ICST conference, December 14 th 2020, published online: June 1 st 2021 567 The effect of the thermal processing on the changes of physical and mechanical behaviour of peat soil in West Donggala, Central Sulawesi Sukiman Nurdin 1) , Stephanus Alexsander 2) , Astri Rahayu 1) , Sriyati Ramadhani 1) , Irdhiani 1) 1) Departemen Teknik Sipil, Tadulako University, Jl. Soekarno Hatta No.KM. 9, Tondo, Mantikulore, Kota Palu, Sulawesi Tengah, Indonesia, 2) Departemen Teknik Sipil Universitas Palangka Raya, Jl. Yos Sudarso, Palangkaraya, Indonesia Corresponding author: s.nurdin@untad.ac.id Abstract. Peat soils have specific characteristics, which one of the traits is enclosing high moisture content that can reach less than 400%. This research would explore peat soils at Lalombi Village, West Donggala due to temperature and time-consuming thermal processing. Properties of peat soils measured that those included moisture content analyses with different degrees of thermal process and different time cycle, the Organic and ash content, Atterberg limit and specific gravity have been measured. The shear strength test conducted with the vane shear apparatus. The thermal process, which increased gradually, shows that moisture content decrease to minus 125,687%. The loss of moisture content predicted because of water placed in a micro and macro void of peat soils could be evaporating, and the moisture content in peat soils after thermal process decline to just only 0,23%. The Shear strength of peats soils after the thermal processing was reached 38 KPa at a temperature of 100 Degree Celsius for 72 hours of thermal processing. Keywords: Peat soils; thermal processing; moisture content; shear strength 1. Introduction Several large islands in Indonesia, such as Sumatra, Kalimantan, Sulawesi and Irian Jaya, have large peatland areas to carry out. Peat has many negative geotechnical properties such as high water content, low shear strength, high organic matter, and low bearing capacity. Consequently, a significant sever-ing high compressibility takes place that makes it one of the most challenging soils for constructing structures over its natural state [1]. A solution for construction on peat soil is always sought because of the peat soil's unfavourable nature. Peat soil has a high organic content as a material in its formation. The common characteristics of peat soils are high water content, low compressibility, and low bearing capacity. Peat soil has extensive water content, so it can say that one of the main Proceeding ICST (2021) e-ISSN: 2722-7375 Vol. 2, June 2021