Tensile strength of large-scale incipient rock joints: a laboratory investigation

In this paper, a testing methodology was developed in the laboratory to measure the tensile strength of large-scale incipient rock joints. In the test, an expansive grout was used to develop the tensile force. Each test comprises two phases: Phase i test and Phase ii test. The Phase i test identified sample failure time, while the Phase ii test measured the corresponding tensile force arising from the expansive grout. Ostensibly homogeneous rock samples without incipient joints were firstly tested to establish the methodology. Tensile strength of block samples containing incipient rock joints was then measured using the established testing scheme. The test results have been compared with those obtained from conventional Brazilian and uniaxial tension tests as suggested by ISRM. The proposed approach is capable of giving a measure of tensile strength of large-scale incipient rock joints, although somewhat smaller strength than that from the standard approaches was occasionally measured in the preliminary tests on ostensibly homogeneous samples. Effects of stress concentration, sample scale, loading rate and expansive tensile force on the testing results were discussed. Furthermore, this simple and practical testing scheme is proposed for the measurement of the in situ tensile strength of rock and incipient discontinuities in the field, which if successful will provide a more scientific guidance on the rock mass classification and engineering design.     

Efficient Generation Portfolio Construction Using Time-Varying Correlations

We constructed a procurement portfolio for the Indian power sector using two variants of the dynamic conditional correlation GARCH model to derive time-varying correlations between major coal indices. We used prices and qualities of observed cargos to adjust indices for quality gaps as well as for freight costs and power plant efficiency factors. Using the relative homogeneity of the energy content of imports from Australia, South Africa, and Indonesia, we found that the regional seaborne market is highly correlated during normal economic conditions, while suffering brief departures in correlation during demand and supply shocks. Our results show that the buying behavior of power producers is aligned with the mean-variance efficient portfolio of delivered prices using time-varying correlation estimates, but not free-on-board coal index prices. This study challenges the notion that thermal coal importers only source material with a freight price advantage and highlights the importance of coal quality gaps in power production.     

Automated statistical matching of multiple tephra records exemplified using five long maar sequences younger than 75 ka,Auckland, New Zealand

Detailed tephrochronologies are built to underpin probabilistic volcanic hazard forecasting, and to understand the dynamics and history of diverse geomorphic, climatic, soil-forming and environmental processes. Complicating factors include highly variable tephra distribution over time; difficulty in correlating tephras from site to site based on physical and chemical properties; and uncertain age determinations. Multiple sites permit construction of more accurate composite tephra records, but correctly merging individual site records by recognizing common events and site-specific gaps is complex. We present an automated procedure for matching tephra sequences between multiple deposition sites using stochastic local optimization techniques. If individual tephra age determinations are not significantly different between sites, they are matched and a more precise age is assigned. Known stratigraphy and mineralogical or geochemical compositions are used to constrain tephra matches. We apply this method to match tephra records from five long sediment cores (≤ 75 cal ka BP) in Auckland, New Zealand. Sediments at these sites preserve basaltic tephras from local eruptions of the Auckland Volcanic Field as well as distal rhyolitic and andesitic tephras from Okataina, Taupo, Egmont, Tongariro, and Tuhua (Mayor Island) volcanic centers. The new correlated record compiled is statistically more likely than previously published arrangements from this area.     

An open source,server-side framework for analytical web mapping and its application to health

In this paper, we detail the design and the implementation of an open source, server-side web mapping framework for the analysis of health data. The framework forms part of a larger project, the goal of which is to provide an analytical web geographical information system (GIS) that enables health experts to analyse spatial aspects of health data. The aim of the framework is to provide a method for the dynamic and flexible spatial visualisation of health data to facilitate data exploration and analysis. Consequently, a dynamic thematic web mapping technique, an extension to the Open Geospatial Consortium (OGC) web map service standard, was developed. The technique combines a data query, processing technique and styling methodology on the fly to generate a thematic map. The resulting thematic map represents a virtual map layer that enables a user to rapidly visually summarise properties of a data-set. A test web interface was developed to assess the efficacy of the web mapping technique. As the dynamic web mapping method builds on existing OGC web mapping standards, it can be readily integrated with the existing lightweight slippy map web clients and virtual globes.     

