Abstracts – Vol. 47 No. 4 December 2016

Professionalism and Ethics of Engineering

By Z.C. Moh

ABSTRACT: Ethics is the branch of philosophy that involves systematizing, defending, and recommending concepts of right and wrong conduct. Ethics is qualitative. It may change with time, circumstance and environment. Practice of ethics requires proper understanding of the time frame. Many professional engineering organizations have a set of Code of Ethics or Code of Practice to regulate or guide their members. Basically they all center around public welfare, sustainable development, professional competence, truthful and faithful, honorable, responsibly and lawfully. Success of engineering projects not only depends upon the engineering professional, but it also closely related to other non-engineering professionals. In the paper, discussions are presented about engineering.

Recent Advances in Pile Testing and Diaphragm Wall Constructions in Japan

By K. Ishihara

ABSTRACT: The first part of this paper consists of brief introduction of the in-situ pile loading tests that have been conducted in Japan over the last two decades in connection with the design and construction of high-rise buildings in areas of soft soil deposits. In addition to the conventional types of tests in which the load is applied at the top and at the toe of the pile (O-cell test), what may be called “pile toe bearing test” and “skin friction test” is introduced. The results of these tests are described and compared with those from the conventional type of the pile loading tests. In-situ prototype tests are also introduced in which bearing power of Barrette type pile is compared with that of the circular type pile.  A special case of in-situ pile loading tests conducted in Singapore is also introduced in which the friction between the circular ring-shaped concrete segment and the surrounding soil deposit was measured directly during excavation of the shaft by applying loads up and down by jacks installed between two adjacent segments in vertical direction. The second part of this paper is a brief description on constructions of large-diameter circular diaphragm walls that was carried out about 10 years ago for the LNG storage tank in the coastal site in Tokyo Bay.  The construction of the large-scale Kawasaki Island in the middle of Tokyo Bay in Japan will also be introduced. The whole scheme and process of construction is for these two undertakings is introduced with some comments on observed behaviour of the walls and on special precaution taken during construction.

Innovation in Soil Improvement Methods

By J. Chu

ABSTRACT:  To mark  Prof  S.  L.  Lee’s contributions to the  research  and  development on soil  improvement,  some  of  the innovative  methods developed  by Prof.  Lee  and  his  team are  reviewed.  These  include  the  dynamic  replacement  and  mixing  method  for  the improvement of peaty soil, the layered clay-sand method for land reclamation using clayey fill, and the biodegradable fiberdrain. Other new soil improvement methods in the related areas are also presented to illustrate the role of innovation in the advancement of soil improvement technologies. These include the drainage enhanced dynamic compaction method for the improvement of clay layers, the underwater dynamic replacement method for the treatment of seabed clayey soil, the vacuum preloading with horizontal drains method, methods to form working platform on top of soft fill for land reclamation using soft fill materials, the NEUSpace method for land reclamation in deep water, and the new types of prefabricated vertical drains (PVDs). Methods for mitigation of liquefaction hazard, making water pond in sand, and prevention of dike failure from over topping using biotechnologies
are also introduced.

KEYWORDS: Land reclamation, Soft soil, Soil improvement, Vacuum preloading, Vertical drains, Horizontal drains

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Lessons Learned from Designing High-rise Building Foundations

By H.G. Poulos

ABSTRACT: The design of tall building foundations involves a systematic process which incorporates ground investigation, ground characterization, preliminary design of the foundation system for the anticipated structural loads, detailed foundation design, load testing of the proposed foundations, modification of the foundation design, if appropriate, and monitoring of the foundation performance as construction proceeds. This paper will describe this process and some of the tools available for implementing the process. It will then set out a series of lessons learned during the design of such foundations, and illustrate these lessons with examples from projects in Asia and the Middle East.

KEYWORDS: Analysis,Design, Foundations, Ground Interpretation, Piled raft, Settlement.

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A Critical Review of Rail Track Geotechnologies Considering Increase Speeds and Axle Loads

By Buddhima Indraratna, Sanjay Nimbalkar and Cholachat Rujikiatkamjorn

ABSTRACT: Ballasted railroads are designed to provide high speed commuter and heavy haul transportation. Ballast is one of most important load bearing components of the track substructure. However, it often experiences excessive settlement, lateral deformation and particle breakage when subjected to large dynamic (cyclic and impact) stresses. In addition, tracks constructed along coastal areas often undergo large settlements over soft compressible estuarine deposits , leading to frequent and costly track maintenance. The use of artificial inclusions such as geogrids, geocomposites, shock-mats (rubber) and prefabricated vertical drains (PVDs) are attractive options to maintain the vertical and horizontal alignment of tracks and to curtail excessive maintenance costs. This critical review paper provides a deeper insight to the recent advancements in rail track geotechnology at increased train speeds and axle loads.

