The diffusivity equation is a partial differential equation (PDE) which can be used for fluid flow modeling in porous media. Determining reservoir parameters from pressure data (i.e., pressure ...transient analysis) is one of the most important steps in the process of field development. This initial evaluation can be used to make decisions about future developments. Wireline Formation Testing (WFT) is one of the most popular techniques for parameter estimation and has received significant attention in recent years. The main problem plaguing WFT is a phenomenon known as the “supercharging effect,” which essentially refers to mud invasion, and this, in turn, alters pressure distribution across the system.
In this study, an analytical solution for fluid flow modeling in spherical coordinates with non-uniform initial pressure is presented. This new procedure takes into account the effect of mud invasion, or, in other words, the supercharging effect. The accuracy of this derivation was validated using previous semi-analytical solutions (the Laplace method) in addition to field data. New type curves and dimensionless parameters, which can be used for pressure transient analysis, are also proposed. This procedure is applied to the WFT data that was obtained from an oil field in the south of Iran, and an excellent agreement (less than 10% error) was observed. In addition, there is considerable uncertainty regarding the radius of investigation for spherical flow. This is important as this parameter greatly affects the applicability of WFT. The analytical derivation of this study was used to determine a reasonable value for this parameter as well.
The control of deformation and stability of the deep excavation walls under seismic and static loads is one of the most important issues in geotechnical engineering. Therefore, in the present study, ...using the finite element method and taking into account Hardening soil's behavioural model, the effect of different parameters affecting the performance of the deep excavation walls with the guardian truss structures using quasi-static analysis and its comparison with static analysis has been performed. According to the most important results, increasing in the geotechnical parameters of soil such as cohesion, friction angle and elastic modulus will reduce the maximum horizontal displacement in the vertical trench wall. Besides, the maximum settling in the adjacent ground and the maximum swelling in the bottom of the excavation will be reduced. In this way, the improvement in soil resistance parameters will increase the safety factor. Conversely, by increasing the horizontal distance between the trusses, the maximum horizontal displacement and the maximum settling in the adjacent ground and the maximum swelling in the bottom of the excavation will increase and the safety factor will be reduced. Also, the findings from this research show that by increasing the horizontal seismic acceleration coefficient (
K
h
) and as the construction stages progress, the maximum horizontal displacement of the wall, the maximum settling of the adjacent ground of the wall and the maximum swelling on the bottom of the trench increase and the safety factor will decrease. As well as, the results obtained from the quasi-static seismic analysis of the vertical trench restrained by the guardian truss structure such as the maximum horizontal displacement of the vertical trench wall and the maximum settling in the adjacent ground and the maximum swelling of the bottom of the excavation are much more than the static analysis.
In this research, the dissolution behaviour and leaching kinetics of Sarcheshmeh chalcopyrite concentrate was investigated in oxidative ammonia/ammonium carbonate solution. Temperature, concentration ...of ammonia and ammonium carbonate, agitation speed, solid to liquid ratio, oxygen flow rate, pH and particle size were chosen as parameters in the experiments. About 70% of copper was effectively recovered at temperature 60°C; ammonia/ammonium carbonate concentrations: 5M NH3+0.3M (NH4)2CO3; agitation speed: 1000rpm; solid to liquid ratio: 1:20g/mL; oxygen flow rate: 1L/min; leaching times: 240min and 80% passing size finer than 42μm. Also kinetic results and morphology and elemental composition of residue at the most suitable conditions show that, the leaching process is controlled by the diffusion of reagents or products from iron oxide passive layer formed on chalcopyrite surface. Activation energy was determined to be 25kJ/mol.
•Higher copper recovery achieved in comparison with acid sulphate leaching at the same condition.•Up to now no one has studied Sarcheshmeh copper concentrate leaching in ammoniacal solution.•This is a comprehensive study on copper concentrate in ammoniacal solution.
An experimental investigation was carried out on the two originally different calcareous sands to obtain the effect of particle size distribution on the shear responses of granular soils in this ...study. Triaxial compression tests were performed on the reconstituted samples of calcareous soils obtained from different locations of the Persian Gulf, including Hormuz Island sand and Bushehr Port sand. To evaluate the effect of the particle size distribution on the mechanical behavior of the two calcareous sands, similar samples were prepared by changing the original gradation curves. In other words, the specimens of Hormuz Island sand were prepared by the original gradation curve of Bushehr Port sand and the specimens of Bushehr Port sand were prepared by the original gradation curve of Hormuz Island sand. The result showed that Hormuz Island sand has higher strength in both original and artificial gradation curves compared to Bushehr Port sand. The particle size distribution can change the stress–strain behavior of soil materials. The results also showed that soils with bigger particles are more likely to break.
