فهرست مطالب علی پاک

As a result of extraction from underground oil reservoirs, the pore pressure in the reservoir decreases and the effective stress increases accordingly. Field measurements in the past two decades have shown that in addition to the change of effective stress, the total horizontal and vertical stress field can also change in and around the reservoir. As a result of the settlement that occurs at the upper part of the reservoir due to the consolidation phenomenon, the stability of this area is reduced and it causes “Stress Redistribution” inside and around the reservoir. The mechanism of stress redistribution is attributed to the “Stress Arching” phenomenon. By the stability reduction at the roof of the reservoir due to the compaction, this area will no longer bear the whole over-burden weight. A part of the over-burden is transferred to more stable areas such as the sides of the reservoir. The current research aims to investigate how the total stresses change around oil and gas reservoirs due to the extraction by a fully-coupled hydro-mechanical (HM) simulation. In order to simulate the process of fluid extraction from the reservoir and to consider the effect of production operations on the geo-mechanical properties of the depleting zone, a Non-linear elastic constitutive model has been used. In this research, a comparison is made between the amounts of the total stresses in the surrounding rock of three different reservoirs in terms of width. In addition, the effects of the difference between the initial stiffness of the reservoir rock and the surrounding medium on the intensity of the stress arching phenomenon are investigated by considering three different stiffness ratios. The conducted studies show that the changes in the total stresses are significant and it is necessary to consider their effect on aspects of the production and the development of field.

In this study, an eniched element free Galerkin framework is developed to investigate the effects of conductive-convective heat transfer on hydraulic fracturing. Weak and strong discontinuities are introduced in field variables using the enrichment strategy. The cohesive crack model is used in this study to simulate the process of initiation and propagation of fractures in saturated deformable porous media. The complicated process of hydraulic fracturing with thermal effects is simulated considering multiple components including fluid flow within the fracture, fluid flow through the host medium, fluid leak-off from the fracture into the surrounding porous rock, heat transfer within the fracture medium, heat transfer through the host porous rock, the heat exchange between the crack medium and the surrounding media, deformation of porous rock due to the hydraulic and thermal loading and crack propagation. To create the discrete equation system, Galerkin technique is applied, and the essential boundary conditions are imposed via penalty method. Then, the resultant constrained integral equations are discretized in space using EFG shape functions. For temporal discretization, a fully implicit scheme is employed. The final set of algebraic equations that form a non-linear equation system are solved using the iterative Newton-Raphson procedure. Numerical simulation results show the accuracy of the formulation as well as the performance of the program in coupling the heat transfer equation inside the crack with other governing equations.

From the point of view of oil reservoir engineering, increasing the production from low permeability reservoirs and damaged wells is one of the most important and challenging issues. Especially if these reservoirs have high oil reserves and have more production potential. The Hydraulic Fracturing method is one of the methods of increasing the extraction of oil reservoirs that have been considered by many researchers in the last few decades.By injecting pressurized fluid into the reservoirs, in situ stresses and tensile strength of the rock can be overcome and cracks can be created in the rock. Geomechanical conditions of the reservoir such as rock hardness, in situ stresses, tensile strength, the permeability of the reservoir, the amount of fluid leak-off inside the crack to the reservoir, etc. directly affect the characteristics of the created Hydraulic Fractur. There are various analytical models for predicting Hydraulic Fractur characteristics. Among these, two models, KGD and PKN, are among the most famous and practical analytical models of Hydraulic Fracture. Both models calculate the crack characteristics by considering the plane strain conditions in two-dimensional space, but with two different approaches (the first model in the horizontal plane and the second model in the vertical plane). In these models, some effective components such as the permeability of the reservoir and the amount of fluid leak-off from the crack walls have not been considered.The aim of this study was to investigate the effects of fluid leak-off, which has a great impact on the success or failure of Hydraulic Fracturing operations. In the present paper, the effect of two important parameters of reservoir rock permeability and fluid leak-off from crack walls to the reservoir on Hydraulic Fracture characteristics, using numerical modeling by XFEM method, has been studied.

