Semester

Summer

Date of Graduation

2006

Document Type

Dissertation

Degree Type

PhD

College

Statler College of Engineering and Mineral Resources

Department

Civil and Environmental Engineering

Committee Chair

Hema J Siriwardane

Abstract

The effectiveness of longitudinal drains was investigated by using experimental and numerical methods. The main objective of the longitudinal drains was to extract and deflect the water flowing through the soil. The influence of water level, drain spacing, slope inclination and soil type was investigated. Results show that the longitudinal drains can reduce the amount of water flowing through the soil significantly.;Several soil types were used in order to cover a wide range of properties. Different soil types were obtained by mixing Ohio River sand and Kaolinite clay in different proportions depending on the desired hydraulic conductivity. In this research the clay content of soils ranged from 5% to 35%. The soils were labeled: A, B, C, D and E.;In order to study longitudinal drains in the laboratory, a versatile physical model was built. This model represents the space between drains. The bed of this model can be inclined to different slope angles so that the performance of longitudinal drains at different slope angles can be investigated. Four different slope angles were used in this study (horizontal, four to one, three to one and two to one). The width of model can also be modified to different values. In this study, three values were selected for the width; six inches, twelve inches, and eighteen inches.;To better understand the behavior of the longitudinal drains, two conditions were studied: transient state and steady state. Transient state is the condition in which the flow of water and piezometric levels are fluctuating within the soil over time. Steady state is the state at which flow and water levels do not show any significant change over time. The performance of longitudinal drains was investigated by performing both laboratory experiments and computational modeling work. The computer model was calibrated by comparing model calculations with experimental data. The computer model was used to predict the performance of field-scale longitudinal drains.;Results from this study show that the longitudinal drains are very effective in reducing seepage through soils. Longitudinal drains remove a significant portion of water that would otherwise flow through the soil. The transient time depends on the soil type used.

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