Book reviews

Theory and management of tropical fisheries. Edited by D. Pauly and G. I. Murphy. Proceedings of the ICLARM/CSIRO Workshop on the Theory and Management of Tropical Multispecies Stocks. 12–21 January 1981, Cronulla, Australia. 1982. 360 p. $US21.50 surface; hardbound.

Animals of the estuary shore : illustrated guide and ecology. By Malcolm B. Jones, 1983. University of Canterbury publication No. 32. 162p., 140 figures, 11 keys. ISBN 0900–392–32–0 (soft cover, spiral bound). Price NZ$7.50.

Numerical ecology. By L. Legendre and P. Legendre, 1983. Elsevier Scientific Publishing Company, Amsterdam. $US83.00.

The control of oil pollution (revised edition). Edited by J Wardley‐Smith. Graham & Trot‐man Limited, London. 1983. 285 p., 98 figures, 17 tables. ISBN 0.86010 3382. £19.00/$US35.00.

Physical oceanography in Australia. Edited by J. Imberger. Reprinted from the Australian Journal of Marine and Freshwater Research, Volume 34, 1–230, 1983. CSIRO, Melbourne 1983.     

Marsh-creek connectivity: Fish use of a tidal salt marsh in Southern California

Salt marsh habitats influenced by southern California's mixed, semi-diurnal tides are, on average, accessible to fishes less than 16% of the time. However, five species (four natives, one oxotic) and a variety of juvenile and adult size classes were collected on the marsh surface during a year-long sampling from June 1997 through June 1998 at Sweetwater Marsh National Wildlife Refuge on San Diego Bay.Fundulus parvipinis andGillichthys mirabilis were the most abundant fish species using the marsh. Analyses of their guts revealed that the marsh surface provides a rich foraging area for fishes on high spring tides.F. parvipinnis with marsh access consumed six times as much food as fishes restricted to creek habitats (on a g-food g-fish^?1 basis) and also fed on additional prey types. Because the salt marsh is an important foraging area for fishes, we recommend that restoration projects (especially those intended to mitigate lost fish habitat) include vegetated areas with interconnecting tidal creeks.     

A suburban sediment budget: Coarse-grained sediment flux through hillslopes,stormwater systems and streams

Sediment in urban stormwater systems creates a significant maintenance burden, while a lack of coarse-grained bed sediment in streams limits their ecological value and geomorphic resilience. Gravel substrates, for example, provide benthic habitat yet are often scoured from the channel bed only to end up in a detention basin or treatment wetland. This dual problem of both ‘too much’ and ‘too little’ coarse-grained sediment reflects a watershed sediment budget that is profoundly altered. We developed a conceptual urban coarse-grained (>0.5 mm) sediment budget across three domains: hillslopes (urban land surfaces), the built stormwater network and stream channels. We then quantified key sources, sinks and storages for a suburban case study, using a combination of hillslope and in-channel monitoring, and interrogation of local government records. Around 36% of the sediment supplied to the stormwater network reached the catchment outlet, a level of sediment delivery much higher than observed in similar-sized natural catchments. The remainder was deposited in the sediment cascade and either stored, or extracted and removed from the catchment (e.g. material deposited in sediment ponds and gross pollutant traps). Conventional urban drainage networks are characterized by high hillslope sediment supply and low storage, resulting in efficient sediment delivery. Channel erosion, deposition in (and extraction from) pipes and channels, and floodplain deposition are small compared to sediment transport through the cascade. An understanding of the sediment budget of urban headwater catchments can provide stormwater and waterway managers with the information they need to address specific sediment problems such as sedimentation in stormwater assets and geomorphic recovery of urban streams. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.     

Identifying large‐scale erosion and deposition processes from airborne gamma radiometrics and digital elevation models in a weathered landscape

