Soil suction is one of the most important physical variables affecting the soil engineering
behavior, moisture content. Suction has a major controlling influence on soil shear strength. The
moisture diffusivity properties of unsaturated properties of soils exert a critical influence on the
depth to which seasonal variations of moisture and suction at the ground surface extend into the
soil mass. Hence, a study of moisture diffusion coefficient is pivotal.
In this research the drying test originally proposed by Mitchell (1979) has been validated
by back calculating the moisture diffusion values using the empirical relation established by
Lytton (2003).
The non-linear flow through unsaturated soils has been simplified to a linear problem for
simplicity in this study. Owing to this simplification, certain refinements have therefore been
applied in the determination of diffusion coefficient. Thermocouple psychrometer was used to
measure the soil suction along the length of the sample and at different times in the laboratory.
Initial suction measurements were done using the filter paper test. Curve fitting procedure
established by (Aubeny and Lytton, 2003), has been used for the determination of the diffusion
coefficient. Analytical validation of the moisture diffusion coefficient, required coefficient of
permeability, ??k??, slope of suction water characteristic curve ??S?? and air entry value ??ho?? as the
major input parameters.
Mitchell (1979) assumed the value of ??ho?? to be 100 cm. In this research air entry value,
??ho?? has been re-evaluated and it comes out to be higher than the pre estimated value. The value
of slope of suction water characteristic curve, ??S?? obtained from pressure plate tests, compares
well to the empirical equation of Lytton (2003).
The results of moisture diffusion coefficient obtained from the empirical equation come
out in the same range as obtained from the refined Mitchell??s (1979) drying test. The refinements
includes introduction of constant temperature environment. Owing to the least variation in
temperature, more reliable and reproducible data was obtained.
The range of moisture diffusion coefficient, ??-values obtained from empirical equation,
comes out to be coherent with the laboratory data. Hence, it can be concluded that the research
was successful.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/2713 |
| Date | 01 November 2005 |
| Creators | Thakur, Anshuman Bramhanand |
| Contributors | Aubeny, Charles, Lytton, Robert L. |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | 4365282 bytes, electronic, application/pdf, born digital |
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