Towards developing a geoscientific approach to sustainable agricultural and rural development

 Conventional practices employed to achieve sustainable agricultural and rural development (SARD) tend to be subjective, focus on effects rather than causes, and have little diagnostic or predictive value. Consequently, many of the management options and solutions adopted to restore degraded natural resources are, often, economically unviable and environmentally unsustainable. These shortcomings are believed to be caused, partly, by overlooking or insufficiently recognizing the role and importance of geology to SARD. This paper demonstrates that geology is the most critical factor in the genesis of biophysical resources and in determining sustainability of agricultural and rural development. A case study from Australia shows how geological principles can be employed to obtain goals of ecological sustainability. A geologically-based model for cold temperate regions is provided to assist resource users and managers in understanding and predicting the genetic influence of geology on the inherent potential, constraint and resilience of the biophysical resources. Received: 7 January 2000 · Accepted: 23 May 2000     

Self-organizing maps for geoscientific data analysis: geological interpretation of multidimensional geophysical data

Data interpretation is a common task in geoscientific disciplines. Interpretation difficulties occur especially if the data that have to be interpreted are of arbitrary dimension. This paper describes the application of a statistical method, called self-organizing mapping (SOM), to interpret multidimensional, non-linear, and highly noised geophysical data for purposes of geological prediction. The underlying theory is explained, and the method is applied to a six-dimensional seismic data set. Results of SOM classifications can be represented as two-dimensional images, called feature maps. Feature maps illustrate the complexity and demonstrate interrelations between single features or clusters of the complete feature space. SOM images can be visually described and easily interpreted. The advantage is that the SOM method considers interdependencies between all geophysical features at each instance. An application example of an automated geological interpretation based on the geophysical data is shown.     

Geodiversity: a significant,multi-faceted and evolving,geoscientific paradigm rather than a redundant term

Using outlines of ten geodiversity-related topics plus some related studies, this paper argues that geodiversity has contributed to many new insights, new avenues of research and new results. The ten topics are: Celebrating, Assessment and Measurement, Geosystem Services, Biodiversity, Geomaterials, Geotourism and Leisure, Geoheritage, National Geoconservation, World Heritage Sites and Global Geoparks, and Sustainability. It is concluded that geodiversity is a) a global, as well as regional/local concept, b) more than just related to biodiversity, important though that is, c) absolutely central to any relationship between the geology-related topics (‘Gs’). It is therefore argued that geodiversity is not a ‘redundant term’ as recently suggested but instead is a significant, multi-faceted and evolving, geoscientific paradigm.     

Digital geoscientific maps: A priority program of the German Society for the Advancement of Scientific Research

In October 1984, the German Society for the Advancement of Scientific Research (DFG) began a 5-year Priority Program to develop a new general concept for computer-assisted field work and construction, production, and evaluation of geoscientific maps with contents either from a single geodiscipline or from various disciplines, as a part of a future geoscientific information system.     

Foliations and shear sense: A modern approach to an old problem

Argument about shear on foliations began in the mid 19^th century and continues to the present day. It results from varying interpretations of what takes place during the development of different types of foliations ranging from slaty cleavages through differentiated crenulation cleavages, schistosity and gneissosity to mylonites. Computer modelling, quantitative microstructural work and monazite dating have provided a unique solution through access to the history of foliation development preserved by porphyroblasts. All foliations involve shear in their development and most can be used to derive a shear sense. The shear sense obtained is consistent between foliation types and accords with recent computer modelling of these structures preserved within porphyroblasts relative to those in the matrix. The asymmetry of curving foliation into a locally developing new one allows determination of the shear sense along the latter foliation in most rocks. The problem of shear on fold limbs and parallelism of foliation and the flattening plane of the strain ellipse is resolved through the partitioning of shearing and shortening components of deformation into zones that anastomose around ellipsoidal domains lying parallel to the XY plane. Conflicts in shear sense occur if multiple reuse or reactivation of foliations is not recognized and allowed for but are readily resolved if taken into account.     

