A generalized relationship between thermal conductivity and matric suction of soils

Geoderma ◽  
2019 ◽  
Vol 337 ◽  
pp. 491-497 ◽  
Author(s):  
Sen Lu ◽  
Yili Lu ◽  
Wei Peng ◽  
Zhaoqiang Ju ◽  
Tusheng Ren
Keyword(s):  
Thermal Conductivity ◽  
Matric Suction

The relationship between thermal conductivity and matric suction of soils

2021 ◽  
Author(s):  
Sen Lu
Keyword(s):  
Thermal Conductivity ◽  
Soil Water ◽  
Land Surface ◽  
Matric Suction ◽  
Dew Point ◽  
Pulse Technique ◽  
Highly Nonlinear ◽  
Wide Range ◽  
Mean Square Errors ◽  
The Relationship

<p>The soil thermal conductivity (λ) and matric suction of soil water (h, the negative of matric potential) relationship has been widely used in land surface models for estimating soil temperature and heat flux following the McCumber and Pielke (1981, MP81) λ-h model. However, few datasets are available for evaluating the accuracy and feasibility of the MP81 λ-h model under various soil and moisture conditions. In this study, we developed a new λ-h model and compared its performance with that of the MP81 model using measurements on 18 soils with a wide range of textures, water contents and bulk densities. The heat pulse technique was used to measure λ, and the suction table, micro-tensiometers, pressure plate device, and the dew point potentiometer were applied to obtain soil water retention curves at the appropriate suction ranges. In the range of pF (the common logarithm of h in cm)≤3, the λ-h relationships were highly nonlinear and varied strongly with soil texture and bulk density. In the dry range (i.e., pF > 3), there existed a universal λ-h relationship for all soil textures and bulk densities, and an exponential function was established to describe the relationship. Independent evaluations using λ-h data on five intact soil samples showed that the new model produced accurate λ data from pF values with root mean square errors (RMSE) with the range of 0.03–0.18W m<sup>−1</sup> K<sup>−1</sup>. While, large errors (RMSEs within 0.17–0.36W m<sup>−1</sup> K<sup>−1</sup>) were observed with λ estimates from the MP81 model. </p>

Use of thermal conductivity sensors to measure matric suction in the laboratory

1989 ◽  
Vol 26 (3) ◽  
pp. 491-498 ◽  
Author(s):  
Pamela Sattler ◽  
D. G. Fredlund
Keyword(s):  
Thermal Conductivity ◽  
Unsaturated Soils ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Test Procedure ◽  
Matric Suction ◽  
Engineering Practice ◽  
Equilibration Time ◽  
Overburden Pressure ◽  
Conductivity Sensor

The measurement of soil suction is pivotal to the application of soil mechanics principles in geotechnical engineering practice related to unsaturated soils. Volume change, shear strength, and seepage analyses all require an understanding of the matric suction in the soil. This note summarizes the use of thermal conductivity sensors to measure matric suction in the laboratory. The thermal conductivity sensor is described along with its mode of operation. A brief description is given of the procedure for calibrating thermal conductivity sensors using a pressure plate apparatus. The measurement of matric suction can be performed in the laboratory on Shelby tube samples. The laboratory measurements of matric suction can be adjusted for the effect of overburden pressure in the field. The required equilibration time for suction measurements is discussed along with details of the test procedure. The applications of the measured suction values to design are briefly discussed.Key words: matric suction, negative pore-water pressure, thermal conductivity sensor, laboratory, undisturbed samples.

scholarly journals A generalized model between thermal conductivity and matric suction of soils

2021 ◽  
Author(s):  
Sen Lu
Keyword(s):  
Thermal Conductivity ◽  
Soil Water ◽  
Land Surface ◽  
Matric Suction ◽  
Dew Point ◽  
Soil Thermal Conductivity ◽  
Pulse Technique ◽  
Highly Nonlinear ◽  
Wide Range ◽  
Mean Square Errors

