فهرست مطالب

International Journal of Civil Engineering
Volume:9 Issue: 4, Dec 2011

  • تاریخ انتشار: 1390/11/06
  • تعداد عناوین: 7
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  • Masoud Miraboutalebi, Faradjollah Askari, Orang Farzaneh Page 247
    In this paper, the effect of bedrock inclination on seismic performance of slopes is investigated. The study was conducted based on dynamic analysis of different slopes, evaluation of the earthquake acceleration in sliding mass, and calculating the permanent displacement of the slope, using Newmark sliding block. The investigation indicates that variation of the bedrock inclination, which results in a change in the predominant period of the slope (Ts), in conditions that the mean period of the time history of the acceleration on critical sliding surface (Tmt) and Ts are close to each other, causes the variation of the acceleration magnitude and the Newmark displacement in the sliding mass and they may reach to their maximum level. Typical results are presented and discussed. A two dimensional model of a typical slope was considered and conducting dynamic analyses, the slope performance was studied for different geometries, strength parameters and shear wave velocities. Such a performance has been studied by assessing the record of acceleration in sliding mass (the mass above the critical sliding surface) and calculating the slope displacement using Newmark method. It is shown that neglecting the effect of bedrock inclination, would lead to non-real results in assessing the seismic slope performance.
  • Akbar Hassanipour, Ali Shafiee, Mohammad Kazem Jafari Page 255
    Shear modulus and damping ratio are important input parameters in dynamic analysis. A series of resonant column tests was carried out on pure clays and sand-clay mixtures prepared at different densities to investigate the effects of aggregate content, confining stress, void ratio and clay plasticity on the maximum shear modulus and minimum damping ratio. Test results revealed an increase in the maximum shear modulus of the mixture with the increase in sand content up to 60%, followed by a decrease beyond this value. It was also found that the maximum shear modulus increases with confining stress, and decreases with void ratio. In addition, minimum damping ratio increases with sand content and clay plasticity and decreases with confining stress. Finally, on the basis of the test results, a mathematical model was developed for the maximum shear modulus.
  • Seyed Naser Moghaddas Tafreshi, Gholamhosein Tavakoli Mehrjardi, Majid Ahmadi Page 265
    The results of laboratory model tests and numerical analysis on circular footings supported on sand bed under incremental cyclic loads are presented. The incremental values of intensity of cyclic loads (loading, unloading and reloading) were applied on the footing to evaluate the response of footing and also to obtain the value of elastic rebound of the footing corresponding to each cycle of load. The effect of sand relative density of 42%, 62%, and 72% and different circular footing area of 25, 50, and 100cm2 were investigated on the value of coefficient of elastic uniform compression of sand (CEUC). The results show that the value of coefficient of elastic uniform compression of sand was increased by increasing the sand relative density while with increase the footing area the value of coefficient of elastic uniform compression of sand was decreases. The responses of footing and the quantitative variations of CEUC with footing area and soil relative density obtained from experimental results show a good consistency with the obtained numerical result using FLAC-3D.
  • Hamed Farshbaf Aghajani, Abas Soroush, Piltan Tabatabaie Shourijeh Page 275
    A comprehensive improved solution for the capillary rise of water in soils is presented. Salient features of the formulation, including; consideration of initial soil suction (if any) prior to capillary rising, and determination of water content variation in the capillary region are elaborately discussed. The solution is verified, and compared with existing models, by means of experimental results available in the literature. The improved formulation is more accurate and versatile than previous solutions for capillary rise.
  • Ali Reza Majidi, Ali Asghar Mirghasemi, Mona Arabshahi Page 282
    In the current study, an effort is made to determine three dimensional bearing capacity of rectangular foundations using Discrete Element Method. The soil mass is modeled as discrete blocks connected with Winkler springs. Different factors affect the geometry of failure surface. Six independent angles are used to define the failure surface. By trial and error, the optimum shape of failure surface beneath the foundation can be found. The paper includes the derivation of the governing equations for this DEM based formulation in three dimensional state as well as parametric sensitivity analyses and comparison with other methods. Moreover, using the current method, bearing capacity coefficients are presented for various friction angles and foundation aspect ratios.
  • Dr. Mojtaba Jahanandish, Mehdi Veiskarami, Dr. Arsalan Ghahramani Page 293
    Foundations behavior is affected by soil behavior which can vary from dilative to contractive depending on the stress level, particularly in dense frictional soils. A relatively simple work hardening/softening constitutive soil model is developed to represent dense frictional soils behaviors under different stress levels. This model is then implemented into the Zero Extension Lines (ZEL) method to theoretically investigate the ultimate bearing capacity and load-displacement curve of foundations over dense frictional soils. Utilization of this model enables the ZEL method to capture different foundations behavior depending on the foundation size. A numerical study on foundations behavior was performed showing the ability of the presented approach in capturing both general and local shear failure mechanisms which results in different load-displacement curves.
  • Mahamoud Hassamlourad, Hossein Salehzadeh, Habib Shahnazari Page 307
    The effect of cementation and grains physical properties on shear behavior of grouted sands is investigated in this paper. Consolidated-undrained thriaxial shear behavior of three grouted carbonate sands having different physical properties including particle size, distribution, particle shape and void ratio is studied. Two sands were achieved from north shores of Persian Gulf, south of Iran, named Hormoz and Kish islands sands and one from south beaches of England named Rock beach sand. The selected sands were grouted using a chemical grout named Sodium Silicate and tested after one month curing time. Tests results show that, effect of bonding on the shear behavior and strength depends on the bonds strength and confining pressure. Also, shear behavior, yields strength and shear strength of grouted sands under constant conditions including initial relative density, bonds strength, confining pressure and loading is affected by sands physical properties. Furthermore, parameters of Mohr-Coulomb shear strength failure envelope including cohesion and internal friction angle of grouted sands under the mentioned constant conditions is affected by soils physical properties and structure.