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"ABSTRACTNowadays, the ways, how to solve the mass transportation problem in the big city become the major problem for the government. Some difficulties come when the mass transportation facilities can't be build at the ground surface because many buildings and services will be disturbed. For avoiding that, the mass transportation facilities usually are built in the underground. It means that we have to excavate the underground to make a tunnel. Excavating a tunnel generates ground displacements and deformations, which can affect the existing buildings and services in urban sites and can lead to unacceptable damages. To predict and to solve the all affects of excavating and tunneling have been a major engineering challenge.A numerical analysis by using the finite difference method was implemented in the aim of developing a procedure for forecasting the all affects induced by tunneling. The influences of the strain-softening of the soil in the tunneling were discussed in this study. To take into account these behaviors, the Mohr-Coulomb criterion with strain-softening behavior were applied and as the comparison data we used the Mohr-Coulomb criterion without strain-softening behavior. We defined a new approximation for defining the strain-softening model. Two new constants obtained from the triaxial test, were used for defining this model. In this definition, the strain-softening behavior of the soil will depend on a;, and the peak values of cohesion and friction angle of the soil. This study presented also the implementation of convergence-confinement method by using the deconfinement modeling and the Sequential Excavation Method (SEM). For deconfinement modeling, we analyzed in two dimensional with plane strain condition. And for the Sequential Excavation Method, we analyzed in axisymmetric condition and in three-dimensional condition. The finite difference software, Fast Lagrangian Analysis of Continua (FLAC), was used for simulating all the problems."

"ABSTRACTThe development and extension of large cities creates a need of multiple shallow tunnels in the soft ground of built areas. Excavating a tunnel generates ground displacements and deformations which can affect existing buildings and services in urban sites and can lead to unacceptable damages. Prediction of the ground settlement caused by the tunnel excavation has been a major engineering challenge. A numerical simulation using finite element method was implemented in the aim of developing a procedure for forecasting the movement induced by tunneling. This study describes the modelling procedure, comparing one procedure in a complete stages of modelling (called phases modelling) taking into account different phases simulating the different kinds of interaction between the tunnel and the soil (deconfinement, lining installation, pore pressure applied on the lining, and weight of the lining) and one in a simple way called `deconfinement modeling', simulating the excavation using a stress decrease vector exerted on the excavation boundary in the opposite to the initial ground stress described by a scalar parameter A. (the deconfinement rate). A shallow lined tunnel is analyzed in a two dimensional analyses, and observations are made for the settlement at the surface and at the tunnel crown, the deformations of the tunnel opening, and the stress path around the tunnel. Comparison is conducted using two soil models : the Mohr-Coulomb model and the CJS model. Observations of the results and comparison with the experimental data demonstrate that the deconfinement modeling is adequate for the analyses of settlement induced by tunneling only if a good modeling of the soil behavior is considered."

"This thesis continues the same research last year with a different condition. It presented a numerical study of the improvement of solt soil using columnar inclusions with Fixed Base End Condition In this new condition the inclusions are assumed reach rock like layer condition. Review of analytical studies has been concentrated to British Standard BS8006, modified Terzaghi theorem, and arching theorem Numerical model in this study is using FLAC3D code to generate 3D model. The materials properties uses in this model refer to typical values. Some of important design variables have been considered in our parametric study. The most efficient platform thickness is 1m for loading 3OkPa or more, in point of view to minimize the proportion stress on soft soil or to maximize ratio of load transferred to columns. Optimal area ratio A, is in range from 5% to 10% its depends on the considered parameters, but 10% is acceptable for most parameters. Study of stress distribution on column indicate that the negative friction will act on top part of column in any level of loading. Due to the mechanism of stress distribution, inclusion system could settle as a group. The maximum of stress reduction ratio S, and stress concentration ratio E, is obtained for the same value as Terzaghi analysis."

