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

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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

PENDIDIKAN UNTUK KEMAJUAN INDONESIA

Manfaatkan dan tingkatkan mutu pendidikan demi kemajuan Indoensia, sebuah wawancara Gouw dengan majalah Konstruksi tahun 1997, lengkapnya bisa dibaca dengan klik link ini: konstruksi-253-mutu-pendidikan-utk-kemajuan-indonesia-1997a

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

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

AN INVESTIGATION ON THE SUITABILE CONSTITUTIVE LAW FOR MODELLING JAKARTA RED CLAY

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