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"ABSTRACTInternal Erosion initiated by water movement along channels called tunnel erosion, oftencrack or defect the dam?s structure. It is one of the main causes of water structure?s (dams,dikes, etc.) collapse. This phenomenon can be divided into 3 phases, tunnelling, collapse, andthe opening of the channel inside the dam [1]:- ?Tunnelling? transport large quantities of particles due to the hydraulic gradient. It?s happenfast in a preferential path especially in some point of dam structure?s weaknesses.- The gradual collapse of the roof of tunnel erosion allows the expansion of the channel.- The opening of the channel is started after the collapse of the channel by tunnel erosion.Research has been done to explain the phenomenon of collapse, but there are still questions,including the formulation, phase, and form of the rupture. Moreover, the equation usedis not always adapted to the various cases of the soil. Research by Hunt and Hanson showedthe different phases of a dam collapse with a rate of expansion of a hole driven only by theconstraint of shearing.Through this numerical study, we find that their hypothesis is not correct, because thereare other parameters that affect this phenomenon and also the effect of traction force. Thestudy is simplified by modelling an earthen dam with a given cavity; where the undrained cohesionis controlled to see at which value of cohesion the fracture achieved. This simplificationis the opposite in the real case, where the cohesion is fixed but the cavity expands. Wefind that the collapse of the earthen dam because of the tunnel erosion occurs in two stages:the arching effect in the channel across the dam that makes vertical sag then collapse, and theexpansion of the channel which is inclined more like a slope. The high of the dam and theform of the ?tunnel? cavity also influenced the failure mode."

"Pada konstruksi MRT Jakarta, pekerjaan tunnelling dilakukan dengan menggunakan alat Tunnel Boring Machine TBM . Salah satu tahap awal pada pelaksanaan pekerjaan terowongan menggunakan TBM adalah pembangunan fasilitas sementara TBM. Penelitian ini bertujuan untuk mengidentifikasi faktor-faktor risiko pada fasilitas sementara TBM yang berpengaruh terhadap kinerja waktu proyek MRT, dampak dan penyebabnya, serta tindakan yang dapat dilakukan terhadap faktor-faktor risiko tersebut. Penelitian dilakukan dengan mengumpulkan data melalui survey kuesioner dan wawancara. Kemudian, data tersebut diolah menggunakan uji-uji stastistik dan analisis kualitatif risiko. Hasil penelitian ini didapatkan lima faktor risiko fasilitas sementara TBM yang berpengaruh terhadap kinerja waktu proyek. Faktor risiko tertinggi pada fasilitas sementara TBM adalah ketidaksejajaran sumbu TBM dengan back anchor. ......Within Jakarta MRT construction, tunnelling work done by using a Tunnel Boring Machine TBM . One of the early stages of the implementation tunnelling work using a TBM is the construction of temporary facilities for TBM. This research has purposes to identify risk factors of temporary facilities for TBM that influence time performance of MRT project, its cause and effects, and also treatment or response that can do for that risk factors. The research was conducted by collecting data through a survey questionnaire and interview. Then, evaluated by statistics test and qualitative risk analyze. The result of this research is acquired five risk factors of temporary facilities for TBM that influence to time performance of MRT project. The highest risk of temporary facilities for TBM is misalignment of TBM axis with back anchor."