Elasto-plastic Behavior of Raghadan Tunnel Based on RMR and Hoek–Brown Classifications

Lining contact pressure and ground deformation of Raghadan transportation tunnel (Amman, Jordan) were investigated. The tunnel is 1.1 km in length and 13.5 m in diameter. This study was intended to integrate useful relations among the widely used rock classification system (RMR: rock mass rating), Hoek–Brown classification, and lining-ground interaction. The materials encountered along the tunnel alignment were limestone, dolomatic limestone, marly limestone, dolomite, and sillicified limestone. The ground conditions along the tunnel alignment including bedding planes, joint sets and joint conditions, rock quality, water flow, and rock strength were evaluated based on the drilled boreholes and rock exposures. Elasto-plastic finite element analyses were conducted to study the effect of rock mass conditions and tunnel face advance on the behavior of lining-ground interaction. The results of the analyses showed that lining contact pressure decreases linearly with the increase in RMR value. Also the results showed that tunnel lining contact pressure and crown inward displacement decreases with the increase in the unsupported distance (distance between tunnel face and the end of the erected lining). Ground displacement above the tunnel crown was found to be increases in an increasing rate with the decrease in the depth above the crown. This displacement was also found to be affected by the RMR value and the unsupported distance.     

Investigation of seawater intrusion using stable and radioisotopes at coastal area south of Beirut,the Capital of Lebanon

In this study, field measurements were made and environmental isotopes and radiological properties were determined in six selected wells located in the coastal area south of Beirut, the capital of Lebanon. It is one of the many district areas in Lebanon, threatened by the penetration of seawater into aquifers. Two sampling campaigns were carried out to determine possible seasonal variations. High electrical conductivity was observed, ranging from 1080 to 7900 μS/cm. The total dissolved solids values ranged from 530 to 5600 mg/L. This is attributed to a seawater intrusion confirmed by high chlorine concentrations that ranged from 400 to 3500 mg/L. Isotope data for δ¹⁸O/δ²H showed enrichment that is relatively small at the end of wet season due to recharge by local precipitation and infiltration. Carbon-14 ages and ²³⁴U/²³⁸U ratios confirmed the presence of young water. No radiological hazard was observed as all values lay below the guidance levels of the WHO.     

The El Achour (Algiers,Algeria) landslide delimitation using the H/V ambient vibration method

We present in this work investigations using seismic ambient vibration to delimitate the El Achour landslide (Algiers), upon which independent geotechnical studies were carried out. Acquisition campaign of ambient vibration on the El Achour site on June 2009 and June 2015, over a surface of about 2 ha, consisted of 64 records of ambient noise with a 10 to 20 m grid size. This approach consists of simple, light, and fast H/V acquisitions, in order to determine the extension of the unstable zone, the depth of the sliding surface, and to test the effectiveness of this method. Two peaks were interpreted as one being for the sliding surface and the other for the lithological interface. As results, in the stable area, they are satisfactory. Indeed, the points in this area are not intermediate peaks which could be related to potential sliding surfaces, which led us to think that we could delineate, using this method, the unstable area from the stable area. The HVSR method allows to determine the thickness of the geological formations and to highlight the lateral and vertical facies changes in broad area.     

A disaster risk management performance index

The Risk Management Index, RMI, proposed in this paper, brings together a group of indicators that measure risk management performance and effectiveness. These indicators reflect the organizational, development, capacity and institutional actions taken to reduce vulnerability and losses in a given area, to prepare for crisis and to recover efficiently from disasters. This index is designed to assess risk management performance. It provides a quantitative measure of management based on predefined qualitative targets or benchmarks that risk management efforts should aim to achieve. The design of the RMI involved establishing a scale of achievement levels or determining the distance between current conditions and an objective threshold or conditions in a reference country, sub-national region, or city. The proposed RMI is constructed by quantifying four public policies, each of which is described by six indicators. The mentioned policies include the identification of risk, risk reduction, disaster management, and governance and financial protection. Risk identification comprises the individual perception, social representation and objective assessment; risk reduction involves the prevention and mitigation; disaster management comprises response and recovery; and, governance and financial protection policy is related to institutionalization and risk transfer. Results at the urban, national and sub-national levels, which illustrate the application of the RMI in those scales, are finally given.     

