Geotextile Filter Studies in Dispersive Clay Used for Earth Dam Construction

Abstract

Research was conducted to evaluate the filtration performance of geotextile in the earth dam constructed with dispersive soils, in order to seek for a method of preventing sinkhole, piping and failure of the earth dam caused by sodium dispersive clay. The test was done by compacting fine grain soils in the mold and water was caused to flow through a small hole punched in a specimen, then discharged through the geotextile placed adjacent to the specimen as a filter. The volume of effluent was recorded while the colour of water was observed, and then flow rates were calculated. The result showed that, at the first interval, the effluent was visibly cloudy indicating the dispersive clay eroded by water, later the effluent became clearer with time and completely clear at last. The rate of flow at the beginning was rather fast and became slower gradually and was almost stable at last. The results indicated that the dispersive clay particles eroded by water were accumulated at the surface of geotextile and gradually formed complex structure which resulted in decreasing in flow rate. When the complex structure was completed, the rate of flow became stable. At the end of the successive flow tests, the apparatus was dismantled and the specimen was extruded and broken to examine the size of the hole. The test result showed that some clay particle filled in the hole and some attached to the surface of geotextile acting as the filter for dispersive clay. The test results also showed that, with different pore size of geotextile, the rate of flow would be different only during the first week, later the rate of flow was nearly the same, and after 29 days from the beginning the rate of flow was rather stable.