The main goal of this study is to numerically investigate the immiscible fluid-fluid displacement at the micro-level under low inertial and buoyancy forces. To this end, a micro capillary tube was ...constructed, and the fluid-fluid interface and fluid-fluid-wall triple line were tracked using VOF (Volume of Fluid)-CSF (Continuum Surface Force) strategy. Mesh-independency analysis was conducted by utilizing the Adaptive Mesh-Refinement (AMR) technique. Simulation results agreed well with the experimental data obtained from literature with the AARD (Average Absolute Relative Deviation) of around 10%. The validated model was then used to generate the CDC (Capillary Desaturation Curve) curves for different wall wettabilities, considering the dynamic contact angle in the simulations. The generated CDC curves at the breakthrough time showed that there are three different zones, namely low-Ca, transitional, and high-Ca region. The only difference between saturation profiles of different wettabilities was in the transition zone, based on the CDC analysis. The saturation and velocity profiles at the central plane of the tube were constructed and compared. Phase separation can happen depending on Ca number and the magnitude of the dynamic contact angle. Eventually, outcomes of the numerical simulator were used to develop new correlations for the residual saturation as functions of dynamic contact angle and Ca number. Nonlinear regression analysis with Levenberg-Marquart algorithm was used to find coefficients of the correlations. The developed correlations showed to be highly robust for the transition and high-Ca regions with the correlation coefficients (R2) up to 0.96 and the maximum AARD of 12%. Results of this study are applicable to both capillary-fingering and viscous-fingering flow-regimes based on the Lenormand's phase-diagrams.
•A numerical model of a micro-tube was generated using VOF-CSF strategy for fluid-fluid and fluid-fluid-surface tracking•Adaptive Mesh Refinement (AMR) was used for Mesh sensitivity analysis and experimental data for physical validation•CDC (Capillary Desaturation Curve) curves were generated considering dynamic contact angle•Three correlations were proposed for residual saturation of the displaced fluid with maximum average relative error of 12%
The present paper implemented a finite-element methodology to simulate the interaction behavior between tunnel and sandy soil deposit when a reverse fault rupture propagated from the base rock to the ...ground surface. The location of shear zones and propagation of subsurface rupture traces through overlying sand were discussed with the changes in the tunnel location, tunnel rigidity and soil relative density. The results indicated that the presence of a tunnel could have a significant influence on the fault rupture path. It was further shown that different factors affected the rotation and displacement of the tunnel. This study also investigated the evolution of a surface deformation profile using both centrifuge experiments and the finite element simulation. The results of finite element studies were verified using centrifuge experiments. Reasonable agreement between numerical and experimental results indicated the credibility of the numerical approach. Verified numerical methodology was then used to present a parametric study, offering further insight into the effect of different parameters on the soil-tunnel interaction phenomenon.
•A finite−element methodology was used to simulate the fault−tunnel interaction.•With increasing the burial depth of tunnel, the larger shear zone develops.•The soil properties are influential in determining the fault rupture paths.•The interaction mechanism should be taken into account in design of tunnels.
In this study, a series of centrifuge tests, modeling reverse fault rupture with 60° dip angle, were conducted in a dry sandy soil with a tunnel embedded in the soil layer. The test results showed ...that the tunnel and soil responses depended on the tunnel position, soil relative density and tunnel rigidity. Tunnels appeared be able to deviate the fault rupture path, while this deviation may be associated with significant rotation and displacement of the tunnel. However, a deeper tunnel was able to diffuse the shear deformation to a wider zone with an unsmooth surface displacement which may cause severe damage to the surface structures. Finally, the tunnel rotation, the location of the fault outcropping, the vertical displacement of the ground surface, the effect of tunnel rigidity on fault rupture path and surface displacement and the effect of soil relative density on fault–tunnel interaction were reported and discussed in this study.
•The reverse faulting tests were conducted in sandy soil, with presence of tunnel.•With increasing the burial depth of tunnel, the larger shear zone develops.•As the density of soil become greater, the number of ruptures decreases.•The number of scraps at the surface is increased with presence of tunnel.
Many engineering structures have been destroyed due to differential displacements on the ground surface, resulting in the instability of foundations and structures. An Earthquake fault rupture may ...cause severe damages even to structures designed to be strong against dynamic excitations. This study investigates the interactions of shallow foundations with the faulting incident, and with soil, reinforced with geo-grids, for the cases of normal and reverse faulting. The results of the numerical studies were verified with the results of experiments conducted at the University of Dundee and the University of Waseda. The subroutine of the new behavioral model was developed and then applied in the numerical modeling. A comparison between the numerical and model test results showed good agreement between numerical and experimental results. Then, the foundation rotations and its separation from the soil during fault rupture, the location of the fault outcropping, the vertical displacement of the ground surface, and the effect of soil reinforced with geo-grids on the fault rupture path and surface displacement, some of them for the first time, were predicted and reported in this paper. The amounts of differential displacement (slope) and surface displacement at the surface were reduced when soil was reinforced with geo-grids. Finally, this research concludes with a few parametric studies.
AbstractA series of centrifuge experiments were conducted to identify different internal failure modes of a group of soil-cement (SC) columns (e.g., shearing and tension due to bending) under ...combined effects of embankment loading and liquefaction-induced lateral spreading. The results were also used to investigate how an increase in the flexural/shear strength of SC columns (using high-strength steel reinforcement bars) can affect their ability to limit settlements or deformations. The centrifuge experiments included two centrifuge tests of liquefiable foundation reinforced by SC columns with and without high-strength steel reinforcement cores during strong earthquake loading. It was found that during and after cracking of the SC columns, shear and tilting failure is the prominent failure mechanism. The test results showed that increasing the flexural capacity of SC columns can reduce the potential for earthquake-induced liquefaction and associated damage. Compared with conventional SC columns, reinforced soil-cement (RSC) columns are more effective in providing confinement for the soil under the embankment during strong shaking events, resulting in lower shaking-induced pore-water pressure and a reduction in the lateral deformation of the soil and embankment.
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