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Direct and Indirect Measurement of Soil
Hu Pan Institute of Geotechnical Engineering, Faculty of Infrastructure Engineering Dalian University of Technology, Dalian, China Yang Qing Faculty of Infrastructure Engineering and The State Key Lab. of Coastal and Offshore Engineering, Dalian University of Technology, Dalian, China Li Pei-yong School of Civil and Safety Engineering, Dalian Jiaotong University, Dalian, China
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ABSTRACT |
Soil suctions can be found in all ground that lies above the water table. It is one of the most important parameters describing the moisture stress condition of unsaturated soils and laboratory measurements of suction can be very useful for assessing the quality of the samples, estimating the in situ effective stress and realistic applications of unsaturated soil mechanics. This paper reports on direct and indirect soil suction measurement methods. Direct suction measurement techniques mainly include axis-transition technique, tensiometer and suction probe. Indirect suction measurement techniques are divided into three categories, namely, measurement techniques of matric suction, osmotic suction and total suction. Indirect matric suction measurement techniques include time domain reflectometry (TDR), electrical conductivity sensors , thermal conductivity sensor(TCS) and in-contact filter paper technique. Indirect osmotic suction measurement techniques chiefly include squeezing technique and saturation extract method. Indirect total suction measurement techniques include psychrometer technique, relative humidity sensor, chilled-mirror hygrometer technique and non-contact filter paper method. These techniques have been widely used in research laboratories and in engineering practice. However, each of these methods has its own limitations and disadvantages, and active research to improve these techniques need to be done in research laboratories and universities. This paper demonstrates working principles, measurement, and application of these methods based one recent literature and geotechnical engineering practice.
Keywords: unsaturated soils, soil suction, suction measurement methods.
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