A simplified formulation for moisture diffusion through partly saturated clays

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to digital@library.tamu.edu, referencing the URI of the item.Includes bibliographical references (leaves 82-84).Issued also on microfiche from Lange Micrographics.Civil works constructed of high plasticity clays can be dramatically affected by strength loss in spite of careful compaction and moisture control. Highway embankments and retaining walls are good example of affected structures. Strength loss due to infiltration of moisture from the ground surface can induce sloughing and shallow slide failures. This issue creates a significant maintenance problem for the Texas Department of Transportation (TxDOT). The postulated mechanism for these slope failures is: 1) Cracks develop in the soil during dry periods 2) Moisture enters the crack and diffuses through the soil during wet periods 3) Soil suction reduction with a concomitant decrease in soil strength precipitates the slope failure. As is evident from the second step in the process described above, the moisture diffusion properties of the soil are important factors in the rate of soil strength degradation. The rate of moisture diffusion through a partly saturated soil can be characterized by a moisture diffusion coefficient α and an exponent n. The main aim of this study is to estimate those diffusion parameters from experimental data. The experimental procedure utilized in this study includes soil suction measurements along undisturbed tube soil samples with one end exposed to the atmosphere and the remaining boundaries carefully sealed. Suction changes due to evaporation from the free surface are monitored as a function of time and location. The experimental and theoretical approach adopted for this research is a generalization of a procedure originally proposed by Mitchell (1979). Moisture diffusion properties of the soil were estimated using a curve fitting procedure which minimizes the difference between theoretical and measured values of suction at a given location in the soil specimen. The results of this experimental program indicate that the theoretical framework and the experimental procedures developed in this research project are very promising. However, the use of improved techniques for the suction measurements could greatly enhance the reliability of the overall test method