A practical and efficient numerical scheme for the analysis of steady state unconfined seepage flows

The scaled boundary finite‐element method (SBFEM), a novel semi‐analytical technique, is applied to the analysis of the confined and unconfined seepage flow. This method combines the advantages of the finite‐element method and the boundary element method. In this method, only the boundary of the domain is discretized; no fundamental solution is required, and singularity problems can be modeled rigorously. Anisotropic and nonhomogeneous materials satisfying similarity are modeled without additional efforts. In this paper, SBFE equations and solution procedures for the analysis of seepage flow are outlined. The accuracy of the proposed method in modeling singularity problems is demonstrated by analyzing seepage flow under a concrete dam with a cutoff at heel. As only the boundary is discretized, the variable mesh technique is advisable for modeling unconfined seepage analyses. The accuracy, effectiveness, and efficiency of the method are demonstrated by modeling several unconfined seepage flow problems. Copyright © 2011 John Wiley & Sons, Ltd.     

Transient seepage analysis in zoned anisotropic soils based on the scaled boundary finite‐element method

The scaled boundary finite‐element method, a semi‐analytical computational scheme primarily developed for dynamic stiffness of unbounded domains, is applied to the analysis of unsteady seepage flow problems. This method is based on the finite‐element technology and gains the advantages of the boundary element method as well. Only boundary of the domain is discretized, no fundamental solution is required and singularity problems can be modeled rigorously. Anisotropic and non‐homogeneous materials satisfying similarity are modeled with no additional efforts. In this study, firstly, formulation of the method for the transient seepage flow problems is derived followed by its solution procedures. The accuracy, simplicity and applicability of the method are demonstrated via four numerical examples of transient seepage flow – three of them are available in the literature. Homogenous, non‐homogenous, isotropic and anisotropic material properties are considered to show the versatility of the technique. Excellent agreement with the finite‐element method is observed. The method out‐performs the finite‐element method in modeling singularity points. Copyright © 2014 John Wiley & Sons, Ltd.     

Middle Jurassic palynomorphs of the Dalichai Formation, central Alborz Ranges, northeastern Iran: Paleoecological inferences

Palynological data are used to draw paleoecological inferences for the Dalichai Formation,northeast of Semnan,northeastern Iran.All samples examined yield well-preserved,diverse palynofloras consisting predominantly of miospores;dinoflagellate cysts,foraminiferal test linings,and fungal spores occur as minor constituents.Fifty-four species of spores(37 genera),18species of pollen(9 genera),and 16 species of dinoflagellate cysts(13 genera)are recognized.Co-occurrence of such miospore species with known vertical ranges as Klukisporites variegatus,Sellaspora asperata,Murospora florida,and Concavissimisporites verrucosus suggests a Middle Jurassic(Bajocian-Callovian)age for the host strata,thus corroborating the available paleozoological evidence.Such spore species as Klukisporites,Cyathidites,and Dictyophyllidites known to have been produced by Pterophyta dominate the palynofloras.Thus the contemporaneous coastal vegetation was characterized by predominance of Pterophyta whereas representatives of Ginkgophyta,Pteridospermophyta,Lycophyta,Coniferophyta,and Bryophyta were rarely represented.This reconstruction implies that a moist,warm climate prevailed in northeastern Iran during the Middle Jurassic(Bajocian-Callovian).This is confirmed by occurrence of fungal spores accompanied by such warm water dinoflagellate cysts as Mendicodinium groenlandicum,Pareodinia ceratophora,and Gonyaulacysta jurassica.Abundance of Amorphous Organic Matter(AOM)signifies a shallow,low-energy,dysoxic-anoxic depositional site for the host strata.Furthermore,the ratio of AOM to marine palynomorphs as well as abundance of blade-shaped to eqiudimensional opaque palynomacerals could indicate low sedimentation rate in a shallow,low-oxygenated marine environment.Additionally,occurrence of chorate dinoflagellate cysts(e.g.,Adnatosphaeridium caulleryi)and acritarchs bearing relatively long processes(e.g.,Micrhystridium)possibly suggests deepening upward in the study section.     

An analytical solution for stresses induced by a post-tensioned anchor in rocks containing two perpendicular joint sets

A new analytical approach for the analysis of stress around a post-tensioned anchor in rock with two perpendicular joint sets is presented. The solution considers nonlinear shear stresses developed along the anchor bond length as well as debonding at the tendon–grout interface. The bearing plate effects are also considered in the analyses. The following assumptions are made: (1) homogeneous and orthotropic elastic rock; (2) half-space rock mass with plane strain conditions; (3) trilinear bond-slip model for the behavior of the tendon–grout interface; (4) an elastic anchor. The employed methodology is to decompose the anchor problem into two problems of simpler loadings: stresses produced under a rigid bearing plate and stresses induced by interfacial shear stresses mobilized along the bond length. Based on the proposed solution, an illustrative example is given and the results show that a large compressive region is formed around the anchor free length. Tensile stress concentrations are also observed around the bond length and near the rock surface outside the bearing plate. A parametric study is also conducted to investigate the effects of joint properties on the induced stresses. The results show that as the number of joints intersecting the anchor axis increases, the magnitude of compressive stresses in the free zone decreases, while the size of compression zone around the anchor increases. To verify the results of the analytical approach, a comparison is made with numerical results obtained by using the finite element method. The analytical solutions compare very well with the results obtained by numerical method.     

