Geotechnical Characterization of Bengkalis’ Peat Using Portable Tools

Abstract

Indonesia's peatland covers almost 10% of its land i.e. about 20 million hectares. Due to economic development, infrastructure construction on peatland is frequently unavoidable. However, determination of geotechnical properties of peat, especially shear strength, is cumbersome due to its very fragile and soft nature. This study is a preliminary work to characterize geotechnical properties of peat using highly portable and low-cost in-situ soil investigation tools i.e. hand cone penetrometer (HCP), resistivity, and particularly soil strength probe (DK), a relatively new apparatus developed by Public Work Research Institute (PWRI) Japan. The location of this study is at Bengkalis Island, Riau Province Indonesia. Laboratory test shows that peat at the location is sapric (highly decomposed) with fibre content about 7-20%. Hand cone penetration values and resistivity range from 50-900 kPa and 41-130 ohm-m, respectively. Peat resistivity strongly correlates to its water resistivity. Soil strength probe penetration is generally higher than HCP i.e., 150-1900 kPa. HCP and DK penetrations correlates strongly. Shear strength from soil strength probe vane cone revealed low cohesion values (1-5 kPa) and friction angle between 14 0 -47 0 . Fibre content has a moderate positive correlation to penetration resistance. Resistivity has a very weak correlation with penetration resistance.