Choy Soon Tan

Stabilization of Marine Clay by Biomass Silica (Non-Traditional) Stabilizers

The presence of marine clay in Iskandar Malaysia Region, Nusajaya had caused expensive solutions in the construction of structures and roads. Alternatively, soil treatment is suggested to increase the strength of the unsuitable material to meet the constructions requirement for foundation and also to achieve the specifications for development work. In this study, a series of laboratory test has been conducted to determine the potential of Biomass Silica (BS), one of the commercial brands namely “SH-85” to stabilize marine clay to form the basis of a strong, reliable land for construction of roads and building. Testing program involves obtaining specimens of marine clays from various locations at Iskandar Malaysia Region, followed by laboratory tests to determine the Atterberg limits and Unconfined Compressive Strength (UCS) for treated and untreated of marine clay soils. The proportions of BS added were 3, 6, 9, 12 and 15% and tested at 0, 3, 7 and 28 days curing periods. The results shows that the Plasticity Index (PI) was reduce with increment of BS content. While, an addition of BS content increase in strength treated soils 60 times more than untreated soils, which is gain in early 7 curing days period. This finding indicates the BS is a suitable stabilizer for the marine clay to become strong foundation for construction of road and building.

Using Project Performance to Measure Effectiveness of Quality Management System Maintenance and Practices in Construction Industry

This paper proposed seven existing and new performance indicators to measure the effectiveness of quality management system (QMS) maintenance and practices in construction industry. This research is carried out with a questionnaire based on QMS variables which are extracted from literature review and project performance indicators which are established from project managements theory. Data collected was analyzed using correlation and regression analysis. The findings indicate that client satisfaction and time variance have positive and significant relationship with QMS while other project performance indicators do not show significant results. Further studies can use the same project performance indicators to study the effectiveness of QMS in different sampling area to improve the generalizability of the findings.

Critical State of Sand Matrix Soils

The Critical State Soil Mechanic (CSSM) is a globally recognised framework while the critical states for sand and clay are both well established. Nevertheless, the development of the critical state of sand matrix soils is lacking. This paper discusses the development of critical state lines and corresponding critical state parameters for the investigated material, sand matrix soils using sand-kaolin mixtures. The output of this paper can be used as an interpretation framework for the research on liquefaction susceptibility of sand matrix soils in the future. The strain controlled triaxial test apparatus was used to provide the monotonic loading onto the reconstituted soil specimens. All tested soils were subjected to isotropic consolidation and sheared under undrained condition until critical state was ascertain. Based on the results of 32 test specimens, the critical state lines for eight different sand matrix soils were developed together with the corresponding values of critical state parameters, M, λ, and Γ. The range of the value of M, λ, and Γ is 0.803–0.998, 0.144–0.248, and 1.727–2.279, respectively. These values are comparable to the critical state parameters of river sand and kaolin clay. However, the relationship between fines percentages and these critical state parameters is too scattered to be correlated.

CYCLIC BEHAVIOUR OF JOHOR SAND

Series of laboratory testing on the investigation of soil liquefaction using cyclic triaxial test had been carried out by researchers around the world but many of the results are contradictory. Thus, it is important to first determine the condition in which the clean sand is most susceptible to liquefaction, then only the liquefaction susceptibility of sand matrix soils could be compared and discussed under this specific condition. This paper presents the undrained behaviour of Johor sand and sand mixed with fines (kaolin) from cyclic triaxial tests. Stress controlled triaxial test apparatus was used to shear the isotropically consolidated soil samples under undrained two-way cyclic loading until the initiation of liquefaction. The liquefaction was defined based on: (i) excess pore pressure was equal to effective confining pressure or (ii) double amplitude strain of 5 % was reached, whichever was achieved first. The results of two-way cyclic triaxial tests on clean sand showed that besides the cyclic stress ratio, the liquefaction resistance of the sand under undrained loading was proportional to effective consolidation pressure and density index. The Johor sand was more liquefiable at its loose state and under low effective consolidation pressure, when subjected to earthquake loading.