<p>Soil thermal conductivity (λ) is an important physical property in land surface parameterization. The soil thermal conductivity (λ) and matric suction of soil water (h, the negative of matric potential) relationship has been widely used in land surface models for estimating soil temperature and heat flux following the McCumber and Pielke (1981, MP81) λ-h model. However, few datasets are available for evaluating the accuracy and feasibility of the MP81 λ-h model under various soil and moisture conditions. In this study, we developed a new λ-h model and compared its performance with that of the MP81 model using measurements on 18 soils with a wide range of textures, water contents and bulk densities. The heat pulse technique was used to measure λ, and the suction table, micro-tensiometers, pressure plate device, and the dew point potentiometer were applied to obtain soil water retention curves at the appropriate suction ranges. In the range of pF (the common logarithm of h in cm)≤3, the λ-h relationships were highly nonlinear and varied strongly with soil texture and bulk density. In the dry range (i.e., pF > 3), there existed a universal λ-h relationship for all soil textures and bulk densities, and an exponential function was established to describe the relationship. Independent evaluations using λ-h data on five intact soil samples showed that the new model produced accurate λ data from pF values with root mean square errors (RMSE) with the range of 0.03–0.18Wm−1 K−1. While, large errors (RMSEs within 0.17–0.36Wm−1 K−1) were observed with λ estimates from the MP81 model. </p>

Installation procedure for thermal conductivity matric suction sensors and analysis of their long-term readings

2007 ◽  
Vol 44 (2) ◽  
pp. 113-125 ◽  
Author(s):  
Elsa Tan ◽  
Delwyn G Fredlund ◽  
Brent Marjerison
Keyword(s):  
Thermal Conductivity ◽  
Ambient Temperature ◽  
Membrane System ◽  
Matric Suction ◽  
Soil Suction ◽  
Correction Factors ◽  
Temperature Changes ◽  
Subgrade Soil ◽  
Long Term Measurement

Thermal conductivity matric suction sensors have enabled continuous and long-term measurement of matric suction and temperature, even in remote locations. Long-term temperature and matric suction readings were obtained from below two thin-membrane-system sites in Torquay and Bethune, Saskatchewan. The method used to install the sensors and the data acquisition system is presented. An understanding of the subgrade soil suction and temperature changes throughout the year was obtained from the data. The change in matric suction and temperature with depth and distance was also determined. Observation of the amplitude and frequency of the fluctuations in the temperature readings provided a better understanding of the changing trends. Environmental effects, such as hysteresis associated with drying and wetting of the sensors and the effect of the ambient temperature on the sensors, were found to influence the matric suction readings. Several correction factors have been proposed to eliminate the influence of the ambient temperature, and the correction methods are compared.Key words: thermal conductivity, matric suction, sensors.

Numerical Modeling of a Thermal Conductivity Matric Suction Sensor

1994 ◽  
Vol 17 (4) ◽  
pp. 415 ◽  
Author(s):  
HJ Pincus ◽  
A Xing ◽  
DG Fredlund
Keyword(s):  
Thermal Conductivity ◽  
Numerical Modeling ◽  
Matric Suction

scholarly journals Calibration of a thermal conductivity sensor for field measurement of matric suction

Géotechnique ◽  
2012 ◽  
Vol 62 (1) ◽  
pp. 81-85 ◽  
Author(s):  
E.C. LEONG ◽  
X.-H. ZHANG ◽  
H. RAHARDJO
Keyword(s):  
Thermal Conductivity ◽  
Field Measurement ◽  
Matric Suction ◽  
Conductivity Sensor

Seasonal pattern of matric suctions in highway subgrades

2010 ◽  
Vol 47 (3) ◽  
pp. 267-280 ◽  
Author(s):  
Quan Nguyen ◽  
Delwyn G. Fredlund ◽  
Lal Samarasekera ◽  
Brent L. Marjerison
Keyword(s):  
Thermal Conductivity ◽  
Seasonal Pattern ◽  
Membrane Surface ◽  
Matric Suction ◽  
Thin Membrane ◽  
Temperature Changes ◽  
Constant Equilibrium ◽  
Subgrade Soil

The performance of “thin membrane surface” (TMS) highways is largely controlled by the strength of the subgrade soil, which in turn is a function of matric suction. Thermal conductivity matric suction sensors were used to indirectly measure in situ matric suctions. In September 2000, 32 thermal conductivity sensors were installed under TMS highways at two locations; namely, Bethune and Torquay, Saskatchewan, Canada, to monitor matric suction and temperature changes with time. This paper presents and interprets the variations in matric suctions measured between the years 2000 and 2005 at the Torquay site. The readings in the field showed a clearly seasonal pattern of matric suction changes that bore a relationship to rainfall near the test sites. Relatively constant equilibrium matric suctions that ranged from 20 to 60 kPa throughout the years were measured under the driving lanes. Conversely, matric suctions under the side slopes were found to vary widely with time and depth, ranging from 100 to 1500 kPa over the years. The greatest variation in matric suction from one location to another location occurred during the month of April. The matric suctions showed low variability during June, whereas larger variations were observed from July to October.

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