Design of earth structures reinforced with polymeric and metallic reinforcements using limit equilibrium methods

Abstract: The use of planar polymeric and metallic reinforcements in mechanically stabilized earth structures has been growing in Indonesia in the last few years. This modern technique has been evaluated to be competitive if compared to other traditional earth retaining structures and has been safely employed in strategic infrastructure development projects in Indonesia. At the same time, there is still a lack of knowledge regarding the design methodologies for the mentioned structures among Civil Engineers. At present, there are two main currents followed by Engineers in order to design reinforced soil slopes and walls: Limit Equilibrium (LE) methods and Finite Element analysis. Several LE methods have been developed for slope stability analysis in the last decades, each is based on different assumptions and hypothesis and all of them utilize the well-known Mohr-Coulomb expression to determine the available shear strength along a potential sliding surface. The aim of this paper is to present the design basis of MSE walls/slopes using Janbu modified and Bishop modified Limit Equilibrium methods. The paper describes also how to include the presence of planar reinforcements in the LE formulations for the global stability and internal stability checks according to the so called “rigid model”. Moreover, the procedure to properly calculate the long-term tensile strength of the planar reinforcements to be used in the LE formula will be presented.

Download full paper: Paper 4_GEO_Indonesia_2016_Lelli_RS design with LE methods


Abstract: Having the origin from the sedimentation of volcanic materials, many experienced Indonesian geotechnical engineers have long suspected that Jakarta reddish and grayish clay may have different characteristics compared to other clayey soils known in many geotechnical text books. Despite of carefully derived design parameters, experiences in the execution of deep excavation, be it open cut slope or protected excavation by either contiguous bored pile or diaphragm walls, often show that the performance of the geotechnical structures were better than predicted by the available design geotechnical software. Although, some engineers have started using more advanced constitutive soil models, such as: Hyperbolic and Cam Clay models. Undoubtedly, many engineers still use the bilinear Mohr-Coulomb model in their analysis. So far, to the author knowledge, there is no published paper discussing about the suitability of the soil models for modelling Jakarta red clay, in particular. Therefore, the author tried to find out which soil constitutive models can better predict the behavior of the Jakarta reddish/grayish clay. Available models in PLAXIS software, e.g.; Mohr-Coulomb, Hardening (hyperbolic), and Soft Soil models, were tried by simulating isotropically consolidated undrained triaxial test and compared it with the actual test data. At this stage it was found that none of the model can correctly predict the stress strain curve neither the correct stress path.

Download Full Paper: GOUW-2014-1021-FindingSuitableModel

Expanded Polystyrene for Road Embankment on Soft Clay

ABSTRACT: Instability and  intolerable deformation always be the problems in constructing high embankment over soft/ loose soils. The prime cause of the problems is the load exerted by the self-weight of the embankment fill itself. Therefore, whenever possible, the use of lightweight materials, such as Expanded Polystyrene (EPS) foam, for the embankment fill will certainly be one of the best solution. This technique has been implemented in the Scandinavian countries. Seeing that it may also be implemented in our country, Indonesia, this paper tries to introduce the engineering characteristics of the EPS foam, as obtained from manufacturer, together with its design aspects.

Download Full Paper: GTL-001-1990_(R) Expanded Polystyrene for Road Embankment on Soft Clay

Effect of Pile Cap Thickness and Magnitude of Lateral Movement on Group Capacity of Laterally Loaded Piles

ABSTRACT: The capacity of laterally loaded group piles are conventionally analyzed by simply reducing the lateral subgrade reaction of the soil, kh. The lateral subgrade reaction is reduced to 0.35 kh, when the piles center to center distance is at 3 pile diameter and linearly increases up to 1.0 kh when the piles center to center distance is equal or higher than 8 pile diameter. It seems there is no consideration to the thickness of the pile cap and magnitude of lateral movement of the piles on this conventional approach. By using 3D finite element geotechnical software, the effect of these two factors can now be investigated. This paper presents the study on the impact of those two factors on lateral capacity of group piles. The study reveals that when base friction of the pile cap and the passive pressure acting against the pile cap is neglected, the effects of the pile cap thickness against group lateral efficiency is marginal and can be safely neglected. The center to center pile spacing and the lateral movement of the piles do play important roles in the capacity of the laterally loaded piles. The greater the pile spacing the greater the lateral group efficiency, so does the lateral movement.

link to download full paper:

Seberapa Besar Pengaruh Efek Gangguan dan Hambatan Alir pada Prefabricated Vertikal Drain ?

Sejauh ini teknik perbaikan tanah yang terbanyak diaplikasikan di Indonesia adalah aplikasi vertikal drain untuk meningkatkan kuat geser undrained dan untuk mempercepat penurunan konsolidasi pada tanah lempung lunak. Terdapat banyak makalah-makalah akademis yang mengatakan bahwa efektifitas vertikal drain perlu diperhitungkan terhadap efek gangguan saat pemasangan (smear effect) dan efek hambatan alir (drain resistance). Makalah ini menganalisa dan membahas seberapa besar efek dua faktor tersebut dalam kasus nyata di dua proyek perbaikan tanah di Balikpapan dan Bontang, Kalimantan, Indonesia. Dari analisa data-data penurunan dan monitoring piezometer terlihat bahwa efek gangguan dan efek tahanan alir tersebut dapat dikatakan tidak berarti. Dengan kata lain dalam proyek dengan vertikal  drain yang dipasang sedalam 12 dan 27m ini kedua efek tersebut dapat diabaikan.

