Tensile strength of compacted clayey soil

The tensile strength of soil has a significant role in the development of tensile cracks, which is a common sight in many earth structures such as slopes, backfills, and dams. Such tensile cracks can result in the failure of the earth retaining structures during rainy period. The Brazilian tensile test (ASTM D3967 – 16, 2012) measures the tensile strength of a rock indirectly. However, in this project, the Brazilian tensile test is applied to compacted clayey soils. This project aims to investigate the parameters that affect the tensile strength of compacted soils such as: compaction method, degree of saturation and soil fabric. For this study, experiments were conducted on a soil sample from Jurong Formation. Specimens were compacted by either standard Proctor (ASTM D698, 2012) and modified Proctor (ASTM D1557, 2012) at five different water contents: 10%, 12%, 15%, 17.5% and 18.5%. Specimens were subjected to the Brazilian tensile test to determine its tensile strength. In total, six series of tests were conducted. The first series consists of samples at the five water contents compacted by standard Proctor compaction. The second test series comprises of specimens at the five water contents compacted by modified Proctor compaction. The results from both test series were used to investigate the effects of compaction method on tensile strength. The results show that the higher the energy used during compaction, the higher the tensile strength. Test series 3 and 4 consisted of specimens at 10% and 12% water content, compacted using standard and modified Proctor, respectively. The specimens are then wetted to a higher water content before the Brazilian tensile test. Test series 5 and 6 consisted of specimens at 17.5% and 18.5% water content, and subsequently dried to a lower water content before the Brazilian tensile test. The results were used to compare the effect of degree of saturation on tensile strength. The results showed that an increase in the degree of saturation caused a decrease in tensile strength and that the opposite is true. The results were also used to compare the effect of different soil fabric on tensile strength, with the experiments showing that flocculated soil structure is weaker than the dispersed soil structure.Bachelor of Engineering (Civil