Evaluation the engineering properties of non-erosion filter materials at Kaboodval emabankment dam, Gollestan Province

Selection suitable filter material for an embankment dam plays a great role in preventing the core and the shoulder materials from erosion. Drain materials functions as to dewater and to decrease the possible increment of pore water pressure through the dam structure and its location. Since the use of drains is part of dam structure, therefore the application of filter material as a transitional zone is necessary.
In this paper the properties of filter material used in Kaboodval dam was investigated. Kaboodval dam is a homogeneous earthfill dam with 35.8 meters height which is located to the south of Ali-abad Katool town of Gollestan Province. The region is mainly consisted of fine grain soil deposits which are produced from the weathering of schistose bedrocks. According to the soil gradation, plastic index and the distribution of the deposits, selection of the suitable materials as non-erosion filter was made. Since the grading of the filter materials has to be within the range of D5 to D50, and to exceeds the critical boundary of D15 limit, therefore the capability of the filter materials regarding the dispersion and erosion was evaluated in this paper. In this regards, the properties of 25 samples were studied. Five of the samples of finer gradation were selected to undergo the dispersive and NEF (non-erosion filter) test. The test results showed that the samples were non dispersive, and according the erosionabilty, sample K11 with D85=0.017mm is most suitable sample for critical filter of D15 gradation. The test results also showed that the D15 of non-erosionable filter were in the range of 0.35 to 0.50 mm. For the case of safety, it is suggested that filter materials of D15 equal to 0.45 mm can be used in this project as non-erosion material.