"Timbunan bertiang merupakan salah satu metode dalam meningkatkan daya dukung tanah lunak ketika dilakukan pekerjaan penimbunan, dimana tanah dasar diberikan perkuatan berupa pondasi tiang. Adapun dengan adanya perkuatan pada tanah lunak ini ternyata dapat mengurangi penurunan yang terjadi. Hal ini disebabkan oleh adanya mekanisme arching effect yang menyebabkan sebagian beban timbunan ditransfer ke pondasi tiang, sehingga tanah lunak mengalami reduksi beban. Penelitian ini merupakan turunan dari penelitian timbunan bertiang, dimana pada penelitian ini akan dianalisis perbedaan antara pondasi tiang yang menggunakan gesekan antara pondasi tiang dan tanah (friction piles) dengan pondasi tiang dengan menggunakan tahanan ujung (end bearing piles), dimana digunakan Program Plaxis 3D Foundation dalam permodelannya. Selain itu, studi ini juga memvariasikan ketinggian timbunan, jarak antar tiang, kekakuan aksial lapisan geosintetik, dan juga susunan pondasi tiang sehingga dapat terlihat pengaruhnya terhadap sistem timbunan bertiang ini. Bahasan dalam penelitian ini mencakup penurunan dan juga prilaku konsentrasi tegangan yang terjadi pada timbunan bertiang, serta pengaruhnya terhadap gaya tarik geosintetik yang terjadi pada pondasi tiang.

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Piled embankment is one of the methods to improve soft soil’s bearing capacity when the embankment construction is done, in which the base soil is given piles as the support. With piles support the soft soil, the settlement of the embankment can be reduced. This is because of the arching effect mechanism which causes some of the loads of the embankment are transfered through the piles, so that the load working on soft soil is reduced. This study is a derivative of piled embankment case study, where this study will analyze the differences of behaviour between the friction piles system and end bearing piles system using Plaxis 3D Foundation for modeling the case. Besides that, this study is also varying the height of embankment, the spacing between piles, the axial stiffness of geosynthetic layer, and the arrangement of piles so that the affection against piled embankment system could be concluded. The discussion of this research concludes the settlements and also the stress concentration behaviour, and also the axial force of geosynthetic layer that occurs in the piled embankment system."

"Perencanaan kota yang masif memaksa pemanfaatan ruang bawah tanah, paling tidak dalam infrastruktur transportasi. Penelitian ini membahas pengaruh terowongan undercrossing terhadap struktur terowongan eksisting, khususnya di bawah Jakarta Clay. Penelitian ini dibagi menjadi 2 langkah menggunakan analisis elemen hingga dengan model Hardening Soil dan menggunakan perangkat FEA. Langkah pertama adalah melakukan analisis balik untuk mendapatkan nilai parameter tanah aktual kemudian dilanjutkan dengan langkah 2, yaitu melakukan analisis undercrossing twin tunnel dengan variasi jarak 0.5D, 1.5D, dan 2.5D. Berdasarkan hasil penelitian lankah pertama menunjukkan penggunaan korelasi E50 = 3500N untuk tanah kohesif dan E50 = 2800N untuk tanah pasiran dengan parameter kekuatan tanah efektif membuahkan hasil yang paling cocok dengan monitoring. Hasil penelitian langkah kedua menunjukkan adanya deformasi vertikal yang terjadi pada struktur terowongan eksisting dan deformasi vertikal pada permukaan tanah menunjukkan hasil dengan pola yang seragam. Kemudian tegangan geser maksimum mengalami perubahan seiring pengeboran terowongan undercrossing 1 dan 2.

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Massive urban planning forces the utilization of basements, at least in transport infrastructure. This study discusses the influence of undercrossing tunnels on existing tunnel structures, especially under Jakarta Clay. This research was divided into 2 steps using finite element analysis with the Hardening Soil model  and using FEA devices. The first step is to conduct a reverse analysis to obtain the actual soil parameter values then proceed with step 2, which is to perform a twin tunnel undercrossing analysis  with distance variations of 0.5D, 1.5D, and 2.5D. Based on the results of the first lankah study, it shows the use of correlation E50 = 3500N for cohesive soil and E50 = 2800N for sand soil with effective soil strength parameters producing results that are most suitable for monitoring. The results of the second step of research showed the presence of vertical deformation that occurred in the existing tunnel structure and vertical deformation on the ground surface showed results with a uniform pattern. Then the maximum shear stress changes as undercrossing tunnels 1 and 2 are drilled."

