Effects of periodic fluctuations of micro‐polar boundary conditions on shear localizations in granular soil–structure interaction

In this work, the interface behavior between an infinite extended narrow granular layer and a rough surface of rigid body is investigated numerically, using finite element method in the updated Lagrangian (UL) frame. In this regard, the elasto‐plastic micro‐polar (Cosserat) continuum approach is employed to remove the limitations caused by strain‐softening of materials in the classical continuum. The mechanical properties of cohesionless granular soil are described with Lade's model enhanced by polar terms, including Cosserat rotations, curvatures, and couple stresses. Furthermore, the mean grain diameter as the internal length is incorporated into the constitutive relations accordingly. Here, the evolution and location of shear band, within the granular layer in contact with the rigid body, are mainly focused. In this regard, particular attention is paid to the effects of homogeneous distribution and periodic fluctuation of micro‐polar boundary conditions, prescribed along the interface. Correspondingly, the effects of pressure level, mean grain diameter, and stratified soil are also considered. The finite element results demonstrate that the location and evolution of shear band in the granular soil layer are strongly affected by the non‐uniform micro‐polar boundary conditions, prescribed along the interface. It is found that the shear band is located closer to the boundary with less restriction of grain rotations. Furthermore, the predicted thickness of shear band is larger for higher rotation resistance of soil grains along the interface, larger mean grain diameter, and higher vertical pressure. Regarding the stratified soil, comprising a thin layer with slightly different initial void ratio, the shear band moves towards the layer with initially higher void ratio. Copyright © 2011 John Wiley & Sons, Ltd.     

Platform Evolution in an Oligo–Miocene Back-arc Basin: An Example from the Central Iran Basin

The Qom Formation is the most important hydrocarbon reservoir target in Central Iran. The Qom platform developed in a back-arc basin during the Oligo–Miocene due to the closing of the Tethyan Seaway. This formation consists of a variety of carbonate and non-carbonate facies deposited on a platform ranging from supratidal to basin. A combination of tectonic and eustatic events led to some lateral and vertical facies variations in the study area. Six third-order depositional sequences and related surfaces were identified regarding vertical facies changes in the studied sections of this Oligo–Miocene succession. According to all results and data, this succession was initially deposited during the Chattian upon a distally steepened ramp of siliciclastic-carbonate composition, including the Bouma sequence. Then, from the late Chattian to the Aquitanian, the platform changed into a homoclinal carbonate ramp with a gentle profile. With respect to tectonic activity, this phase was a calm period during the deposition of the Qom Formation. Finally, a drowned carbonate platform and a rimmed shelf emerged during the Burdigalian, terminated by the continental deposits of the Upper Red Formation. Regarding all geological characteristics, three main tectono-eustatic evolutionary phases have been recognized in the Qom back-arc basin.     

Heavy mineral distribution as related to environmental conditions for modern beach sediments from the Susanoglu (Atakent,Mersin, Turkey)

Geochemical works were conducted on anthropogenically effective lithologic unit exposing along the Susanoglu coast in Mersin, Turkey. For this purpose, beach sand sediments from 33 stations were collected and heavy metal and oxide concentrations were analyzed. To determine the source of heavy metals (natural and anthropogenic), simple and multivariate statistical analyses were applied. According to factor analysis, three factors were determined. The first factor consists of SiO₂, Al₂O₃, Na₂O, K₂O, TiO₂, Cr, Ni, Cu and Mo and total variance is explained with 27.502% and expressed as “natural process factor”. These elements (Cr, Ni, Cu, Mo) are closely associated with geogenic materials and came from same sources of ultrabasic rocks (ophiolite). The second factor consists of CaO, MgO, TiO₂, MnO, Ni, Pb, Zn and W and total variance is explained with 21.505% and expressed as “anthropogenic factor”. These elements (Pb, Zn, Cd, V, W) are anthropogenic and are mainly due to the effluent or industrial input/activities and came from different sources of pollution in the study area. The third factor consists of Pb, Cd and Sb and total variance is explained with 9.748% and expressed as “intermediate factor”. The factor analysis and the cluster analysis are in support of each other. Cr, Ni, Co, Cd, Hg and Mo concentrations are greater than Turkish acceptable values and they show toxic effect. Al, Cu, Pb, Cd and Mo concentrations in beach sand deposits in the Susanoglu coast are found as 1.44, 1.26, 1.21, 1.02 and 1.04 mg/kg and higher than those in Kızkalesi beach sands. However, all other heavy metal contents are determined in low concentrations.     

