Presas de relaves de arena de gran altura: desafíos principales
IntroductionThe design, construction and operation of tailings sand dams represent an important geotechnical task in terms of stability, especially under foreseen strong seismic events. analyses the effect of fines content and permeability on the seismic performance of tailings sand dams in Chile. He also pointed out the fact of the significant growth of the mining production, which has led to the necessity of large tailings deposits, many of them resulting in dams with increasing height. Consequently, the study of the geotechnical behaviour of granular materials under high confining pressures becomes necessary. This article extends the contents of permeability, drained and undrained resistance of sands under high pressures previously studied by . The attention here is focused initially on the compressibility and cyclic resistance of tailings under high confinement pressures. Then, crushing and deformation of gravel and rock-fill materials under high confinement pressures are studied because they form part of the drainage system of tailing dams. The use of numerical analysis in the study of the stability of tailings dams is subsequently introduced. Furthermore, the observational method is considered as an important tool of assessment of tailings dams performance. Finally, new trends of mine 18 . Obras y Proyectos 20, [17][18][19][20][21][22][23][24][25][26][27][28][29] waste disposal are mentioned to tackle challenges of space and efficient use of water.
Deformation of sands at high confinement pressuresOedometric compressibility in sands is very low, independent of the initial void ratio for confining pressures lower than 1 MPa. Oedometric compressibility of these materials begins to increase as particles break up, when compressibility of the granular skeleton becomes independent of the initial arrangement. Figure 1 shows the results of oedometric compressibility of tailings sands samples S1 to S5 with uniformity coefficient C u (d 60 /d 10 ) between 1.0 and 3.2, of natural Ottawa quartz sands samples (Murthy et al., 2007), of rounded particles and with C u between 1.5 and 2.7, and of Hostun sand (Colliat-D'Angus, 1986), of angular particles and with C u of 1.7. Figure 1 shows that rounded Ottawa sand particles undergo a sudden change in compressibility due to the break-up of particles when they are subjected to effective vertical stresses s' v > 30 MPa. In Hostun sand, however, the increase in compressibility is progressive, due first to loss of particle angularity and then to the gradual break-up of particles. For s' v > 40 MPa, both types of sands exhibit a similar degree of compressibility.Tailings sands in general exhibit low compressibility up to s' v = 1 MPa, provided they have a void ratio of at least 0.8 approximately, evidenced by a moderate volumetric change similar to the one observed in the sands discussed above. At pressures of s' v > 1 MPa, compressibility begins to increase progressively, due to breaking of the more angular edges o...
