Integrative testing device for investigating the hydro-mechanical behavior of highly expansive clay

Highly expansive clay is prone to cause extensive engineering damage, which can also be a potential construction material owing to the desirable characteristics of the active clay minerals in soils. Therefore, it is essential to understand the geotechnical characteristics of highly expansive clay. In this study, integrative apparatus was developed to examine the hydro-performance behavior of highly expansive clay, including the swelling ability and hydraulic and compression properties. Unlike that in the traditional method involving loading by a loading frame, a unique dual-piston system was used to convert the water injection pressure into the loading pressure with a static magnification factor of 0.729, and to transfer the real-time swelling pressure of the specimen in the vertical direction. A series of traditional tests were conducted on bentonite specimen using the proposed device, and aforementioned soil parameters were simultaneously or continuously obtained, i.e., the swelling pressure, saturated hydraulic conductivity, and deformation of the same specimen. The test results exhibited a high repeatability, and the test system was considered to be highly reliable. The integrative testing device can be an effective tool to examine the hydro-mechanical behaviors of highly expansive clay.