An improved distributed sensing method for monitoring soil moisture profile using heated carbon fibers

Ding-Feng Cao ab, Bin Shi a, Guang-Qing Wei c, Shen-En Chen d, Hong-Hu Zhu a

School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China

Department of Civil and Environmental Engineering Department, Engineering College, University of Wisconsin-Madison, Madison, WI,53706, USA

Suzhou NanZee Sensing Technology Co. Ltd, Suzhou 215123, China

Department of Civil and Environmental Engineering, University of North Carolina at Charlotte, NC 28223, USA

Measurement, 2018.

DOI: 10.1016/j.measurement.2018.03.052


Soil moisture variation with respect to depth directly affects the engineering properties of soil and the health state of plants. At the present, there are few techniques that can satisfactorily quantify the vertical moisture profile within the soil medium. In this paper, a fiber optic sensor-based distributed temperature sensing (DTS) technique is introduced for soil moisture profile mapping. In this technique, a carbon fiber heated sensing-tube (CFHST) is integrated into conventional fiber optic sensing cable to improve the sensitivity, accuracy and spatial resolution of the measurement of soil moisture profile. The CFHST consists of three parts: the inner tubing, the carbon fiber heated cable (CFHC) tightly wrapped on inner tubing, and the interface screw installed on both ends of the inner tubing. The length of a unit CFHST is adjustable according to the actual demand of a specified application. The power supply model and installation method in field are introduced. Laboratory tests were conducted to establish the relationship between soil moisture and thermal response of CFHST. A foundation pit dewatering test was also carried out to validate the field performance of this monitoring technique. The test results show that the borehole-embedded sensor monitored and recorded the continuous change of soil moisture profile accurately (RMSE = 0.046 m3/m3). This technique can effectively capture the distribution profile of soil moisture along the depth direction, which provides a new approach to investigate the physical and hydrological properties of soils.

Keywords: soil moisture profile, distributed temperature sensing (DTS), carbon fiber, fiber optic sensing


[1] T. Pastuszka, J.Krzyszczak, C. Sławiński, & K. Lamorski, Effect of time-domain reflectometry probe location on soil moisture measurement during wetting and drying processes, Measurement. 49 (2014) 182-186.

[2] X.B. Tu, A.K.L. Kwong, F.C. Dai, L.G. Tham, & H. Min, Field monitoring of rainfall infiltration in a loess slope and analysis of failure mechanism of rainfall-induced landslides, Eng. Geol. 105 (2009) 134-150.

[3] M.W. Gui, Y.M. Wu, Failure of soil under water infiltration condition, Eng. Geol. 181 (2014) 124–141.

[4] J. Kim, S. Jeong, S. Park, & J. Sharma, Influence of rainfall-induced wetting on the stability of weathered soils slopes, Eng. Geol. 75 (2004) 251-262.

[5] P. Dobriyal, A. Qureshi, R. Badola, S.A. Hussain, A review of the methods available for estimating soil moisture and its implications for water resource management, J. Hydrol. 458 (2012) 110-117.

[6] S.U. Susha lekshmi, D.N. Singh, M.S. Baghini, A critical review of soil moisture measurement, Measurement. 54 (2014) 92-105.

[7] M. Rezaei, E. Ebrahimi, S. Naseh, & M. Mohajerpour, A new 1.4-GHz soil moisture sensor, Measurement, 45 (2012) 1723-1728.

[8] Y.L. Then, K.Y. You, M.N. Dimon, & C.Y. Lee, A modified microstrip ring resonator sensor with lumped element modeling for soil moisture and dielectric predictions measurement, Measurement. 94 (2016) 119-125.

[9] H. Vereecken, J.A. Huisman, H. Bogena, et al., On the value of soil moisture measurements in vadose zone hydrology: A review, Water Resour. Res. 44 (2008) 1-21.

[10] Y. Matsukura, & K.I. Takahashi, A new technique for rapid and non-destructive measurement of rock-surface moisture content; preliminary application to weathering studies of sandstone blocks, Eng. Geol. 55 (2000) 113-120.

[11] J.F.H. Strassert, K. Tim, T.H.G. Wienemann, I. Wakako, N et al., Monitoring of soil moisture and groundwater level using ultrasonic waves to predict slope failures, Jpn. J. Appl. Phys. 48 (2009) 617-620.

[12] D.A. Gunn, J.E. Chambers, S. Uhlemann, et al., Moisture monitoring in clay embankments using electrical resistivity tomography, Constr. Build. Mater. 92 (2015) 82-94.

[13] L. Weihermüller, J.A. Huisman, S. Lambot, et al., Mapping the spatial variation of soil water content at the field scale with different ground penetrating radar techniques, J. Hydrol. 340 (2007) 205-216.

[14] J.D. Weiss, Using fiber optics to detect moisture intrusion into a landfill cap consisting of a vegetative soil barrier, J. Air Waste Manage. Assoc. 53 (2003), 1130–1148.

[15] T. Read, O. Bour, J.S. Selker, et al., Active‐distributed temperature sensing to continuously quantify vertical flow in boreholes, Water Resour. Res. 50 (2014) 3706-3713.

[16] C. Sayde, C. Gregory, M. Gil-Rodriguez, et al., Feasibility of soil moisture monitoring with heated fiber optics, Water Resour. Res. 46 (2010) 1–8.

[17] A.M. Striegl, & S.P. Loheide, Heated distributed temperature sensing for field scale soil moisture monitoring. Ground Water. 50 (2012) 340–347.

[18] M. Gil-Rodríguez, L. Rodríguez-Sinobas, J. Benítez-Buelga, et al., Application of active heat pulse method with fiber optic temperature sensing for estimation of wetting bulbs and water distribution in drip emitters, Agric. Water Manage. 120 (2012) 72–78.

