Insights into anisotropic swelling pressure of compacted GMZ bentonite: Fid-Bau Portal

Insights into anisotropic swelling pressure of compacted GMZ bentonite

Lu, Yu / Ye, Wei-min / Wang, Qiong / Chen, Yong-gui

To construct an engineering barrier in a deep geological repository, bentonite generally should be laid out in blocks, which are commonly pre-prepared through uniaxial static compactions. The way of compaction and installation of the bentonite blocks will inevitably influence swelling performance of the bentonite compacted and eventually buffer functions of the engineering barrier system constructed. In this article, a new experimental apparatus was developed and cubic GMZ bentonite specimens with different initial suctions and dry densities were statically compacted. Swelling pressures were measured parallel to and perpendicular to the compaction direction/axis of the cubic specimens prepared in different ways. Results confirmed existence of the residual lateral stress and sidewall friction. The swelling pressure parallel to is higher than that perpendicular to the compaction axis, and its anisotropy coefficient tends to decrease to a certain degree upon hydration. Specimen with higher initial suction swells much quicker and exhibits a more significant intermediate period. The initial suction effects on anisotropy coefficient depend on hydration. The measured swelling pressure significantly increases with increasing dry density with about a 9.6- times increase as the density increased from 1.5 to 1.9 Mg/m³. The anisotropy coefficient of swelling pressure increases at first and then decreases a little bit with increasing dry density (e.g., the final anisotropy coefficient exhibited a 1% decrease while dry density changed from 1.8 to 1.9 Mg/m³).