Download full paper: GOUW-2015-1125-EfekGangguan-HambatanAlir-PVD



Abstract: The application of geosynthetics for reinforced earth, also known as mechanically stabilized earth, is gaining popularity in Indonesia. At the same time, many engineers have started using geotechnical finite element software in designing the geosynthetics reinforced earth. Unfortunately, many of them still do not know the importance of elongation factor in determination of the geosynthetics stiffness to be input into the finite element calculation. Some engineers even said that elongation of the geosynthetics need not be considered in selecting the right geosynthetics material, only the breaking strength and the type of geosynthetics need to be considered. Such misconception can lead to bad performance or even failure of the geosynthetics reinforced earth. This paper elaborates the importance of the elongation factor and the correct procedure in determining the stiffness of geosynthetics materials for finite element software input.

Keywords: Elongation, stiffness, geosynthetics, finite element analysis

Download full paper: Gouw-2015-0927-ElongationFactorinGeosynthetics-Proc-SLOPE 2015

DISC – Penggolongan Kepribadian

Prilaku manusia bisa dikategorikan dalam 4 huruf DISC. Yang artinya lebih kurang:

D = Dominance,
Kategori orang yg menekankan hasil nyata dan mempunyai tingkat keyakinan tinggi. Tipe No nonsense. Biasanya selalu melihat gambaran besar (sasaran akhir), berani menerima tantangan2, bicara lurus dan tidak bertele-tele.
Biasanya pemimpin besar politik masuk kategori ini. Contoh: Churchill, Lee Kuan Yew, Lincoln dll.

I = Influence,
Kategori orang yg menekankan mempengaruhi/merayu orang, keterbukaan dan hubungan satu sama lain. Prilaku umum: antusiastik, optimistik, suka kerja sama, dan sangat tidak suka kalau diacuhkan.
Biasanya artis2 tergolong ini.

S = Steadiness,
Orang yg menekankan kerja sama, ketulusan dan ketergantungan satu sama lain. Prilaku utama: tidak suka diburu-buru, pendekatan masalah tenang termasuk alon alon asal ke lakon, supportive dan sederhana.
Biasanya orang2 jenis ini tidak suka perubahan. Tipe ingin hidup tenang, intrinsik agak tidak suka tantangan baru. Memerlukan dorangan seorang pemimpin.

C = Conscientious,
Orang yg menekankan kualitas, akurasi, presisi, keahlian, dan kompetensi.
Prilaku utama: menikmati ketidak-tergantungan pada orang lain (independen), selalu mencari alasan objektif, menggali hingga detail, was was kalau kalau berbuat salah.
Engineer harus mempunyai sifat ini.

Kalau digambarkan dalam figuratif binantang adalah sbb:

D = Hiu
I = Teddy bear
S = Domba
C = Burung hantu

Termasuk golongan manakah anda?

Live like a Pencil

A Pencil Story
I believe I was born for a purpose!
I hesitated what I am for?
I seek and realized I am born to write!
To write meaningfully…
And I start writing…
Inherently, at times I make mistake…
But I know mistake is only a word…
And I can learn from the mistake…
Mistake is a clue to redo,
Redo in a different way,
I have the in built power
to get up and make correction!
One of the days I do worn up,
I was dull and blank….
However, I believe what is important is inside,
So, I go and sharpen myself,
To dig the inner side of me,
And I find I can write even better.
Although my life is getting shorter,
and will eventually die off..
But I know, what I will leave behind is a legacy for the world to read and learn!!
(GTL-SG-MRT-150818 freely rewritten from BillyK)

A Geotechnical Short Course on Ground Improvement


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Jakarta, 1-3 September 2015

Covering theoretical design calculation,execution, monitoring and interpretation. Practice design and data interpretation session shall be given.

  1. PRECOMPRESSION With VERTICAL DRAINS: Basic Principles, Type of Vertical Drains, Application, Design Method and Calculation, Installation, Instrumentation, Monitoring, Interpretation, Asaoka Method, and Case Histories.
  2. VACUUM PRELOADING: Surcharging vs Vacuum Method; Execution; Monitoring System; Improved Ground; Application Examples and Case Histories (with projects in Indonesia and Vietnam)
  3. Liquefaction potential analysis:What is Liquefaction; Liquefaction Phenomenon; Liquefaction induced Damages; Identifying Liquefaction Potential; Cyclic Stress Ratio – CSR; Assessing Liquefaction through SPT data; Assessing Liquefaction Potential through CPT data; Liquefaction of Deeper Layer; Calculation Examples. Analysis of Liquefaction potential by using Novo Liquefaction software shall be given.
  4. DYNAMIC COMPACTION: Equipment, Mechanism, Execution procedure, Design Guidlines and Case Histories.
  5. VIBROCOMPACTION – VIBROFLOATATION – STONE COLUMNS: Vibro Compaction Mechanism, Dry Process, Wet Process, Vibroflotation, Vibrocat, Stone Columns, Design Guidelines, Case Histories.
  6. JET GROUTING: Various Grouting Techniques, Equipment, Execution, Formation, Cementand Composition, Application of Jet Grouting.

click here for detail, 2015-09-010203 – Course Ground Improvement