Common Mistakes in Designing MSE Wall with Finite Element Method

Abstract:  Fast computer processors have made complicated engineering computation techniques, such as finite element method, that was once require hours and hours of computing time, has now been made possible to run all the computation in less than an hour. Since the early 2000s, the availability of commercial geotechnical finite element software combined with faster, smaller, and cheaper notebook computer has made finite element method more accessible to many engineers. However, it is very often the engineers learn just how to operate the software through the tutorial manual without really understand the underlying geotechnical engineering knowledge, they do not realize the old saying: “Garbage in garbage out”. This paper, albeit may not complete, tries to elaborate the common mistakes found in applying the finite element geotechnical software in designing geosynthetics mechanically stabilized earth wall. It does not consider the construction process of the reinforced soil wall where the fill is being built up, during which most of the geogrid strain is developed.
Download full paper: GTL-2018-11th ISG-Seoul-FEMonMSEDesign-S11-07

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PILE LOAD TEST FREQUENTLY ASKED QUESTIONS

There are a few available methods to obtain load-settlement curve of a pile. Likewise, there are many methods to determine the ultimate pile capacity from a load-settlement curves. Although pile load tests have been widely used over the past decades, there are still many questions regarding its practice and interpretation. Frequently asked questions include: when does a pile test considered to have failed? From an economic point of view, a failure in pile load test can cost quite a lot of money. To what load can the pile be loaded till it is considered to have failed? Can a pile loaded to failure still be used as a working pile? Is pile driving analyzer (PDA) test reliable? Can PDA test replace static load test? Is it necessary to calibrate PDA test results with static load test results? Why is PDA test result interpreted as 1 dimensional wave and not 3 dimensional? What is bidirectional pile load test (also known as O’cell)? When should O’cell be used? Can a pile tested with O’cell be used as a working pile? What are the differences between kentledge load test, static load test with reaction piles and bidirectional pile load test? Do the three different pile tests produce the same results? This paper aims to shed light on these questions.

Keywords: Pile static load test, Dynamic load test, Bidirectional test, Ultimate pile capacity, Fail Pile

Full paper download:Gouw-180617-Pile Load Test FAQ-published

DYNAMIC COMPACTION DESIGN GUIDELINE FOR PRACTICING ENGINEERS

ABSTRACT: During an earthquake, saturated fine sands tends to lose its bearing capacity due to the earthquake induced and accumulated excess pore water pressure. The phenomenon, known as liquefaction, is one of the earthquake hazards that need to be mitigated in an earthquake prone area such as the archipelagos of Indonesia. The occurrence of an earthquake cannot be prevented and, with the present knowledge, is difficult – if not impossible – to predict. However, liquefaction potential can be mitigated by carrying out proper ground improvement methods.   The most common ground improvement schemes that have been widely implemented in mitigating liquefaction potential of saturated fine sands in Indonesia are dynamic compaction and vibro-compaction. However, many practicing engineers are still not familiar with the methods. This paper presents the design, execution, and evaluation methods of dynamic compaction. Two case histories on real projects are also presented as examples.

Full paper download: 04-Gouw-2018-Jun-SEAGS-E-J-32-40-J04-DC-Proposed-Design-Guideline-a

Consolidation parameters – alternative to Casagrande and Taylor methods

ABSTRACT: For decades, consolidation parameters are derived graphically. Pre-consolidation pressure is derived by Casagrande method where technician has to pick the point of smallest curvature from e-log s’ curve. Coefficient of consolidations is derived by Taylor’s method where technician has to draw a linear line from deformation vs square root of time curve. Both graphical methods can lead to different results depending on the technician’s judgment. Given the same e-log s’ curve, pre-consolidation pressure determined by different interpreters easily varies by three folds. Great variations also obtained in determining coefficient of consolidation through Taylor’s method. As soil compresses, void ratio reduces and so does permeability, hence the higher consolidation pressure the lower coefficient of consolidation should be. However, it is often found that plot of coefficient of consolidation vs consolidation pressures goes up and down irregularly. The author tries to derive pre-consolidation pressure by ‘Parallel Rebound Method’, that is: first line is drawn through unloading part of e-log s’ plot, second line is drawn tangent through initial part of e-log s’ curve parallel to the first line, third line is the normal consolidation line. The intersection of the third line with the second line is the pre-consolidation pressure. With regard to coefficient of consolidation, Asaoka’s method is employed to determine 100% consolidation under constant load, certain degree of consolidation time is then decided to derive coefficient of consolidation. It was found that the resulted coefficient of consolidation curve reduces consistently with higher consolidation pressures. With the help of computer spreadsheet program and mathematical formulation, both methods appear to give consistent results. It was concluded ‘Parallel Rebound Method’ and Asaoka’s method lead to better results in deriving pre-consolidation pressure and coefficient of consolidation, respectively

