Compressibility and permeability of sand–silt tailings mixtures

Abstract

Microstructure showing the involvement of the fine and coarse grains in the soil skeleton is evaluated. Incremental loading tests using a stress-dependent permeameter are conducted on the mixtures of poorly graded sand and nonplastic fines originating from tailings. The results are compared with the published data of various tailings. It is shown that increasing the fines content from 0 to 100%, the involvement of the fine and coarse components of soil skeleton can be classified into four categories: no fines involvement (<10% fines), fines partially involved (10% —35% fines), increasing cushioning effect surrounding the coarse (35% — 40% fines), and constant cushioning effect (> 40% fines). At the same consolidation stress, the void ratio, e, rapidly decreases for fines less than 30%, then almost remains constant between 30% and 50% fines, and gradually increases for fines exceeding 50%. The hydraulic conductivity, k, decreases more than 20-fold as the fines content increases from 12% to 50%, then remains constant. k is proportional to [e3/(1+e)]A and inversely proportional to S2, where A is a factor describing the effect of particle angularity and S is the specific surface. Finally, the influence of fines content on the seepage-induced internal stability is discussed.

The Application of Geosynthetics in Tailings Storage Facilities: A General Review

“…It could be used to conduct one-dimensional consolidation testing using incremental loading followed by a hydraulic conductivity (k) test after each consolidation stage without causing specimen disturbance. Detailed descriptions of this apparatus are given by [36,37].…”

“…A study of the effect of the fines content of tailings on the soil skeleton and its compressibility was conducted using silty sand (SM), initially containing 18% non-plastic fines (<75 µm) and with a specific gravity of ~2.65. The diameters of the particles at which 10%, 30%, 50%, and 60% by mass were finer, denoted as d 10 , d 30 , d 50 , d 60 , respectively, were 0.035 mm, 0.12 mm, 0.18 mm, and 0.23 mm [36]. The coarse fraction of the host sand (>75 µm) was classified as poorly graded sand (SP), with coefficients of uniformity and curvature of 2.5 and 0.8, respectively.…”

“…Tailings are sourced from crushing and grinding ores, and the consequent irregular shape of tailings particles results in more tortuous flow paths, changing k compared to similar-sized natural soil. The effect of fines content on the k of tailings was investigated using the stress-dependent permeameter with the same aforementioned host sand material [36]. At the same consolidation stress, the test results showed that there was an over 20-fold decrease in k as the proportion of fines increased from 12% to 40%.…”

“…This paper serves as a summary of recent findings relating to the application of geosynthetics in TSFs. Topics include the impact of fines within tailings on compressibility and permeability [26,36]; the development of equations predicting leakage through circular [37] and non-circular [38,39] geomembrane holes overlain by saturated tailings and underlain by a highly permeable subgrade; the effect of the subgrade's permeability [40]; and the effect of a lateral drainage system within tailings [25] on leakage. Piping and internal erosion are discussed [41], as is the opening width of defective seams [42].…”

Stability Analysis of Cemented Tailings Backfill in Stope Considering Layered Structural Characteristics

“…The filling process comprises three steps as follows [7][8][9]. First, a high cement-sand ratio slurry is employed to fill the bottom of the goaf in the room to form higher bottom strength [10][11][12]. Subsequently, a slurry with a relatively low cement-sand ratio is adopted to fill the middle of the goaf in the rooms, with the aim of lowering filling costs.…”