The Spatial Variability of Random Fill Shear Strength Based on In-Situ Large Scale Direct Shear Test in the Kuwil Kawangkoan Dam Construction

Random material is regularly utilized for constructing dam embankments. Although random material offers construction cost saving as well as environmental damage reduction, evaluation of random material shear strength is very challenging. Large size particles in random material prevent reliable data acquirement using regular field or lab test. Unfortunately, disastrous dam failure can originate from misinterpretation of random material shear strength. An in-situ large scale direct shear device, 70 cm × 70 cm × 30 cm, was devised by Indonesian Geotechnical Inztitute in collaboration with Bandung Institute of Technology and Universiti Teknologi Malaysia. This device suits shear strength evaluation of random material in-situ. This manuscript presents a case study where the large-scale testing device was applied to investigate the spatial variability of random material shear strength in 6 locations of the Kuwil Kawangkoan dam, Indonesia. Test results indicated that the shear strength variability was attributed to the random material content itself, including granular-rich or fine grain-rich materials. This in-situ large test offers an appealing approach for evaluating shear strength and shear-strain behavior of random material. The testing results can be used to direct the decision in dam construction, whether the current design should be re-evaluated or be continued. Considering the simplicity, economic, and data that can be obtained, this in-situ large scale test is highly recommended as routine practice in a dam project.