Field Jet Erosion Tests on Benbrook Dam, Texas

This report summarizes the results of eight field Jet Erosion Tests (JETs) performed on Benbrook Dam, TX. The results from these tests will be used by the U.S. Army Corps of Engineers, Fort Worth District, in assessments of the erosion resistance of the Benbrook Dam with regards to possible overtopping by extreme flooding. The JETs were performed at four different locations, i.e., two locations at the lowest crest elevation and two locations at the mid-slope face of the downstream embankment. Variations in estimated critical hydraulic shear stress and erosion rate values may have been caused by differences in soil composition, i.e., when the material changed from silt/sand to clay. The resulting values of the Erodibility Coefficient, Kd, and Critical Stress, τc, are very useful information in assessing the stability of Benbrook Dam during an overtopping event. Because of the observed natural variability of the materials, combining the erosion parameters presented in this report with the drilling logs and local geology will be imperative for assessing erosion-related failure modes of Benbrook Dam.

The Newton Stones and writing in Pictland, part 1

In the grounds of Newton House near Insch in Aberdeenshire are two Pictish monuments. One is an inscribed stone that also has an incised Pictish mirror symbol, and the other is a Pictish symbol stone with a notched double-disc above a serpent and z-rod symbol. The inscribed stone, commonly referred to as the Newton Stone, has an ogham inscription on one edge that continues onto an added stemline, and on the top front is a unique horizontal, six-line alphabetic inscription. This article examines the documentary record for these two monuments, which were moved from their original location in the 18th and 19th centuries respectively. Through analysis of the documentary evidence, and in comparison with the local geology, the area of the original findspot of the Newton Stone and associated symbol stone is identified. The original landscape of these stones is compared with the topographical features of other Pictish monuments, particularly those in Donside. This comparison reveals that the topographical and liminal features in the original vicinity of the Newton Stone and symbol stone correspond with the wider pattern of the siting of Pictish symbol stones and Pictish cemeteries, and the association between a potentially Pictish-age settlement and these monuments may be suggested through examination of local place-names.

Investigating the Mineral Composition of Peat by Combining FTIR-ATR and Multivariate Analysis

The mineral content of peat has received little attention until the last few decades, when peat cores have been increasingly used to study past dust deposition. Paleodust deposition is commonly reconstructed through elemental datasets, which are used to infer deposition rates, storminess patterns, mineral composition, source identification, and fertilization effects. To date, only a few studies have directly analyzed the mineralogy (by XRD and SEM) and particle size of peat mineral matter, and the conducted studies have usually been constrained by the need to remove a large amount of organic matter, which risks altering the mineral component. One alternative is to use quick, nondestructive techniques, such as FTIR-ATR, that require little sample preparation. In this study, we analyzed by FTIR-ATR both the bulk peat and ash fractions of a sequence taken in a minerogenic mire that covered a wide inorganic matter content range (6%–57%). Aided by principal component analysis on transposed IR spectral data, we were able to identify the main minerals in bulk peat and ash, quartz, mica (likely muscovite), K feldspar (likely microcline), and plagioclase (likely anorthite), which are consistent with the local geology of the mire catchment. Changes in mineral composition during the last ca. 2800 years were coeval with previously reconstructed environmental changes using the same core. Our results suggest that FTIR-ATR has great potential to investigate peat mineral matter and the processes that drive its compositional change.

Trace Element (Fe, Co, Ni and Cu) Dynamics Across the Salinity Gradient in Arctic and Antarctic Glacier Fjords

Around the Greenlandic and Antarctic coastlines, sediment plumes associated with glaciers are significant sources of lithogenic material to the ocean. These plumes contain elevated concentrations of a range of trace metals, especially in particle bound phases, but it is not clear how these particles affect dissolved (<0.2 µm) metal distributions in the ocean. Here we show, using transects in 8 glacier fjords, trends in the distribution of dissolved iron, cobalt, nickel and copper (dFe, dCo, dNi, dCu). Following rapid dFe loss close to glacier outflows, dFe concentrations in particular showed strong similarities between different fjords. Similar dFe concentrations were also observed between seasons/years when Nuup Kangerlua (SW Greenland) was revisited in spring, mid- and late-summer. Dissolved Cu, dCo and dNi concentrations were more variable and showed different gradients with salinity depending on the fjord, season and year. The lack of consistent trends for dCu and dNi largely reflects less pronounced differences contrasting the concentration of inflowing shelf waters with fresher glacially-modified waters. Particles also made only small contributions to total dissolvable Cu (dCu constituted 83 ± 28% of total dissolvable Cu) and Ni (dNi constituted 86 ± 28% of total dissolvable Ni) within glacier plumes. For comparison, dFe was a lower fraction of total dissolvable Fe; 3.5 ± 4.8%. High concentrations of total dissolvable Fe in some inner-fjord environments, up to 77 µM in Ameralik (SW Greenland), may drive enhanced removal of scavenged type elements, such as Co. Further variability may have been driven by local bedrock mineralogy, which could explain high concentrations of dNi (25–29 nM) and dCo (6–7 nM) in one coastal region of west Greenland (Kangaatsiaq). Our results suggest that dissolved trace element distributions in glacier fjords are influenced by a range of factors including: freshwater concentrations, local geology, drawdown by scavenging and primary production, saline inflow, and sediment dynamics. Considering the lack of apparent seasonality in dFe concentrations, we suggest that fluxes of some trace elements may scale proportionately to fjord overturning rather than directly to freshwater discharge flux.