中国北方石墨矿床及赋矿孔达岩系碳同位素特征及有关问题讨论

本文综合了中国北方孔达岩系和石墨矿床的碳同位素数据 10 2件 ,发现片麻岩石墨 透辉岩石墨 <大理岩石墨 <石墨大理岩方解石 <大理岩方解石 ;混合岩化岩石中石墨δ1 3C总介于有机碳和无机碳之间 ;不同地体片麻岩石墨δ1 3C极为一致 ,变化于 - 2 2 .8‰～ - 2 1.48‰ ,略低于世界有机质平均值 - 2 6± 7‰ ;大理岩的原岩碳酸盐δ1 3C高于 2‰ ,与2 330～ 2 0 6 0 Ma期间全球性δ1 3Ccarb正向漂移事件一致。地质流体是碳同位素分馏、均一化的重要因素 ,是石墨矿床的 3种主要碳源之一 ,是碳的 5种存在形式之一 ,也是碳循环的重要媒介和方式 ;导致热液矿床δ1 3C=- 5‰左右的因素较多 ,依据δ1 3Ccalcite - 5‰得出成矿物质和流体来自地幔的结论值得怀疑 ;中国北方孔达岩系形成于古元古代 ,可能为 2 30 0～ 2 0 5 0 Ma。     

A simplified computational approach for prediction of transient climatic conditions in underground mine airways

Summary A simplified approach for prediction of transient climatic conditions in an underground airway os presented. The dry surface temperature of the airway is calculated using a finite difference scheme, whereas the wet surface temperature is determined following the concept of pseudo-base-temperature of air and using the value of thermal gradient at the dry surface as obtained from the finite difference solution of the temperature profile in the dry rock. The air-current temperatures are regularly evaluated after a suitable time span so as to simulate a real-case situation, and the re-evaluated air-current temperatures are used for further calculations. For increasing age of the airway the wet surface temperature obtained by the finite difference scheme, with an appropriate value of thermal diffusivity, is compared with its value determined by the pseudo-base-temperature approach.     

GeoNDT: a fast general-purpose computational tool for geotechnical non-destructive testing applications

The non-destructive testing (NDT) plays a crucial role in geotechnical engineering and geophysical applications, especially in the design of earthquake-resistant foundations, geotechnical field investigation, and material characterization and detection of underground anomaly. Currently, the existing signal interpretation methods in NDT measurements still predominantly rely on empirical relations or subjective judgements. In this paper, we present the GeoNDT software, which is developed to provide an advanced physics-based signal interpretation method for NDT characterization of multiphase geomaterials. GeoNDT is able to model the propagation of stress waves and dispersion relations in dry (elastodynamic), saturated (two-phase poroelastodynamic), and three-phase frozen (multiphase poroelastodynamic) geomaterials using the meshless spectral element method. GeoNDT is flexible, general-purpose, and can be used seamlessly for advanced signal interpretation in geophysical laboratory testing including the bender element and ultrasonic pulse velocity tests, characterization of complex multiphase geomaterials, and in situ shallow seismic geophysics including the falling weight deflectometer and multichannel analysis of surface waves tests. The advanced physics-based signal interpretation feature of GeoNDT allows the quantitative characterization of geophysical and geomechanical properties of geomaterials and multilayered geosystems independently without making any simplified assumptions as common in the current practice.

     

Effective medium methods and a computational approach for estimating geomaterial properties of porous materials with randomly oriented ellipsoidal pores

The role of effective medium approaches and the differential scheme in estimating the overall elastic moduli of a porous medium with randomly oriented pores is examined. The analytical estimates of the elastic moduli are compared with approximations available in the literature that are valid for small pore aspect ratios. Accuracy of the analytical estimates is further established by performing finite element simulations. Finite element estimates are obtained for a model of a porous medium containing three families of spheroidal pores arranged in a mutually orthogonal configuration. This model is regarded as a close approximation to a porous medium with randomly oriented pores. Also, experimental data available for several sandstones and granites was used to analytically examine the influence of the aspect ratio of pores on overall properties. This information is also used to provide an estimate for the permeability of the porous medium.     

The Vajont slide: Instrumentation— Past experience and the modern approach

The Vajont slide case history is reviewed from the instrumentation point of view.

In the first part, the situation before the major slide of October 9, 1963 is presented, in relation to the studies made and measures adopted to control the rate of movement. The measurements which were made are then discussed with respect to the slide and the theories that were developed at the time on the failure mechanism.

In the second part, the Vajont slide is considered from the modern geotechnical point of view. If engineers had had the benefit in 1960 of the knowledge we have now, over twenty five years later, what kind of instruments would they have installed and what measurements would they have made? The answers to these questions are discussed with reference to the possible prediction of the slide failure and the choice of a strategy to control the rate of failure.

Some aspects of the questions raised in the geotechnical community by the Vajont slope are still unresolved today, and require further research before we can safely predict the behaviour of a slide in a condition of incipient failure when, for reasons still not fully understood, the safety factor drops far below one.     