Effect of fines content on critical state parameters of sand matrix soils

Natural sand does always contain significant amounts of fine particles, known as sand matrix soils. The development of critical state for sand and clay are both well established. However, limited researchers focused on the sand matrix soils. This paper discusses the effect of fines content on the critical state parameters of sand matrix soils. Two types of plastic fines with different plasticity (kaolin and bentonite) were mixed into poorly graded Johor clean sand at different percentages to form the sand matrix soils. The critical state was obtained from the strain controlled triaxial compression test. All tested soils had been isotropically consolidated to four different effective confining pressures and sheared under consolidated undrained condition until the critical state was ascertained. The critical state line was plotted for each sand matrix soils on space and compression spaces. Based on linear regression analysis, the critical state parameters, M, λ and Γ were obtained and the ranges are from 0.807 to 1.102, 0.062 to 0.160 and 1.732 to 2.431, respectively. The trend of the critical state lines of sand matrix soils in both stress and compression space coincides with the concept of threshold fines content. The threshold fines content identified for sand-kaolin mixtures is 25 % kaolin while it is 20 % bentonite for sand-bentonite mixtures.

Plasticity Behaviour of Sand Matrix Soils

Natural sand does always contain significant amounts of fine particles, but previous study always assumes that the typical engineering characteristic of clean sand was remarkably representing as to all types of sand matrix soils. Studies reported that additional of plastic fines could either impose additional or reduce the liquefaction resistance of sand matrix soils. Therefore, the aim of this paper is to examine the plasticity behaviour of sand matrix soils through experimental study. The Atterberg Limit test was carried out on plastic fines mixtures and sand matrix soils. Results show that the plasticity behaviour is depending on the type of presenting plastic fines. The absorption of clay mineral is the key element to in manipulating the plasticity behaviour of plastic fines. It can be concluded that the absorption of montmorillonite is better compare to kaolinite.

Effect of Fines Content on Liquefaction Susceptibility of Sand-Kaolin Mixtures

Recent empirical observations reveal that not only the clean sand is susceptible to liquefaction hazard, both silty sand and clayed sand are also liquefiable. This paper presents the cyclic behaviour of sand-fines mixtures at various fines content. The sand-fines specimens were reconstituted by mixing clean sand with different percentages of plastic fines (kaolin) by weight to a constant relative density of 20 % using dry tamping method. The specimen had been tested with stress controlled cyclic triaxial test under consolidated undrained condition with effective confining pressure of 100 kPa, cyclic load of 0.1 kN and cyclic frequency of 0.5 Hz. The results show that the liquefaction resistance of sand matrix soils increased as fines content increased from 0 to 25 %, whereas this trend was reversed for value of fines content greater than 25 %. In fact, the 25 % of kaolin by weight is also the threshold fines content of sand-kaolin mixtures. Hence this finding justifies that the concept of fines threshold content could be used to significantly explain the influence of fines content on the liquefaction susceptibility of sand-fines mixtures.

Effect of Plasticity on Liquefaction Susceptibility of Sand-Fines Mixtures

The usability of the clay fraction as one of the criteria in the assessment of liquefaction susceptibility is questionable since year 2001. The use of plasticity index to replace clay fraction as a controlling parameter in the criterion is proposed. This paper aims to compare the usability of different parameter in describing the cyclic behaviour of sand-fines mixtures with various plasticity characteristics. The sand-fines mixtures were reconstituted by mixing clean sand with two types of plastic fines at different percentages by weight, at a standardized ratio of 80% of clean sand with 20% of plastic fines. All soil samples were mixed using the dry tamping method to achieve a constant relative density of 20% throughout the specimen. The soil specimens are tested with stress controlled cyclic triaxial apparatus under consolidated undrained condition, with an effective confining pressure of 100kPa. The soil specimens were considered liquefy when the value of pore pressure is equivalent to the initial cell pressure, resulting zeroes effective stress in soil specimen. The results showed that the liquefaction resistance of the sand-fines mixtures increased as the value of plasticity index increased. The plasticity index is a better indicator to describe the liquefaction susceptibility of sand-fines mixtures compare to clay content, plastic limit and activity.