Mineralogical and geochemical characterization of listwaenite from the Semail Ophiolite, Oman

The late Cretaceous-lower Tertiary hydrothermal alteration of serpentinized peridotite in the Semail ophiolite has formed two distinct types of listwaenite. Type I is characterized by the presence of calcite (Type IA) or dolomite (Type IB)+fuchsite±spinel. Type II is dominated by silicate minerals (quartz, chlorite, fuchsite)±calcite+dolomite±magnetite±apatite±plagioclase. Most listwaenites occur as veins along thrust fault zones within the ophiolite mélange. High Cr and Ni contents, abundant occurrence of Cr-spinel within a matrix of red-brown ferruginous carbonates within a micro-vein network of goethite, and the relics of mesh texture indicate an ultramafic protolith. Type I and II listwaenites represent different stages of hydrothermal alteration. The mineralogical and chemical distinctions of both types are the response to the extent of the reactions between the protoliths and the solutions leading to different stages of metasomatic replacement. The hydrothermal fluids involved in the formation of Type I listwaenite were enriched in Ca, Mg, and CO₂, whereas Type II listwaenite bodies were formed from a hydrothermal fluid enriched in SiO₂. REE and trace elements in both listwaenite types were extracted in part from adjoining peridotite. No Au anomaly in the study areas has been detected.     

An inverse method of modeling thermal histories from apatite fission-track data

Apatite fission-track (FT) ages and track length distributions are important sources of information about the thermal histories of rocks. Recent advances in the understanding of track annealing in apatite provide a solution to the forward problem of predicting FT ages and track length distributions that result from a given thermal history. In this paper, a method is presented to address the inverse problem—estimation of the thermal history from FT data. The inverse method uses an iterative approach (the downhill simplex) to systematically modify a starting thermal history to achieve satisfactory statistical agreement between the predicted and observed FT age and track length distribution. However, because of analytical uncertainties, a unique thermal history does not exist. Monte Carlo simulations are used to take into account the uncertainties in the data and yield a spectrum of possible thermal histories. The results are based on the isothermal annealing model of Laslett et al. ([1], Chem. Geol. Isot. Geosci. Sect., Vol. 65) but because the method uses forward predictions and not an analytical formula specific to a single annealing model, alternative annealing models could be used within the same framework. This method is an improvement in interpreting fission-track data because the range of thermal histories permitted by the data can be evaluated.To demonstrate the method, it is applied to several sets of test data created by forward modeling of idealized thermal histories. The results show that the age at which the sample cooled through its closure temperature and the most general features of the thermal history are revealed. However, data from partially annealed samples have wide spectra that reflect large uncertainties in the form of the thermal history. For such samples, FT data alone are not likely to provide strong tests of geologic hypotheses. Conversely, geologic information may play a crucial role in constraining the thermal history spectrum. In application to uplift-related cooling, this inverse method can provide much more realistic assessments of the cooling rate and its uncertainty than are otherwise possible.     

Silver and silver-bearing minerals at the Um Samiuki volcanogenic massive sulphide deposit, Eastern Desert, Egypt

The Um Samiuki Zn–Cu–Pb–Ag mineralisation, south Eastern Desert, Egypt is hosted by felsic volcanic rocks which form part of the 712-Ma-old, east-west-trending Shadli Volcanic Belt. Two major occurrences of massive sulphides are present at the top of rhyolitic breccia in the Western and Eastern mine areas. In each occurrence, a bornite-bearing zone is overlain by a pyrite-chalcopyrite-bearing zone and underlain by a disseminated, Cu-depleted zone. In the massive sulphide ore, sphalerite, chalcopyrite, pyrite, galena, bornite and tetrahedrite–tennantite are major minerals, whereas arsenopyrite, pyrrhotite, molybdenite and magnetite are accessory phases. Covellite and digenite are common secondary minerals. Bornite, tetrahedrite–tennantite and covellite contain high amounts of silver (averages of 1.97, 1.39 and 1.82 wt% respectively). Based on mineralogical balance calculations, bornite and covellite accommodate 80% of silver in the Um Samiuki deposit. Ag was incorporated in the crystal structure of the early-crystallised copper sulphides and sulphosalts and silver minerals. The temperature, sequential precipitation of the fluids and the structure of the crystallising phases control the distribution of silver. Post-depositional deformation and metamorphic processes caused liberation, remobilisation and redeposition of silver within the massive sulphides.Editorial handling: D. Lentz     

