Three‐dimensional nonlinear finite element analysis of pile groups in saturated porous media using a new transmitting boundary

The dynamic behaviour of pile groups subjected to an earthquake base shaking is analysed. An analysis is formulated in the time domain and the effects of material nonlinearity of soil, pile–soil–pile kinematic interaction and the superstructure–foundation inertial interaction on seismic response are investigated. Prediction of response of pile group–soil system during a large earthquake requires consideration of various aspects such as the nonlinear and elasto‐plastic behaviour of soil, pore water pressure generation in soil, radiation of energy away from the pile, etc. A fully explicit dynamic finite element scheme is developed for saturated porous media, based on the extension of the original formulation by Biot having solid displacement (u) and relative fluid displacement (w) as primary variables (u–w formulation). All linear relative fluid acceleration terms are included in this formulation. A new three‐dimensional transmitting boundary that was developed in cartesian co‐ordinate system for dynamic response analysis of fluid‐saturated porous media is implemented to avoid wave reflections towards the structure. In contrast to traditional methods, this boundary is able to absorb surface waves as well as body waves. The pile–soil interaction problem is analysed and it is shown that the results from the fully coupled procedure, using the advanced transmitting boundary, compare reasonably well with centrifuge data. Copyright © 2007 John Wiley & Sons, Ltd.     

Simultaneous use of cable and collar to prevent local scouring around bridge pier

Various methods to control scour around bridge piers have been proposed.In the present study the application of cable or collar and a combination of cable and collar were examined experimentally,as countermeasures against local scouring at a smooth circular bridge pier,close to threshold flow conditions of initiation of uniform sediment motion.The results show that the simultaneous use of cable and collar has high efficiency in reducing the scour depth.The best configuration was found for a cable-pier diameter ratio of 0.15 and thread angle of 15°,in which the scour depth in upstream of the pier reduced to about 53%.In the case of a pier protected with cable and collar the scouring postponed more than pier protected with collar and the rate of scouring is less than in pier protected with collar.These advantages can reduce the risk of pier failure when the duration of flood is short. The results indicate that the scour reduction increases as the cable diameter increased and the thread angle decreased.     

Reduction of local scour around bridge pier groups using collars

In this paper reduction of scour around group of two and three piers using circular collar has been carried out for the case of clear-water flow over uniform sediment. The efficiency of collars, with different sizes and spaces between piers is studied through experiments in group of two and three piers. The result reveals that collar has more influence in reduction of scour depth in rear piers than the first pier. Also, when the spacing between the piers increases the area without protection between the piers is washed away resulting deeper scour holes at the rear piers.     

Petrographisch-lagerstättenkundliche Untersuchung der Kupferlagerstätte Sar Cheshmeh (Süd-Iran)

Zusammenfassung Die Cu-Lagerstätte Sar Cheshmeh liegt im Süd-Iran in einer Vulkanitzone, die in 150 km Abstand nördlich parallel zur Zagrosüberschiebung verläuft. Die Lagerstätte ist an einen latitandesitischen bis rhyodazitischen Gesteinskomplex gebunden. Die auftretenden zonaren Vererzungen und hydrothermalen Alterationen des Nebengesteins weisen auf eine porphyry copper-ore-Lagerstätte hin. Aus den vorliegenden Untersuchungen und im Sinne der Plattentektonik ergibt sich, daß der Sar Cheshmeh-Gesteinskomplex von Magmen des Kontinentralrandes gebildet wurde. Gleiches gilt für die Andesitformation von Ardestan im zentralen Iran. Die Wurzel der Magmenherde liegt wahrscheinlich in einer Tiefe von ca. 140 bis 160 km, was in etwa der Tiefenlage der Benioff-Zone entspricht.

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The copper ore deposit of Sar Cheshmeh in South Iran is situated in a volcanic zone which runs 150 kms north parallel to the Zagros overthrust. The orebody lies within a latitandesite-rhyodazite complex. The mineral zoning and the hydrothermal alteration of the rocks indicate a porphyry copper ore deposit. According to the plate tectonic theory the Sar Cheshmeh rock complex is formed by rocks of the continental margin type. The same applies to the andesite formation of Ardestan in Central Iran. The magmas orginated probably at a depth of 140–160 kms, this being also the depth of the Benioff zone.

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Résumé Le gisement métallifère de cuivre de Sar Cheshmeh en Iran du Sud est situé dans une zone volcanique parallèle au charriage du Zagros, à 150 km au nord. Il se trouve dans un complexe de latiteandésite-rhyodacite. La zone minéralisée et l'altération hydrothermale des roches indiquent un gisement de minerai de cuivre porphyrique. Selon la théorie des plaques, le complexe des roches de Sar Cheshmeh est formé de roches du type marge continentale. Cela vaut aussi pour la formation andésitique d'Ardestan en Iran central. Le magma provient probablement d'une profondeur de 140 à 160 km, ce qui corresponde à peu près à la Zone de Bénioff.

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— Sar Cheshmeh — , 150 . - . , porphyry copper-ore, . . - . — —, Sar Cheshmeh . , . , , 140 160 , .

     

Short-run forecasting of United States coal production

Summary This paper focuses on short-range modelling and forecasting of aggregate US monthly coal production. The 1976–83 time-series data suggest a multiplicative autoregressive integrated moving average (ARIMA) model to replicate national level monthly coal production. The identified model required 12-month seasonal differencing and has an autoregressive component of lag 1 and a moving average component of lag 12. Model predictions for 1984 were very reasonable when compared with actual production: cyclical patterns were correctly replicated and the deterministic increasing trend was properly identified. The estimated model was enhanced by updating it with data for 1984. Intervention analysis was used to determine the impact of labour negotiations in coal production. Information relative to the identified ARIMA model was then used to model the intervening event of labour negotiations. Intervention modelling produced forecasts for 1984 superior to those identified by the ARIMA model. The mean predicted 1984 US monthly coal production of 1976–84 ARIMA and intervention models were 96.05 and 99.65% of the observed value of 74 178 thousand short tons per month, respectively. Simplicity of the ARIMA and intervention models, the realiability of their predictions, and the ease of updating make them very attractive when compared with large scale econometric models for use in short-term coal production forecasting.     

