UV-Synthesized Polyacrylamide-Based Polymer Sensor for Measuring Soil-Water Characteristic Curves in Unsaturated...

Area of Science:

• Soil Mechanics
• Materials Science
• Sensor Technology

Background:

• Accurate measurement of soil suction is crucial for understanding unsaturated soil behavior.
• Traditional methods for determining the soil-water characteristic curve (SWCC) can be complex and limited in range.
• Development of novel sensors for in-situ soil property assessment is an active research area.

Purpose of the Study:

• To develop and evaluate a hydrogel-based superabsorbent polymer sensor (HSPS) for measuring soil suction.
• To utilize the HSPS for establishing the soil-water characteristic curve (SWCC) of unsaturated soils.
• To provide a cost-effective and efficient alternative for suction measurement in soil mechanics.

Main Methods:

• Synthesis of polyacrylamide (PAM) hydrogels with varying crosslinking degrees via UV-induced free radical polymerization.
• Characterization of hydrogels using FT-IR and TGA; investigation of swelling, water retention, and kinetic behavior.
• Integration of synthesized polymers into a modified high-sensitivity pressure sensor operating on the osmotic principle for suction measurement.

Main Results:

• Lower crosslinking density enhanced hydrogel swelling capacity up to 3000%; saline environments reduced absorption.
• Swelling kinetics followed anomalous diffusion and were described by the pseudo-second-order Schott model.
• The HSPS-3 demonstrated reliable suction measurements up to 1 MPa with minimal temperature sensitivity, validating the SWCC in natural soil.

Conclusions:

• The developed HSPS offers a simple, cost-effective, and efficient method for measuring soil suction.
• The sensor enables the determination of SWCC, revealing bimodal characteristics consistent with soil's dual pore structure.
• This technology expands the practical range and applicability of SWCC determination in unsaturated soil mechanics.