A vacuum-refilled tensiometer for deep monitoring of in-situ pore water pressure

Document Type : Research Article

Authors

1 Department of Civil Engineering, Sharif University of Technology, Tehran, Iran

2 Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering, Hohai University, 1 Xikang Road, Nanjing 210098, China

3 Department of Civil and Environmental Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong

4 Department of Civil Engineering, Sharif University of Technology, Tehran, Iran.

Abstract

Real-time measurement of soil water pressure has been recognized as an essential part of investigating water flow in unsaturated soils. Tensiometry, amongst different measuring techniques, is a common method for direct evaluation of water pressure. However, the lower limit of measurable water pressure by a conventional tensiometer becomes even more limited by increasing its length in the vertical installation. This paper describes development of a vacuum-refilled tensiometer (VRT) for monitoring soil water pressure independent of installation depth. This is achieved by fixing the distance between pressure sensor and ceramic cup together with incorporating an ancillary vacuum-refilling assembly into its design. The assembly allows for more efficient replacement of diffused air into the ceramic cup and reservoir with water. The new tensiometer is designed to withstand both negative and positive water pressure of up to almost one bar. In addition, the response time of the tensiometer to a change in negative water pressure for its working range (≥ -80 kPa) is very quick, in the order of seconds and one minute at most. The long-term performance of the new tensiometer is evaluated through a five-month monitoring program in the laboratory, simulating cyclic wetting and drying in the field.

Keywords

Main Subjects

References

References:
1. Livingston, B.E. "A method for controlling plant moisture", The Plant World, 11, pp. 39-40 (1908).
2. Or, D. "History of soil science who invented the tensiometer?", Soil Sci. Soc. Am. J., 65, pp. 1-3 (2001).
3. Tarantino, A., Ridley, A.M., and Toll, D.G. "Field measurement of suction, water content, and water permeability", Geotech. Geolo. Eng., 26, pp. 751-782 (2008).
4. Marinho, F.A.M., Take, W.A., and Tarantino, A. "Measurement of matric suction using tensiometric and axis translation techniques", Geotech. Geolo. Eng., 26, pp. 615-631 (2008).
5. Stannard, D.I. "Tensiometers-theory, construction, and use", Geotech. Test. J., 15, pp. 48-58 (1992). 
6. Bianchi, W.B. "Measuring soil moisture tension  changes", J. Agricul. Eng., 43, pp. 398-399 (1962).
7. Watson, K.K. "A recording field tensiometer with rapid response characteristics", J. Hydro., 5, pp. 33-39 (1967).
8. Hubbell, J.M. and Sisson, J.B. "Advanced tensiometer for shallow or deep soil water potential measurements", Soil Sci., 163, pp. 271-277 (1998).
9. Sisson, J.B., Gee, G.W., Hubbell, J.M., Bratton, W.L., Ritter, J.C., Ward, A.L., and Caldwell, T.G. "Advances in tensiometry for long-term monitoring of soil water pressures", Vadose Zone J., 1, pp. 310-315 (2002).
10. Faybishenko, B. "Tensiometer for shallow and deep measurements of water pressure in vadose zone and groundwater", Soil Sci., 165, pp. 473-482 (2000).
11. Raj, M. and Sengupta, A. "Rain-triggered slope failure of the railway embankment at Malda, India", Acta Geotech., 9(5), pp. 789-798 (2014).
12. Garg, A., Li, J., Hou, J., Berretta, C., and Garg, A. "A new computational approach for estimation of wilting point for green infrastructure", Measurement, 111, pp. 351-358 (2017).
13. Ridley, A.M., Dineen, K., Burland, J.B., and Vaughan, P.R. "Soil matrix suction: Some examples of its measurement and application in geotechnical engineering", Geotechnique, 53, pp. 241-253 (2003).
14. Hubbell, J.M. and Sisson, J.B. "Portable tensiometer use in deep boreholes", Soil Sci., 161, pp. 376-381 (1996).
15. Oliveira, O.M. and Marinho, F.A.M. "Suction equilibration time for a high capacity tensiometer", Geotech. Test. J., 31, pp. 101-105 (2008).
16. Liu, J., Chen, R., Sadeghi, H., and Ng, C.W.W. "A field study of stress-dependent soil-water characteristic curves and permeability functions of a loess soil for landfill covers", The 1st Int. Conf. on Geo-Energy and Geo-Environment, 1, Hong Kong, pp. 118-119 (2015).
17. ASTM "Standard practice for classification of soils for engineering purposes (unified soil classification system)", ASTM standard D2487, Am. Soc. for Test. and Mat., West Conshohocken, Pa (2006).
18. Ng, C.W.W., Sadeghi, H., and Jafarzadeh, F. "Compression and shear strength characteristics of compacted loess at high suctions", Can. Geotech. J., 54(5), pp. 690-699 (2017). https://doi.org/10.1139/cgj-2016- 0347.
19. Ng, C.W.W., Baghbanrezvan, S., Sadeghi, H., Zhou, C., and Jafarzadeh, F. "Effect of specimen preparation techniques on dynamic properties of unsaturated finegrained soil at high suctions", Can. Geotech. J., 54(9), pp. 1310-1319 (2017). https://doi.org/10.1139/cgj- 2016-0531.
20. Sadeghi, H., Hossen, S.B., Chiu, A.C.F., Cheng, Q., and Ng, C.W.W. "Water retention curves of intact and re-compacted loess at different net stresses", The 15th Asian Reg. Conf. on Soil Mech. and Geotech. Eng. (15ARC), Geotech. Soc. Spec. Publ., 2(4), Fukuoka, Japan, pp. 221-225 (2016).
21. Ng, C.W.W., Sadeghi, H., Hossen, S.B., Chiu, A.C.F., Alonso, E.E., and Baghbanrezvan, S. "Water retention and volumetric characteristics of intact and recompacted loess", Can. Geotech. J., 53(8), pp. 1258- 1269 (2016). https://doi.org/10.1139/cgj-2015-0364.
22. Ridley, A.M., Marsland, F., and Patel, A. "Tensiometers: their design and use for civil engineering purposes", Proc. of the 1st Int. Conf. on Site Charact., 2, Atlanta, pp. 851-856 (1998).
23. Whalley, W.R., Lock, G., Jenkins, M., Peloe, T., Burek, K., Balendonck, J., Take, W.A., Tuzel, I.H., and Tuzel, Y. "Measurement of low matric potentials with porous matrix sensors and water-filled tensiometers", Soil Sci. Soc. Am. J., 73, pp. 1796-1803 (2009).
Scientia Iranica
Volume 27, Issue 2
Transactions on Civil Engineering (A)
March and April 2020
Pages 596-606

Files

Cited by

History

  • Receive Date: 21 August 2017
  • Revise Date: 24 February 2018
  • Accept Date: 05 May 2018

Share

How to cite

Statistics