Shear strength of Kerteh beach sand based on direct shear test / Noor Ezlyn Othman

The soil at the proposed site for embankment construction in Kerteh has been identified as loose sandy soil based on the in situ test conducted during the planning stage. The soil strata for the study area generally consist of layers of loose sandy silt to loose silty sand begins from depth of 15 meters from the surface. Dynamic Compaction and Vibro Compaction ground improvement work were performed at the area to improve the top 6 m. Quality tests using Cone Penetration Test (CPT) were conducted on site. However, the pre treatment CPT has qc values not correlated with laboratory test, therefore, the cohesion, c and internal resistance, 0 is unknown. Laboratory direct shear test using electronic-controlled ELE DS7 software has been proposed as part of the overall study on the sandy beach area in Kerteh, in which the loadings for the direct shear test are based on the actual stress experienced by the soil samples at site. Result of the direct shear test in terms of angle of shearing resistance, 0 has been compared with the 0 determined from Robertson and Campanella (1983) correlation. The mean angle of shearing resistance from the direct shear test was found out to be 30°, indicating that the Kerteh Beach sand was in loose state and of type silty sand (Budhu, 2002). Soil type obtained from sieve analysis has also verified the type stated by Azazi et. al (2004). Analysis on the effect of fine content on 0 showed that the fine content had no direct influence on 0. However, while presence of less than 10% of fine content cannot be directly related to the value of 0, it may cause a significant difference when compared to 0 obtained from Robertson and Campanella (1983) correlation. For fine content higher than 10%. no conclusions could be made because all the tested samples had less than 10% fine content. It was found out that the correlation may give more accurate value at 0 values ranging between 31-35°. The direct shear test result also revealed that as the c value increases, the 0 value will decrease. For cohesion ~ o kPa, the average differences between both correlated and direct shear 0 was 3.4 %.