Full paper download:170921s-19ICSMGE-GTL-ConsolidationParameters

EFFECTS OF PILE LATERAL MOVEMENT, PILE SPACING AND PILE NUMBERS ON LATERALLY LOADED GROUP PILES

ABSTRACT: Based on 3D finite element numerical analysis on 3×3 pile group Gouw and Hidayat (2015) suggested that that when base friction of the pile cap and the passive pressure acting against the pile cap are neglected, the effects of the pile cap thickness against group lateral efficiency is marginal and can be safely neglected. They also briefly mentioned that the center to center pile spacing and the lateral movement of the piles also affect the capacity of the laterally loaded group piles. To investigate the effect of the magnitude of pile lateral movement and pile spacing to larger pile groups, the study was continued by carrying further analysis on 5×5 and 9×9 pile groups, taking the same modelling assumption where base friction and passive resistance induced by pile cap were neglected. The study revealed that pile group lateral efficiencies were found to be larger when the center to center pile spacing were wider. It was also found the greater the number of piles in the group the lower the pile lateral efficiency. However, pile head lateral (horizontal) movement only have marginal effect on the lateral efficiency of group piles.

Full paper download: 170926s-PILE2017-GTL-Efffect of Lateral Movement

The Important Role of Execution and CQA/CQC Plans in Building with Geosynthetics

Matteo Lelli1, Gouw Tjie-Liong2, Riccardo Laneri3, Marco Cerro

Abstract: The use of geosynthetics for the construction of mechanically stabilized earth retaining structures is constantly growing in Indonesia. These structures have shown economic advantages if compared to traditional mass gravity retaining structures. However, the importance of their execution is sometimes underrated. Construction Quality Control and Quality Assurance plans are often meagre and sometimes even missing. Mechanically stabilized earth structures rely on the collaboration between the compacted soil and the geosynthetic reinforcement. If one of these two components is not properly installed or other factors such as drainage system do not comply with the project specifications, unsuitable structure deformations or even failures may occur. This paper aims to share some good construction practices in order to build reinforced earth structures using geosynthetics. Furthermore, the Authors propose some simple but effective testing procedures which can be included in CQC and CQA plans. The scope of this paper is therefore to give guidance to project Owners, Designers and Construction Companies to deliver cost effective, safe and durable geotechnical structures built with geosynthetics.

Full paper download: 171003s-GeonsintetikIndonesia2017

Gara-gara DUIT!!

Kalau saya cermati, corporate capitalist dunia serakah semua!
Semua mendorong dan selalu menginginkan GROWTH, PERTUMBUHAN.
Pertumbuhan apa? tidak lain tidak bukan berujung pada uang masuk sebesar-besarnya dan uang keluar sekecil-kecilnya. Alias untung sebesa-besarnya.
Lalu muncullah SALES-SALES atau lebih kerennya MARKETING (baik yang etis maupun tidak) yang berujung kepada mendorong manusia ke arah konsumerisme.

contoh: bank yang alih fungsi ikutan jualan asuransi !!

Semua hal di atas kemudian mendorong kepada persaingan-persaingan individu-individu dan perusahaan perusahaan. Baik persaingan sehat ataupun tidak sehat, dan yang celaka sering nampaknya sehat tetapi dibelakang menusuk.
Ketimpangan pendapatan pun terjadi, pendapatan CEO di US dengan pendapatan pegawainya bisa 400 kali lipat!! Apalagi di Indonesia!! Orang berkata itu wajar!! (Pandangan pebisnis dan ekonom).

Ujung-ujungnya, muncullah ketimpangan dan kesenjangan sosial yang semakin dalam, dan lahirlah kecemburuan sosial yang tidak jarang berujung lahirnya orang-orang radikal, teroris (dan ISIS mungkin?) seperti yang kita lihat sekarang.
Tidakkah kita berpikir bahwa pebisnis-pebisnis yang notabene “serakah” namun dihaluskan dengan bahasa “Pertumbuhan” juga sebenarnya radikal bila ditelaah lebih dalam? Radikal dalam mencari uang dan untung? Yang kemudian ditutupi dengan sedikit charity sana sini????

Itu dari sisi bisnis, kemudian dari sisi politik? Sama saja, dari uang berujung politik dan kekuasaan, berusaha saling menjatuhkan dengan segala cara. Serang menyerang, tata krama pun dilupakan (lihat saat kampanye presiden Amerika dan lihat sekarang saat demam pilkada di negara kita). Semua gara gara duit. GARA GARA DUIT.

