International Journal of Civil Engineering

Effects of basic Oxygen steel slag (BOS) on strength and durability of kaolinite

Mahmoud Reza Abdi

The use of various slags as by-products of steel industry is well established in civil engineering applications. However, the use

of BOS slag in the area of soil stabilization has not been fully researched and developed despite having similar chemical

composition and mineralogy to that of Portland cement. This paper reports on efforts to extend the use of BOS slag to soil

stabilization by determining possible beneficial effects it may have on compressive strength and durability. Results of laboratory

tests conducted on kaolinite samples stabilized with lime and treated with various percentages of BOS slag are presented. Tests

determined strength development of compacted cylinders, moist cured in a humid environment at 35° C and durability by freezing

and thawing method. Results showed that additions of BOS slag to kaolinite samples singularly or in combination with lime

increased unconfined compressive strength and durability. These characteristics were significantly enhanced by the concurrent

use of lime and BOS slag for stabilization of kaolinite.

Effect of curing time on shear strength of cohesive soils stabilized with combination of lime and natural pozzolana

Khelifa Harichane

When geotechnical engineers are faced with cohesive clayey soils, the engineering properties of those soils may need to be

improved to make them suitable for construction. The aim of this paper is to study the effect of using lime, natural pozzolana or

a combination of both on the geotechnical characteristics of two cohesive soils. Lime or natural pozzolana were added to these

soils at ranges of 0-8% and 0-20%, respectively. In addition, combinations of lime-natural pozzolana were added at the same

ranges. Test specimens were subjected to compaction tests and shear tests. Specimens were cured for 1, 7, 28 and 90 days after

which they were tested for shear strength tests. Based on the experimental results, it was concluded that the combination limenatural

pozzolana showed an appreciable improvement of the cohesion and internal friction angle with curing period and

particularly at later ages for both soils.

Experimental study of geotextile's drainage and filteration propertis under different hydraulic gradients and confining pressures

Zahra Zahmatkesh

Geotextiles are one of the most widely used synthetic materials in filtration and drainage applications. Since in real

applications, geotextiles are subjected to various hydraulic gradients and confining stresses, hydraulic behavior of geotextiles

under different circumstances is of great practical importance. In this study filtration and drainage properties of several

nonwoven needle-punched geotextiles with different properties and unit mass per area of 200g/m2, 400g/m2, 500g/m2 and

800g/m2, under various confining stresses and hydraulic gradients, were studied using standard permittivity

and transmissivity equipments. Prepared samples were subjected to hydraulic heads in the range of 10cm to 60cm and

confining stresses up to 1000kPa and their hydraulic behavior was investigated accordingly. In this study the flow regime

through the geotextile fibers and also the anisotropic behavior of geotextile permeability were investigated. The results show

that transmissivity will decrease exponentially with increasing the normal stress until a residual value is reached, and

permittivity and transmissivity coefficients were seen to decrease with increasing the hydraulic gradient. The flow regime has

found to be non-turbulent in all cases.The Geotextile hydraulic behavior is of great usage in the design of landfill covers,

design of embankments and irrigation structures drainage systems, and in the design of protection systems in river

engineering.

Effect of inorganic salt solutions on some geotechnical properties of soil-bentonite mixtures as barriers

Nader Shariatmadari

The main task in the design and construction of impermeable liners in landfills is to block the migration of pollutants to the groundwater

systems or to reduce its rate to a reasonable amount. That is why environmental regulations force governments to construct engineered

waste dumps for waste management purposes. These liners are exposed to various types of chemical, biological, and physical processes

and are affected by the leachate which is produced from decomposition of waste materials accompanying methane gas. The leachate

includes a lot of components such as water and different types of salts. For this reason, the geotechnical characteristics of clay liners

which are evaluated in laboratories using distilled water or tap water might be far different from the representative sample of the in-situ

conditions. There are some evidences regarding the effect of these salts on the physical and mechanical properties of clay barriers which

could affect the long-term performance of these liners. Since the main criterion for impermeable bottom liners in landfills is their

hydraulics conductivity, the increase of this parameter could have a considerable environmental impact. This paper embraces the results

of a recent study on the effect of three inorganic salts, NaCl, CaCl2 and MgCl2 on some geotechnical properties of a common used clay

soil in impermeable bottom barrier in Kahrizak landfill, the main waste disposal center of the Tehran Metropolitan. Also the effect of

bentonite content by adding different percentage of this special clay mineral, 10 and 20 percent, on these properties was investigated.

