مطالعه ي رفتار سازه نگهبان شمع و تاي بك با بكار گيري مدل رفتاري الاستوپلاستيك جامع دو سطحه و سطح مرزي

چكيده انگليسي :

The Study of the Behavior of Tie back Walls with Soldier Pile Using the Unified Bi Surface Elasto Plastic Model and Bounding Surface Model Kobra Niknam k niknamsafarikuchi@cv iut ac ir Date of Submission 2011 04 20 Department of Civil Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor A M Halabian mahdi@cc iut ac irAbstract Earth retaining wall systems are used for stabilizing deep excavations Present research aims tounderstand the behavior of a retaining wall system with tieback and soldier pile under static loadingconditions and dynamic excitation as well Tieback wall construction commonly involves four basic stages soldier pile installation excavation installation and pre tensioning tiebacks and finally face stabilization Tiebacks are performed in two bonded and unbounded parts The bounded part is first constructed tofacilitate applying the pre tensioning load The key factor in design of anchored retaining walls is that oflateral earth pressure It is necessary to use appropriate constitutive model which is capable of predictionthe behavior of soil on different stress states Hence the first objective of this research was to model thetieback retaining wall systems using a unified bi surface elasto plastic model constitutive model for thematrix soil 1 This model have been already implemented in a finite difference code FLAC3D 35 Modelparameters were obtained based on the results of a triaxial test Lateral earth pressure behind wall wascompared with the existing empirical earth pressure envelop Furthermore results were compared with thenumerical results using Cam Clay and Mohr Coulomb models Having better perception of wallperformance a parametric study was conducted in which the results give more information regardinginfluence of different affecting parameters including the location of first tendon from the ground surface magnitude of anchor forces embedded depth of the soldier pile relative stiffness of the piles and soil pilesspacing and tendon bonded length on the wall behavior Due to importance of earthquake excitationfollowed by destructive effects on retaining structures such as tieback walls investigation on dynamicbehavior of this type of anchored walls is essential A suitable model for dynamic soil structure interactionshould capture the hysteretic behavior and energy absorbing characteristics of real soils The secondobjective of this research was to implement a newly introduced plasticity model developed for simulation ofmonotonic and cyclic loading of sandy soils to the commercial finite difference code FLAC3D using itsUser Defined Model UDM capability The model is developed 2 based on the general two surfaceplasticity concept and the bounding surface plasticity theory and is capable to simulate accuratelyvolumetric and stress strain behavior of soils under monotonic and cyclic loading hence the relatedobservations like accumulation of pore pressure cyclic mobility and cyclic liquefaction could be modeledutilizing this model in any numerical method The plasticity model was implemented with an integrationscheme based on the cutting plane method Throughout a calibration process a single set of modelconstants can be used to simulate stress strain response under different initial void ratios and variablyconfined pressures The model was validated through a comparison process of the simulated responses withthe results obtained from experiments under monotonic and cyclic loading conditions Furthermore theload deflection response of a single concrete pile foundation was calculated for an axial loading and thebearing capacity of a rectangular shallow footing was determined using the implemented bounding surfacemodel The seismic responses of tieback walls under severe earthquake were examined taking into accountthe cyclic non linear behavior of soil Keywords Tieback wall Soldier pile Earth pressure Constitutive model Monotonicand cyclic loading

نيكنام، كبري

مطالعه ي رفتار سازه نگهبان شمع و تاي بك با بكار گيري مدل رفتاري الاستوپلاستيك جامع دو سطحه و سطح مرزي

فشار جانبي خاك , اندركنش ديناميكي