Long Nguyen-Tuan

A Column Experiment to Study the Thermo-Hydro-Mechanical Behaviour of Expansive Soils

The study of heat transfer, water flow, and swelling pressure development in engineered clay barriers and the evaluation of the influence of these phenomena on the barrier properties are important issues for predicting the performance of nuclear waste repository facilities. In this work, an experimental setup is presented especially meant to assess the response of the sand–bentonite mixture under conditions close to that of the buffer in a radioactive waste repository. A newly developed column device for laboratory testing of coupled thermo-hydro-mechanical (THM) behaviour of clay-buffer materials is introduced and its calibration, verification and the first experimental data are presented and discussed. The main features of the column device are: hydraulic and thermal gradients are possible to be applied; water content, suction and temperature development can be measured continuously at three locations along the sample height; swelling stress can be measured at top and the bottom of the sample. Measuring transient temperature, water content and suction simultaneously at the same height levels and with special care to minimise the sample disturbance is one of the advantages of the column device proposed here when compared to that previously reported in the literature. The main objectives of this paper are: (1) to describe the experimental device, (2) to introduce the sensors implemented and their calibration, and (3) to present and discuss the first experimental results obtained with the new equipment. The first experimental results show promise in the ability of the newly developed column device to provide reliable data for assessing the THM behaviour of expansive materials that are foreseen as buffer material in high level waste repositories.

Thermo-Hydro Mechanical Column Experiment to Study Expansive Soil Behaviour

Understanding the heat transfer, water flow, and swelling pressure development in engineered clay barrier and the evaluation of the influence of these phenomena on the barrier performance are important issues in constructing nuclear waste repositories. The thermal, hydraulic and mechanical processes that take place within the clay barrier during its functioning lifetime are strongly coupled and therefore difficult for experimental and numerical modelling. In order to collect valuable experimental data for predicting the long term barrier functionality it is necessary to carry out tests with known and controlled initial and boundary conditions as well as to measure temperature, water content and mechanical stress along the specimen in a reliable and robust way. For this reason a new apparatus has been developed for laboratory testing of coupled thermo-hydro-mechanical behaviour of clay-buffer material under conditions close to the situation in the field. The main objectives of this paper are: (1) to describe the experimental device; (2) to introduce the sensors implemented and their calibration, and (3) to present the first experimental results obtained with the new equipment.