Influence of drying and wetting on the wave propagation in partially saturated soils

The propagation of sound waves in Del Monte sand filled by an air-water mixture is studied by a linear model. Even if it does not include an operator to describe the hysteresis of the capillary pressure curve, hysteresis is accounted for: the wave analysis is performed for the two limit cases of main drying and main wetting. In the van Genuchten law both drying and wetting data are applied. Four waves appear: one transversal wave and three longitudinal waves. For the waves driven mainly by the skeleton it could be expected that the influence of consideration of the hysteresis in the capillary pressure curve is negligible. In contrast, the numerical results for the waves driven by the pore fluids exhibit a smaller influence than expected. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Rate of consolidation of stone column-improved ground considering change in permeability and compressibility during consolidation

In the available mathematical formulations to determine the rate of radial consolidation of stone column-improved ground, the soil properties especially permeability and compressibility are assumed to be constant during consolidation process. However, permeability changes with void ratio (void ratio also changes with consolidation) and compressibility of soil varies along the consolidation curve (compressibility is a function of effective stress and void ratio). Thus, these properties are not constant during consolidation period. In the present paper, mathematical formulation is developed to determine the rate of consolidation of stone column-improved ground due to radial flow considering change in permeability and compressibility of soft soil during consolidation period. Equal strain approach has been considered in the analysis. The parabolic variation in permeability and compressibility within smear zone are incorporated in the formulation. It is observed that the variation of degree of consolidation due to change in stress concentration ratio and diameter ratio reduces when variable soil properties are considered. The difference between the degree of consolidation obtained considering variable and constant soil properties is almost constant due to variation of smear zone parameters. The time required to achieve 90% degree of consolidation increases or decreases (depending on the properties of soil) by around 50%–100% or up to 25%, respectively, when change in soil properties during consolidation is considered.     

Saturated and unsaturated flow of ground water to a regular horizontal drain system in nonhomogeneous layered soils

The paper presents a mathematical formulation of the problem of drainage of nonhomogeneous soil by a regular system of horizontal drains in the framework of hydrodynamic and hydraulic theories. Algorithms for approximate solution of the problem are described. Comparison of numerical and analytical solutions substantiates the theoretical dependences.Translated from Vychislitel'naya i Prikladnaya Matematika, No. 64, pp. 65–73, 1988.     

A model for long-term global air quality prediction and development of efficient control strategies in Turkey

This paper presents an environmental model which differentiates fuel consumption by sectoral use and allows for the reduction of emissions by coupling different emission control technologies to energy conversion and end-use activities. The model can be coupled to any energy model for forecasting air pollutant emissions and developing efficient emission control strategies. An energy-economy module has been integrated into the model and an equilibrium solution for the three-component model is obtained by utility maximization. Effects of emission limits on energy activities and on macroeconomical variables are investigated by restricting total pollutant emissions to the standards of the European Community. Numerical results are presented in the form of long-term forecasts focusing on the pollutants SO₂ and NO_x. Emission control measures, implied from the model results, are discussed revealing an efficient emission control strategy.     

A new model for prediction the strain field and extrusion pressure in ECAE process of circular cross section

In this research in order to predict the strain distribution and extrusion load in equal channel angular extrusion (ECAE) process of circular cross section a new three dimensional kinematically admissible velocity field has been developed based on Bezier formulation. The strain distribution in deformation zone and the effects of various terms on extrusion load were determined. The results were compared both with the experimental and numerically predicted results reported in the literature. It was found that extrusion pressure decreases with increasing both the die angle and the outer curved corner angle and increases with increasing the friction coefficient. Also, it was exhibited that increasing the angle of outer curved corner increases the inhomogeniety of strain field of deformation zone. The predictions were in a good agreement with the FEM and experimental results reported by previous researchers for different die angles and frictional conditions.