Ah….. suka tidak suka, akui atau tidak, kita semua sudah jadi budak duit!! Jadi pantaskah manusia meng-klaim dirinya makhluk paling bermartabat?? Kawanan singa bila sudah kenyang ada kijang lewat tidak akan diganggu. Manusia??? Sudah manusiawi kah kita??? Atau kita tidak lebih dari binatang yang haus akan harta????

GTL, 3 Feb 2017

Computer Game = Narkoba Modern

Hai generasi muda, bila kalian bermain game lebih dari 2 jam sehari, sadarlah bahwa kalian sudah jadi KORBAN pencipta game.
Ketagihan game sama rusaknya dengan ketagihan narkoba!!!

Coba hitung berapa jam hilang dalam 24 jam hidupmu dalam bermain game. Jangan banyak alasan!!! Kalau anda mulai mencari cari alasan membenarkan diri untuk main game lebih dari 2 jam sehari, maka itu artinya kalian sudah jadi KORBAN KETAGIHAN NARKOBA MODERN BERNAMA COMPUTER/INTERNET GAMING!!!

Sebagian dari anda yang muda muda mungkin TIDAK SUKA dan langsung akan bereaksi. Membantah bahwa saya kuno. Bahkan membantah dan mengatakan: “Tanpa Game saya bisa mati!!”. (Maaf saja, mati saja sekalian!!)

Tapi kalau boleh saya saran: Baca 3x, endapkan, dan renungkan.

Anak muda harus berani berpikir dan bertindak KRITIS TERHADAP DIRI SENDIRI. Bersikap terbuka dan berkepala dingin, menampung, menimbang dan memikirkan pendapat / teori / tindakan orang lain dan diri sendiri. Memakai otak secara jernih.

Lalu harus BERANI MENGAKUI KESALAHAN DIRI SENDIRI. Dan tidak hanya pandai dalam mencari-cari alasan untuk pembenaran diri. Karena kalau anda selalu bereaksi dengan mencari-cari alasan untuk pembenaran diri, atau bahkan lebih jelek lagi berusaha menyerang balik. Maka itu artinya anda membuat tembok tinggi terhadap kemajuan diri anda sendiri.

Setelah berani mengakui kesalahan diri sendiri, harus lalu berusaha SELALU MEMPERBAIKI DIRI dan MENCARI KEBENARAN yang HAKIKI. Bukan kebenaran yang membenarkan diri sendiri.

Ingat semakin tua semakin sulit mengubah diri. Pohon selagi tunas muda bisa dengan mudah dipindahkan, setelah besar, tua dan berakar dipindahkan akan sangat sukar dan bahkan bisa layu dan mati.

Saya pun bukan orang yang hebat, bukan orang yang baik, bukan orang yang pandai, apalagi sempurna. Sayapun sering malas, sering ingin yang enak-enak saja. Namun saya berpiir harus MENDISIPLINKAN DIRI. Dan perlu selalu belajar dan belajar, belajar memperbaiki prilaku diri dan memperbaiki pengetahuan dan tindakan saya sehari-hari.

Terlalu banyak di dunia ini untuk dipelajari. Namun terlalu singkat waktu yang kita miliki.

Bermain itu boleh, relax itu perlu, tetapi hidup harus memiliki PRIORITAS dan DISIPLIN DIRI. KESEIMBANGAN HIDUP sangatlah perlu.

Percayalah, tulisan itu ungkapan hati seorang ayah, seorang guru dan seorang dosen yang menangis dan sangat terluka hatinya karena melihat anak muda didekatnya menghabiskan waktu terlalu banyak dalam internet gaming.

GTL, 5 Feb 2017

HIGH HYBRID REINFORCED SOIL SLOPE AS RUNWAY SUPPORT – A CASE STUDY

Abstract: The use of hybrid Reinforced Soil Slopes combining anchored gabion units and high strength geogrids for infrastructures development is growing in Indonesia. Hybrid RSS are considered a valid and competitive alternative to other traditional earth retaining structures. Despite this growth, civil engineers and construction companies are not yet familiar with the related design and construction aspects. This paper intends to share the Author’s experience regarding the design and the construction of the first stage of a 25 m high hybrid RSS for the new touristic airport at Central Sulawesi, Indonesia. It is worth to note that the RSS was built on soft and weathered clay shales and cohesive backfilling materials were used as part of the reinforced soil mass. This paper aims to present the main technical issues related to the project, the design process, which was carried out using both FEM and Limit Equilibrium method software, and the relevant construction aspects.

Download for full paper: 161107-11-gtl-6th-arc-on-geosynthetics