A novel multifunctional apparatus for testing unsaturated soils

There are limited studies in the development of testing apparatus on unsaturated soils due to the complex structure, tedious calibration process, and large demands on test time and skills. In this study, a novel multifunctional apparatus (MFA) has been designed and manufactured for testing the unsaturated soils. This state-of-the-art testing apparatus is based on modular design and can be configured to conduct a variety of tests such as pressure plate test, oedometer test, direct shear test, and triaxial creep test under suction-controlled conditions. This apparatus has a high-grade stainless-steel chamber which is used to measure the total volume changes of an unsaturated soil specimen in triaxial creep tests. Based on the calibration results, the creep coefficient for MFA is about half of the coefficient for a typical double-cell system. Additionally, the MFA is designed in a manner to enable testing specimens with different dimensions and to control soil suction based on different techniques. Typical calibration results, test procedures, and experimental results obtained from this apparatus are presented and discussed in detail. Finally, the performance of this apparatus is well verified by the experimental results. It is found that the MFA is capable of and reliable for performing above-mentioned tests and accurately investigating engineering behaviour of both saturated and unsaturated geomaterials.