JHomogenizer: a computational tool for upscaling permeability for flow in heterogeneous porous media

This paper presents an object-oriented programming approach for the design of numerical homogenization programs, called JHomogenizer. It currently includes five functional modules to compute effective permeability and simple codes for computing solutions for flow in porous media. Examples with graphical output are shown to illustrate some functionalities of the program. A series of numerical examples demonstrates the effectiveness of the methodology for two-phase flow in heterogeneous reservoirs. The software is freely available, and the open architecture of the program facilitates further development and can adapt to suit specific needs easily and quickly.     

An operational framework for communicating flood warnings to indigenous farmers in southern Nigeria: a systems thinking analysis

GeoJournal - In March 2012, the Nigerian meteorological agency forecasted massive flooding for parts of the country, with the displacement of large parts of the population as a consequence. Delta...     

Residual luminescence in modern debris flow deposits from western Taiwan: A single grain approach

In an active fold-and-thrust belt, sediment is commonly transported in the form of debris and colluviums, and the ages of such deposits can be important for seismic hazard assessment. These sediments are mainly transported by high concentration flows that travel very short distances before burial, and therefore have very few opportunities for daylight exposure and bleaching, which limits the application of luminescence dating in such environments. Luminescence studies on modern debris flow deposits and channel sediments in central Taiwan indicate a mixed population of bleached and unbleached grains. The well bleached grains constitute a small proportion of the sediments and could only be identified using the single grain dating technique; doing single aliquot analysis may result in overestimation of the age of such sediments by 3–25 ka. The data reveal that outwash sediments are better bleached than debris flow sediments. Our results show that quartz that has experienced partial resetting can be used for luminescence dating only through the use of the single grain technique.     

Geothermal systems ancient and modern: a geochemical review

Geothermal systems occur in a range of crustal settings. The emphasis of this review is on those occurring in regions of active or recently active volcanism, where magmatic heat at depths up to 8 km leads to convection of groundwater in the upper crust. Hot water (and steam) flows are controlled by the permeability of the crust and recent data have emphasised the dominance of secondary permeability, especially fractures. Drilling to depths of up to 3 km in these systems encounters near-neutral pH alkali chloride waters with temperatures up to about 350°C and chloride contents generally in the range 500 to 15,000 mg kg^?1 although much higher salinities are encountered in some systems such as in the Imperial Valley, California. Stable isotope studies indicate the predominance of a meteoric source in the majority of geothermal systems although seawater predominates in some regions, such as Reykjanes, Iceland. Mixing of waters from both sources also occurs in some systems and some magmatic fluid may also be present.The major element geochemistry of geothermal fluids is determined by a set of temperature-dependent mineral-fluid equilibria although chloride and rare gas contents appear to be independent variables reflecting the sources of these components (sedimentary or volcanic rocks, seawater, magmatic fluids, etc).Boiling in the upper portion of geothermal systems is accompanied by the transfer of acidic gases (CO₂ and H₂S) to the resultant steam which may penetrate the surface as fumarolic activity or become condensed into shallow groundwaters giving rise, with oxidation, to distinctive low pH sulphate bicarbonate water.Fluid inclusion, stable isotope and mineral alteration studies have led to the recognition in many Tertiary hydrothermal ore deposits of physical and chemical environments analogous to those encountered in the present-day systems. The vein-type gold-silver, Carlin-type gold and porphyry-type copper-molybdenum deposits of the western United States are particularly well studied examples. Sub-ocean floor equivalents of the terrestrial geothermal systems have been recognized in ocean floor spreading centres such as the East Pacific Rise and deep-sea submersible vehicles have allowed visual observation of sea floor hot springs actively depositing metal sulphides. These environments may parallel those of the Cyprus-type massive sulphide depositing systems, while sub-sea floor systems of the type responsible for Kuroko-type massive sulphide deposits may eventually be encountered in island are settings.     

gLucifer: next generation visualization framework for high-performance computational geodynamics

High-performance computing provides unprecedented capabilities to produce higher resolution 4-D models in a fraction of time. Thus, the need exists for a new generation of visualization systems able to maintain parity with the enormous volume of data generated. In attempting to write this much data to disk, each computational step introduces a significant performance bottleneck, yet most existing visualization software packages inherently rely on reading data in from a dump file. Available packages make this assumption of postprocessing at quite a fundamental level and are not very well suited for plotting very large numbers of specialized particles. This necessitates the creation of a new visualization system that meets the needs of large-scale geodynamic modeling. We have developed such a system, gLucifer, using a software framework approach that allows efficient reuse of our efforts in other areas of research. gLucifer is capable of producing movies of a 4-D data set “on the fly” (simultaneously with running the parallel scientific application) without creating a performance bottleneck. By eliminating most of the human efforts involved in visualizing results through postprocessing, gLucifer reconnects the scientist to the numerical experiment as it unfolds. Data sets that were previously very difficult to even manage may be efficiently explored and interrogated without writing to disk, and because this approach is based entirely on memory distributed across as many processors as are being utilized by the scientific application, the visualization solution is scalable into terabytes of data being rendered in real time.     

