Assessment of Various Methods to Measure the Soil Suction
Armand Augustin Fondjo1, Elizabeth Theron2, Richard P. Ray3

1Armand Augustin Fondjo*, Department of Civil Engineering, Central University of Technology, Free State, South Africa.
2Prof. Elizabeth Theron, Department of Civil Engineering, Central University of Technology, Free State, South Africa.
3Prof. Richard P. Ray, Structural and Geotechnical Engineering Department, Széchenyi István Egyetem University, Győr, Hungary.
Manuscript received on September 11, 2020. | Revised Manuscript received on September 30, 2020. | Manuscript published on October 10, 2020. | PP: 171-184 | Volume-9 Issue-12, October 2020 | Retrieval Number: 100.1/ijitee.L79581091220 | DOI: 10.35940/ijitee.L7958.1091220
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© The Authors. Blue Eyes Intelligence Engineering and Sciences Publication (BEIESP). This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Abstract: The foundation of the lightweight structures is commonly in unsaturated state conditions because located above the ground-water table. The matric suction governs the hydro-mechanical behaviour of unsaturated soils. Soil suction estimation is challenging both in the field and lab. The indirect and direct techniques are utilized to measure the soil suction. Several types of equipment utilized to measure the soil suction have been developed with innovative technology. However, there are constraints on reliability, suction range estimation, application, etc. The primary objective of this study is to review, describe the working principle, report limits, and benefits of various techniques utilized to measure the soil suction and select the cost-effective. A comparative study on direct and indirect technique of soil suction estimation is conducted base on recent literature, with a focus on suction range, procedure, type of suction, processing time, and application (lab/field). The apparatus utilized to measure directly or indirectly the matric suction found in the literature displays the highest range in the order of 1500 kPa except for the filter paper. The thermocouple psychrometer and the transistor psychrometer can measure a maximal total suction of 8000 kPa. The chilled-mirror hygrometer can measure a maximal total suction of 30000 kPa in the laboratory. The filter paper technique and the chilled-mirror hygrometer are cost-effective techniques. However, the filter paper technique is likely the easiest and low-cost technique to measure the matric suction and total suction for the full range with extreme care in the test procedure both in the field and lab. 
Keywords: Chilled-mirror hygrometer, Filter paper, Matric suction, Osmotic suction, Suction range, Total suction.