Deep excavations in soft clayey soils usually cause excessive ground settlement and wall movements due to the creep in soft soils. One of the commonly used methods for predicting these displacements is numerical analysis, however, in most cases for modeling soft clayey soils, soil behavior is considered to be time-independent. So, the effect of excavation time and creeping in soft soils are ignored. In this paper, the impact of the time of construction of the excavation and creep effect that occurs in soft soils are studied using three case studies. These three excavations are stabilized using a combination of soil anchorage and soil nailing methods. For studying the time influence and creep effect in soft soils with numerical modeling, excavations are modeled using three different soil constitutive models, namely Mohr-Coulomb, Hardening Soil (HS), and Soft Soil Creep (SSC) models. The real field records by installed in-situ instruments are employed to evaluate the performance of three constitutive models for simulating the excavation wall behavior. The obtained results show that for realistic simulation of the behavior of deep excavations, the construction time and the corresponding creeping behavior should be included in the numerical modeling procedure in order to better match the numerical predictions with the time-independent behavior of soft soils.

Casing collapse is one of the costly and safety-threatening incidents in the oil industry. For example in Kupal oil field, Iran, approximately, a third of the wells have been removed from the production cycle due to casing collapse, which in some cases have led to the total loss of those wells. Since most of these cases have occurred in Gachsaran Formation, it is necessary to use an appropriate method to determine the geomechanical characteristics of this formation, especially, the layer considered as caprock for the underlain Asmari reservoir under the real conditions of temperature and pressure at real depths. In this paper, after discussing the effect of temperature, loading rate, and confining pressure on general geomechanical behavior of rocks, and in particular, the caprock of the Asmari reservoir, the results of geomechanical experiments performed under different temperature and pressure conditions on this type of rock are presented, and their comparison with the corresponding results determined by other researchers are discussed. The obtained results from the experiments demonstrate that under constant loading rate, each 1.0 MPA increase in confining pressure increases the strength of the caprock about 1.0 MPa. Conversely, every 1 °C increase in temperature decreases the caprock strength almost 0.2 MPa.

Measurement of temporal-spatial distribution of surface subsidence as a result of production from hydrocarbon reservoirs is a relatively common practice worldwide; however, it is set aside in Iran, although it seems that prediction of subsidence trend at the beginning of the reservoir life can be beneficial in future production estimates. In this paper, the accuracy of the numerical modeling for calculating subsidence process is evaluated by comparison with the in-situ measurements recordings, as well as those designated from analytical solutions for two hydrocarbon reservoirs in the USA, and the Netherlands. It was observed that the numerical simulations can well trace the subsidence trend in spite of elastic behavior assumption, and other simplifications considered. Although, the real mechanism of subsidence is inelastic, and parameters variations are possible. Afterwards, the distribution of temporal-spatial surface subsidence in a specified zone of Kupal oil field, Iran, was predicted. Moreover, unlike the verification examples, in which pressure changes in the whole reservoir had been considered to determine settlements, the “production history” of some wells was used in the simulations. It was concluded that production from the selected area in the Kupal oil field has resulted in surface subsidence in the range of 26 to 32 cm in the period between years of 1372-1396.

Positioning of the phreatic surface in a dam body plays a critical role in the stability of tailing dams. Soil-atmosphere interaction eects, such as precipitation, runo, interception, inltration, and evaporation, on the one hand, and unsaturated soil eects, such as capillary rise, on the other, cause signicant changes in the situation of the phreatic surface.
In this paper, rst, dierent mechanisms that aect the phreatic line level in the tailing dams and their corresponding equations are studied, and a computer program is developed for calculating the uctuations of the phreatic line. Then, for evaluating the usefulness of the program in real time problems, the stability of \Sarcheshmeh" copper mine tailing dam in Rafsanjan city, Iran, has been studied. Plaxis software Ver.8.0 has been used for modeling this tailing dam. Necessary parameters for modeling this dam have been obtained from the results of dierent laboratory tests on tailing materials, and information available from synoptic stations of the meteorological organization of Iran in the area. After determining the amount of change in the phreatic level for a special period of time, the stability of the dam was studied, based on calculating the factor of safety under different conditions.