Predicting flow liquefaction,a constitutive model approach

In this paper, flow liquefaction criterion for contractive loose sands is analytically extracted based on the fundamental definition of flow liquefaction. In order to obtain the closed form of this criterion, Dafalias–Manzari constitutive model is employed; so the stress ratio at the onset of flow liquefaction is presented as a function of model parameters, state parameter and void ratio. Flow liquefaction line, as a graphical form of suggested criterion in stress space, shows that the peak points of undrained stress paths with same void ratios are not necessarily in a straight line. In order to validate the reliability of proposed flow liquefaction line to predict the onset of instability, it has been compared with the results of experimental tests performed on Toyoura, Ottawa and Leighton Buzzard sands. The verification results show that the present criterion can satisfactorily predict the onset of flow liquefaction in monotonic and cyclic undrained tests of saturated sands as well as the structural collapse in constant deviatoric stress tests of loose dry sands.     

Paleoseismological Analysis Along the Astara Fault System (Talesh Mountain, North Iran)

The Astara Fault System(AFS) is located in the northwest Alborz, east of Talesh Mountain(TM) and west of the South Caspian Basin(SCB). The AFS is one of the basement rock faults in Iran that is heavily involved in seismotectonic activity of the Talesh region, and to which subsidence of the SCB is attributed. There is little information available concerning previous AFS seismic activities and its properties. In order to elucidate the seismic behavior and activities of the AFS, we conducted a research study on paleoseismology of the fault. Based on paleoseismic evidence, two scenarios could be taken into consideration, one of which has three and another has four seismic events with magnitudes Mw in the range of 6.7 to 7.2. Evidence of these seismic events is within sedimentary succession as they have occurred during the past 3 ka(this age is determined based on the deposition rate of the region). Six carbon samples were taken for C~(14) age determination tests, the results of which clearly demonstrated that the EvIV(scenario A) and EvⅢ(scenario B) had occurred before 27,444 cal BP, while other events occurred in the time period between 27,444 cal BP and 3 ka ago. If we consider the occurrence of three or four seismic events(based on the two scenarios) to be between 27,444 cal BP and 3 ka ago, the average recurrence interval is 7,119 ± 1,017, but evidence for these events has been removed. If we assume EvI to be the youngest event(in both scenarios), the minimum elapsed time is therefore 3 ka.     

Initial assessment of recharge areas for large karst springs: a case study from the central Zagros Mountains,Iran

Sousan Spring emerges from the Keyno Anticline, Zagros Mountains (Iran), and the mean annual discharge is ~24 m³/s. Geological and hydrochemical evaluations suggest that the spring recharge is from the limestone Ilam-Sarvak Formation (Cretaceous) but the Mafaroon Fault, a major thrust feature, influences the regional groundwater flow path by juxtaposing other strata. Geological, geochemical, stable isotope and water balance studies were employed to interpret this behavior. Using the isotope data, the sources and elevations of the recharge area were found. Temporal variations of the isotopic data were compared with variations of electrical conductivity (EC). Unexpectedly, high EC was associated with a relative increase of discharge and depletion of δ¹⁸O. Several hypotheses were investigated and approximate water balance studies employed for validation. It was found that an elongated catchment on the Keyno Anticline plus a lesser catchment on a pair of parallel anticlines recharge the aquifer. While the long groundwater flow path along the Keyno Anticline plus guidance by Mafaroon Fault and the adjacent Garou shaly strata lead to increased EC in the Sousan Spring at the end of the dry season, a flow pulse from two adjoining anticlines (Mahalbakh and Shirgoon) arrives at the same time to increase the discharge and deplete the δ¹⁸O signal. Apparently the spring did not experience true base flow conditions during the recorded hydrological year. Although the spring response to specific precipitation events was similar to typical karst aquifers, standard interpretation of recession curves and related coefficients will not be practical at Sousan.     

Effects of environmental factors on classification of loessderived soils and clay minerals variations,northern Iran

Land-use type under different topographic conditions and human activities affects soil development. We investigated the effects of land-use, topography and human activity on soil classification changes in the Toshan watershed in northern Iran. Seven representative pedons derived from loess parent materials were studied on different land-uses and topographic positions. The studied pedons in forest (FO) on backslopes and footslope were classified as Calcic Haploxeralfs and Typic Haploxeralfs, respectively. The soils in abandoned lands (AB) and orchards (OR), where formerly under natural forests, located on the shoulder and backslopes positions were classified as Calcic Haploxeralfs and Vertic Haploxeralfs, respectively. Well-developed argillic horizons as indicators for higher degrees of soil evolution were observed in more-stable areas under the natural forest or less disturbed areas. Clay lessivage through these soil profiles have led to formation of Typic or Calcic Haploxeralfs, while under croplands (CP) were classified as Typic Calcixerepts. Conversion of sloping deforested areas to CP along with inappropriate management have accelerated soil erosion, resulting in unstable conditions in which decalcification and formation of developed soils cannot occur. Paddy cultivation in flat areas has caused to reduced conditions and formation of Typic Haplaquepts. Because of unfavorable conditions for chemical weathering (e.g. lower water retention compared to more-stable areas) no vermiculite was detected in the CP. The results showed that evolution and classification of the studied soils were strongly affected by land-use type, topography and management.