Laboratory tests like liquid limit, compaction, 1D consolidation and free swell tests were performed for this purpose. Results indicated

that all of these salts could have a considerable effect on the geotechnical properties of the mixtures. The main reason of such effects is

the changes which occur in diffuse double layer of clay particles.

Drained and undrained sand behaviour by multilaminate bounding surface model

Seyed Amirodin Sadrnejad

The present paper is devoted to a new critical state based plasticity model able to predict drained and undrained behaviour of

granular material. It incorporates a bounding surface plasticity model describing in multilaminate framework to capitalize on

advantages of this mathematical framework. Most of the models developed using stress/strain invariants are not capable of

identifying the parameters depending on directional effects such as principal stress rotation and fabric this is mainly because

stress/strain invariants are scalar quantities. The principal features of this model can be postulated as considering both inherent

and induced anisotropy, principal stress rotation. Since the local instability of saturated sand within post-liquefaction is highly

dependent on the residual inherent/induced anisotropy, bedding plane effects and also the stress/strain path the new mode is

competent to be employed in this regard. The constitutive equations of the model are derived within the context of non-linear

elastic behaviour for the whole medium and plastic sliding of interfaces of predefined planes. As follows, the constitutive

equations are described in detail and then the experimental results and sensitive analysis of key material constants are shown

which all imply the power of the model in predicting of soil behaviour under any condition in soil structures.

A laboratory study on the pore pressure generation model for Firouzkooh silty sands using hollow torsional test

Mohammad Hassan Baziar

This paper discusses the applicability of a simple model to predict pore water pressure generation in non-plastic silty soil during

cyclic loading. Several Stress-controlled cyclic hollow torsional tests were conducted to directly measure excess pore water pressure

generation at different levels of cyclic stress ratios (CSR) for the specimens prepared with different silt contents (SC=0% to 100%).

The soil specimens were tested under three different confining pressures (&sigmaƉ= 60, 120, 240 kPa) at a constant relative density

(Dr=60%), with different silt contents. Results of these tests were used to investigate the behavior of silty sands under undrained

cyclic hollow torsional loading conditions. In general, beneficial effects of the silt were observed in the form of a decrease in excess

pore water pressure and an increase in the volumetric strain. Modified model for pore water pressure generation model based on

the test results are also presented in this paper. Comparison of the proposed pore pressure build up model with seed’s model

indicates the advantage of proposed model for soil with large amount of silt.

Liquefaction resistance of sand-silt mixtures using laboratory based shear wave velocity

Rouzbeh Dabiri

Laboratory data, which relate the liquefaction resistance of Firoozkooh sand and non-plastic silt mixtures to shear wave velocity are

presented and compared to liquefaction criteria derived from seismic field measurements by Andrus and Stokoe [1]. In the work

described herein, cyclic triaxial and resonant column tests were conducted on specimens of clean sand and sand-silt mixtures with silt

content up to 60%, prepared at different densities. Cyclic undrained strength and small strain shear wave velocity were determined

for identical specimens formed by undercompaction method. It was found that silt content affects cyclic resistance and shear wave

velocity. In addition, the laboratory results indicated that using the existing field-based correlations will overestimate the cyclic

resistance of the Firoozkooh sand-silt mixtures when silt content is 60%. For clean sand and the specimens containing up to 30% fines,

results of this study on cyclic resistance are fairly consistent with Andrus and Stokoe correlations. These findings suggest the need for

further evaluation of the effects of non-plastic fines content upon liquefaction criteria derived from seismic field measurements.