KEYWORDS:  Ballasted railroads, Cyclic loads, Particle breakage, Geosynthetics, Prefabricated vertical drains

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Performance and Analyses of Thick Soft Clay Deposit Improved by PVD with Surcharge Preloading and Vacuum Consolidation – A Case Study at CMIT

By P.V. Long, L.V. Nguyen and A.S. Balasubramaniam

ABSTRACT: Ground improvement using PVD was applied successfully for increasing foundation stability and controlling residual settlements of the container yard constructed on 35m thick soft clay deposit at CMIT, Vietnam. The treated area is about 40ha including vacuum consolidation combined with 6.3m embankment surcharge for a strip of 57 m along the river bank (VCA) and conventional surcharge preloading using 9.1m sand fill embankment for the remaining area.  The monitored data indicated that PVD thickness of 3 mm arranged in spacing of 0.9 m to 1.2 m can be used successfully for improvement of thick soft clay deposit in both methods of embankment preloading with and without vacuum pumping.  Performance of reduced embankment combined with vacuum pumping is very much better than that of conventional embankment preloading in terms of shortening construction time, reducing lateral displacement, increasing stability, and minimizing residual settlement. Back calculated ch value is dependent on the assumptions of smear effects including smear zone ratio, d/dm and permeability ratio, Rs=kh/ks. For ds/dm= 2 as commonly used, the back-calculated ch value is directly proportional to Rs and the value of Rs in vacuum consolidation seems significantly smaller than that in embankment preloading. Using the back-calculated results of compressibility and flow parameters, the time-settlements re-calculated by 1-D method are in very good comparison with measured data for both conventional preloading and vacuum consolidation considering the vacuum pressure as an induced vertical stress distributed uniformly in the PVD zone.  Analyses of factor of safety from observed pore pressures during embankment construction illustrated that the commonly used stability chart as given by Wakita & Matsuo (1994) is too conservative for PVD improved soft ground. Secondary compression behavior of thick soft ground improved by PVD including back calculation for coefficient of secondary compression and estimation of long term residual settlement have also been provided.

KEYWORDS: Settlement, Soft clay, Ground improvement, PVD, Vacuum consolidation

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Characteristics of Hardpan Calcrete of the Nyalau Formation and Impact on Design of Foundations

By A.C.Y. Sim, D.E.L. Ong, L.Y. Tai, W.H. Ting, E.P.S. Chai and J. Bachat

ABSTRACT: Nyalau Formation, found in Bintulu Division in Sarawak, Malaysia was formed by a thick array of shallow water marine and paralic sedimentary rocks. The formation is of predominantly sandstone origin and also the lesser known ‘limestone’ which is described as hardpan calcrete in this paper. Changes of sea levels during the mid-Pleistocene epoch resulting in the formation of raised terrace wheremarine deposits sedimented and subsequently followed by depositions of the coastal alluviums and inland peat swamps. The interaction of the depositions may have contributed to the formation of the hardpan calcrete. Laboratory tests such as petrographic thin section, X-Ray Diffraction (XRD), uniaxial compressive strength, point load tests, in-situ static load tests had been carried out on the hardpan calcrete to obtain the engineering design parameters to formulate a possible detailed design methodology on shallow foundation and its as sociated construction work progress. Several practical and effective solutions had also been proposed at locations where the hardpan calcrete layer was present. Use of finite element analyses in design has also successfully provided valuable in-sights into the complex soil-structure interaction.

KEYWORDS: Nyalau Formation, Hardpan calcrete, Shallow foundations, Foundation load tests

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Ground Improvement via Vacuum Consolidation Method in Vietnam

By T.H. Seah, T.B. Kim and T.D. Nguyen

ABSTRACT: In recent years, vacuum consolidation method has been extensively used in Vietnam on various types of infrastructural projects. The main reason for adopting this method is that the construction cost is relatively close to the conventional prefabricated vertical drain method with less surcharge fill and shorter construction time. Hauling or transporting large amount of fill has been a major problem in most infrastructure projects. With the stringent settlement requirements specified by the Vietnamese Government, ground improvement via vacuum consolidation has become very popular hence attracting various International vacuum consolidation specialists to participate in Vietnamese projects. This paper describes the vacuum consolidation design and the construction practice in Vietnam along with some examples on the performance of vacuum consolidation works for highway projects.

KEYWORDS: Vacuum consolidation, Vertical drain, Surcharge, Highway.

