Measurement of Suction of Thick Textured Soil using Filter Paper Method and Equivalent Tensiometer — EQT
This paper is a study of the correlation between the humidity, density and matrix suction of non-plastic soil taken from a region located near the city of Rio de Janeiro. The study was conducted through laboratory tests, using minilysimeters and equipment that indirectly measured the humidity through soil suction: in effect, an automated tensiometer, an equivalence tensiometer (EQ2), a TDR and a specially adapted system, which measures the suction in situ, using filter paper. The electronic instruments were connected to a data logger and placed in three mini-lysimeters. Cycles of wetting and drying of the confined material were simulated. The soil was characterised. This characterisation enabled the determination of physical indexes, density, plasticity, grain size, porosity, and the characteristic curve of water retention, using the Richards pressure pan (cooker) test. The results obtained by the instruments, humidity and matrix suction, were compared with the characteristic curve. Overall, the equipment was satisfactory. The low presence of clay in this soil, around 7%, and its associated high porosity, were factors in limiting water retention. The equilibrium time of the soil humidity and the filter paper, obtained at intervals of fifteen days, presented better results than the weekly intervals (seven days). The equivalence tensiometer EQ2 compared to the filter paper presented quite efficient results for high suction values.
KeywordsWater Retention Electronic Instrument Soil Humidity Soil Suction High Suction
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