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.     

A Hierarchical Bayesian Model Averaging Framework for Groundwater Prediction under Uncertainty

Groundwater prediction models are subjected to various sources of uncertainty. This study introduces a hierarchical Bayesian model averaging (HBMA) method to segregate and prioritize sources of uncertainty in a hierarchical structure and conduct BMA for concentration prediction. A BMA tree of models is developed to understand the impact of individual sources of uncertainty and uncertainty propagation to model predictions. HBMA evaluates the relative importance of different modeling propositions at each level in the BMA tree of model weights. The HBMA method is applied to chloride concentration prediction for the “1,500‐foot” sand of the Baton Rouge area, Louisiana from 2005 to 2029. The groundwater head data from 1990 to 2004 is used for model calibration. Four sources of uncertainty are considered and resulted in 180 flow and transport models for concentration prediction. The results show that prediction variances of concentration from uncertain model elements are much higher than the prediction variance from uncertain model parameters. The HBMA method is able to quantify the contributions of individual sources of uncertainty to the total uncertainty.     

The study of the hydrogeological setting of the Chamshir Dam site with special emphasis on the cause of water salinity in the Zohreh River downstream from the Chamshir Dam (southwest of Iran)

Dissolution of evaporite formations, emergence of salty water springs, and intrusion of deep saline waters are important causes in changing the quality of surface water. The study area is part of the reservoir and downstream of Chamshir Dam, which is located in watershed of the Zohreh River 20?km southeast of Gachsaran City (southwest Iran). To construct powerhouse and related structures for supplying water to agricultural lands located in downstream of dam, water quality of Zohreh River was studied by eight sampling stations in the study area. Early studies showed that water quality of the Zohreh River decreases severely downstream of the Chamshir Dam. Spatial variations diagram of major ions, Piper and composition diagrams of water samples in selected stations mark the presence of two slight and major contaminating zones at sampling station R₄ and R₅. In these zones, concentration of Ca, SO₄ and Na, Cl ions increase suddenly. Results of hydrogeological, hydrochemical, lithological and tectonics studies showed that even though there are several low discharges springs in the contaminated zone they cannot be related to surface dissolution of evaporate layers by Zohreh River. There is an important fault zone including Chamshir faults I and II in the contamination zones through which intrusion of sulfate brackish and chloride brine waters occur along the fault zone and then enter Zohreh River below its base level. In the absence of any surface evidence, the fault zone is the main cause of salinity. Evaluation of water balance salinity in contaminated zones shows that the discharge rate of saline waters to the river is not low and cannot be separated. These findings show that there are serious restrictions upon the purposes of the project.     

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.     

Occurrence,distribution and source of arsenic in deep groundwater wells in Maydavood area,southwestern Iran

Groundwater in some deep wells of Maydavood aquifer, southwestern Iran, contains relatively high concentrations of arsenic. Detailed hydrochemical analysis of these groundwaters (with ICP-OES instrument) showed that concentrations of iron, manganese, nickel, and vanadium are also high in them and concentrations of total arsenic in 81% of deep wells are greater than World Health Organization’s permissible value (10 ppb). XRF analysis of surrounding geological formations and aquifer sediments proposed that original source of arsenic in aquifer material can be attributed to minerals from Asmari Formation. It appears that a key mechanism for arsenic mobilizing to deep wells is microbial biodegradation of petroleum related organic matters (PROMs), which exist in aquifer sediments and originates from the bedrock of the aquifer (Gachsaran Formation). This process is followed by microbially mediated reductive dissolution of arsenic-bearing iron/manganese oxyhydroxides/oxides and further by nickel and vanadium mobilizing to groundwater. According to hydrogeochemical conditions and cluster analysis, water wells in Maydavood aquifer are divided to four subgroups: the wells with mildly reducing condition (subgroup I), moderately reducing condition (subgroup II), reducing condition (subgroup III), and high reducing condition (subgroup IV). Affected wells to arsenic are belonged to subgroups III and IV.     

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.