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Laboratory Study on Dynamic Properties of Compacted Residual Soil in Malaysia

By Y. Tanaka and M.L. Lee

ABSTRACT:  This paper examines the dynamic deformation properties of a selected residual soil sample in Malaysia through a series of laboratory tests. The laboratory tests conducted include cyclic triaxial tests on the compacted residual soil with a measurement of deformation responses at small strains, and shaking table tests on a small soil block whereby the acceleration responses at different levels were analysed. The results showed that the dynamic deformation properties of the soil, namely the variation of shear modulus over a shear stain were ranging between 10-5 and 10-2. The results showed that the laboratory apparatus used herein were capable of evaluating the deformation properties of residual soil, and the G values obtained were comparable to those published data.

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On The Preconsolidation Pressure: Experience Based on Testing the Holocene Marine Clay of Peninsula Malaysia

By M.J. Dobie

ABSTRACT:  Prediction  of  the  consolidation  settlement  of  very  soft  alluvial  clays  in  general  requires  knowledge  of  the  compressibility characteristics of the deposit, but in particular it requires an accurate determination of the preconsolidation pressure.  This defines the value of vertical effective stress where settlement behaviour changes from overconsolidated (OC) to normally consolidated (NC).  In the OC stress range  settlements  are  likely  to  be  relatively  small,  but  once  into  the  NC  range,  they  can  become  very large.    Therefore  the  accurate determination of the preconsolidation pressure is essential if reliable consolidation settlement predictions are to be made.  This is examined in detail by back analysing settlement data from two trial embankments which were built over 13m of Holocene marine clay at Juru (south of Butterworth),  as  part  of  the  geotechnical  investigations  carried  out  for  the North-South  Expressway  project over  the  period  1990  to  1991, then   making   comparisons   to   settlement   calculated   from   measured   compressibility   properties.    The   definitive   determination   of preconsolidation pressure is derived from the behaviour of the trial embankment itself,  which is then compared  with assessments based on undrained shear strength, oedometer test results and piezocone tests.  Issues and potential misuse of all these test methods are examined, and test procedures described to minimise related inaccuracy.

KEYWORDS: Preconsolidation pressure, Holocene marine clay, Embankment settlement, Oedometer, Undrained shear strength, Piezocone 

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Tunnelling Past Critical Structures in Kuala Lumpur: Insights from Finite Element Analysis and T-Z Load Transfer Analyses

By C.W. Boon and L.H. Ooi

ABSTRACT:  The contribution of this paper is the discussion of three case histories of tunnelling past critical structures. The first case history is on a 15-storey tower building seated on a raft foundation. The analyses provide insight with regard to the need to adapt the TBM operating performance, as the presence of the building is found to be capable of inducing larger volume loss. The second case history is on a flyover bridge, of which the pile toes are at an elevation higher than the tunnel crown. In the third case history, the piles of a Light Rail Transit (LRT) bridge were in the way of the tunnel. The piles had to be removed and underpinned with new piles which terminate below the tunnel invert. For these two case histories, we demonstrate the use of the load transfer t-z and Q-z method (Seed & Reese, 1967), which can be implemented easily into a spreadsheet, to estimate the pile settlements induced by tunnelling. The load transfers on the piles were found to be affected by (i) the soil settlement trend, which could be either increasing or decreasing with depth, and (ii) the shaft and end-bearing stiffness. The potential influences of (i) a soft base for bored piles and (ii) pile groups are discussed. Finally, insights obtained from the t-z and Q-z analyses are used to derive the influence zones due to tunnelling, and they show similar trends to the influence zones previously proposed by Jacobsz et al. (2004) derived from centrifuge tests. The line joining the points of inflection of multiple subsurface Gaussian settlement profiles (Mair et al., 1993) at different depths was found to define the boundary at which the trend of soil settlement changes from increasing with depth to decreasing with depth.

KEYWORDS: Tunnelling induced settlements, Face pressure, T-Z method, Load transfer method, Influence Zone

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A Comparison of Performance of Deep Excavation using the Top Down and Bottom Up Methods in Kenny Hill Formation

By J.G. Tan and L.H. Ooi

ABSTRACT: This paper presents the comparison of performance between two deep retention systems using the Top down and Bottom Up methods in Kenny Hill Formation. Both the deep excavations are for the Klang Valley MRT underground stations; namely the Bukit Bintang and Merdeka stations which have similar retained depth of 33.5m and 31m respectively and both having 1.2m thick Diaphragm walls. Both the stations are designed with the same design criteria and factor of safety. The selection of type of retention systems, strutting system, construction sequences and timing and instrumentations are discussed. The predicted and measured diaphragm walls displacements and Strutforces at different stages are then compared and discussed.