Patterns of erosion and deposition are difficult to identify and measure at catchment and regional scale but it may be possible to infer their distribution from remote sensing using easily measured surrogate variables. Airborne geophysical surveys provide data on gamma ray emissions from surface and near‐surface material and allow estimation of K, Th and U content. Gamma ray signatures are largely determined by lithology but also change with weathering and with erosion and deposition, and may be used as a partial surrogate for those processes. Comparison of gamma ray signatures with topographic characteristics closely related to sediment transport capacity, downstream sorting of sediments, and the extent of erosion and deposition shows strong linkages. Studies in four small catchments in southeastern Australia indicate that K consistently increases as slopes become steeper while Th and U may either increase or decrease. This suggests the presence of fresh rock rather than weathered material and implies removal of material by erosion, although some patterns may result from systematic changes in lithology across catchments. Analysis by lithology confirms the increase in K with slope in granites, metamorphosed sediments and basalt, and also shows a tendency for U to decrease with slope in the granites and basalt. Gamma ray emissions vary only slightly with catchment area (a surrogate measure of water discharge) suggesting that water erosion is limited or that discharge is not closely related to area. Gamma radiometric profiles down hillslopes, averaged across the full range of gradients, show that, in most cases, radioelements initially decrease, probably reflecting increased weathering, but then increase close to valley floors because of accumulation of fine sediments. Analysis by lithology confirms the increase in radioelements close to valley floors in granites and metamorphosed sediments but the trend is less clear in basalt. Gamma ray profiles down floodplains are variable and indicate the amount of deposition and accumulation of weathered material in valley openings and exposure of bedrock in valley constrictions. Simple erosion and deposition models, based on the conservation of mass equation, and applied to the four catchments, show that all radioelements increase as the potential for deposition increases. They reach a low point in zones of no net erosion or deposition and subsequently increase as erosion becomes more intense and weathered material is lost from slopes. Analysis by lithology largely confirms this pattern. The usefulness of airborne geophysical survey data is limited by flight line spacing with most data being flown at a 200–400 m spacing in Australia. However, general trends in erosion and deposition can still be distinguished and there is capacity for calibrating long‐term erosion and deposition models once better approaches to interpretation of gamma ray data have been developed. Copyright © 2000 John Wiley & Sons, Ltd.     

Late Pleistocene and Holocene coastal palaeoeconomies: A reconsideration of the molluscan evidence from northern Spain

The worldwide increase in shell midden deposits on coastlines during the Holocene has been variously explained as the result of human population growth, economic intensification, changes in the visibility of midden deposits with changes in sea level, or climatic and environmental changes. Since coastlines are relatively unstable in geological and ecological terms, and since many archaeological sequences span periods of major climatic change, a critical issue is the ability to disentangle palaeoenvironmental from cultural and anthropogenic effects. We draw on a case study from the cave sequences of northern Spain to illustrate the problems and possibilities of palaeoeconomic and palaeoenvironmental interpretation, using studies of palaeogeographical context and analysis of abundance, taxonomic representation, ecological tolerances, size, growth structures, and other physical and chemical characteristics of the molluscs themselves. We demonstrate that the dominant, but by no means exclusive, factor in archaeologically visible long‐term changes in shell‐gathering behavior is environmental change rather than cultural change. © 2003 Wiley Periodicals, Inc.     

The West Spitsbergen Fold Belt: The result of Late Cretaceous-Palaeocene Greenland-Svalbard convergence?

The West Spitsbergen Fold Belt, together with the Eurekan structures of northern Greenland and Ellesmere Island, are suggested to be the result of Late Cretaceous-Palaeocene intracontinental compressional tectonics. The Late Palaeozoic –Mesozoic rocks of western Spitsbergen are characterized by near-foreland deformation with ramp-flat, top-to-the east thrust trajectories, whereas structurally higher nappes involving Caledonian complexes are typified by more listric thrusts and mylonite zones. A minimum of 40 km of shortening is estimated for the northern part of the West Spitsbergen Fold Belt. The axial trends in the West Spitsbergen and the North Greenland Eurekan fold belts parallel the principal fault zones which accommodated the separation of Greenland and Svalbard after Chron 25/24. In northern Greenland, north directed Eurekan thrusts associated with mylonites and cleavage formation represent at least 10 km of shortening. Between 50 and 100 km of shortening is estimated for the markedly arcuate Eurekan Fold Belt of Ellesmere Island, but the principal tectonic transport is eastwards. Kinematic reconstructions suggest that Svalbard was linked to North America before the opening of the Eurasian Basin and Norwegian — Greenland Sea. In the Late Cretaceous — Palaeocene interval, the relative motion between Greenland and North America was convergent across the Greenland — Svalbard margin, giving rise to the West Spitsbergen Fold Belt and the Eurekan structures of North Greenland.