[19] F. Ciocca, & I. Lunati, Heated optical fiber for distributed soil-moisture measurements: a lysimeter experiment, Vadose Zone J. 4 (2012) 2344-2344.

[20] C. Sayde, J.B. Buelga, L. Rodriguez-Sinobas, et al., Mapping variability of soil water content and flux across 1–1000 m scales using the Actively Heated Fiber Optic method, Water Resour. Res. 50 (2014) 7302–7317.

[21] D.F. Cao, B. Shi, H.H. Zhu, et al., A distributed measurement method for in-situ soil moisture content by using carbon-fiber heated cable, J. Rock Mech. Geotech. Eng. 7 (2015) 700-707.

[22] D.F. Cao, B. Shi, H.H. Zhu, et al., Performance evaluation of two types of heated cables for distributed temperature sensing-based measurement of soil moisture content, J. Rock Mech. Geotech. Eng. 8 (2016) 212-217.

[23] D.F. Cao, B. Shi, J.F. Yan, et al., Distributed method for measuring moisture content of soils based on C-DTS, Chinese Journal of Geotechnical Engineering. 36 (2014) 910-915. (in Chinese)

[24] J.F. Yan, B. Shi, H.H. Zhu, et al., A quantitative monitoring technology for seepage in slopes using DTS, Eng. Geol. 186 (2015) 100–104.

[25] H. Su, S. Tian, Y. Kang, et al., Monitoring water seepage velocity in dikes using distributed optical fiber temperature sensors, Austom. Constr. 76 (2017) 71-84.

[26] J.S. Selker, L. Thevenaz, H. Huwald, et al., Distributed fiber‐optic temperature sensing for hydrologic systems, Water Resour. Res. 42 (2006) 1-8.

[27] F. Suárez, J.E. Aravena, M.B Hausner, et al., Assessment of a vertical high-resolution distributed-temperature-sensing system in a shallow thermohaline environment, Hydrol. Earth Syst. Sci. 15 (2011) 1081-1093

[28] T. Vogt, P. Schneider, L. Hahn-Woernle, et al., Estimation of seepage rates in a losing stream by means of fiber-optic high-resolution vertical temperature profiling, J. Hydrol. 380 (2010) 154-164.

[29] T. Vogt, M. Schirmer, & O.A. Cirpka, Investigating riparian groundwater flow close to a losing river using diurnal temperature oscillations at high vertical resolution, Hydrol. Earth Syst. Sci. 16 (2012) 473.

[30] T.I. Coleman, B.L. Parker, C.H. Maldaner, et al., Groundwater flow characterization in a fractured bedrock aquifer using active DTS tests in sealed boreholes, J. Hydrol. 528 (2015) 449-462.

[31] K.T.V. Grattan, & T. Sun, Fiber optic sensor technology: an overview, Sensors Actuators A: Physical, 82 (2000) 40–61.

[32] S.W. Tyler, J.S. Selker, M.B. Hausner, et al., Environmental temperature sensing using Raman spectra DTS fiber-optic methods, Water Resour. Res. 45 (2009) 1–11.

[33] K. Matsumoto, & T. Suzuki, Measurement of thermal conductivity of ice slurry made from solution by transient line heat-source technique (analytical discussion on influence of latent heat of fusion), Int. J. Refrig. 30 (2007) 187-194.

[34] G. Florides, & S. Kalogirou, First in situ determination of the thermal performance of a u-pipe borehole heat exchanger, in Cyprus, Appl. Therm. Eng. 28 (2008) 157-163.

[35] S. Lu, T. Ren, Y. Gong, et al., Improved model for predicting soil thermal conductivity from water content at room temperature, Soi Sci. Soc. Am. J. 71 (2007) 8-14.

[36] S.O. Chung, & R. Horton, Soil heat and water flow with a partial surface mulch, Water Resour. Res. 23 (1987) 2175-2186.

[37] M.V.B.B. Gangadhara Rao, & D.N. Singh, A generalized relationship to estimate thermal resistivity of soils, Can. Geo. J. 36 (1999) 767-773.

[38] T. Lhendup, L. Aye, & R.J. Fuller, In-situ measurement of borehole thermal properties in Melbourne, Appl. Therm. Eng. 73 (2014) 287-295.

[39] M.Z. Yu, X.F. Peng, & X.D. Li, A simplified model for measuring thermal properties of deep ground soil, Exp. Heat Transfer, 17 (2004) 119-130.

[40] W. Choi and R. Ooka, Effect of natural convection on thermal response test conducted in saturated porous formation: comparison of gravel-backfilled and cement-grouted borehole heat exchangers, Renewable Energy, 96 (2016) 891-903.

[41] N.H. Abuhamdeh, and R.C. Reeder. Soil thermal conductivity: effects of density, moisture, salt concentration, and organic matter, Soil Sci. Soc. Am. J. 64 (2000) 1285-1290.

[42] J. Benítez-Buelga, L. Rodriguez-Sinobas, R.S. Calvo, M. Gil-Rodriguez, C. Sayde and J.S. Selker, Calibration of soil moisture sensing with subsurface heated fiber optics using numerical simulation, Water Resources Research, 52 (2016) 1-11.

[43] T.L. Rowlandson, A.A. Berg, P.R. Bullock, et al., Evaluation of several calibration procedures for a portable soil moisture sensor, J. Hydrol. 498 (2013) 335–344.

[44] Z. Yin, T. Lei, Q. Yan, et al. A near-infrared reflectance sensor for soil surface moisture measurement, Comput. Electron. Agric. 99 (2013) 101-107.