A finite element–based approach for predictions of rigid pile group stiffness efficiency in clays

This paper presents a finite element parametric study of several variables that affect the stiffness efficiency of rigidly capped pile groups with a view to developing a solution for preliminary design purposes. Previous empirical solutions from linear elastic work had identified a significant dependence of stiffness efficiency on pile group size and group spacing, and in this study, the effect of the pile length-to-diameter ratio, the compressibility of a stiff bearing stratum beneath the pile group and the depth below ground level to the stiff bearing stratum are also considered. Pile groups in a soft clay/silt are modelled using PLAXIS 3D Foundation in conjunction with a soil model that captures the stress dependency of soil stiffness. The trends from the soft soil study have been formulated into a set of equations which can be used to predict the stiffness efficiency of pile groups. This new approach captures more variables than previous simpler empirical prediction methods and performs better when applied to a database of 29 published pile group case histories.     

A cavity expansion–based solution for interpretation of CPTu data in soils under partially drained conditions

A cavity expansion–based solution is proposed in this paper for the interpretation of CPTu data under a partially drained condition. Variations of the normalized cone tip resistance, cone factor, and undrained-drained resistance ratio are examined with different initial specific volume and overconsolidation ratio, based on the exact solutions of both undrained and drained cavity expansion in CASM, which is a unified state parameter model for clay and sand. A drainage index is proposed to represent the partially drained condition, and the critical state after expansion and stress paths of cavity expansion are therefore predicted by estimating a virtual plastic region and assuming a drainage-index–based mapping technique. The stress paths and distributions of stresses and specific volume are investigated for different values of drainage index, which are also related to the penetration velocity with comparisons of experimental data and numerical results. The subsequent consolidation after penetration is thus predicted with the assumption of constant deviatoric stress during dissipation of the excess pore pressure. Both spherical and cylindrical consolidations are compared for dissipation around the cone tip and the probe shaft, respectively. The effects of overconsolidation ratio on the stress paths and the distributions of excess pore pressure and specific volume are then thoroughly investigated. The proposed solution and the findings would contribute to the interpretation of CPTu tests under a random drained condition, as well as the analysis of pile installation and the subsequent consolidation.     

Research on the inversion of elemental abundances from Chang’E-2 X-ray spectrometry data

The elemental abundances of lunar surface are the important clues to study the formation and evolution history of the Moon. In 2010, China＇s Chang＇E-2 （CE-2） lunar orbiter carried a set of X-ray spectrometer （XRS） to investigate the elemental abundances of the lunar surface. During CE-2＇s life span around the Moon, the XRS ex- perienced several events of solar flare. The X-ray solar monitor onboard recorded the spectra of solar X-rays at the same time. In this paper, we introduced the XRS instrument and data product. We analyzed the characteristics of the XRS data. Using the data obtained during an M solar flare event which had occurred on Feb. 16, 201 l, we derived the elemental abundances ofMg, A1, Si, Ca and Fe of the lunar surface in the Oceanus Procellarum. Finally, we dis- cussed the factors that influence the accuracy of the inversion.     

A hybrid discrete–finite element model for numerical simulation of geomaterials

A hybrid discrete–finite element model is introduced for simulation of mechanical behavior of geomaterials. The soil or rock is modeled as a system of discrete balls that interact through normal and shear springs. The balls can be bonded at the contact points to withstand the applied deviatoric stresses. The important feature of this model is that the confining walls that can be imagined for example as the surrounding membrane or the mold in a physical test are modeled by deformable finite elements. This allows simulation of laboratory test features more realistically compared to the situations where the surrounding walls are rigid. The relationships between micro- and macro-properties are investigated in this paper as well. These relationships and the corresponding curves are helpful tools in calibration of the numerical model for the macroscopic elastic properties.     

Current trends in formats and coordinate transformations of geospatial data — based on MyGeoData Converter

With the rise in the number of applications using geospatial data and the number of GIS applications, the number of people who come into contact with geospatial data is increasing, too. Despite many attempts to introduce standardized formats in this area, they are often ignored by software developers as well as the users themselves for various reasons. When creating or exporting geographical data, users choose the format with regard to the software they use, or for which the data are intended. Users then have to deal with conversion of data formats, and considering its use also the issue of their transformation to the appropriate spatial reference system. This work presents findings related to this issue, obtained from several years of operation of an online service for the conversion and transformation of geographical data which is heavily used by users from all over the world. It presents statistics of individual formats use and spatial reference systems of geospatial data use from the point of view of both input and output data. The results, besides other things, are shown in the form of a pie chart map in which various needs of users from a variety of countries can be seen. The results of this work can be used especially by developers of applications which use geospatial data; it will allow them to quickly understand current user needs.     

