Large-Scale in Situ Direct Shear Test in the Construction of Keureuto Dam, Indonesia

A large-scale in situ direct shear test was developed to evaluate the shear strength behavior of random fill material for dam construction in Indonesia. A 70 × 70 × 30 cm large square soil inside a shear box was fabricated in situ. The testing mechanism followed a stress-controlled procedure. The term of random fill material is commonly used for dam construction to the major composition of earth-fill dams in Indonesia. The shear strength characteristic of random fill material may vary depending on the actual particle size distribution. In this paper, in situ shear strength testing on random fill was conducted in Keureuto Dam, Indonesia. The random fill material was majorly composed of coarse material: gravel and sand. A total of 4 samples were tested in situ with a variety of vertical stresses. The testing results showed that plastic deformation started to occur between shear strain of 1–2%. Dilative behavior with an increase in shear displacement was observed in all samples indicating dense condition of the material. Shear strength was evaluated using linear Mohr–Coulomb equation and exponential formula. The results show that both equations are preferable in this case. However, the linear curve is suggested to be intercepted at zero in order to represent non-cohesive behavior of the material. The shear strength of random fill material in this study may provide a new database as a contribution to the practice in dam construction in Indonesia.