Experimental study on compressibility and permeability characteristics of dewatered slurry cake backfill

After the slurry is dewatered by pressure filtration, the dewatered slurry cake is formed. After loading and unloading, transportation and other processing links, the dewatered slurry cake is broken into pieces of different sizes. Dewatered slurry cake backfill has obvious dual-porosity characteristics, including macro-pores between cakes and micro-pores inside cakes. In order to guide the filling operation of the dewatered slurry cake, the compressibility and permeability of the dewatered slurry cake backfill are studied in this research. The compaction of the dewatered slurry cake as the load increases during the backfilling is simulated by using the large-scale solid waste compression-permeation experimental system. The change of pore structure in the sample during compression is analyzed based on the CT scan. And the change of permeability of dewatered slurry cake backfill in the process of compression is studied at the same time. The results show that the sample of the dewatered slurry cake is compacted gradually with the increase of external load. The scale difference between the macro-pores and the micro-pores decreases gradually, and the dual-porosity characteristics weakens with the process of compression. When the overlying load is 295 kPa, the volume ratio of air of the sample is 5%. At this time, the sample becomes a homogeneous lump slurry cake, and the corresponding compaction degree is 0.87. In addition, the permeability of the sample also changes from a medium permeability grade at the initial stage (0 kPa) to a weak permeability grade. Considering the operability and economy, it is suggested that the compaction degree should be set as 0.85 during the backfilling of the dewatered slurry cake.