Importance of coloured inversion technique for thin hydrocarbon sand reservoir detection – A case in mid Cambay basin

Cambay basin is an intra-cratonic rift graben formed as a result of rifting which was occurred in late Cretaceous with Deccan lava eruption through linear trending NNW to SSE directional basin. The Deccan basalt forms the basement over which more than 7–11 km thick piles of Tertiary sediments have been deposited during syn-rift and post-rift phases of basin development. Cambay basin has been considered as one of the significant hydrocarbon prolific basin in India. The biggest challenge in current days for this basin is further exploration or exploration under development stage in small marginal field or unexplored left out areas in the basin part as most of the areas are already explored/discovered by various small to big E&;P (exploration &; production) industrial players. In this present study one such small marginal field has been chosen for “Exploration under Development” portfolio in mid Cambay basin. The amount of oil-in-place volume, investment and techno-economics analysis of small marginal field has made this study area. In view of further hydrocarbon exploration in this area this kind of study will provide a robust support in limited dataset. The reservoir sand quality of the study area is discrete, thin and less permeable. This kind of sand body detection through classical seismic interpretation approach is difficult and there will be always a big amount of uncertainties for findings the pay reservoir sand. In view of the limitation of available data and challenging geological setup of the reservoir, a quantitative approach has been taken to detect the thin reservoir sand in this study area. Primarily coloured inversion technique has been applied on post-stack seismic data based upon well to seismic correlation and reservoir sand detection in seismic interpretation and well log property analysis. This technique has produced higher detectability impedance/property volume with respect to normal post-stack seismic data signature. Based on high contrast impedance/elastic property further seismic based attribute analysis on reservoir section has been performed. The attribute analysis has been made along surface and 3D seismic data level, provided clear image about the thin hydrocarbon sand reservoir. Based upon quantitative interpretation approach coloured inverted volume the prospect was chosen for further drilling in the study area and drilling of that sand was turned to be a hydrocarbon discovery prospect. The unconventional approaches e.g. coloured inversion with limited dataset for this kind of small marginal field has potential to find the hydrocarbon.     

Assimilating spatially dense data for subsurface applications—balancing information and degrees of freedom

The degrees of freedom (DOF) in standard ensemble-based data assimilation is limited by the ensemble size. Successful assimilation of a data set with large information content (IC) therefore requires that the DOF is sufficiently large. A too small number of DOF with respect to the IC may result in ensemble collapse, or at least in unwarranted uncertainty reduction in the estimation results. In this situation, one has two options to restore a proper balance between the DOF and the IC: to increase the DOF or to decrease the IC. Spatially dense data sets typically have a large IC. Within subsurface applications, inverted time-lapse seismic data used for reservoir history matching is an example of a spatially dense data set. Such data are considered to have great potential due to their large IC, but they also contain errors that are challenging to characterize properly. The computational cost of running the forward simulations for reservoir history matching with any kind of data is large for field cases, such that a moderately large ensemble size is standard. Realization of the potential in seismic data for ensemble-based reservoir history matching is therefore not straightforward, not only because of the unknown character of the associated data errors, but also due to the imbalance between a large IC and a too small number of DOF. Distance-based localization is often applied to increase the DOF but is example specific and involves cumbersome implementation work. We consider methods to obtain a proper balance between the IC and the DOF when assimilating inverted seismic data for reservoir history matching. To decrease the IC, we consider three ways to reduce the influence of the data space; subspace pseudo inversion, data coarsening, and a novel way of performing front extraction. To increase the DOF, we consider coarse-scale simulation, which allows for an increase in the DOF by increasing the ensemble size without increasing the total computational cost. We also consider a combination of decreasing the IC and increasing the DOF by proposing a novel method consisting of a combination of data coarsening and coarse-scale simulation. The methods were compared on one small and one moderately large example with seismic bulk-velocity fields at four assimilation times as data. The size of the examples allows for calculation of a reference solution obtained with standard ensemble-based data assimilation methodology and an unrealistically large ensemble size. With the reference solution as the yardstick with which the quality of other methods are measured, we find that the novel method combining data coarsening and coarse-scale simulations gave the best results. With very restricted computational resources available, this was the only method that gave satisfactory results.     

