Modification of Pinhole Apparatus for Identification and Classification of Dispersive Clay Soils


In this research, modification of pinhole apparatus is made as required by specification of the American Society for Testing and Materials (ASTM D4647 – 93)[3], which works on the basis that distilled water is passed horizontally under the influence of flow of hydraulic amount (50 mm) through a small hole diameter (1 mm) in the soil sample. The nature of the solution, which passes through the sample under the primary head (50 mm) gives index through which a principle to distinguish between dispersive and non-dispersive clays, where the flow of clay diffuses dark and increasingly hole diameter that operate in the sample quickly resulting in an increase in the flow rate.The apparatus has been modified to take into consideration any angle with the horizon (from zero up to 90o) and thus can represent cases of flow closer to reality, as the standard apparatus is applicable to prove horizontally, i.e., it is assumed inevitably flow horizontal (horizontal flow) and direction perpendicular to the layers of the soil. Since the primary application to pinhole is in the earth dams, the flow of water through the earth dam rarely is horizontal. So the current development represents more accurately practice.In addition, the modification included a method to prepare the sample in the compaction model in a manner similar to standard compaction test when the moisture content and dry density are required. This required the use of a pipe pushed in the compaction mold to extract the pinhole test sample. The model is cut to the desired length and then admitted into the cylinder of the pinhole accurately, and this way assures getting a sample with the required properties of density and water content accurately and easily while ensuring homogeneity of the soil instead of the previous method. As well as water tank has been developed through mobile sitting on a metal platform to achieve different mobile hydraulic heads provided by the test specification.