Solutions for Exterior Orientation in Photogrammetry: A Review

The determination of the attitude, the position and the intrinsic geometric characteristics of the camera is recognised as the fundamental photogrammetric problem. It can be summarised as the determination of camera interior and exterior orientation parameters, as well as the determination of 3D coordinates of object points. The term "exterior orientation"of an image refers to its position and orientation related to an exterior (object space) coordinate system. Several methods can be applied to determine the parameters of the orientation of one, two or more photos. The orientation can be processed in steps (as relative and absolute orientation) but simultaneous methods (such as bundle adjustments) are now available in many software packages. Several methods have also been developed for the orientation of single images. They are based in general on geometric and topological characteristics of imaged objects.
This paper presents a survey of classical and modern methods for the determination of the exterior parameters in photogrammetry, some of which are available as software packages (with practical examples) on the Internet. The methods presented are classified in three principal groups. In the first, a selection of approximate methods for applications that do not require great accuracy is presented. Such methods are also used to calculate values required for iterative processes. In the second group, standard point–based methods derived from collinearity, coplanarity or coangularity conditions are briefly reviewed, followed by line–based approaches. The third group represents orientation methods based on constraints and on concepts of projective geometry, which are becoming of increasing interest for photogrammetrists. In the last section, the paper gives a summary of existing strategies for automatic exterior orientation in aerial photogrammetry.     

Morphometric relationships of penaeid shrimps in a coastal lagoon: Spatio-temporal variability and management implications

Spatio-temporal variability in the length-weight relationship of four sympatric shrimp species (Farfantepeneus aztecus, F. brasiliensis, F. duorarum, andF. notialis) was evaluated in the Celestun lagoon, Mexico. Monthly samples were taken throughout 2 yr in three hydrological zones (seaward, middle, and inner) and climatic seasons (Nortes, Dry, and Rainy). Significant intraspecific and interspecific differences in the length-weight relationships were detected among climatic seasons and hydrological zones, reflecting positive allometric growth.F. notialis registered the highest condition (weight at length), followed byF. duorarum, F. aztecus, andF. brasiliensis. The lowest values in condition were consistently registered during Nortes and at the seaward zone. All species showed a pattern consistent with a density-dependent effect on condition, that is a negative correlation between individual mean weight and total relative abundance. The immediate implication for managing this important multispecific coastal artisanal resource that is supported by our study is the restriction of fishing effort in the seaward zone, mainly during the Nortes seasons.     

CARBON EMISSIONS FROM MEXICAN FORESTS: CURRENT SITUATION AND LONG-TERM SCENARIOS

Estimates of carbon emissions from the forest sector in Mexico are derived for the year 1985 and for two contrasting scenarios in 2025. The analysis covers both tropical and temperate closed forests. In the mid-1980s, approximately 804,000 ha/year of closed forests suffered major perturbations, of which 668,000 ha was deforestation. Seventy-five percent of total deforestation is concentrated in tropical forests. The resulting annual carbon balance from land-use change is estimated at 67.0 × 10⁶ tons/year, which lead to net emissions of 52.3 × 10⁶ tons/year accounting for the carbon uptake in restoration plantations and degraded forest lands. This last figure represents approximately 40% of the country's estimated annual total carbon emissions for 1985–1987. The annual carbon balance from the forest sector in 2025 is expected to decline to 28.0 × 10⁶ t in the reference scenario and to become negative (i.e., a carbon sink), 62.0 × 10⁶ t in the policy scenario. A number of policy changes are identified that would help achieve the carbon sequestration potential identified in this last scenario.