Geotechnical design with apparent seismic safety factors well-bellow 1

The paper demonstrates that whereas often in seismic geotechnical design it is not realistically feasible to design with ample factor of safety against failure as is done in static design, an “engineering” apparent seismic factor of safety less than 1 does not imply failure. Examples from slope stability and foundation rocking illustrate the concept. It is also shown that in many cases it may be beneficial to under-design the foundation by accepting substantial uplifting and/or full mobilization of bearing capacity failure mechanisms.     

Buckling behaviour of single pile and pile bent in the Scotch Road Bridge

The buckling behaviour of the 360 × 152 steel H-piles supporting the integral abutments of the Scotch Road Bridge, located in Trenton, New Jersey, has been studied for the cases of single pile and pile bent. Three-dimensional finite-element models for single pile and pile bent have been developed to study the behaviour of these fully embedded piles under axial and lateral loading. An iterative analysis based on extracting the eigenvalues and eigenvectors (mode shapes) that correspond to the pile(s) critical buckling loads has been adopted. The pile(s) and the surrounding sand were modelled using solid continuum elements in the finite-element model. Material non-linearity is accounted for in both the piles and the soil in the base state of the model. A parametric study has been utilized to determine the effect of the geometric and material properties of the pile and the surrounding sand on the predicted critical buckling loads of the piles. The effects of four parameters have been studied: soil stiffness, pile length, type of connection, and combining vertical and lateral loads. The results from the parametric study showed that the variation of the percentage change in the sand stiffness, pile length, and combining vertical and lateral loads with the critical buckling loads of the 360 × 152 H-piles is nonlinear. Furthermore, the parameters studied are more influential in affecting the critical buckling load of a single pile than a pile bent, with the exception of the ‘type of connection’ parameter.     

Dynamic soil–structure interaction analysis of a telescope at the Javalambre Astrophysical Observatory

This paper presents the dynamic soil–structure analysis of the main telescope T250 of the Observatorio Astrofísico de Javalambre (OAJ, Javalambre Astrophysical Observatory) on the Pico del Buitre. Vibration control has been of prime concern in the design, since astrophysical observations may be hindered by mechanical vibration of optical equipment due to wind loading. The telescope manufacturer therefore has imposed a minimal natural frequency of 10 Hz for the supporting telescope pier. Dynamic soil–structure interaction may significantly influence the lowest natural frequency of a massive construction as a telescope pier. The structure clamped at its base has a resonance frequency of 14.3 Hz. A coupled finite element–boundary element (FE–BE) model of the telescope pier that accounts for the dynamic interaction of the piled foundation and the soil predicts a resonance frequency of 11.2 Hz, demonstrating the significant effect of dynamic soil–structure interaction. It is further investigated to what extent the coupled FE–BE model can be simplified in order to reduce computation time. The assumption of a rigid pile cap allows us to account for dynamic soil–structure interaction in a simplified way. A coupled FE–BE analysis with a rigid pile cap predicts a resonance frequency of 11.7 Hz, demonstrating a minor effect of the pile cap flexibility on the resonance frequency of the telescope pier. The use of an analytical model for the pile group results in an overestimation of the dynamic soil stiffness. This error is due to the large difference between the actual geometry and the square pile cap model for which the parameters have been tuned.     

Hydro-climatic trends in the Abay/Upper Blue Nile basin,Ethiopia

Trends of the three hydro-meteorological variables precipitation, temperature and stream flow, represented by 13, 12, and 9 gauging stations, respectively, within the Abay/Upper Blue Nile basin have been studied to support water management in the region. The Trends were evaluated over different time periods depending on data availability at the stations. The statistical Mann–Kendall and Pettitt tests have been used to assess trends and change points respectively. The tests have been applied to mean annual, monthly, seasonal, 1- and 7-days annual minimum and maximum values for streamflow, while mean annual, monthly and seasonal timescales were applied to meteorological variables. The results are heterogeneous and depict statistically significant increasing/decreasing trends. Besides, it showed significant abrupt change of point upward/downward shift for streamflow and temperature time series. However, precipitation time series did not show any statistically significant trends in mean annual and seasonal scales across the examined stations.Increasing trends in temperature at different weather stations for the mean annual, rainy, dry and small rainy seasons are apparent. The mean temperature at Bahir Dar – typical station in the Lake Tana sub basin, has been increasing at the rate of about 0.5 °C/decade, 0.3 °C/decade in rainy season (June–September), 0.6 °C/decade in small rainy season (March–May), and 0.6 °C/decade in dry season (October–February). Other stations in the Abay/Upper Blue Nile show comparable results. Overall it is found that trends and change point times varied considerably across the stations and catchment to catchment. Identified significant trends can help to make better planning decisions for water management. However, the cause attributes to the observed changes in hydro-meteorological variables need further research. In particular the combined effects of land use/land cover change and climate variability on streamflow of Abay/Blue Nile basin and its tributaries needs to be understood better.     

