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چكيده انگليسي :

Numerical Analysis of Bearing Capacity of Skirted Foundations Hassan Habibian habibian hassan@cv iut ac ir June 21 2009 Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiM A Rowshan Zamir mohamali@cc iut ac irAbstractSome of the advantages of skirted foundations which have extended their applications in offshore are improvement of bearing capacity of foundation against vertical horizontal loads and moments betterperformance under cyclic loads more accurate faster easier and cheaper installation in comparison with otherchoices like piles especially in deep water and sometimes the capability of uninstallation in order to use inanother place However the use of such structural skirts in conjunction with conventional shallow structuralfoundations has not been widely employed nor have the improvements in bearing capacity occurring from theiruse been investigated in detail However there are few researches on skirted foundation for inshore structures andthey are limited to some special type of soils Therefore more extensive and accurate studies on bearing capacityof these foundations and the influencing parameters are necessary to make them applicable for conventionalstructures In this dissertation the results of numerical analysis of surface foundations reinforced with skirts under verticalloads are presented The factors which influence the bearing capacity of these foundations including soil strengthand stiffness parameters shape and width of foundation foundation base roughness skirt depth skirt roughness skirt thickness skirt stiffness numerical behavior model of soil plug and skirt arrangement are investigated andanalyzed and by comparing the bearing capacity of skirted foundation with the bearing capacity of surfacefoundation without skirts effect of using skirts was determined and presented as the bearing capacity ratio Furthermore the bearing capacity of skirted foundation was compared with ones of the foundation at the skirtdepth in different of skirt roughnesses Also a modified bearing capacity equation is proposed for skirtedfoundations Numerical analysis was carried out using the ABAQUS FEM software by explicit method Four nodequadrilateral elements for axisymmetric and plane strain and eight node brick elements for 3D analysis was used Analysis were done in two stage including geostatic stress generation stage and loading stage Loading wasconducted by displacement controlled method Three shapes of foundations including circle square and strip withrigid bases and two type of skirts including rigid and flexible were modeled In order to model the roughness ofskirts the interactions elements were employed In addition the foundations were investigated in three width of0 5 1 and 2 meters and the skirts were modeled in three depth of 0 5 1 and 2 meters By displacing theconnection point of the skirts from edge of foundation base to the inner positions in circle and strip skirtedfoundations and by adding the skirts in square skirted foundations the effect of skirt arrangement on bearingcapacity of foundation was studied Changing the numerical model behavior of soil plug with elastic and rigidmodel separately the effect of soil plug on bearing capacity was investigated The results of analysis showed thatusing the skirts in the conditions of this work increases the bearing capacity of surface foundations from 1 1 to 2times depending on soil and foundation properties Key WordsStructural Skirts Skirted Foundation Bearing Capacity Equation Numerical Analysis

حبيبيان، حسن

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