Swelling and seepage characteristics of loosely packed bentonite pellet-contained materials
MA Guoliang1，ZHANG Huyuan1，2，JI Ze1，TAN Yu1
(1. School of Civil Engineering and Mechanics，Lanzhou University，Lanzhou，Gansu 730000，China；
2. Key Laboratory of Mechanics on Disaster and Environment in Western China，Ministry of Education，Lanzhou University，Lanzhou，Gansu 730000，China)
Abstract：In the high-level radioactive waste repository，the researchers proposed to fill the construction joints in the engineering barriers with bentonite pellet-contained materials. However，the current understanding of the effect of particle size distribution on the hydro-mechanical properties of bentonite pellet-contained materials is limited. Swell index tests，free swelling strain tests，and hydraulic conductivity tests were conducted on four typical gradations of bentonite pellet-contained materials. Results show that different gradations led to different packing dry densities and thus different swell indexes. However，the pellet fraction would affect the expanded volume of materials. The swelling strains of bentonite pellet-contained materials changed rapidly in the initial stage of immersion. The expansion deformation rates for the pellet-contained materials were 1﹣2 orders of magnitude larger than that of the compacted bentonite powder. Subsequently，the expansion deformation rates continued to decrease and became consistent with the expansion deformation rate of the compacted bentonite powder. The hydraulic conductivity of bentonite pellet-contained materials decreased rapidly by 3﹣4 orders of magnitude within the initial 60 minutes，and then decreased slowly and tended to a stable value. Both the initial packing dry density and gradation of bentonite pellet-contained materials can affect the maximum swelling strain and saturated hydraulic conductivity.
2020, Vol. 39 