The results show that by constructing new dikes, the safety factor decreases. Also, the results show that those parameters that increase the phreatic level reduce the safety factor, and the stability of the tailing dam will be threatened. Among dierent parameters affecting the phreatic level, capillary rise was found to be the most signiffcant factor in regard to tailing dam stability when constructed in arid areas.

Settlement and tilt of structures due to the liquefaction of subsoil layers is a major cause of damage during earthquake. Among dierent soil prole types, two-layered sub soil is very common. The numerical study presented in this research addresses the eects of dierent parameters that are in uential on liquefaction in saturated sand deposits underlying the foundation of structures. In this regard, a 3D nite element model, with a fully coupled dynamic analysis of saturated porous media has been utilized. For the constitutive model, a well-calibrated bounding-surface plasticity model, capable of accounting for the monotonic and cyclic response of saturated sand, in a wide range of densities and conning pressures, has been used. Another main feature of the proposed numerical model is taking the variations of permeability into account during liquefaction. The numerical simulations of this study have been performed using OpenSEES, which is an Open-source software framework. In this research, two 3D u-p elements with novel variable permeability functions have been used, which were implemented in OpenSEES. The numerical model has been veried by simulation of a series of centrifuge experiments performed on models of footing and the analysis results are compared with experimental measurements. After verication of the numerical model, comprehensive parametric studies were conducted and, based on the obtained results the eects of the parameters were reported. The results showed that existance of a lique- able layer plays a signicant role in shallow foundation settlement during earthquake. In two- layered subsoil, if the footing rests on the liqueable layer, the underlying dense sand can reduce the amount of settlement more eectively.

R‌u‌b‌b‌l‌e-m‌o‌u‌n‌d b‌r‌e‌a‌k‌w‌a‌t‌e‌r‌s a‌r‌e c‌o‌m‌m‌o‌n m‌a‌r‌i‌n‌e s‌t‌r‌u‌c‌t‌u‌r‌e‌s, w‌h‌i‌c‌h m‌a‌k‌e a c‌a‌l‌m a‌n‌d s‌a‌f‌e a‌r‌e‌a f‌o‌r s‌h‌i‌p‌s t‌o b‌e‌r‌t‌h. T‌o p‌r‌o‌t‌e‌c‌t t‌h‌e‌s‌e s‌t‌r‌u‌c‌t‌u‌r‌e‌s f‌r‌o‌m s‌e‌a w‌a‌v‌e a‌t‌t‌a‌c‌k, a‌r‌m‌o‌u‌r‌e‌d l‌a‌y‌e‌r‌s c‌o‌n‌s‌i‌s‌t‌i‌n‌g o‌f r‌o‌c‌k‌s o‌r c‌o‌n‌c‌r‌e‌t‌e b‌l‌o‌c‌k‌s a‌r‌e p‌u‌t o‌n t‌h‌e‌i‌r o‌u‌t‌e‌r s‌u‌r‌f‌a‌c‌e. P‌r‌o‌v‌i‌d‌i‌n‌g t‌h‌e s‌t‌a‌b‌i‌l‌i‌t‌y o‌f a‌n a‌r‌m‌o‌u‌r l‌a‌y‌e‌r i‌s o‌f g‌r‌e‌a‌t i‌m‌p‌o‌r‌t‌a‌n‌c‌e i‌n t‌h‌e d‌e‌s‌i‌g‌n o‌f b‌r‌e‌a‌k‌w‌a‌t‌e‌r‌s. U‌n‌t‌i‌l n‌o‌w, d‌e‌s‌i‌g‌n o‌f t‌h‌e a‌r‌m‌o‌u‌r l‌a‌y‌e‌r h‌a‌s b‌e‌e‌n b‌a‌s‌e‌d o‌n e‌m‌p‌i‌r‌i‌c‌a‌l f‌o‌r‌m‌u‌l‌a‌e a‌n‌d p‌h‌y‌s‌i‌c‌a‌l t‌e‌s‌t‌s. I‌n t‌h‌e‌s‌e c‌o‌n‌v‌e‌n‌t‌i‌o‌n‌a‌l a‌p‌p‌r‌o‌a‌c‌h‌e‌s, w‌a‌v‌e p‌a‌r‌a‌m‌e‌t‌e‌r‌s a‌r‌e c‌o‌r‌r‌e‌l‌a‌t‌e‌d t‌o t‌h‌e a‌r‌m‌o‌r w‌e‌i‌g‌h‌t. T‌h‌e c‌u‌r‌r‌e‌n‌t r‌e‌s‌e‌a‌r‌c‌h a‌i‌m‌s t‌o s‌t‌u‌d‌y t‌h‌e s‌t‌a‌b‌i‌l‌i‌t‌y o‌f t‌h‌e a‌r‌m‌o‌u‌r l‌a‌y‌e‌r b‌y a n‌u‌m‌e‌r‌i‌c‌a‌l m‌e‌t‌h‌o‌d, e‌m‌p‌l‌o‌y‌i‌n‌g t‌h‌e c‌o‌m‌m‌e‌r‌c‌i‌a‌l c‌o‌d‌e F‌L‌O‌W-3D. I‌n t‌h‌e p‌r‌e‌s‌e‌n‌t r‌e‌s‌e‌a‌r‌c‌h, t‌h‌e e‌f‌f‌e‌c‌t‌s o‌f g‌e‌o‌m‌e‌t‌r‌i‌c‌a‌l p‌a‌r‌a‌m‌e‌t‌e‌r‌s, s‌u‌c‌h a‌s b‌r‌e‌a‌k‌w‌a‌t‌e‌r s‌l‌o‌p‌e a‌n‌d a‌r‌m‌o‌u‌r d‌i‌a‌m‌e‌t‌e‌r a‌n‌d, a‌l‌s‌o, p‌h‌y‌s‌i‌c‌a‌l p‌a‌r‌a‌m‌e‌t‌e‌r‌s, s‌u‌c‌h a‌s w‌a‌v‌e h‌e‌i‌g‌h‌t a‌n‌d p‌e‌r‌i‌o‌d a‌n‌d s‌t‌i‌l‌l w‌a‌t‌e‌r d‌e‌p‌t‌h, o‌n t‌h‌e s‌t‌a‌b‌i‌l‌i‌t‌y o‌f t‌h‌e a‌r‌m‌o‌u‌r, a‌r‌e s‌t‌u‌d‌i‌e‌d. F‌o‌r t‌h‌i‌s p‌u‌r‌p‌o‌s‌e, f‌o‌u‌r l‌o‌c‌a‌t‌i‌o‌n‌s c‌o‌n‌s‌i‌s‌t‌i‌n‌g o‌f b‌r‌e‌a‌k‌w‌a‌t‌e‌r t‌o‌e, s‌t‌i‌l‌l -w‌a‌t‌e‌r l‌e‌v‌e‌l a‌n‌d m‌a‌x‌i‌m‌u‌m o‌f w‌a‌v‌e r‌u‌n-u‌p a‌n‌d r‌u‌n-d‌o‌w‌n l‌e‌v‌e‌l‌s a‌r‌e s‌e‌l‌e‌c‌t‌e‌d f‌o‌r p‌l‌a‌c‌e‌m‌e‌n‌t o‌f t‌h‌e a‌r‌m‌o‌u‌r. T‌h‌e b‌r‌e‌a‌k‌w‌a‌t‌e‌r i‌s a‌s‌s‌u‌m‌e‌d t‌o b‌e h‌i‌g‌h-c‌r‌e‌s‌t‌e‌d a‌n‌d t‌r‌a‌p‌e‌z‌o‌i‌d‌a‌l i‌n s‌h‌a‌p‌e. T‌h‌e a‌r‌m‌o‌u‌r‌s a‌r‌e c‌u‌b‌i‌c‌a‌l a‌n‌d r‌i‌g‌i‌d. A‌l‌s‌o, m‌o‌n‌o‌c‌h‌r‌o‌m‌i‌c w‌a‌v‌e‌s a‌r‌e u‌s‌e‌d i‌n t‌h‌i‌s s‌t‌u‌d‌y. A‌n‌a‌l‌y‌s‌e‌s a‌r‌e u‌n‌d‌e‌r‌t‌a‌k‌e‌n t‌o d‌e‌t‌e‌r‌m‌i‌n‌e f‌o‌r‌c‌e‌s a‌n‌d m‌o‌m‌e‌n‌t‌s a‌c‌t‌i‌n‌g o‌n t‌h‌e a‌r‌m‌o‌u‌r, w‌h‌i‌c‌h i‌s a‌s‌s‌u‌m‌e‌d t‌o h‌a‌v‌e n‌o i‌n‌t‌e‌r‌l‌o‌c‌k‌i‌n‌g b‌e‌t‌w‌e‌e‌n i‌t f‌o‌r t‌h‌e s‌a‌k‌e o‌f s‌i‌m‌p‌l‌i‌c‌i‌t‌y. T‌h‌e r‌e‌s‌u‌l‌t‌s s‌h‌o‌w t‌h‌a‌t w‌a‌v‌e b‌r‌e‌a‌k‌i‌n‌g t‌y‌p‌e h‌a‌s a‌n i‌m‌p‌o‌r‌t‌a‌n‌t e‌f‌f‌e‌c‌t o‌n t‌h‌e f‌o‌r‌c‌e a‌n‌d s‌t‌a‌b‌i‌l‌i‌t‌y o‌f t‌h‌e a‌r‌m‌o‌u‌r. A‌l‌s‌o, r‌e‌s‌u‌l‌t‌s i‌n‌d‌i‌c‌a‌t‌e t‌h‌a‌t t‌h‌e a‌r‌m‌o‌u‌r p‌l‌a‌c‌e‌d i‌n t‌h‌e s‌t‌i‌l‌l w‌a‌t‌e‌r a‌n‌d m‌a‌x‌i‌m‌u‌m w‌a‌v‌e r‌u‌n-d‌o‌w‌n l‌e‌v‌e‌l‌s a‌r‌e s‌u‌b‌j‌e‌c‌t‌e‌d t‌o t‌h‌e m‌o‌s‌t s‌e‌v‌e‌r‌e w‌a‌v‌e f‌o‌r‌c‌e‌s. F‌i‌n‌a‌l‌l‌y, s‌o‌m‌e f‌o‌r‌m‌u‌l‌a‌e a‌r‌e p‌r‌e‌s‌e‌n‌t‌e‌d f‌o‌r c‌o‌m‌p‌u‌t‌i‌n‌g w‌a‌v‌e f‌o‌r‌c‌e‌s, m‌o‌m‌e‌n‌t‌s a‌n‌d s‌t‌a‌b‌i‌l‌i‌t‌y n‌u‌m‌b‌e‌r‌s f‌o‌r a‌r‌m‌o‌u‌r b‌l‌o‌c‌k‌s i‌n d‌i‌f‌f‌e‌r‌e‌n‌t l‌o‌c‌a‌t‌i‌o‌n‌s. U‌s‌i‌n‌g t‌h‌e‌s‌e f‌o‌r‌m‌u‌l‌a‌e a‌l‌l‌o‌w‌s t‌h‌e u‌s‌e‌r t‌o c‌o‌m‌p‌a‌r‌e t‌h‌e s‌t‌a‌b‌i‌l‌i‌t‌y m‌o‌d‌e‌s o‌f t‌h‌e a‌r‌m‌o‌u‌r f‌o‌r d‌i‌f‌f‌e‌r‌e‌n‌t w‌a‌v‌e c‌h‌a‌r‌a‌c‌t‌e‌r‌i‌s‌t‌i‌c‌s.

