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Showing 6 results for Soft Clay

S. N. Moghaddas Tafreshi,
Volume 6, Issue 4 (12-2008)

This paper presents the numerical analysis of seismic soil-pile-superstructure interaction in soft clay using free-field soil analysis and beam on Winkler foundation approach. This model is developed to compute the nonlinear response of single piles under seismic loads, based on one-dimensional finite element formulation. The parameters of the proposed model are calibrated by fitting the experimental data of largescale seismic soil-pile-structure tests which were conducted on shaking table in UC Berkeley. A comparative evaluation of single piles shows that the results obtained from the proposed procedure are in good agreement with the experimental results.
S.a. Naeini, R. Ziaie_moayed,
Volume 7, Issue 2 (6-2009)

In recent years, soil reinforcement is considered of great importance in many different civil projects. One of the most significant applications of soil reinforcement is in road construction. Sub grade soil and its properties are very important in the design of road pavement structure. Its main function is to give adequate support to the pavement from beneath. Therefore, it should have a sufficient load carrying capacity. The use of geosynthetics in road and airfield construction has shown the potential to increase the soil bearing capacity. One category of geosynthetics to particular, geogrid, has gained increasing acceptance in road construction. A geogrid is a geosynthetic material consisting of connected parallel sets of tensile ribs with apertures of sufficient size to allow strike-through of surrounding soil, stone, or other geotechnical material. Geogrid reinforcement of sub grade soil is achieved through the increase of frictional interaction between the soil and the reinforcement. Geogrid have been successfully used to provide a construction platform over subgrades. In this application, the geogrid improves the ability to obtain compaction in overlying aggregates, while reducing the amount of material required be removing and replacing. Relative agreement exists that substantial benefits can be achieved from the inclusion of geogrids within the pavement systems however, the quantity of the improvement is in relative disagreement. This paper presents the effects of plasticity index and also reinforcing of soft clay on CBR values. Three samples of clay with different plasticity index (PI) values are selected and tested without reinforcement. Then by placing one and two layer of geogrid at certain depth within sample height, the effects of reinforcement and PI on CBR values are investigated in both soaked and unsoaked conditions. The results shows that as the PI increase the CBR value decreases and reinforcing clay with geogrid will increase the CBR value.
Khelifa Harichane, Mohamed Ghrici, Said Kenai,
Volume 9, Issue 2 (6-2011)

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.

J. Nazari Afshar, M. Ghazavi,
Volume 12, Issue 1 (1-2014)

The Stone-column is a useful method for increasing the bearing capacity and reducing settlement of foundation soil. The prediction of accurate ultimate bearing capacity of stone columns is very important in soil improvement techniques. Bulging failure mechanism usually controls the failure mechanism. In this paper, an imaginary retaining wall is used such that it stretches vertically from the stone column edge. A simple analytical method is introduced for estimation of the ultimate bearing capacity of the stone column using Coulomb lateral earth pressure theory. Presented method needs conventional Mohr-coloumb shear strength parameters of the stone column material and the native soil for estimation the ultimate bearing capacity of stone column. The validity of the developed method has been verified using finite element method and test data. Parametric studies have been carried out and effects of contributing parameters such as stone column diameter, column spacing, and the internal friction angle of the stone column material on the ultimate bearing capacity have been investigated.
Abdulazim Yildiz, Firdevs Uysal,
Volume 14, Issue 2 (3-2016)

This paper investigates the time dependent behaviour of Sunshine embankment on soft clay deposit with and without prefabricated vertical drains. An elasto visco-plastic model was used to investigate the influence of anisotropy and creep effect on the settlement behaviour of the embankment. The constitutive model, namely ACM accounts for combined effects of plastic anisotropy and creep. For comparison, the problem is also analysed with isotropic Modified Cam Clay model which does not consider creep effect. To analyse the PVD-improved subsoil, axisymmetric vertical drains were converted into equivalent plane strain conditions using two different mapping approaches. The results of the numerical analyses are compared with the field measurements. The numerical simulations suggest that the anisotropic creep model is able to give a better representation of soft clay response under an embankment loading. The isotropic model which neglects effects of anisotropy and creep may lead to inaccurate predictions of soft clay response. Additionally, the numerical results show that the mapping method used for PVD improved soft clays can accurately predict the consolidation behaviour of the embankment and provide a useful tool for engineering practice.

Maryam Haghbin,
Volume 14, Issue 7 (10-2016)

In the present research, an analytical method is applied to determine the bearing capacity of strip footing on two layers of the soil. Bearing capacity of the footing is calculated according to soil resistance beneath the foundation and virtual retaining wall method. In the said method, the active and passive force on the retaining wall are considered equal on the edge in order to determine the bearing capacity of the footing. Regarding two layers of soil, the active and passive forces of each layer is found and their resultant is applied to calculate footing bearing capacity. This method has many advantages including the possibility to determine the depth of rupture surface of the soil beneath the footing, and to study the effect of the soil second layer on footing bearing capacity. Moreover, the effect of soil improvement beneath the footing as well as the depth and width of compacted area on bearing capacity of footing are also studied here in this research. In general, the studied parameters in this project consist of soil layers thickness, soil cohesion and friction angle, footing depth and width, the width of compacted soil beneath the footing, and the depth of underground water. By programming in MATLAB, the calculation and deduction was fulfilled. The results were compared with the bearing capacity of the footing on one layer of the soil in various situations in order to study the effect of various parameters in two layers of the soil. Finally, this bearing capacity of the footing was compared with the previous experimental methods and reliable results were obtained.

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