Effect of Different Peat Size and Pre-Consolidation Pressure of Reconstituted Peat on Effective Undrained Shear Strength Properties

Abstract

Shear strength of the soil is one of the most important parameters in engineering design, especially during the pre- or post-construction periods, since it is mainly used to measure and evaluate the foundation or slope stability of soil. Peat normally known as a soil that has a very low value of shear strength, and in order to determine and understand the shear strength of the peat, it is a difficult task in geotechnical engineering due to several factors such as types of fabrics, the origin of the soil, water content, organic matter and the degree of humification. The aim of this study is to determine the effective undrained shear strength properties of reconstituted peat of different sizes. All the reconstituted peat samples were formed with the size that passed the opening sieve of 0.425 mm (<R0.425) and 3.35 mm (<R3.35) and were pre-consolidated with the pressure of 50 kPa, 80 kPa and 100 kPa. The results of effective undrained shear strength properties for reconstituted peat <R3.35 samples were 16 kPa, 19 kPa and 21 kPa for cohesion, and 37°, 38° and 41° for the angle of friction, respectively. Moreover, the effective shear strength properties for the reconstituted peat <R0.425 were 11 kPa, 12 kPa and 12 kPa for cohesion and 23°, 27° and 30° for the angle of friction, respectively. The effective undrained shear strength properties result obtained from the tests show that the reconstituted peat <R3.35 has higher strength than reconstituted peat <R0.425. For relationship deviator stress-strain, σ^d _max and excess pore pressure, Δu, show both of <R0.425 and <R3.35 are gradually increase as when as σ’ and σ_c increased. However, at the final stage of the test, the graph is slightly declined due to the increment in stiffness of the specimen. The physical properties of the reconstituted peat <R0.425 and <R3.35 have also been investigated in order to correlate with the findings of the properties for the undrained shear strength.