1. Unreinforced concrete canals are one type of sensitive and important water conveyance structures. Whereas these structures are inevitably constructed on different types of soils, investigation of geotechnical issues related to the interaction of soil and concrete lining is important for reducing damages to the canals. These damages in the hydraulic canals are observed in the forms of cracking in the concrete lining and their large displacement. Due to numerous cases observed in Iran, construction of irrigation canals on the problematic soil has led to serious damage to the structure of canals and finally losses a lot of costs. One of the most common types of problematic soils is expansive soils. Every year many of new structure are constructed on the swelling soils, over 60% of these structures suffered minor damages such as cracking and approximately 10% of these structures are heavily damaged that cannot be repaired.In a comprehensive definition, expansive soils are referred to the soils which have the potential of swelling and shrinkage and show significant volumetric changes and eventually lead to serious damages to different structures, especially light structures. These damages in the hydraulic canals are observed in the forms of cracking in the concrete lining and their tuck. Over time and with the occurring of melting and freezing cycles, lining fine micro cracks are become larger and provide a situation for water penetration and plant growth then these factors eventually lead to changes of hydraulic canal characteristics and finally its destruction. Since the repair and rehabilitation of damaged structures impose huge costs on project, doing research for understanding the mechanism of interaction between the soil and canal lining seems necessary.Therefore, by considering the presented introduction, construction of canals on problematic soils such as expansive soils is inevitable and appropriate procedures should be followed to reduce the damages.For this purpose, in this study the section of trapezoidal canal with real dimensions has been modeled by Geo-Studio (2007) software and interaction of the soil-concrete lining and the effect of considering filter layer under canal have been studied in the impounding conditions and finally the result of numerical analyses have been compared to in-situ observations. Since the soil of canal bed is in the unsaturated condition and has a swelling potential, firstly it is necessary to mention the background of previous studies for numerical modeling of unsaturated soil behavior and efforts have been done by researchers to implementation presented theories2. The behavior of an unsaturated expansive soil can be formulated using the theory of unsaturated soils, using two independent stress variables, the constitutive relationships for the soil structure and water phase, and flow laws for the water phase [1-4]. The two stress state variables are net normal stress, (σ-ua), and matric suction (ua-uw), where σ is total normal stress, ua is pore-air pressure, and uw is pore-water pressure. Changes in the void ratio and degree of saturation of an unsaturated soil can be expressed as functions of the stress state variables to form two three-dimensional constitutive surface [5]. Approximate volume change (and water content) coefficients should be adequate for most engineering analyses. Procedures for the approximation of the volume change coefficients assist in the implementation of unsaturated soil mechanics into geotechnical engineering practice. The primary interactive processes involved with a volume change analysis of an unsaturated expansive soil are stress deformation and water flow. The stress-deformation process is governed by static equilibrium, while the water flow is governed by water continuity equation. Solutions for volume change require that both the equilibrium equation and the continuity equation be solved. The solutions can be obtained using either a coupled or an uncoupled approach.As mentioned, the behavioral models of unsaturated soils are complex. In addition a large number of parameters required for analysis and there are many problems related to measuring or calculating the values of these input parameters. Because of that, these behavioral models are rarely used by geotechnical engineers.According to the conducted surveys, these behavioral models are not applied to common software of geotechnical engineering. Therefore, some geotechnical engineers have wrongly assumed these kinds of soils as a saturated soil and used the related behavioral models such Cam-Clay or Modify Cam-Clay. In recent years, many attempts have been made by researchers to apply behavioral models of unsaturated soils and using these models in geotechnical engineering softwares. For applying these models, simplifying assumptions are made but these should not undermine the accuracy of the results. Based on the review of the available technical resources, the behavioral models of unsaturated soils are applied only to the two pieces of geotechnical engineering software so far which are Plaxis2D 2010 and GeoStudio 2007. In this research, GeoStudio 2007 software package is used for modeling. The basis of this software for modeling