Date of Award

Spring 2020

Project Type

Thesis

Program or Major

Civil Engineering

Degree Name

Master of Science

First Advisor

Jean Benoît

Second Advisor

Majid Ghayoomi

Third Advisor

Philippe Reiffsteck

Abstract

Currently, most Departments of Transportation, including the NHDOT, use borehole infiltration testing to characterize the hydraulic conductivity of soils for the design of stormwater Best Management Practices (BMP’s). The test essentially replicates the laboratory constant or falling head experiment except that it is conducted in a borehole. These field measurements are then used to estimate hydraulic conductivity using methods published in the 1950s by Hvorslev which lack rigorous analysis and depend on numerous assumptions. Tests are also time consuming and their punctual nature requires testing at several locations and depths to obtain reliable values of permeability.

A proposed solution is a tool called a Permeafor, an instrument originally developed in France to measure relative permeability in situ. The instrument consists of an approximately 2.5 foot long, 2 inch diameter cylindrical probe that is driven into the ground and stopped at specific depths while water is injected through a 2 inch long recessed perforated section. During use, the relationship between flow and hydraulic head is measured and expressed as a ratio. This ratio can be correlated to hydraulic conductivity using a theoretical shape factor based on the test configuration. Thus far, the comparison of Permeafor results in New Hampshire to commonly accepted laboratory and in situ permeability test methods has shown that the instrument has excellent potential to rapidly and more accurately assess the permeability of granular soils. In addition, a combination of driving resistance and soil permeability has shown that the Permeafor may also be useful in delineating stratigraphic details.

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