Depositional facies of the subsurface Neogene Surma Group in the Sylhet Trough of the Bengal Basin,Bangladesh: record of tidal sedimentation

The Bengal Basin, in the north-eastern part of the Indian subcontinent, contains a thick (± 22 km) early Cretaceous-Holocene sedimentary succession. The Neogene succession in the Sylhet Trough of the basin reaches a thickness of more than 6 km of which the Surma Group contains important sandstone reservoirs. Lithologically, the group consists of a succession of alternating shales, siltstones, sandy shales and sandstones, with minor conglomerates. This research work is a sedimentological analysis of the subsurface Neogene succession encountered in the petroleum exploration wells in the Sylhet Trough of the Bengal Basin. Detailed lithologic logs of the cores, based on considering texture and sedimentary structure, permit a subdivision into eight lithofacies, e.g., a shale-dominated facies, interbedded fine sandstones and mudstones, ripple-laminated sandstones, parallel-laminated sandstones, massive sandstones, cross-bedded sandstones, cross-bedded sandstones with pebble/granule lag and conglomerates. Characteristic sedimentary structures of the Surma Group, such as flaser-, wavy- and lenticular-bedding, bipolarity of ripple cross-stratification, evenly laminated sand/silt-streaked shales, reactivation surfaces within cross-bedded sandstone sets, mud-drapes on foreset laminae and herringbone cross-stratification as well as small-scale vertical sequences (several fining-upward cycles) are diagnostic for tidal influence. On the basis of the lithofacies associations and prograding character of the deposits revealed from the electrofacies associations, the Surma Group sediments have been interpreted as representing deposits of tide-dominated deltaic depositional setting.     

The predictability of near-coastal currents using a baroclinic unstructured grid model

A limited domain, coastal ocean forecast system consisting of an unstructured grid model, a meteorological model, a regional ocean model, and a global tidal database is designed to be globally relocatable. For such a system to be viable, the predictability of coastal currents must be well understood with error sources clearly identified. To this end, the coastal forecast system is applied at the mouth of Chesapeake Bay in response to a Navy exercise. Two-day forecasts are produced for a 10-day period from 4 to 14 June 2010 and compared to real-time observations. Interplay between the temporal frequency of the regional model boundary forcing and the application of external tides to the coastal model impacts the tidal characteristics of the coastal current, even contributing a small phase error. Frequencies of at least 3 h are needed to resolve the tidal signal within the regional model; otherwise, externally applied tides from a database are needed to capture the tidal variability. Spatial resolution of the regional model (3 vs 1 km) does not impact skill of the current prediction. Tidal response of the system indicates excellent representation of the dominant M ₂ tide for water level and currents. Diurnal tides, especially K ₁, are amplified unrealistically with the application of coarse 27-km winds. Higher-resolution winds reduce current forecast error with the exception of wind originating from the SSW, SSE, and E. These winds run shore parallel and are subject to strong interaction with the shoreline that is poorly represented even by the 3-km wind fields. The vertical distribution of currents is also well predicted by the coastal model. Spatial and temporal resolution of the wind forcing including areas close to the shoreline is the most critical component for accurate current forecasts. Additionally, it is demonstrated that wind resolution plays a large role in establishing realistic thermal and density structures in upwelling prone regions.     

Istanbul natural gas network rapid response and risk mitigation system

This paper describes a rapid response and risk mitigation system Istanbul Natural Gas Distribution Network Seismic Risk Reduction Project (IGRAS) for the Istanbul Natural Gas Network (IGDA?). Upon the trigger signal received from the earthquake early warning system in Istanbul, the real-time algorithm at IGRAS system district regulators checks the threshold levels of ground-motion parameters and interrupts the gas flow if any exceedance is detected. Then the system: (1) produces almost real-time earthquake hazard maps by using on-line strong-motion data from the strong-motion network in Istanbul: (2) estimates the distribution of damage to the natural gas network; and (3) transfers these damage distribution maps to stakeholders to enable dispatching rapid response teams to high damage areas.     

Dependency of unit shaft resistance on in-situ stress: Observations derived from collected field data

In this study, a database comprised of 30 pullout pile load tests was collected from geotechnical literature and analyzed to investigate the dependency of unit shaft resistance on effective vertical stress. The collected database consists of steel pipe, timber, and concrete piles, with varying normalized penetration depth with respect to pile diameter, driven into loose to very dense sand. Different correlations for the uplift lateral earth pressure coefficient K, Bjerrum-Burland ratio , and the average unit shaft resistance f _ave were derived using different assumptions. A comparison between measured and predicted capacities of the collected piles using the developed correlations indicated that the assumption of values of K and that were constant with depth did not provide a reasonable fit for the measured capacities of the collected piles and thus this assumption is inappropriate. The best correlations for K and that yield a reasonable fit to the measured capacities of the collected piles were found to be functions of sand relative density, pile diameter, and level of effective vertical stress. This indicates that average unit shaft resistance does not reach a limiting value, but rather continues to increase with depth. Moreover, the correlations for K and in terms of effective stress revealed that average unit shaft resistance increases as pile diameter decreases and this increase depends on initial sand relative density. Comparisons of measured and predicted pullout capacities of the collected piles using the best-obtained correlations for K and were made and compared to predictionsobtained from other methods. On the basis of these comparisons, it is concluded that the correlations for K and in terms of effective stress give results comparable to those obtained from other methods, without stipulating limiting values for the average unit shaft resistance.     

Weak field limit and tests of a relativistic theory of gravity

Static spherically-symmetric solutions to the linearized field equations of a generalized scalartensor theory of gravity are derived. The gravitational potential outside such a source is determined; it is found that this potential can have an intermediate range variation. The question of whether such an intermediate range variation would manifest itself in two experiments is addressed.