of unsaturated expansive soils is the behavioral model and presented equations by Vu and Fredlund [4]. For verifying the accuracy of the results, presented example by these researchers was modeled by the software and the proposed behavioral model for unsaturated soils was assigned to it. By comparing the results, accuracy and precision of the software can be realized and the software gives a close agreement between the results by application of both coupled and uncoupled analysis methods, which has been previously described. It should be noted that the input parameters of the software and the solution of the equations are simplified as much as possible toward the method of Vu and Fredlund to be applicable for geotechnical engineers. Thus, SIGMA/W software can be used to estimate the amount of swelling with appropriate accuracy in unsaturated expansive soils that are affected by changes in wetting conditions and consequently caused negative pore pressures. SIGMA/W, which is in the GeoStudio software package, is based on the finite element method for stress-deformation analysis of earth structures. Its comprehensive formulation makes it possible to solve any kind of simple and complex problem. For instance, by using this software, both simple linear-elastic deformation analysis and complicated effective-stress analysis based on non-linear elastoplastic behavior can be conducted. When this software is used together with other products of GeoStudio package, changes in pore pressure and its distribution in soil mass due to the external loading can be computed by using coupled and uncoupled formulation. In addition, SIGMA/W can be used for modeling of soil interaction with beam or bar elements.In this study Tabriz Plain Canal is selected as a case study. The irrigation and drainage network of Tabriz plain is under construction in six regions and 40000 hectares in the northwestern part of Iran. The length of the main canal is 29 km, the width of floor is between 2.5 to 5.0 m, and its height is between 2 to 2.75 m. The slope of canal walls is 1 (vertical) to 1.5 (horizontal). The canal lining is made of unreinforced concrete. In the construction phase of first 10 km, due to a heavy rain and flooding, a part of canal was filled with water. After the water was emptied out, cracks and heave were observed in some parts of the canals. In order to investigate this phenomenon, an undisturbed soil specimen was obtained from heaved zone and a free swelling test was performed.3. The results of laboratory tests show that the surface soils of Tabriz plain are composed of silt and clay. In this research, standard methods are used to predict swelling potential of these soils. Generally there are two indirect methods for anticipating the swelling potential in references, Seed et al. method (1962) [6] and Van der Merve method (1964) [7]. The result show that the swelling potential of soil samples vary from low to high and the result of free swelling test show that the free swell height and the swelling pressure of undisturbed sample are about %5.4 and 40 kPa respectively. These values show that the soil heave should be considered in lightweight structure designing such as Tabriz plain canal.As observed in in-situ investigation, the swelling phenomenon has led to cracking and relative displacement of canal panels in joint locations from few to 30 mm. To prevent the occurrence of this phenomenon, using a filter layer with 30 cm thickness was proposed in this project. Application of filter layer doesn’t have direct effect on soil heave but the properties of filter material lead to reduce the swelling potential. The filter is composed of granular material so it can uniformly transfer the local pressure of canal bed soils to lining and lead to reduce the relative displacement of adjacent panels. Another parameter is the weight of filter layer. This layer applies about 5 kPa additional pressure to expansive canal bed soil although this pressure isn’t more than the swelling pressure but it can compensate that amount of swelling pressure.This proposed method was tentatively performed in 50 m length of real canal. For evaluation the efficiency of this method, surveying points were observed on canal section and displacement of these points were measured.The in-situ surveying records showed that the performance of filter layer led to reducing the swelling potential and the relative displacement of panels decreased from 30mm to 5 mm. As mentioned before, in this research the actual dimensions of the under construction water canal of the irrigation and drainage network of Tabriz plain, which is located on the expansive soils, is used for numerical modeling. Three series of joint are considered in canal section, two joints in canal walls in the level of 0.5 meter from floor and one joint in canal floor. As a real condition for modeling of joint, two centimeter space is vertically considered in lining surface. For the simulation of the initial conditions (local conditions), it has been assumed that the canal bed soil is somewhat dried and a constant suction is established in the soil. For modeling the infiltration into the soil, water level inside the canal is applied as a water head to the lining elements. The lining has been modeled by beam elements. Generally, it is assumed that in the initial conditions, a suction equal to 200 kPa was available in the environment. In the first step of analysis, the initial in-situ stress conditions are applied to the model and primary balance is obtained. In this step linear elastic behavior is considered for the soil and concrete lining and the environmental suction of -200 kPa is considered in the computation. For analysis of heave coupled case, the soil behavior is considered elastoplastic and the proposed model by Vu and Fredlund [4] is used to predict the behavior of unsaturated expansive soils. This should be considered that all equations used in the computations and the mechanism of soil behavior are functions of time.Since the aim of the presented research is to study the soil-lining interaction behavior in various moisture conditions and also the effect of implementation of filter layer to control the swelling of canal bed soil by using site investigation and numerical methods and comparing the results of two methods, two types of analyses are done in this research. In the first case, the filter layer has not been considered under the lining and calculations have been performed and in other case, the filter layer has been considered and all calculations have been repeated. In any of cases, the water level in the canal is assumed as constant and 2 meter above the floor.4. The results of numerical analyses and in-situ observations have acceptable consistent in prediction of the deformation shape of panels, the values of displacement and the effect of filter layer on these phenomenon. The use of a filter layer under the concrete lining leads to the relative reduction of general heave in unsaturated expansive bed soil and also prevents the lining cracking.The intersection point of the canal wall with floor, the upper corner of the canal wall and middle point of lining length are considered as the locations of concentration of internal forces in the canal section. The joints along the wall act as a hinge, the values of moment in these points are zero and they have a functional role to control the cracking in the canal wall. The optimization of the location of joints and the modification of the geometric properties of canal section are others ways to reduce the lining damages in canals which are constructed on expansive soils.

Hydraulic fracturing, the process of creating cracks in the ground by injecting a viscous fluid into a well under high pressure, has been widely used in oil and gas industry to stimulate low-permeability petroleum reservoirs. The resultant field data from hydraulic fracturing operations exist mostly in the form of pressure-time curves and the determination of actual hydraulic fracture geometry using this data alone is impossible. Therefore, the design of hydraulic fracturing process and the prediction of fracture pattern are possible only by relying on the advanced mathematical and numerical models. Thus, several analytical and numerical models including 2D, pseudo 3D, and 3D models have been developed during last decades to predict the location, direction, and extension of hydraulic fractures in oil reservoirs. In the present paper, after introducing applications and the mechanism of hydraulic fracturing process, different approaches for analyzing the problem and predicting the crack pattern in petroleum reservoirs will be discussed. Finally, the framework and formulation of a numerical model with the capability of simulating 3D fractures and considering geomechanical reservoir effects and two-phase fluid flow will be presented.

Numerical modeling of very soft soil layers consolidate under the weight of that material in the consolidation nalysis And consolidation of dredged material discharged in the tailings dams is used, over several decades Recent special attention has been. In this paper, taking into account the effects of large strain and permeability changes and compactibility Loose soil layers during consolidation, applying finite difference method to solve, and use a New method for interval Mjzasazy place during periods of filling, a Computer, formodeling the different conditions is produced by the weight consolidation process. Then through Comparison of model results with field values and the results were Shtsnjy computer, programs, Performance analysis of real problems in the model has beenvaluated. Numerical modeling of very soft soil layers consolidate under the weight of that material in the solidation analysis And consolidation of dredged material discharged in the tailings dams is used, over several decades Recent special attention has been. In this paper, taking into account the effects of large strain and permeability changes and compactibility Loose soil layers during consolidation, applying finite difference method to solve, and use a New method for interval Mjzasazy place during periods of filling, a Computer, for modeling the different conditions is produced by the weight consolidation process. Then through Comparison of model results with field values and the results were Shtsnjy computer, programs, Performance analysis of real problems in the model has been valuated.