Abstract: “To understand the behavior of mudflow as one of notorious mass movement in geotechnical engineering, two rheology parameters should be obtained as yield stress and viscosity. Water content for mudflow could be equal to or higher than liquid limit. Viscosity could be obtained using a flow box test. Flow box test uses couple theory from Terzaghi’s trap door and Bingham model. There is a limitation for flow box test that it needs yield stress (i.e., undrained cohesion) value for deriving viscosity. Hence, fall cone penetration test could be used to determine yield stress by using the empirical equation based on its penetration. This test uses 80 g of cone with 30o cone angle. In this paper, the authors use kaolin, bentonite, Parakan Muncang, and Cipali. The range of water content of each soil is from plastic limit and over liquid limit. The results show that the shear strength of kaolin and Parakan Muncang is higher than bentonite and Cipali. This may due to the type of soil mineral. Henc”

Keywords: mudflow, liquid limit, undrained shear strength, fall cone penetration