Effective Depth of Curtain Grouting Case Study of Gonggang Dam, Magetan Regency, East Java Province

Abstract

One of way to fulfill of water requirements is build of dam. Soil or rocks of dam based foundation are not always comply with criteria of planning. To complete the criteria of planning, so improvement the weak zones must be done for stronger/stable foundation and no leakage in foundation. One of method to improvement soil/rock is grouting. The purpose of this research is determine and analyze the effective depth of curtain grouting in case study of Gonggang dam. Gonggang dam type is earth and rock fill dam type. Effective Depth of grouting should known in order to perform grouting in effective, efficient and economic. Data of field observation which used in determination for effective depth, are drill log, core drill log, permeability test, and section along dam. The data used to calculate permeability coefficient of each depth simulation before and after performed grouting. Furthermore, leak debit calculated for each profile for each grouting depth. Data of grouting depth and leak debit used to create a graphic. Based on relationship graphic of grouting depth and leak debit identified that effective depth of curtain grouting in case study of Gonggang dam is 35 meter with leakage debit is 2,21 liter/second After the safety number for leakage to each profile counted, actually, there are many profile with safety number are less one. Thereby, Gonggang dam are not secure yet for leakage. For safety or the safety numbers are more than one, then the most effective and efficient way that is decrease permeability coefficient value ( k ) after grouting from the initial k< 5,71 x 10-5 cm/second to be k  2 x 10-5 cm/second.