A Geothermal Plant from a Time-Scale Perspective

In recent years, geothermal energy use from low-temperature sandstone reservoirs has sharply increased. Nonetheless, the injection of heat-depleted geothermal fluids has not been an easy task because of well/formation damage and operational/economic issues. Sønderborg geothermal plant is a case example of heat-mining from a low-temperature reservoir. It is in the northeast of Sønderborg towards Augustenborg Fjord. The present work takes into consideration the regional and local geology of the Sønderborg area, construction of the wells, field experience and water chemistry. The main issues of the geothermal plant appear to be related to the construction of the wells and reinjection of the heat-depleted brine. Our water chemistry analysis and PHREEQC simulations indicate that geothermal brine was saturated with respect to carbonate and barite minerals. The excess of Ca2+ and SO42− ions could have led to the formation and precipitation of carbonate and sulfate scales. Moreover, the increment of iron concentration over time could suggest the ingress of oxygen and pitting corrosion due to the presence of halide ions.

Hydrogeophysical Characterization of the Marizal–São Sebastião Aquifer System in the Surroundings of the Limpec Sanitary Landfill, Camaçari, Bahia, Brazil

ABSTRACT. A detailed hydrogeophysical survey was conducted using the geoelectrical method in the surroundings of the LIMPEC sanitary landfill, municipality of Camaçari, Bahia, Brazil. Twenty-six vertical electrical soundings (VESs) were done, configured according to the Schlumberger electrode array and spaced up to 400 m between current electrodes. Hydrogeological quali-quantitative information was obtained by integrating geoelectrical results to data from wells and local geology information, namely: (i) an apparent resistivity map showed the occurrence of a conductivity anomaly, possibly attributed to the contamination plume, dispersed within the saturated zone, and presenting a SSE convection direction; (ii) one-dimensional inversions allowed to interpret the stratigraphic pattern, identify static level depth and the occurrence of possible contamination plumes, and indicate the direction of groundwater flow, which was also towards SSE; (iii) two-dimensional inversions produced inverted geoelectrical profiles, with a mean error below 2%, and confirmed the occurrence of possible contamination plumes disseminated within the unsaturated zone and dispersed within the saturated one. The geoelectrical facies with the highest resistivity values (> 600 ohm.m) were related to the São Sebastião Formation. Facies with intermediate values (100 to 800 ohm.m) regarded the Marizal Formation. In turn, those with the lowest values (< 100 ohm.m) were related to contamination plumes and/or eventual occurrences of silt/clay; (iv) the parameters of porosity, hydraulic conductivity, and transmissivity were estimated between 19.2 and 34.2%, 0.11 and 3.37 x10-3 cm/s, and 4.7 and 145.6 m²/d, respectively; and (v) local free aquifer vulnerability was classified as high, according to the evaluation using the GOD method.Keywords: geoelectrical method, urban solid waste, hydrodynamic parameters. Caracterização Hidrogeofísica do Sistema Aquífero Marizal – São Sebastião, no Entorno do Aterro Sanitário Limpec, Camaçari, Bahia, BrasilRESUMO. Um estudo hidrogeofísico de detalhe, utilizando o método geoelétrico, foi conduzido no entorno do aterro sanitário LIMPEC, município de Camaçari, Bahia, Brasil. Vinte e seis sondagens elétricas verticais (SEVs), sob configuração do arranjo Schlumberger de eletrodos, com espaçamento de até 400 m entre os eletrodos de corrente foram executadas. Informações quali-quantitativas de âmbito hidrogeológico foram alcançadas a partir da integração dos resultados geoelétricos a dados de poços e informações da geologia local, a saber: (i) o mapa de resistividade aparente revelou a ocorrência de uma anomalia condutiva, possivelmente atribuída à pluma de contaminação, dispersa na zona saturada, apresentando sentido de convecção na direção SSE; (ii) as inversões unidimensionais possibilitaram interpretar o padrão estratigráfico, identificar a profundidade do nível estático, a ocorrência de possíveis plumas de contaminação e apontar o sentido do fluxo hídrico subterrâneo também para SSE; (iii) as inversões bidimensionais geraram perfis geoelétricos invertidos, com erro médio inferior a 2%, e confirmaram a ocorrência de possíveis plumas de contaminação disseminadas na zona não saturada e dispersas na zona saturada. Os fácies geoelétricos de maiores valores de resitividade (>600 Ohm.m) estão atribuídos à Formação São Sebastião. Os fácies de valores intermediários (100 a 800 Ohm.m), referem-se à Formação Marizal. Já os de menores valores (<100 Ohm.m), a plumas de contaminação e/ou eventuais ocorrências de silte/argila; (iv) os parâmetros porosidade, condutividade hidráulica e transmissividade foram estimados serem entre 19,2 a 34,2%, 0,11 a 3,37 x10-3 cm/s e 4,7 a 145,6 m²/d, respectivamente; e (v) a vulnerabilidade do aquífero livre local foi classificada como alta, segundo avaliação realizada utilizando o método GOD. Palavras-chave: método geoelétrico, resíduos sólidos urbanos, parâmetros hidrodinâmicos.