Geochemical characteristics and age of metamorphic sole rocks within a Neotethyan ophiolitic mélange from Konya region (central southern Turkey)

Palaeo- and Neo-Tethyan-related magmatic and metamorphic units crop out in Konya region in the south central Anatolia. The Neotethyan assemblage is characterized by mélange and ophiolitic units of Late Cretaceous age. They tectonically overlie the Middle Triassic–Upper Cretaceous neritic to pelagic carbonates of the Tauride platform. The metamorphic sole rocks within the Konya mélange crop out as thin slices beneath the sheared serpentinites and harzburgites. The rock types in the metamorphic sole are amphibolite, epidote-amphibolite, garnet-amphibole schist, plagioclase-amphibole schist, plagioclase-epidote-amphibole schist and quartz-amphibole schist. The geochemistry of the metamorphic sole rocks suggests that they were derived from the alkaline (seamount) and tholeiitic (E-MORB, IAT and boninitic type) magmatic rocks from the upper part of the Neotethyan oceanic crust. Four samples from the amphibolitic rocks yielded ⁴⁰Ar/³⁹Ar isotopic ages, ranging from 87.04 ± .36 Ma to 84.66 ± .30 Ma. Comparison of geochemistry and geochronology for the amphibolitic rocks suggests that the alkaline amphibolite (seamount-type) cooled below 510 ± 25 °C at 87 Ma whereas the tholeiitic amphibolites at 85 Ma during intraoceanic thrusting/subduction. When all the evidence combined together, the intraoceanic subduction initiated in the vicinity of an off-axis plume or a plume-centered spreading ridge in the Inner Tauride Ocean at 87 Ma. During the later stage of the steady-state subduction, the E-MORB volcanics on the top of the down-going slab and the arc-type basalts (IAT/boninitic) detached from the leading edge of the overriding plate, entered the subduction zone after ~2 my and metamorphosed to amphibolite facies in the Inner Tauride Ocean. Duration of the intraoceanic detachment (~87 Ma) and ophiolite emplacement onto the Tauride-Anatolide Platform (Tav?anl? Zone), followed by subsequent HP/LT metamorphism (~82 Ma) spanned ~5 my in the western part of the Inner Tauride Ocean.     

山西省柳林奥陶系古岩溶顶部方解石充填物

山西省柳林马五１地层顶部古岩溶发育，其孔、洞、缝中充填着大量的粒状、镶嵌状淡水方解石。根据方解石充填物的碳氧稳定同位素分布特征，包裹体的均一温度和盐度，阴极发光特征，可以把方解石充填物分为早期充填物和晚期充填物。     

Development of FLEMOcs – a new model for the estimation of flood losses in the commercial sector

Abstract

The estimation of flood damage is an important component for risk-oriented flood design, risk mapping, financial appraisals and comparative risk analyses. However, research on flood-loss modelling, especially in the commercial sector, has not gained much attention so far. Therefore, extensive data about flood losses were collected for affected companies via telephone surveys after the floods of 2002, 2005 and 2006 in Germany. Potential loss determining factors were analysed. The new Flood Loss Estimation MOdel for the commercial sector (FLEMOcs) was developed on the basis of 642 loss cases. Losses are estimated depending on water depth, sector and company size as well as precaution and contamination. The model can be applied to the micro-scale, i.e. to single production sites as well as to the meso-scale, i.e. land-use units, thus enabling its countrywide application.

Citation Kreibich, H., Seifert, I., Merz, B. & Thieken, A. H. (2010) Development of FLEMOcs – a new model for the estimation of flood losses in the commercial sector. Hydrol. Sci. J. 55(8), 1302–1314.     

