Determination of soil-water characteristics curves of sands using the evaporation method

• Main Author: On, Roger Zhi Wei
• Other Authors: Leong Eng Choon
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2024
• Subjects: Engineering
• Online Access: https://hdl.handle.net/10356/177815
• Institution: Nanyang Technological University

Commonly, the Soil-Water Characteristic Curves (SWCCs) of sands are determined using the suction table and the Tempe cell method. Lately, a commercial system (HYPROP 2) has been increasingly used to determine SWCCs and permeability function in the low suction range (0-200 kPa). The HYPROP 2 is based on the evaporation method. The HYPROP 2 uses two small tensiometers and a weighing balance to work out the soil-water characteristic curve and permeability function using a software to perform inverse analysis. For sands, the Tempe Cell has sufficient suction range to obtain the complete SWCC. However, the experiment is time-consuming as regular measurements are required to track the changes in sands’ water content and suction over time. Commercial equipment such as the HYPROP 2 by Meter Group AG has been developed to expedite the experimental process of obtaining the SWCC of soils from 0 to 200 kPa suction using the evaporation method but is very costly. Moreover, such commercial equipment requires a steep learning curve and proper training to use them effectively. Recently, researchers have explored other innovative methods to obtain the SWCC of sands such as the utilisation of low-cost capacitive and resistive moisture content sensors with data loggers. In this project, a simpler setup compared to the HYPROP 2 was used. This simpler setup consists of a small tip tensiometer connected to a pressure transducer to read suction and low-cost capacitive and resistive moisture sensors to read water content in order to obtain the SWCC of sands. The performance of low-cost capacitive and resistive sensors was compared with the more expensive ECH2O EC 5 and the TEROS 10 moisture sensors to evaluate their performance and capabilities to obtain the SWCCs. Subsequently, the developed SWCCs from this simplified setup were compared against the SWCC obtained from the Tempe Cell. The effects of sand type and evaporation rate were also evaluated.