Euler-Euler two-phase flow simulation of tunnel erosion beneath marine pipelines

In this study an Euler-Euler two-phase model was developed to investigate the tunnel erosion beneath a submarine pipeline exposed to unidirectional flow. Both of the fluid and sediment phases were described via the Navier-Stokes equations, i.e. the model was implemented using time-averaged continuity and momentum equations for the fluid and sediment phases and a modified k−ε turbulence closure for the fluid phase. The fluid and sediment phases were coupled by considering the drag and lift interaction forces. The model was employed to simulate the tunnel erosion around the pipeline laid on an erodible bed. Comparison between the numerical result and experimental measurement confirms that the numerical model successfully predicts the bed profile and velocity field during the tunnel erosion. It is evident that the sediments are transported as the sheet-flow mode in the tunnel erosion stage. Also the transport rate under the pipe increases rapidly at the early stage and then reduces gradually at the end of the tunnel erosion beneath pipelines.     

Cretaceous subduction-related volcanism in the northern Sanandaj-Sirjan Zone, Iran

Cretaceous volcanic rocks (SCV) are widely developed in the northern part of the Sanandaj-Sirjan Zone, northwest Iran. Based on the mineralogy, texture and geochemical composition these rocks are divided in two main groups, the first and main one situated in the central part of the study area and the second one in the northeast. The former is dominantly basalts, andesitic basalts, and andesites and the latter comprises andesite, trachy-andesite to acidic variants, with porphyritic to microlithic porphyry and vitrophyric textures. Beside the differences between these two groups, the chemical compositions all of these rocks show a calc-alkaline affinity and enrichment in LIL elements (Rb, Ba, Th, U, and Pb) and depletion in Nb, Ti, and Zr, as evident in spider diagrams normalized to primitive mantle. The rocks are particularly enriched in Rb and depleted in Nb and Ti, as well as displaying high Rb/Sr and Rb/Ba ratios and low ratios of incompatible elements such as Nb/U (<10; range, 0.6–9), Th/U (<2), and Ba/Rb (<20). The significant U enrichment relative to neighbouring Nb and Th in the mantle-normalized variation diagram is mainly a result of source enrichment by slab-derived fluids. Significantly lower Nb/U ratios are observed in arc volcanics. These low values are generally ascribed to the strong capacity of LILE and the inability to transfer significant amounts of HFSE via slab-derived hydrous fluid. The results of geochemical modelling suggest a mantle lithospheric source that was metasomatized by fluids derived from a Neo-Tethyan subducted slab during the Middle to Late Cretaceous in the northern part Sanandaj-Sirjan Zone.     

Unification of vertical datums by GPS and gravimetric geoid models using modified stokes formula

In general, neighboring vertical datums can be compared directly at one or more common points on the border between the datums. This direct method requires leveling and gravity measurements. Such a direct connection is not possible if the datums are separated by an ocean or another body of water. Then a rigorous mathematical model, an indirect approach, may be useful. In order to connect regional vertical datums, a rigorous mathematical model is derived based on a method by Rummel and Teunissen. In this study, two vertical datums are connected indirectly by means of a combination of precise geocentric positions of tide gauge sites and their geoid heights in one geocentric coordinate system and their height values in the respective height datums. This method is used to connect the Swedish and the Finnish height systems. The difference between Swedish RH70 and the Finnish N60 height systems is estimated to —12.1±2.7 cm. The results are mostly in good agreement with those of the direct approach by Sjöberg and by Ekman and the indirect approach by Pan and Sjöberg.     

On the structural age of the Rhoscolyn antiform,Anglesey, North Wales

In the Rhoscolyn area of Anglesey, the late Precambrian interbedded psammites and pelites of the Monian Supergroup are folded into a kilometre‐scale antiform, plunging about 25°NE and with an axial surface dipping about 40°NW. Numerous folds of up to a few tens of metres in wavelength are present on both limbs of this antiform. These smaller‐scale folds also plunge about 25°NE but clearly belong to two separate episodes of folding, and it has become a matter of longstanding controversy as to whether the larger antiform belongs to the first or second of these episodes. Close examination of the cleavage/bedding asymmetries from all the lithologies, however, shows that the large antiform is a second‐generation structure, and that on the gently dipping northwest limb, the sense of cleavage/bedding asymmetry of the earlier cleavage in the psammitic units has been almost uniformly and homogeneously reversed (so that it appears to be axial planar to the antiform), while in the pelitic units the sense of cleavage/bedding asymmetry of the earlier cleavage has been preserved. Many of the small‐scale complexities of the observed cleavage/bedding relationships may be explained by appealing to differences in the timing of the formation of buckling instabilities relative to this reorientation of the early cleavage in the psammites during the second deformation. A first‐order analysis of the finite strains from around the large‐scale antiform shows that the orientation of the first cleavage prior to the second deformation was steeply dipping to the southeast. The second deformation correlates with the southeast‐verging Caledonian deformation affecting the Monian and Ordovician units elsewhere in northwest Anglesey, while the northwest‐verging first deformation event, which is not present in the Ordovician rocks, must have occurred before they were deposited. Copyright © 2004 John Wiley & Sons, Ltd.     

Maximum mass of a hot neutron star with a quark core

We have considered a hot neutron star with a quark core,a mixed phase of quark-hadron matter,and a hadronic matter crust and have determined the equation of state of the hadronic phase and the quark phase.We have then found the equation of state of the mixed phase under the Gibbs conditions.Finally,we have computed the structure of a hot neutron star with a quark core and compared our results with those of the neutron star without a quark core.For the quark matter calculations,we have used the MIT bag model...