Determination of site-specific soil-water characteristic curve from a limited number of test data— A Bayesian perspective

Determining soilewater characteristic curve(SWCC) at a site is an essential step for implementing unsaturated soil mechanics in geotechnical engineering practice, which can be measured directly through various in-situ and/or laboratory tests. Such direct measurements are, however, costly and timeconsuming due to high standards for equipment and procedural control and limits in testing apparatus. As a result, only a limited number of data points(e.g., volumetric water content vs. matric suction)on SWCC at some values of matric suction are obtained in practice. How to use a limited number of data points to estimate the site-specific SWCC and to quantify the uncertainty(or degrees-of-belief) in the estimated SWCC remains a challenging task. This paper proposes a Bayesian approach to determine a site-specific SWCC based on a limited number of test data and prior knowledge(e.g., engineering experience and judgment). The proposed Bayesian approach quantifies the degrees-of-belief on the estimated SWCC according to site-specific test data and prior knowledge, and simultaneously selects a suitable SWCC model from a number of candidates based on the probability logic. To address computational issues involved in Bayesian analyses, Markov Chain Monte Carlo Simulation(MCMCS), specifically Metropolis-Hastings(M-H) algorithm, is used to solve the posterior distribution of SWCC model parameters, and Gaussian copula is applied to evaluating model evidence based on MCMCS samples for selecting the most probable SWCC model from a pool of candidates. This removes one key limitation of the M-H algorithm, making it feasible in Bayesian model selection problems. The proposed approach is illustrated using real data in Unsaturated Soil Database(UNSODA) developed by U.S. Department of Agriculture. It is shown that the proposed approach properly estimates the SWCC based on a limited number of site-specific test data and prior knowledge, and reflects the degrees-of-belief on the estimated SWCC in a rational and quantitative manner.     

TEXPRESS v1.0: A MATLAB toolbox for efficient processing of GDGT LC–MS data

Liquid chromatography–mass spectrometry (LC–MS) analysis of glycerol dialkyl glycerol tetraethers (GDGTs) from sediment and soil samples has become a widely adopted approach for reconstructing past ocean and continental climate variables such as temperature and pH. The LC–MS data used for constructing these GDGT climate proxies are taken directly from the peak area values of individual GDGT [M+H]⁺ ions, often determined from manual peak integration due to unreliable computer integrators in commercial software, particularly in cases of complex baselines, asymmetric peak shapes and peak coelution. Manual integration is not only time consuming, but also prone to user induced inconsistency when individuals utilize different criteria for peak/baseline definition. To overcome these problems, we have developed a user friendly, graphical user interface (GUI) programmed in the MATLAB environment, allowing users to efficiently and reproducibly perform batch processing and peak integration of LC–MS data. The program, “TEXPRESS” v1.0 (“tetraether index express”), incorporates modern chemometric based techniques for baseline definition and deconvolution of complex chromatographic peaks and we show that LC–MS data processed using the TEXPRESS toolbox are in strong agreement with results obtained from manual peak integration. We provide a general overview of the concepts and architecture of the TEXPRESS toolbox and discuss the advantages of chemometric based peak integration methods for processing branched and isoprenoid GDGT LC–MS data.     

Mass Extinction——A Fundamental Indicator for Major Natural Divisions of Geological History

In the Phanerozoic, there are three major geological boundaries: Precambrian/Cambrian.Permian/Triassic and Cretaceous/Tertiary. Studies of these boundaries in China and over the world stronglysuggest that they have the following similar features: mass extinctions of many taxa, positive anomalies ofplatinum-group metals, and abrupt changes of stable isotopes (δ~(13)C). It is quite probable that these were theconsequences of some rare catastrophic events of extraterrestrial origin. Hence, the three above-mentionedmass extinction events may be regarded as key indicators for the division of the geological history of thePhanerozoic.     

