Permeability characteristics of volcanic ash soil in Papua New Guinea

Volcanic ash soils have been encountered in the Highlands Region of Papua New Guinea during road construction. Considerable difficulties have been encountered due to the unusual characteristics of these volcanic ash soils. Basic classification tests were undertaken to determine the material properties of the prepared sample. Samples were prepared in three moisture conditions; natural, air-dried and oven-dried. Two test methods were used for determining permeability of the material, the Falling Head Permeameter test and One Dimension Consolidation Test. The latter was used as an alternative test method. From this investigation it was concluded that following drying, volcanic ash soil experienced decreases in plasticity, variation in particle size and increases in permeability characteristics. Suggested recommendations for the use of volcanic ash soils are outlined based on test results. A number of studies done on the unusual characteristics of other volcanic derived soils have also been evaluated as providing background material for the understanding of this study.