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Abstrak :
Tesis ini membahas pemodelan numerik untuk perilaku interface terhadap beban monotonik (geser). Analisis dilakukan dengan menggunakan model Direct Shear Test oleh karena kemudahannya. Pemodelan numerik dilakukan dengan menggunakan program Fast Lagrangian of Continua (FLAC) Code. Model konstitutif interface yang dipakai adalah Modifikasi Mohr Coulomb dengan Fungsi Hiperbolik. Secara umum, model ini dapat mensimulasi perilaku interface terhadap beban geser. Pada kasus pasir padat (dense), interface mengalami kontraktansi diikuti dengan dilatansi. Untuk pasir lepas (loose), interface hanya mengalami kontraktansi saja selama pembebanan geser. Untuk memodelkan kontraktansi dan dilatansi pada interface digunakan Hukum Dilatansi. Kajian lebih lanjut menyimpulkan bahwa pada kondisi batas yang berbeda, maka plastisitas pada CNV muncul terlebih dahulu kemudian diikuti dengan CNS kemudian CNL. Munculnya pola deformasi berbentuk lenticular juga terlihat pada zona interface setelah pembebanan geser. Studi aplikasi pada tiang pancang menggarisbawahi bahwa asumsi untuk properti interface tentunya akan mempengaruhi perilaku sistem tiang pancang. ......This thesis presents a numerical model to study the behavior of the interface under monotonic loadings (shearing). The Direct Shear Model was used in the analysis because of its simplicity. The numerical model was performed by using Fast Lagrangian of Continua (FLAC) Code. The interface model used here is the Modified Mohr Coulomb Model with a hyperbolic Law. In general, this model is sufficient to simulate the interface behavior. Under shearing, the interface exhibits contractancy followed by dilatancy in the case of dense sand. For the loose sand case, the interface experience contractancy throughout shearing. The generation of contractancy and dilatancy was created by using a simple dilatancy law. A further study with different boundary condition outlined that the yielding state in CNV test starts at the very beginning, then followed by the CNS and the CNL test. The occurence of a lenticular shape was also observed in this study. This explains the deformation shape of the interface zone after shearing. An application to a pile foundation system outlined that the interface strength and the density of the soil influence the pile responses.

Abstrak :
Several studies have already been published in order to better understand the behaviour of interfaces. Different experimental methods, including direct shear tests, simple shear test, and tortional ring test, and also various constitutive models were presented to modelize the behaviour of the interface. These studies revealed that the main factors that affect the behaviour of the interface include the roughness of the interface, the soil mineralogy, the soil density, and the normal stress applied. This work was therefore directed primarily to better understand the overall behaviour of the interface and the influence of these factors in a monotonic and cyclical solicitation. Through the simulation of a direct shear test at constant normal stress (CNL) in FLAC 5.0, several typical behaviours, including degradation of shearing resistance and contractancydilatancy, have been observed and modelled. At first, the law of Mohr-Coulomb and its correspondent failure criterion have been implemented. Then several models have been proposed to model more precisely the behaviour. Finally, two cyclicals laws, the law of Ramberg-Osgood law and Byrne, originally developed for the soil, have been implemented in this model. This study has verified the consistency of the results and has determined whether the injection of such laws is sufficient to modelize the behaviour of the interface under cyclic loading.

Abstrak :
The internal erosion is a common mode of failure in earth dams. The phenomenon of filtration process corresponds to a transport over long distances of fine particles under the effect of seepage forces. The filters arranged by both sides of the clay core are supposed to be dimensioned so to stop this transfer. In a granular material, the constriction is very important in the filtration process. It is the narrowest path linking pores. If there is a fluid flow and the constriction size is larger than the diameter of particle, the particle follows its route. On the other hand, if the constriction size is smaller than the diameter of particle, the particle is stopped. Then, the curve of cumulative size constrictions for a granular material is identified as the key characteristic of the filtration process. This characteristic depends on the density and size distribution curve of the filter. The objective of this research is to find and compare the curve with three different approaches by using periodic conditions. These three approaches are MEDTD (Discrete Element Method Triangulation Delaunay), the probabilistic approach and the inverse approach by experiment.