Comparison of Static and Dynamic Analysis of Multi-Storied Building

Vibration of ground is the main cause of earthquake damage to building structures. There are many factors responsible for the strength of earthquake shaking at a site including the earthquake's magnitude, the site's proximity to the fault, the local geology, and the soil type. The natural disasters have been fast recurring all over the world causing great concern and damage to man and their properties. Among these disasters Earthquake is an endogenous natural disaster, which occurs suddenly without any warning. The vast devastation of engineering systems and facilities during the past earthquakes has exposed serious deficiencies in the prevalent design and construction. Shear wall is one of the most commonly used lateral load resisting in high rise buildings. Shear wall can be used to simultaneously resist large horizontal load and support gravity load. In the study, one tall RCC building of 13 stories is assumed to be situated in seismic zone V is analysed using two methods (Static and Dynamic Analysis). The share walls are taken at different position of building. The comparison of the different shear wall models is studied in this work against the different parameters like time period, bending moment, shear force, storey drift, displacement

Londinium's Landward Wall: Material Acquisition, Supply and Construction

ABSTRACT The construction of a free-standing stone wall was a significant occasion in Londinium's history, remarkable for the quantity of masonry used and for the continuing additions to the defences over at least three identifiable phases. Since the local geology in the London Basin does not offer suitable building stone, Londinium's walls offer an exceptional example by which to examine the logistics of construction and the transportation of materials in the context of Romano-British building projects. We examine the sources of the materials used, their transport and the scale of labour and investment involved in the construction of the Landward Wall using an energetics-based methodology. Finally, we provide new insights into Londinium's Landward Wall and the socio-economic and practical implications of its construction. Supplementary material is available online (https://doi.org/10.1017/S0068113X21000088) and comprises technical data related to the architectural energetics.

A Preliminary Geothermal Prospectivity Mapping Based on Integrated GIS, Remote-Sensing, and Geophysical Techniques around Northeastern Nigeria

Spatial mapping of potential geothermal areas is an effective tool for a preliminary investigation and the development of a clean and renewable energy source around the globe. Specific locations within the Earth’s crust display some manifestations of sub-surface geothermal occurrences, such as hot springs, a volcanic plug, mud volcanoes, and hydrothermal alterations, that need to be investigated further. The present area of investigations also reveals some of these manifestations. However, no attempt was made to examine the prospectivity of this terrain using the efficient GIS-based multicriteria evaluation (MCE) within the scope of the Analytic hierarchy process (AHP). The integration of remote sensing, Geographic information system (GIS), and other geophysical methods (Magnetic and gravity) was performed to map the promising geothermal areas. Multiple input data sets such as aero-magnetic, aero-gravity, aero-radiometric, digital elevation model (DEM), geological map, and Landsat-8 Operational Land Imager (OLI) data were selected, processed, and use to generate five thematic layers, which include heat flow, temperature gradients, integrated lineaments, residual gravity, and lithology maps. The five thematic layers were standardized and synthesized into a geothermal prospectivity map. The respective ranks and weight of the thematic layers and their classes were assigned based on expert opinion and knowledge of the local geology. This research aims to apply an efficient method to evaluate the factors influencing the geothermal energy prospects, identify and map prospective geothermal regions, and, finally, create a geothermal prospectivity model.