Effects of grain morphology on critical state: a computational analysis

We introduce a new DEM scheme (LS-DEM) that takes advantage of level sets to enable the inclusion of real grain shapes into a classical discrete element method. Then, LS-DEM is validated and calibrated with respect to real experimental results. Finally, we exploit part of LS-DEM potentiality by using it to study the dependency of critical state (CS) parameters such as critical state line (CSL) slope \(\lambda \), CSL intercept \(\varGamma \), and CS friction angle \(\varPhi _{\mathrm{CS}}\) on the grain’s morphology, i.e., sphericity, roundness, and regularity. This study is carried out in three steps. First, LS-DEM is used to capture and simulate the shape of five different two-dimensional cross sections of real grains, which have been previously classified according to the aforementioned morphological features. Second, the same LS-DEM simulations are carried out for idealized/simplified grains, which are morphologically equivalent to their real counterparts. Third, the results of real and idealized grains are compared, so the effect of “imperfections” on real particles is isolated. Finally, trends for the CS parameters (CSP) dependency on sphericity, roundness, and regularity are obtained as well as analyzed. The main observations and remarks connecting particle’s morphology, particle’s idealization, and CSP are summarized in a table that is attempted to help in keeping a general picture of the analysis, results, and corresponding implications.     

A porosity-gradient replacement approach for computational simulation of chemical-dissolution front propagation in fluid-saturated porous media including pore-fluid compressibility

In dealing with chemical-dissolution-front propagation problems in fluid-saturated porous media, the chemical dissolution front represented by the porosity of the medium may have a very steep slope (i.e., a very large porosity gradient) at the dissolution front, depending on the mineral dissolution ratio that is defined as the equilibrium concentration of the dissolved minerals in the pore-fluid to the solid molar density of the dissolvable minerals in the solid matrix. When the mineral dissolution ratio approaches zero, the theoretical value of the porosity gradient tends to infinity at the chemical dissolution front. Even for a very small value of the mineral dissolution ratio, which is very common in geochemical systems, the porosity gradient can be large enough to cause the solution hard to converge when the conventional finite element method is used to solve a chemical dissolution problem in a fluid-saturated porous medium where the pore-fluid is compressible. To improve the convergent speed of solution, a porosity-gradient replacement approach, in which the term involving porosity-gradient computation is replaced by a new term consisting of pore-fluid density-gradient and pressure-gradient computation, is first proposed and then incorporated into the finite element method in this study. Through comparing the numerical results obtained from the proposed approach with the theoretical solutions for a benchmark problem, it has been demonstrated that not only can the solution divergence be avoid, but also the accurate simulation results can be obtained when the proposed porosity-gradient replacement approach is used to solve chemical-dissolution-front propagation problems in fluid-saturated porous media including pore-fluid compressibility.     

A novel computational approach for large deformation and post‐failure analyses of segmental retaining wall systems

Segmental retaining wall (SRW) systems are commonly used in geotechnical practice to stabilize cut and fill slopes. Because of their flexibility, these systems can tolerate minor movements and settlements without incurring damage or crack. Despite these advantages, very few numerical studies of large deformations and post‐failure behavior of SRW systems are found in the current literature. Traditional numerical methods, such as the finite element method, suffer from mesh entanglement, thus are unable to simulate large deformations and flexible behavior of retaining wall blocks in SRW systems. To overcome the above limitations, a novel computational framework based on the smoothed particle hydrodynamics (SPH) method was developed to simulate large deformations and post‐failure behavior of soils and retaining wall blocks in SRW systems. The proposed numerical framework is a hybrid continuum/discontinuum approach that can model soil as an elasto‐plastic material and retaining wall blocks as independent rigid bodies associated with both translational and rotational degrees of freedom. A new contact model is proposed within the SPH framework to simulate the interaction between the soil and the blocks and between the blocks. As an application of the proposed numerical method, a two‐dimensional simulation of an SRW collapse was simulated and compared to experimental results conducted under the same conditions. The results showed that the proposed computational approach provided satisfactory agreement with the experiment. This suggests that the new framework is a promising numerical approach to model SRW systems. Copyright © 2014 John Wiley & Sons, Ltd.