolasco José Barrancos Germán Padilla Pedro A. Hernández Nemesio M. Pérez 《Pure and Applied Geophysics》2008,165(1):95-114
Significant changes in the diffuse emission of carbon dioxide were recorded in a geochemical station located at El Hierro,
Canary Islands, before the occurrence of several seismic events during 2004. Two precursory CO2 efflux increases started thirteen and nine days before two seismic events of magnitude 2.3 and 1.7, which took place near
El Hierro Island, Canary Islands, on March 23 and April 15, reaching a maximun value of 51.1 and 46.2 g m−2 d−1, respectively, five and eight days before the two seismic events. Other similar increases started thirteen and five days
before the occurrence of two seismic events of magnitude 1.3 and 1.5 which took place on October 15 and 21 respectively, reaching
the maximum values four and one day before the earthquakes. These changes were not related to variations in atmospheric or
soil parameters. The Material Failure Forecast Method (FFM), which analyzes the rate of precursory phenomena, was successfully
applied to forecast the first seismic event that took place in El Hierro Island in 2004. 相似文献
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Cristina Medina Guillermo M. Álamo Juan J. Aznárez Luis A. Padrón Orlando Maeso 《地震工程与结构动力学》2019,48(7):772-791
Although the seismic actions generally consist of a combination of waves, which propagates with an angle of incidence not necessarily vertical, the common practice when analyzing the dynamic behavior of pile groups is based on the assumption of vertically incident wave fields. The aim of this paper is to analyze how the angle of incidence of SV waves affects the dynamic response of pile foundations and piled structures. A three-dimensional boundary element-finite element coupling formulation is used to compute impedances and kinematic interaction factors corresponding to several configurations of vertical pile groups embedded in an isotropic homogeneous linear viscoelastic half-space. These results, which are provided in ready-to-use dimensionless graphs, are used to determine the effective dynamic properties of an equivalent single-degree-of-freedom oscillator that reproduces, within the range where the peak response occurs, the response of slender and nonslender superstructures through a procedure based on a substructuring model. Results are expressed in terms of effective flexible-base period and damping as well as maximum shear force at the base of the structure. The relevance and main trends observed in the influence of the wavefront angle of incidence on the dynamic behavior of the superstructure are inferred from the presented results. It is found that effective damping is significantly affected by the variations of the wave angle of incidence. Furthermore, it comes out that the vertical incidence is not always the worst-case scenario. 相似文献
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F.?GervillaEmail author J.?A.?Padrón-Navarta T.?Kerestedjian I.?Sergeeva J.?M.?González-Jiménez I.?Fanlo 《Contributions to Mineralogy and Petrology》2012,164(4):643-657
The Golyamo Kamenyane serpentinite is a portion of a metaophiolite, located in the Upper High-Grade Unit of the metamorphic basement of the Eastern Rhodope Metamorphic Complex, SE Bulgaria. It consists of metaharzburgite and metadunite hosting layers of metagabbro and some chromitite bodies. All these lithologies were affected by ultrahigh-pressure (UHP) metamorphism and subsequent retrograde evolution during exhumation. Chromite from chromitites can be classified into four textural groups: (1) partly altered chromite, (2) porous chromite, (3) homogeneous chromite and (4) zoned chromite. Partly altered chromite shows unaltered, Al-rich cores with unit cell size of 8.255 Å and Cr# [Cr/(Cr + Al) atomic ratio] = 0.52–0.60, Mg# [Mg/(Mg + Fe2+) atomic ratio] = 0.65–0.70 and Fe3+/(Fe3+ + Fe2+) = 0.20–0.30, surrounded by porous chromite, with a cell size of 8.325 Å, Fe3+/(Fe3+ + Fe2+) < 0.20 and values of Cr# and Mg# evolving from 0.60 to 0.91 and 0.65–0.44, respectively, from core to rim. The chemical composition of porous chromite varies within the following ranges: Cr# = 0.93–0.96, Mg# = 0.48–0.35 and Fe3+/(Fe3+ + Fe2+) = 0.22–0.53. Its unit cell size is very constant (8.350 Å). Most pores in porous and partly altered chromite are filled with chlorite, which also occurs between chromite grains. Homogeneous chromite has Fe3+/(Fe3+ + Fe2+) = 0.55–0.66, Cr# = 0.96–0.99, Mg# = 0.32–0.19 and a cell size of 8.385 Å. The cores of zoned chromite are similar to those of partially altered chromite, but the rims are identical to homogeneous chromite. Although chlorite predominates in the silicate matrix of homogeneous and zoned chromite, it coexists with some antigorite, talc and magnesiohornblende. Mineral data and thermodynamic modeling allow interpretation of the alteration patterns of chromite as the consequence of a two-stage process developed during retrograde metamorphic evolution coeval with fluid infiltration. During the first stage, chromite reacts in the presence of fluid with olivine to produce chlorite and Cr- and Fe2+-rich residual chromite (ferrous chromite) at ~700 to ~450 °C. This dissolution–precipitation reaction involves continuous chromite mass loss resulting in the development of a porous texture. This stage takes place progressively on cooling under water-saturated and reducing conditions. The second stage mainly consists of the formation of homogeneous chromite with ferrian chromite composition by the addition of magnetite to the porous ferrous chromite during a late oxidizing hydrothermal event. 相似文献
10.
Pedro A. Hernández Germán Padilla Eleazar Padrón Nemesio M. Pérez David Calvo Dácil Nolasco Gladys Melián José Barrancos Samara Dionis Fátima Rodríguez Hirochika Sumino 《Applied Geochemistry》2012
Reported herein are the results of eight soil CO2 efflux surveys performed from 2006 to 2011 at Timanfaya Volcanic Field (TVF), Lanzarote Island with the aim of evaluating the long- and short-term temporal variations of the diffuse CO2 emission. Soil CO2 efflux values ranged from non-detectable up to 34.2 g m−2 d−1, with the highest values measured in September 2008. Conditional sequential Gaussian simulations (sGs) were applied to construct soil CO2 efflux distribution maps and to estimate the total CO2 output from the studied area at the TVF. Soil CO2 efflux maps showed a high spatial and temporal variability. Total CO2 emission rates ranged between 41 and 518 t d−1, February 2011 (winter) being the season when maximum diffuse CO2 emission rates were observed. To investigate the influence of external variables on the soil CO2 efflux, a geochemical station (LZT01) was installed at TVF to measure continuously the soil CO2 efflux between July 2010 and March 2012 Since external factors such as barometric pressure, rainfall, soil water content, soil and air temperatures, and wind speed influence strongly the observed soil CO2 effluxes, multiple regression analysis was applied to the time series recorded by the automatic geochemical station LZT01 to remove the contribution of these external factors. The influence of meteorological variables on soil CO2 efflux oscillations accounts for 13% of total variance, with barometric pressure, rainfall and/or soil water content having the most influence in the control of the soil CO2 efflux. These observations along with the results from the eight soil gas surveys performed at TVF indicate that the short and long-term trends in the diffuse CO2 degassing are mainly controlled by environmental factors. 相似文献