"Geografis Indonesia berlokasi pada kawasan Ring of Fire yang  membuat Indonesia menjadi salah satu negara yang sangat rawan terhadap gempa. Sambungan pondasi dengan pile cap  termasuk bagian yang rawan rusak ketika terjadi gempa. Melihat hal tersebut dan masih jarangnya penelitian terkait perilaku spun pile yang tersambung ke pile cap, maka dilakukan penelitian tersebut pada studi ini. Studi numerik kinerja spun pile D1200 akibat pembebanan monotonic pada tanah soft clay bertujuan untuk melihat perilaku dari spun pile yang tersambung pada pile cap dengan basis kondisi di pelabuhan. Studi dilakukan dengan 2 tahap yaitu studi validasi dan studi parametrik

Studi parametrik pada penelitian ini dilakukan untuk menjawab rumusan masalah dan tujuan penelitian. Studi parametrik dilakukan dengan variasi rasio tulangan longitudinal beton pengisi spun pile, kuat geser tanah, panjang free standing, dan besar gaya aksial. Permodelan pada studi ini menggunakan software Lpile dan SAP2000. Software Lpile ditujukan untuk memodelkan kurva p-y tanah yang digunakan sebagai model tanah nonlinier pada SAP2000. Permodelan SAP2000 dilakukan dengan pembebanan pushover dan permodelan penampang dengan section designer.

Hasil permodelan pada studi ini dianalisis dengan melihat kapasitas penampang, kurva load-displacement, daktilitas, dan proses terbentuknya sendi plastis. Hasil studi menunjukkan bahwa penambahan beton pengisi spun pile akan menambah kapasitas penampang. Penambahan rasio tulangan beton pengisi, semakin besar kuat geser tanah, dan semakin besar gaya aksial menunjukkan peningkatan pada kekuatan dan kekakuan struktur. Namun, pada penambahan panjang free standing menunjukkan penurunan kekuatan dan kekakuan struktur.

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Geographically, Indonesia is located in the Ring of Fire area which makes Indonesia become one of the countries most prone to earthquakes. The connection of pile-pile cap is prone to damage when earthquakes occur. Refer to that things dan there are only a few study about behavior of connection spun pile-pile cap, the research was carried out in this study. Numerical Study Of Spun Pile D1200 Performance Due To Monotonic Loading In Soft Clay Soil aims to see the behavior of spun pile-pile cap connection which refer to a port condition. The study was conducted in 2 stage, there are validation studies and parametric studies.

Parametric study in this research is aim to answer the problem formulation and  research objectives. Parametric Studies are carried out with variations in the ratio of longitudinal reinforcement of spun pile infill, soil shear strength, free standing length, and axial load. On this study, the structure modelling used Lpile and SAP2000. Lpile was used to get p-y curves of the soil that will use to nonlinier soil modelling on SAP2000. SAP2000 modeling carried out with pushover loading and using section designer to model the spun pile section.

The results of this study analize was analyzed with strength capacity, load-displacement curves, ductility, and the process of plastic hinge. The results showed that the addition of concrete infill will increase the strength capacity of spun pile. The addition of reinforcement ratio of concrete infill, the greater soil shear strength and axial load showed an increase in structural strength and stiffness. However, the addition of the length of free standing shows a decrease in structural strength and stiffness."

"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."

