Measuring Pore-water Pressure in Partially Frozen Soils

• Main Author: Kia, Mohammadali
• Other Authors: Dr. David C. Sego & Dr. Norbert R. Morgenstern, Arenson, Lukas (BGC engineer, previous post-doc at Civil and Environmental Engineering Department), Wilson, G. Ward (Civil and Environmental Engineering Department, University of Alberta), Szymanski, Jozef (Civil and Environmental Engineering Department, University of Alberta), Morgenstern, Norbert R. (Civil and Environmental Engineering Department, University of Alberta), Rostron, Ben (Earth and Atmospheric sciences, University of Alberta), Blatz, James (Civil and Environmental Engineering Department, University of Manitoba), Sego, David C. (Civil and Environmental Engineering Department, University of Alberta)
• Format: Thesis
• Language: English
• Published: University of Alberta. Department of Civil and Environmental Engineering. 2012
• Subjects: envir; geo; Ice; permafrost
• Online Access: http://hdl.handle.net/10402/era.29202

Specialization: Geotechnical Engineering Degree: Doctor of Philosophy Abstract: Knowledge of pore-water pressure is essential to predict the ‘effective stress’ that controls the ‘resistance and deformation’ of a soil and to assess the ‘flow’ of water through it. Flow of water towards the freezing fringe controls the amount of frost heave in freezing soils. Drainage of this excess water controls subsequent thaw settlements as the frozen soil thaws. Further, the rate of dissipation of pore-water pressures control the thaw-instability in warming permafrost slopes. Not all of the water in a soil is ice at subzero temperatures; therefore, these soils are ‘partially frozen’. Hence, the challenges associated with measuring pore-water pressure distribution in freezing, thawing, and frozen soils can all be considered as one category: measuring pore-water pressures within a ‘partially frozen soil’. Therefore, measurement of pore-water pressures in partially frozen soils and having methods for estimating the pore-water pressure response to the applied loads are desirable. In this research, first a new instrument was developed to accurately conduct these measurements. Then, the measured pore-water pressures were used to study stress transmission within a partially frozen soil under applied loads, as well as under warming conditions. It was shown that if a sufficient amount of unfrozen water exists in a soil at subfreezing temperatures, it provides a continuous liquid phase that transfers pressures independent from the solid phase. Therefore, effective stress material properties and analysis should be used to evaluate the resistance and deformation of these partially frozen soils. This is of practical significance in analyzing stability and in modeling constitutive behavior of soil masses in warm and warming permafrost, especially for assessing geohazards associated with climate change. It is also of practical significance in analyzing and designing foundations, retaining structures, underground facilities, and frozen-core ...