Date of Award

Fall 2021

Project Type

Thesis

Program or Major

Civil Engineering

Degree Name

Master of Science

First Advisor

Jean Benoit

Second Advisor

Igor Tsukrov

Third Advisor

Philippe Reiffsteck

Abstract

There are currently several in situ and laboratory methods of determining hydraulic conductivity of soils, however, it remains a difficult parameter to obtain accurately and economically. Current laboratory tests are performed on soil specimens that are disturbed by the sampling process and only represent a portion of the overall site. Some in situ testing methods are also available such as the pump test but are expensive and provide an average value of conductivity for the site. As a result of this averaging, critical zones of high or low hydraulic conductivity in the profile could be missed and represented by a misleading overall estimate. To characterize hydraulic conductivity for the design of stormwater best management practices (BMP’s), the New Hampshire Department of Transportation currently uses a traditional field test, the borehole infiltration testing. The interpretation method of this test uses general assumptions and lacks vigorous analysis due to its development in the 1950’s.

The proposed solution to these issues is to use a Permeafor, an instrument originally developed in France to measure horizontal hydraulic conductivity in situ. This property is determined by means of flowing water into the soil at any given depth, then obtained through the relation of applied hydraulic head and resulting flow. The tool has been designed, built, and tested here at the University of New Hampshire. Using knowledge acquired during preliminary testing, several modifications in the testing procedure have been made, simplifying, and improving the method as well as the equipment used. The tool has been currently used extensively on five different sites across the state, where the soil varied in characterization from coarse to silty sands. Along with these fields tests, several more established and accepted in situ and laboratory methods, along with finite element modeling of the testing procedure, have been completed in order to verify the results found from the Permeafor. The work completed in this research shows the Permeafor is able to rapidly hydraulically characterize soils at different depths to generate profiles of hydraulic conductivity. Thus, proving that the Permeafor is a useful tool in bridging the gap between time consuming testing at few locations and efficient broad scale permeability testing.

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