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چكيده انگليسي :

Investigation the Behaviour of Piled Raft Foundations with Dissimilar Piles Taha Rostamzade Lasbomahale t rostamzadelasbomahale@cv iut ac ir Date of Submission 28 2 2012 Department of Civil Egineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisors Dr M A Roshanzamir mohamali@cc iut ac irDr M vafaeian mahmood@cc iut ac irAbstract Piled rafts have been proved to be an effective and economical foundation to control total anddifferential settlements as well asimprove bearing capacity Piled raft foundations are loading systems thatload transfer is transmitted by them and are pile groups that cap in them has the bearing effect Particularlyin the soft clay these systems are used in heavy structure bridges foundation and heavy machineryfoundations In general pile groups are added to the following two reason First bearing capacity of raftfoundation for endure of exerted load is lower than sufficient quantity Secondly bearing capacity of raftfoundation is sufficient but differential and general settlement of foundation is greater than allowedvalue The conventional design of a piled foundation is based on a bearing capacity approach and neglectsthe contribution of the raft Pile groups are frequently designed with equal or similar pile lengths However the signi cant interaction effects among equal length piles imply that this may not be the optimizedcon guration This paper presents the optimization analyses of piled rafts and freestanding pile groups where pile lengths are varied across the group to optimize the overal foundation performance In a piledraft the length and arrangement of piles has a signi cant effect on the stresses and de ections of the raft The use of piles with different dimensions and properties below a raft is an innovative concept and canoptimize the design of a piled raft The behavior of a piled raft is affected by the 3D interaction between thesoil piles and raft Numerical methods which are approximate have been developed widely in the last twodecades because numerical methods are less costly and may be used to consider many kinds of different soiland foundation geometries compared to eld and model tests In this study Piled raft foundation is based onsettlement control changes the dimensions and system arrangement is done for reducing of settlements andlateral deflection of system In this study finite element approach has been used Piled raft foundation islinear elastic and soil are assumed to have Mohr Coulomb model and elastoplastic Studies on parameterslike distance between piles length of piles diameter of them different vertical and lateral loadingmagnitude number of piles and piles to soil modulus of elasticity proportion for two models of pile groupwith same length and different length constant sum of pile length is done Increasing of vertical bearingareas piles distance diameter of piles ratio of modulus of pile to soil and increasing the over length of thepiles to reach the over length of vertical bearingare effective parameters to reduce the lateral changes Forthe pile group raising of the length of the internal piles and decreasing of the length of the external piles haspositive influence on vertical settlements of the system but if length of the identical piles is less thanoverlength of vertical bearing with decrement of the length of the internal piles and increasing of the lengthof the external piles lateral deformation of the center of the raft foundation is reduced Otherwise changesin piles length haven t any effect on the system deformation chiefly in low safety factors about 2 to 3 Keywords Piled raft foundation finite element method parametric analysis mohr coulomb model

رستم زاده لسبومحله، طاها

بررسي رفتار پي هاي گسترده شمعي با شمع هاي متفاوت

روش اجزاي محدود , تحليل پارامتريك , مدل موهر-كولمب