International Journal of Innovative Technology and Exploring Engineering (IJITEE) ISSN: 2278-3075, Volume-8 Issue-9, July 2019 3154 Published By: Blue Eyes Intelligence Engineering & Sciences Publication Retrieval Number: H7457068819/19©BEIESP DOI:10.35940/ijitee.H7457.078919 Abstract: Sand is known as the main material in land reclamation works to develop and widen an area. It is important for the Geotechnical Engineer to ensure the sand used can accommodate the burden imposed from the structures to be built on it. Previous researchers have conducted studies on the strength of sand, whether focusing on the sand itself or with the presence of fines. However, the study of sand grain size effects in sand mixtures in affecting sand behavior is extremely limited. The sizes and angularity of the sand particle are believed to contribute to the behavior of sand mixtures soil. Hence, the study to investigate the effect of sand grain size on sand mixtures in term of undrained strength is being carried out. The sand was sieved to coarse sand, medium sand and fine sand then each size was mixed with kaolin at 0 %, 20 % and 40 %. The undrained strength was obtained from triaxial test on undrained condition. As a result, it is found that the maximum deviator stress, q max increases with the decrease of fines (kaolin) content. On the other hand, at the same fines content, increased of sand size leads to the increased of q max, which means the increased of undrained shear strength. In addition, the angular shape of sand particle was thought to contribute to the high value of undrained shear strength for the sand mixtures. Index Terms: Shear strength, kaolin, coarse sand, medium sand, fine sand. I. INTRODUCTION Sand in natural condition may have an amount of fines, whether as plasticity fines or non-plasticity fines or both. For many years, research related to the effects of fines content in sand fine mixtures was found well studied. In the past 5 years, studies on engineering behaviour of sand composed of various amount of fines have been conducted by [1], [2], [3], [4], [5], [6] and [7]. Loss of shear strength may lead to liquefaction phenomenon in granular soils. Shear strength of granular soils may decreased or increased with the presence of fines. This behaviour was proven by [8], in which they showed that the strength of mixtures reduced with increases of silt from 0 % to 30 %, then the strength increases thereafter. This transition is known as a threshold value. However, [9] show the transition occurs between 20 % to 40 % of fines content. As reported by [10] on the characteristics of liquefied soils, natural liquefied soils occured at various fine content from 15 % to 70 % of fines. However, other factors as pointed Revised Manuscript Received on July 10, 2019. Bakhtiar Affandy Othman, Malaysia-Japan International Institute of Technology, Universiti Teknologi Malaysia, Kuala Lumpur, Malaysia. Aminaton Marto, Malaysia-Japan International Institute of Technology, Universiti Teknologi Malaysia, Kuala Lumpur, Malaysia. Faizal Pakir, Faculty of Civil and Enviromental Engineering, Universiti Tun Hussein Onn Malaysia, Batu Pahat, Johor, Malaysia. Amirzaki Salikin, Research Centre of Soft Soil (RECESS), Universiti Tun Hussein Onn Malaysia, Batu Pahat, Johor, Malaysia. out by [11] such as confining pressure, type of soil, relative density of soil, particle size and gradation of the soil, depositional environment, aging and cementation as well as historical environment need to be considered. The relationship of fines content with minimum void ratio, e min and maximum void ratio, e max had been studied by [12]. As mentioned by [13], the value of e max and e min are influenced by the grain shape, as example, decreases of angularity will decreased the value of e max and e min . Research conducted by [14] stated that the engineering behaviour of soils is influenced by the shape of particles. It can be seen from the study done by [15] on various types of sand such as natural sand and crushed sand; they found that the critical state parameters, Γ increase with decreased of particle shape in term of roundness, R. [16] highlighted that the frictional strength is strongly influenced by particle shape; as an example, shearing resistance increases with increases of angularity of particles due to the decreases of ratio of rolling to sliding contacts. [17] summarized some results from year 1968 to 1999 on the effects of particle size gradation on liquefaction resistance. From the research results, some researchers claim that mean grain size (D 50 ) of 1.0 mm to 0.1 mm causes decreasing in liquefaction resistance, while some researchers show that the D 50 = 0.08 mm is more susceptible to liquefaction. Based on the research done by previous researcher, evaluation on field case histories of liquefaction potential for 50 years around the world have been figured out by [18]. From Figure 1, [18] concluded that about 78 % liquefaction out of 155 incidents occur when the mean grain size, D 50 is lied between 0.113 mm to 0.338 mm. [17] show that there is no relationship can be concluded between the coefficient of uniformity, C U and coefficient of curvature, C C with the cyclic resistance. The results have been shown to be in agreement with [19]. Figure 1 D 50 for liquefied soils [18] Influence of Grain Sizes on Undrained Strength of Sand Mixtures Bakhtiar Affandy Othman, Aminaton Marto, Faizal Pakir, Amir Zaki Salikin