Comparison of methods of algebraic strain estimation from Rf/ɸ data: A unified theory of 2D strain analysis

A unified development of the subject of the algebraic strain analysis methods using Rf/ɸ data is outlined, embodying the main features the theories of Shimamoto and Ikeda, Mulchrone et al. and Yamaji. It is shown that the theories yields an identical strain ellipse from the same data set. However, error estimation in that of Shimamoto and Ikeda is difficult owing to the distortion of its parameter space: Resolution of their method depends on the choice of a reference orientation in the plane where strain markers are observed. In this respect, the remaining two theories have advantages. The hyperbolic vector mean method was developed in the Minkowski 3-space, thereby linked seamlessly with the visualizing methods of Rf/ɸ data, optimal strain and its confidence region. In addition, the residuals of the optimal strain ellipse determined by this method have clear physical meanings concerning logarithmic strains needed to transform a unit circle to given ellipses.     

A compression model for sand–silt mixtures based on the concept of active and inactive voids

A compression model for sand–silt mixtures is needed in geotechnical engineering, for example in the analysis and prediction of deformation of levees and embankments due to internal erosion. In this paper, we introduce a novel concept of dividing the voids of a granular material into two hypothetical fractions: active and inactive voids. The active voids are kinematically available to the compression process. The inactive voids are kinematically unavailable to the compression process. The volume of active voids is dependent on the initial density and effective stress level. The volume of inactive voids is dependent on the amount of fines in the mixture. The current paper considers 1-D and isotropic compression behavior of sand–silt mixtures at stress levels lower than 2 MPa, so no substantial particle breakage is expected to occur. To successfully predict the void ratio for a sand–silt mixture during compression loading, we need (1) a mathematical expression for the evolution of the active void ratio during compression and (2) a relationship between the inactive void ratio and fines content of the mixture. For sand–silt mixtures with any amount of fines, the proposed model requires five material parameters, which are determined from two compression tests, and four minimum void ratio tests on sand–silt mixtures with different fines content. The performance of the proposed model is verified for six different types of sand–silt mixture with various fines contents, by comparing the predicted void ratios with the measured data from the experiments. The comparisons show a good agreement between the predictions and the measured data and prove the suitability of the proposed model for the prediction of compressibility of sand–silt mixtures with any amount of fines.     

First data on the isotopes of Sm—Nd and Sr for Cretaceous—Paleogene granitoids of primors’e and some problems of their genesis

Doklady Earth Sciences -     

Potentials of alternate polarization of Envisat ASAR data in geological mapping — A case study in Kurnool Group of rocks,Andhra Pradesh

The application of SAR data is a proven technology in geological studies but very few accounts are available in India, which can evaluate and demonstrate the utility of microwave signatures as an important tool for geological mapping. In this connection, the significance of polarization is an important parameter in enhancing geological elements. Present study reveals that the simple polarization composite prepared from different polarization channels can significantly aid the delineation of geological features as demonstrated from the Proterozoic metasedimentary sequences of Kurnool Group. The polarization colour composites reveal that different sedimentary units can be differentiated on the basis of variable back scattering return in different polarization channel. Further geological structures of regional importance can also be delineated in these colour composite images. Comparative analysis of different composite images with published geological maps, illustrates the capabilities of the microwave polarization in enhancing geological elements and how they can be used in updating geological data.     

Formation Mechanism of the Tongyu Gold Deposit,Shaanxi——A Discussion of a Model for the Formation of Syntectonic Gold Deposits

The formation of the Tongyu gold deposit, controlled by regional polyphase deformation-metamorphism.is closely related to the regional composite antiform-shear slip fracture zone. Late-stage reworking of theTaihua Group accounts for the enrichment of ore substances. It is a typical syntectonic gold deposit. The formation and evolution of the deposit involved four stages: (Ⅰ) the state of preparation of ore sub-stances, in which primary source beds originated: (Ⅱ) the stage of remobilization of ore substances, in whichregional progressive metamorphism and migmatization and thermodynamic-chemical differentiation led toremobilization of gold and its initial local concentration: (Ⅲ) the stage of gold deposit formation, in which re-gional folding produced concordant and cross shear-slip fractures and under the dynamic action gold was sepa-rated and migrated in a certain direction and concentrated to form a gold deposit: (Ⅳ) the stage ofsuperpositon, reworking and exposure of orebodies, in which the block uplifted and the deposit againunderwent reworking through faulting and mechanical differentiation.Thermodynamic mineralization played adominant role in the formation of the deposit.     

