Laboratory and In Situ Determination of Hydraulic Conductivity and Their Validity in Transient Seepage Analysis

Soonkie Nam,John Petrie,Panayiotis Diplas,Marte Gutierrez

doi:10.3390/w13081131

Abstract

This paper critically compares the use of laboratory tests against in situ tests combined with numerical seepage modeling to determine the hydraulic conductivity of natural soil deposits. Laboratory determination of hydraulic conductivity used the constant head permeability and oedometer tests on undisturbed Shelby tube and block soil samples. The auger hole method and Guelph permeameter tests were performed in the field. Groundwater table elevations in natural soil deposits with different hydraulic conductivity values were predicted using finite element seepage modeling and compared with field measurements to assess the various test results. Hydraulic conductivity values obtained by the auger hole method provide predictions that best match the groundwater table’s observed location at the field site. This observation indicates that hydraulic conductivity determined by the in situ test represents the actual conditions in the field better than that determined in a laboratory setting. The differences between the laboratory and in situ hydraulic conductivity values can be attributed to factors such as sample disturbance, soil anisotropy, fissures and cracks, and soil structure in addition to the conceptual and procedural differences in testing methods and effects of sample size.

Highlights

Understanding and predicting water movement or seepage in soils is a vital part of hydraulic and geotechnical engineering
The movement of water through soil is generally slow and assumed to be laminar. This flow is described by Darcy’s law, which states that the velocity of a flowing liquid (v) through a porous medium is directly proportional to the pressure gradient causing the flow and is the product of the hydraulic gradient (i) and the hydraulic conductivity (k)
The results indicate that the highest k from auger hole (AH) produced the best agreement with the observed changes in the groundwater table (GWT)

Summary

Introduction

Understanding and predicting water movement or seepage in soils is a vital part of hydraulic and geotechnical engineering. The movement of water through soil is generally slow and assumed to be laminar. This flow is described by Darcy’s law, which states that the velocity of a flowing liquid (v) through a porous medium is directly proportional to the pressure gradient causing the flow and is the product of the hydraulic gradient (i) and the hydraulic conductivity (k). Darcy’s law is valid in unsaturated soils, but the hydraulic conductivity becomes a function of the water content or the matric suction. Hydraulic conductivity is the most critical parameter used to understand the flow of water through soils. Evaluating slopes with rain events or fluctuating water levels becomes a common approach to better understand the slopes’ stability [3,4]

Objectives

Findings

Discussion

Conclusion