International Journal of Civil Engineering

Effect of bedrock inclination on seismic slope stability according to Iran seismically data

F. Askari

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 may cause the acceleration magnitude and the displacement in the sliding mass to reach to their maximum level.

This may happen in conditions that the mean period of the acceleration time history on failure surface (Tmt) and the

predominant period of the slope (Ts ) are close to each other. 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.

Low-amplitude dynamic properties for compacted sand-clay mixtures

A. Shafiee

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.

Experimental and numerical investigation on circular footing subjected to incremental cyclic loads

S. N. Moghaddas Tafreshi

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”.

An improved solution to capillary rise of water in soils

Abbas Soroush

Evaluating the rate and maximum height of capillary rise is of prime interest in unsaturated soil mechanics. Antecedent solutions

to this problem have dwelled mostly on determining the maximum capillary rise height, overlooking moisture and suction changes

in the capillary region. 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 rise, and determination of water content

variation in the capillary region are elaborately discussed. Results reveal that suction head variation within the capillary region

is non-linear, where the curvature decreases as water rises to higher elevations. The solution is verified and compared with

existing solutions, by means of two sets of experimental data available in the literature. The comparison suggests that the

improved formulation is more accurate and versatile than previous solutions for capillary rise.

Three dimensional bearing capacity analysis of shallow foundations using discrete element method

A.A. Mirghasemi

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.

Investigation of foundations behavior by implementation of a developed constitutive soil model in the ZEL method

M. Jahanandish

Foundations behavior is affected by soil behavior which can vary from dilative to contractive depending on the stress level,

particularly in dense frictional soils. The Zero Extension Lines (ZEL) method has been generally developed to predict the

foundations behavior. Knowledge of soil behavior enables the ZEL method to predict the general and local shear failure modes.

In this paper, a relatively simple work hardening/softening soil constitutive model is developed to represent dense frictional soils

behavior under different stress levels. This model is based on the accumulation of the plastic work during a simple direct shear

test and its relationship to stress ratio to establish the hardening law. Verifications have been made for the developed soil model.

The model is then implemented into the ZEL method to theoretically investigate the bearing capacity and load-displacement

behavior of foundations over dense frictional soils. Utilization of this model enables the ZEL method to capture different modes

of failure depending on the foundation size. A numerical study on foundations behavior was performed showing the ability of the

presented approach in capturing both failure modes.

Undrained triaxial shear behavior of grouted carbonate sands

M. Hassanlourad

The effects of cementation and the physical properties of grains on the shear behavior of grouted sands are investigated in this

paper. The consolidated-undrained triaxial shear behavior of three grouted carbonate sands with different physical properties,

including particle size distribution, particle shape and void ratio, was studied. Two sands were obtained from the north shores

of the Persian Gulf, south of Iran, called Hormoz and Kish islands sands, and one sand was obtained from the south beaches

of England and called Rock beach sand. The selected sands were grouted using a chemical grout of sodium silicate and tested

after one month of curing. Test results showed that the effect of bonding on the shear behavior and strength depends on the bond

strength and confining pressure. In addition, the shear behavior, yield strength and shear strength of grouted sands under

constant conditions, including the initial relative density, bonds strength, confining pressure and loading, were affected by the

physical properties of the sands. Furthermore, the parameters of the Mohr-Coulomb shear strength failure envelope, including

the cohesion and internal friction angle of grouted sands under constant conditions, were affected by the physical properties

and structure of the soils.