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CONTENTS
Volume 2, Number 4, December 2010
 

Abstract
In this paper, Soil-Structure Interaction (SSI) effect is investigated using a new and integrated approach. Faster solution of time dependant differential equation of motion is achieved using numerical representation of wavelet theory while dynamic Infinite Elements (IFE) concept is utilized to effectively model the unbounded soil domain. Combination of the wavelet theory with IFE concept lead to a robust, efficient and integrated technique for the solution of complex problems. A direct method for soil-structure interaction analysis in a two dimensional medium is also presented in time domain using the frequency dependent transformation matrix. This matrix which represents the far field region is constructed by assembling stiffness matrices of the frequency dependant infinite elements. It maps the problem into the time domain where the equations of motion are to be solved. Accuracy of results obtained in this study is compared to those obtained by other SSI analysis techniques. It is shown that the solution procedure discussed in this paper is reliable, efficient and less time consuming as compared to other existing concepts and procedures.

Key Words
soil structure interaction; infinite elements; wavelet theory; fourier transformation; numerical analysis.

Address
Mohamad Hossein Bagheripour, Reza Rahgozar and Mohsen Malekinejad: Dept. of Civil Engineering, University of Kerman, Kerman, Iran

Abstract
A new prediction model is derived for the uplift capacity of suction caissons using a hybrid method coupling genetic programming (GP) and simulated annealing (SA), called GP/SA. The predictor variables included in the analysis are the aspect ratio of caisson, shear strength of clayey soil, load point of application, load inclination angle, soil permeability, and loading rate. The proposed model is developed based on well established and widely dispersed experimental results gathered from the literature. To verify the applicability of the proposed model, it is employed to estimate the uplift capacity of parts of the test results that are not included in the modeling process. Traditional GP and multiple regression analyses are performed to benchmark the derived model. The external validation of the GP/SA and GP models was further verified using several statistical criteria recommended by researchers. Contributions of the parameters affecting the uplift capacity are evaluated through a sensitivity analysis. A subsequent parametric analysis is carried out and the obtained trends are confirmed with some previous studies. Based on the results, the GP/SA-based solution is effectively capable of estimating the horizontal, vertical and inclined uplift capacity of suction caissons. Furthermore, the GP/SA model provides a better prediction performance than the GP, regression and different models found in the literature. The proposed simplified formulation can reliably be employed for the pre-design of suction caissons. It may be also used as a quick check on solutions developed by more time consuming and in-depth deterministic analyses.

Key Words
suction caissons; uplift capacity; genetic programming; simulated annealing; nonlinear modeling.

Address
Amir Hossein Alavi: School of Civil Engineering, Iran University of Science and Technology, Tehran, Iran
Amir Hossein Gandomi: School of Civil Engineering, Iran University of Science and Technology, Tehran, Iran
College of Civil Engineering, Tafresh University, Tafresh, Iran
Mehdi Mousavi: Dept. of Civil Engineering, Faculty of Engineering, Arak University, Arak, Iran
Ali Mollahasani: Dept. of Civil Engineering, Ferdowsi University of Mashhad, Mashhad, Iran

Abstract
An extended model for the response of a rigid footing on a reinforced foundation bed on super soft soil is proposed by incorporating the rough membrane element into the granular bed. The super soft soil, the granular bed and the reinforcement are modeled as non-linear Winkler springs, non-linear Pasternak layer and rough membrane respectively. The hyperbolic stress-displacement response of the super soft soil and the hyperbolic shear stress-shear strain response of the granular fill are considered. The finite deformation theory is used since large settlements are expected to develop due to deformation of the super-soft soil. Parametric studies quantify the effect of each parameter on the stress-settlement response of the reinforced foundation bed, the settlement and tension profiles.

Key Words
geosynthetic reinforcement; finite deformation theory; granular bed; rigid footing; soft soil; hyperbolic response; settlement; tension.

Address
K. Ramu: Dept. of Civil Engineering, JNT University College of Engineering, Kakinada, India - 533 003
Madhira R. Madhav: JNT University, 159, Road No. 10, Banajara Hills, Hyderabad 500 034, India

Abstract
The effect of grain crushing on the deformation of sand in 1D compression and 1D creep at high stresses was investigated theoretically and experimentally. An approach was proposed to formulate the process of grain crushing in sand in accordance with the laws of fracture mechanics and energy conservation. With this approach, the relation between the void ratio and the amount of grains crushed in 1D compression was derived. Laboratory test data were used to verify this derived relation. In addition, it was observed that there are similarities in evolution of grain size distribution in 1D compression and 1D creep tests. This implies that the changes in microstructure in sand under 1D compression and 1D creep are comparable.

Key Words
sand; grain crushing; grain size evolution; creep; compression; fracture mechanics.

Address
Z. Wang: Geotechnical and Structural Engineering Research Center, Shandong University, Jinan, Shandong, China, 250061
R.C.K. Wong: Dept. of Civil Engineering, Schulich School of Engineering, The University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4

Abstract
This article describes a laboratory research on stabilizing tropical peat using ordinary Portland cement (OPC) as a binding agent, and polypropylene and steel fibres as chemically inert additives. California bearing ratio (CBR) and unconfined compressive strength (UCS) tests were carried out to evaluate the increase in the strength of the stabilized samples compacted at their optimum moisture contents and air cured for up to 90 days. The results show that the UCS values of stabilized peat samples increased by as high as 748.8% by using OPC (5%), polypropylene fibres (0.15%), and steel fibres (2%). The CBR values of the samples stabilized with OPC (5%), polypropylene fibres (0.15%), and steel fibres (4%) showed an increase of as high as 122.7%. The stabilized samples showed a shrinkage in volume upon air curing and this shrinkage was measured by an index called, volume shrinkage index (VSI). The highest VSI recorded was 36.19% for peat without any additives; and the minimum was 0% for the sample containing 30% OPC, 0.15% polypropylene fibres and 2% steel fibres. The technique of stabilizing peat with OPC, polypropylene and fibres, coupled with air curing, appears to be cost-effective compared with other frequently used techniques.

Key Words
peat; cement; polypropylene fibres; steel fibres; optimum moisture content; California bearing ratio; unconfined compressive strength; volume shrinkage index.

Address
Behzad Kalantari: Dept. of Civil Engineering, University of Hormozgan, Bandar Abbas, Iran
Arun Prasad: Dept. of Civil Engineering, Banaras Hindu University, Varanasi, India
Bujang B.K. Huat: Dept. of Civil Engineering, University Putra Malaysia, Serdang, Selangor, Malaysia


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