"Dalam fase konstruksi, kondisi tanah eksisting memiliki peran penting. Di antaranya adalah sebagai penahan beban konstruksi, beban bangunan, dan beban lainnya untuk kemudian diteruskan hingga ke kedalaman atau lapisan tanah tertentu. Salah satu jenis tanah yang lazim ditemukan dalam kegiatan konstruksi adalah tanah lunak. Tanah lunak di Indonesia tersebar pada hampir 20 juta hektar atau 10% luas total daratan Indonesia (ESDM, 2019). Tanah lempung lunak yang memiliki karakteristik khusus dapat mengakibatkan permasalahan di dalam dunia konstruksi seperti rendahnya daya dukung tanah, resiko kestabilan pada galian tanah, dan penurunan jangka panjang yang besar. Prefabricated Vertical Drain (PVD) dengan Vacuum Consolidation Method adalah salah satu jenis metode perbaikan tanah yang digunakan oleh perusahaan-perusahaan di bidang geoteknik untuk pengerjaan perbaikan tanah dengan pendekatan konsolidasi. Metode ini biasanya tidak memerlukan penggunaan beban tambahan apabila kekuatan vacuum dapat mencapai 80 kPa atau lebih. Namun apabila beban yang dibutuhkan adalah lebih dari 80 kPa untuk mencapai target perbaikan tanah, maka beban tambahan bisa ditambahkan di atas sistem vacuum. Penelitian ini fokus terhadap studi kasus perbaikan tanah pada “Proyek Apartemen Tangerang”. Berdasarkan hasil data lab dan pengujian in-situ (CPT dan SPT), dapat dideterminasi kedalaman lapisan lunak tanah lempung lanauan mencapai 14-15m dengan nilai N-SPT rata-rata 0-2. Stratifikasi tanah dan parameter geoteknik selanjutnya digunakan dalam pemodelan PVD dan vakum menggunakan perangkat lunak elemen hingga PLAXIS 2D. Hasil pemodelan kemudian dikomparasi dengan data aktual monitoring lapangan dan didapat data penurunan tanah lapangan dan pemodelan masing-masing sebesar 1.36m dan 1.41m. Selanjutnya nilai deformasi lateral lapangan berkisar di 40-70cm pada permukaan. Sedangkan dari hasil pemodelan numerik didapatkan total deformasi lateral sebesar 36,7cm dengan nilai pergeseran sebesar ≤4cm berada hingga jarak ±10m dari area perbaikan tanah. Ketersediaan data uji lab yang lengkap serta penentuan parameter geoteknik yang tepat dapat menjadi kunci utama untuk menghasilkan pemodelan PVD dan vakum yang akurat

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In the construction phase, the existing soil condition has an important role. Some of it are to support construction loads, building loads, and other loads to be distributed to a certain depth or layer of soil. One type of soil that is commonly found in construction activities is soft soil. Soft soil in Indonesia is spread in over almost 20 million hectares or 10% of Indonesia's total land area (ESDM, 2019). Soft clay soils with particular characteristics can cause problems in the construction stage such as low soil bearing capacity, risk of stability in excavation, and large long-term settlements. Prefabricated Vertical Drain (PVD) with Vacuum Consolidation Method is one of soil improvement method used by companies in the geotechnical field for soil improvement work using consolidation approach. This method usually does not require the use of additional loads when the vacuum strength can reach 80 kPa or more. However, if the required working load is more than 80 kPa to achieve the soil improvement target, then additional loads can be added on top of the vacuum system. This research focuses on a case study of land improvement in the "Tangerang Apartment Project". Based on the results of laboratory data and in-situ testing (CPT and SPT), it can be determined that the depth of the soft silty clay layer reaches 14-15m with an average N-SPT value of 0-2. Soil stratification and geotechnical parameters were then used in PVD and vacuum modeling using PLAXIS 2D finite element software. The results of the modeling are then compared with the actual data of field instruments monitoring and obtained data of soil settlement in the field and modeling are 1.36m and 1.41m, respectively. Furthermore, the value of the lateral displacement from monitoring ranges from 40-70cm on the surface. Meanwhile, from the results of numerical modeling, the total lateral deformation is 36.7cm with lateral displacement value up to 4cm located up to a distance of ±10m from the soil improvement area. The availability of complete lab data and the determination of the right geotechnical parameters can be the main keys to produce accurate PVD and vacuum models."