Assessment of sandy soil water permeability methods

Qualitative assessment of soil permeability is important for designing drainage systems and waterworks. According to the research results, soil permeability factor depends on sample preparation, test method and conditions. The article summarizes the results of analyzing the factors that influence the permeability of sandy soils: filtration conditions (steady-state and non-steady-state), sample area, compaction method, and sample height. Water permeability of sand in field conditions was determined by filling a pit with water at a constant head and a stable flow rate. The soil surveyed was medium-grained sand of medium density located above the groundwater table. Permeability testing in laboratory conditions was carried out using filtration tubes with the area of 20 and 85 cm2. The height of the soil samples was 50 and 100 mm. The laboratory test results showed that the sand permeability factor greatly depends on the compaction method: layer-by-layer compaction, vibration compaction. Different permeability factor values for the surveyed soil were caused by non-uniform vertical compaction of the sample. With the standard test method, the deviation of laboratory test results from the field test results reached 16 to 28%. When using sand compaction by tamping, the results closest to the actual permeability can be achieved by selecting an optimum weight drop height and reducing the sample height. Meanwhile, filtration conditions and sample area have a negligible effect on sand permeability. The article demonstrates that selecting an optimal compaction method ensures the error of permeability factor determination in laboratory conditions within 5%.