Testing a new combined (U,Th)–He and U/Th dating approach on Plio-Pleistocene calcite speleothems

The geochronology of cave deposits in the Cradle of Humankind UNESCO World Heritage Site in South Africa provides a timeframe essential for the interpretation of its fossils. The uranium-lead (U–Pb) and uranium-thorium disequilibrium (U/Th) dating of speleothems, mostly flowstones that underlie and blanket the fossil-bearing sediments, have been effective in this sense, but U–Pb is limited by the requirement of ∼1 ppm U concentrations and low common Pb contents, and U/Th has a c. 500 ka limit of applicability. Here we report age results for calcite-aragonite speleothems obtained using a new combined uranium-thorium-helium ((U,Th)–He) and U/Th dating routine. We reproduced within analytical uncertainty, the published U–Pb or U/Th ages for (a) flowstone in three drill core samples in the range 2000–3000 ka, (b) a flowstone hand sample taken at surface with an age of 1800 ka, and (c) five underground flowstone samples in the range 100–800 ka. Calcite retentivity for He under cave conditions is thus demonstrated. In the few cases where helium loss was observed in speleothems, only some of the subsamples were affected, and to varying degrees, suggesting loss by lattice damage not related to diagenetic processes, rather than volume diffusion. In the 100 to 800 ka range, the combined U/Th disequilibrium and (U,Th)–He method also yielded reliable values for initial (²³⁰Th/²³⁸U) and (²³⁴U/²³⁸U) activity ratios. Importantly, most subsamples had high initial (²³⁰Th/²³⁸U) values, ranging from 1.0 to 19.7, although having low Th/U ratios. This is probably due to incorporation of Fe–Mn oxides-hydroxides dust, on which ²³⁰Th was previously adsorbed. Such samples are mostly not dateable by U/Th without the additional input from the He analysis. If not detected and corrected for, such high initial (²³⁰Th/²³⁸U) values can lead to inaccurate U/Th and U–Pb ages. Our study shows that the incorporation of He analysis in U/Th dating has broad potential application, with four methods for calculating the ages, in carbonates from different environments where U-Pb or U/Th dating would not work.     

Petrogenesis of Dashenshan I-type granodiorite: implications for Triassic crust–mantle interaction,South China

Triassic granodiorites in South China (SC) provide an opportunity to examine crust–mantle interactions that may have been caused by a mantle plume. Here we present a combined study of chronological, geochemical, and Sr–Nd–Hf isotopic compositions for Dashenshan granodiorites. These are high-K, calc-alkaline, I-type granodiorites that yield a U–Pb zircon age of 211 ± 3 Ma. They are metaluminous to weakly peraluminous (A/CNK < 1.1), with 3.04–3.89 wt.% Na₂O and 3.24–3.86 wt.% K₂O, and Na₂O/K₂O ratio ranging from 0.79 to 1.11. These granodiorites contain 67.7–72.6 wt.% SiO₂ but show moderate Mg^# values (44.2–57.8) and variable contents of Ni (3.6–29.9 ppm) and Cr (7.6–53.5 ppm). They exhibit light rare earth element (REE) enrichment and flat, heavy REE patterns with negative Eu anomalies (Eu/Eu* = 0.52–0.87). They also display strongly negative Ba, Sr, Nb, Ta, P, and Ti anomalies and positive Rb, Th, K, and Pb anomalies. Dashenshan granodiorites have high whole-rock initial ⁸⁷Sr/⁸⁶Sr ratios (0.7121–0.7172), negative ε_Nd (t) values (–8.8 to –6.8), and negative zircon ε_Hf (t) values (–6.6 to –3.3). These results suggest that the Dashenshan granodiorites were generated by a mixing between crustal melt and mantle-derived magma in an extensional setting. We conclude that generation of the Dashenshan pluton may reflect an interaction between a mantle plume and the overlying SC crust.     

Multiple statistical approaches for the discrimination of mangrove species of Rhizophoraceae using transformed field and laboratory hyperspectral data

This study aims at discriminating eight mangrove species of Rhizophoraceae family of Indian east coast using field and laboratory spectra in spectral range (350–2500 nm). Parametric and non-parametric statistical analyses were applied on spectral data in four spectral modes: (i) reflectance (ii) continuum removed, (iii) additive inverse and (iv) continuum removed additive inverse. We introduced continuum removal of inverse spectra to utilize the advantage of continuum removal in reflectance region. Non-parametric test gave better separability than parametric test. Principal component analysis and stepwise discriminant analysis were applied for feature reduction and to identify optimal wavelengths for species discrimination. To quantify the separability, Jeffries–Matusita distance measure was derived. Green (550 nm), red edge (680–720 nm) and water absorption region (1470 and 1850 nm) were found to be optimal wavelengths for species discrimination. The continuum removal of additive inverse spectra gave better separability than the continuum removed spectra.