POLYMER SENSOR FOR DETERMINATION OF SOIL FREEZING CHARACTERISTIC CURVE

Abstract

Due to climate change happening all around the world and seasons being affected, there are temperature variations that affect the environment, especially soil. Harsh climate and temperature changes are known to affect the soil structure and buildings. It is becoming more common to use rapid measurements of soil water characteristic curves (SWCC) and soil freezing characteristic curves (SFCC) to find a way of considering unsaturated soil mechanics. However, convenient methods of soil properties determination are time and financially consuming. There is a need to create rapid measurements of the soil properties and their validation. There are a variety of methods, both direct and indirect, that have been developed to measure soil suction which is associated with determining SWCC and SFCC. Several researchers such as Fredlund D. G., Fredlund M.D., Xing A., Gardner R., Vanapalli S. K., and Rahardjo H. have explored this field to create mathematical equations and technology to expand relatively young unsaturated soil areas. One of the rapid measurement technologies is a polymer sensor which provides faster soil observations. The specific objectives of this thesis are to: (1) measure and validate SFCC using sensor technology; (2) create envelopes of the SFCC for different soil types using available sources; and (3) analyze the results of the work and discuss the connections and possible recommendations. For the testing of natural soil, Astana-1 soil near Nazarbayev University is chosen to be observed. Two specimens with 99% and 95% Wet of optimum were considered to see differences that might appear. Properties of the soil were determined, and sensors were used to measure soil structure change under freezing conditions. To validate the direct measurements of SFCC there was also an indirect test conducted utilizing a High suction polymer sensor (HSPS) and Dewpoint potentiometer (WP4C) where soil’s SWCC was obtained and Clapeyron equation was used to find SFCC values. Past research articles were collected to examine the soil’s SWCC and estimations of SFCC were made to create the envelope for each soil type by USCS classification. Results indicate that laboratory testing and validations of Astana-1 soil correspond to the lower limit of the Clayey Sand envelope from past research. The limitation of the work is the possibility of the freezing temperature effect on soil structure such as pore-size distribution and pore arrangement. Considering soil structure, optimizing methodology and conducting tests with different soil types with different wet of optimum may result in better soil envelopes validation and decreasing the time to get the properties of the soil.