Model for Quantitatively Estimating Marine Biogeographic Provinciality——A Case Study of the Permian Marine Biogeography Provincialism

The relationship between the number, position and orientation of lithosphericplates and marine biogeographic provinciality may be quantified since the spatial distribution oforganisms is primarily controlled by latitude-related temperature gradients and geographicalbarriers-two dynamic biogeographic determinants whose variation is closely related to thespatial disposition of continents and oceans. This paper modifies Schopf s (1976) model forquantitatively estimating shallow marine provinciality in recognition of latitude-related tem-perature gradients as the primary biogeographical factor. A test of the modified model againstmodern marine zoogeography reveals high consistency between them. Using this modified mod-el and the Permian palaeogeographical reconstruction maps of Scotese and McKerrow (1990),fifteen shallow benthic marine provinces are estimated to be Early and Late Permian in agerespectively. A comparison of the estimated Permian marine provinciality with previouslyrecognised empirical provincial patterns reveals a high degree of congruity, which may implythat there existed moderate to high latitudinal thermal gradients during the Permian, a levelprobably similar to that of the present world.     

Application of ASTER data for exploration of porphyry copper deposits: A case study of Daraloo–Sarmeshk area,southern part of the Kerman copper belt,Iran

The Cenozoic Urumieh–Dokhtar Magmatic Belt (UDMB) of Iran is a major host to porphyry Cu ± Mo ± Au deposits (PCDs). Most known PCDs in the UDMB occur in the southern section of the belt, also known as the Kerman Copper Belt (KCB). Three major clusters of PCDs are distinguished in the KCB and include the Miduk, Sarcheshmeh and Daraloo clusters. The Daraloo and Sarmeshk deposits occur in a northwest–southeast-trending fault zone that is characterized by the presence of a narrow zone of alteration–mineralization that contains a series of Oligocene granitoids and Miocene porphyritic tonalite–granodiorite plutons that cut Eocene andesitic lava flows and pyroclastic rocks. Here we use various techniques, including different ratio images, minimum noise fraction, pixel purity index, and matched filter processing to process ASTER data (14 bands) and generate maps that portray the distribution of hydrothermal minerals (e.g., sericite, kaolinite, chlorite, epidote and carbonate) related to PCD alteration zones. In order to validate the ASTER data, follow-up ground proofing and related mineralogical work was done which, in all cases, proved to be positive. The results of this work have identified the regional distribution of hypogene alteration zones (i.e., phyllic, argillic, propylitic and silicic), in addition to areas of secondary Fe-oxide formation, which are coincident with known sites of PCDs. The regional distribution and extent of the alteration zones identified also highlighted the role of regional structures in focusing the mineralizing/altering fluids. These results demonstrate very convincingly that ASTER imagery that uses the appropriate techniques is reliable and robust in mapping out the extent of hydrothermal alteration and lithological units, and can be used for targeting hydrothermal ore deposits, particularly porphyry copper deposits where the alteration footprint is sizeable.     

A natural analogue for the long-term corrosion of copper nuclear waste containers—reanalysis of a study of a bronze cannon

The study of natural analogues is often used to support long-term predictions of the safety of geological disposal of used nuclear fuel. The case of a bronze cannon, submerged in seawater-saturated clay sediments for a period of 310 a, is reassessed with reference to a corrosion mechanism developed for copper nuclear waste containers in a conceptual disposal vault in the Canadian Shield. Redox reactions between Cu, Fe and dissolved O₂ are believed to have played an important role in the corrosion of the bronze cannon and also form an essential part of the corrosion mechanism proposed for nuclear waste containers. Limited rates of mass transport through compacted clay are also important in determining the corrosion behaviour of both the cannon and the containers.     

Effect of particles on the photodegradation of PAHs in natural waters—A case study for the Yellow River

Photodegradation of chrysene, benzo (a) pyrene and benzo (g, h, i) perylene in natural water of the Yellow River was studied using simulation sunlight. The effects of particulates on the photodegradation were explored. Several results arose from this stud…