Liquid transfer through preferential flow paths in compacted clay /
| Main Author: | |
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1990.
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| Subjects: | |
| Online Access: | ProQuest, Abstract Link to OAKTrust copy |
| Abstract: | Compacted clay is an essential component of the double liner systems that are commonly used in hazardous waste retaining facilities. High Leakage rates, which are inconsistent with the laboratory hydraulic conductivities of the clay, have been detected in many of these installations. This behavior has been attributed to the presence of preferential flow paths in the field compacted clay liners. The present research study was initiated with the objective of investigating the occurrence and distribution of these preferential flow paths and determining their significance in controlling the liquid flow through the compacted clay. The research study was completed in two separate phases. The work accomplished during the first phase of the study included the selection of two soils which are typical of those used in clay liner construction, subjecting them to a detailed laboratory characterization, and conducting a series of large scale permeameter tests to identify the various factors that control the formation and distribution of preferential flow paths in the compacted clay. By using a dye in the permeant liquid it was established that the flow occurs in a relatively uniform manner near the surface of the compacted clay layer but converges into a few preferential pathways as it moves downwards. The measurement of hydraulic conductivity at different depths of the layer revealed that this parameter increases significantly as the depth increases. No significant influence due to the initial clod size was observed. Good correlation was obtained between the measured hydraulic conductivity and the compaction water content whereas the dry density values showed little correlation with the conductivity. In the second phase of the study an analytical model was developed to simulate the flow mechanisms observed during the experimental phase. This model uses a continuum approach to address transient flow into a system of preferential flow paths, direct infiltration into the intact clay matrix and the interaction between these two flow regimes. Additionally, this analytical method has the capability to accommodate spatial and time variation of the flow properties of the medium. The model predictions for the breakthrough times compared closely with those observed. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Civil engineering." |
| Physical Description: | xi, 165 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |