25
Jul

Pile Load Test Frequently Asked Questions

Written by Gouw Tjie Liong, Ir., M.Eng, ChFC, PhD. Posted in GTL Paper, Publication

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

25
Jul

Dynamic Compaction Design Guideline for Practicing Engineers

Written by Gouw Tjie Liong, Ir., M.Eng, ChFC, PhD. Posted in GTL Paper, Publication

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

14
Oct

Consolidation parameters – alternative to Casagrande and Taylor methods

Written by Gouw Tjie Liong, Ir., M.Eng, ChFC, PhD. Posted in GTL Paper, Publication

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

Geotechnical Course

  • Soil Mechanis
  • Soil Investigation
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  • PIT, PDA, Sonic Logging
  • Slope Stabilization
  • Geotechnical Instrumentation
  • Deep Excavation
  • Ground Improvement
  • Geotechnical Instrumentation
  • Earthquake
  • Liquefaction Analysis
  • Application of Geotechnical Software
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