Analysis of Piping at Kedung Uling Earthfill Dam, Wonogiri Regency, Central Java Province, Indonesia

Kedung Uling earthfill dam is located between Eromoko and Wuryantoro district, Wonogiri Regency, Central Java, Indonesia. Water leaked from the dam was found and could decrease volume of dam. The objectives of this study are to identify piping and to recommend for solving piping problem. In order to determine the piping direction and litological pattern, investigation of 10 boreholes with various depth has been carried out. This investigation aim to determine characteristics of soil and rock by analyzing 45 cm of thickness of undisturbed samples and to perform permeability test. Permeability test have been conducted by falling head method with 3 different depths. Leaking at the dam was analyzed by Slide 6.0 software. The results indicated that litology of dam have been identified as claystone, sand and tuff. The piping passed under the eastern abutment of the dam is the accumulation of groundwater in the aquifers formed by 8-10 meters thick layer of sand. The total debit of piping is 17,774 cm3/sec. The Factor of safety of piping is under the minimum of standard namely 3,6. Grouting is one of alternative method to minimize the piping. Grouting was simulated to reduce permeability value and increase soil strength. By grouting, the total debit of piping was reduced to 3.314 cm3/sec