HIGH-SUCTION POLYMER SENSOR FOR MEASUREMENT OF SOIL-WATER CHARACTERISTIC CURVES

Abstract

Soil failure is deemed one of the most prevalent disasters in the world, with several problems occurring each year, including slope instability, foundation failure, and many others. Given the loss of many lives and considerable economic damage, soil properties should be properly acquired, particularly soil-water characteristic curves (SWCC), which are part of unsaturated soil properties. SWCC is an interaction between soil suction and moisture content, where the complexities lie in obtaining soil suction. There are numerous techniques for obtaining soil suction, both direct and indirect; however, numerous challenges exist due to instrument inaccuracy, methodology complexity, and suction range limitations. This work concentrated on the development of a high-suction polymer sensor (HSPS) to simplify the methods for obtaining soil suction value throughout a wide range of measurements. Polymers with superabsorbent properties were utilized as they have high-water uptake due to its significant osmotic gradient. The polymers were inserted into the apparatus, and numerous polymers were made before the test, namely polyvinyl alcohol (PVA), polyvinyl alcohol-copolymer-acrylamide (PVA-co-AAm), and polyacrylamide (PAM). The study used two samples: Nazarbayev University (NU) soil which is located in Astana, Kazakhstan (natural soil) and a combination of 60% sand with 40% kaolin, 60S40K (engineered soil). Unimodal and bimodal best-fitting equations were utilized to identify the soil type based on its soil pores. The results showed that the HSPS can substitute for the conventional apparatus to measure soil suction from low to mid-range areas, with an accuracy comparable to one, indicating that the HSPS measurement is reliable. The study found that PAM has the highest capacity to monitor soil suction, particularly over long periods, with a potential of approximately 2 MPa. The HSPS even demonstrated that it can measure soil suction during freeze-thaw cycles. Further research into HSPS and polymer studies is required to improve its ability to quantify soil suction over an extensive range, especially in the high-range area.