Effect of compaction and direct shear test values on peat soil of Batubara Regency, Sumatera Utara Province

Abstract

Peat soil is an organic soil and is usually found in low-lying areas where the water table is near the ground surface. The peat Soil has very large water reserves, high compression and has a low carrying capacity. This study aims to ascertain the index properties, to classify the peat soil classification according to ASTM 4427-92 (2002), to get the optimum water content and maximum dry unit weight by Standard Proctor test, and to analyze the shear strength of peat soil by direct shear test. The peat soil had water content (w) of 752.833 % and specific gravity (Gs) of 1.533. According to ASTM 4427-92 (2002), the peat soil was classified as high-ash peat with more than 15 % ash and as slightly acidic peat with a pH between 4.5 and 6.5. From the Standard Proctor test, the peat soil had an optimum water content of 37.235 % and 0.474 gr/cm3 maximum dry unit weight (γdmax). The Standard Proctor test increased the value of the dry unit weight (γd) of 0.169 gr/cm3 to 0.519 gr/cm3. The original internal friction angles (φ) and cohesion (c) were 0.885º and 0.015 MPa respectively while the Standard Proctor test resulted in 5.294º of internal friction angle (φ) and 0.023 MPa of cohesion (c).