Slurry Deposition Method for Reconstituted Specimen in Triaxial and Consolidation Tests
Igor Abreu Abreu1; Stephanie Oliveira Moura e Sa1; Waldyr Lopes Oliveira Filho1; Andy Fourie2
1 UFOP; 2 UWA
Resumo
It is always challenging to obtain in situ engineering properties of cohesionless soils and coarse mining tailings in the laboratory due to difficulties to preserve or replicate factors such as density, fabric, and stress/strain history. Frozen techniques, covering sampling, specimen trimming and testing, have been developed over the years giving satisfactory results, but they are far from being practical considering their complexity and troublesome procedures. Reconstitution methods are usually the preferable choice and several options exist for specimen preparation. In this paper a special case of water pluviation technique called slurry deposition is reported and used to determine shear strength and consolidation properties of a fine sand tailings with high silt content (48%). Reasons for selecting this method are various: first of all underwater settling conditions simulate better tailings deposit formation; secondly the technique also minimize or eliminate particle segregation; thirdly higher initial degree of saturation can be obtained; lastly slurry deposition specimen preparation requires simple equipment comprised of an open acrylic glass cylinder tube (specimen diameter and height regulated by solids content), two rubber stoppers (one with a hole and a tube and valve), and a testing mold. For triaxial testing, a 140 x 70 mm cylinder specimen (height x diameter) was prepared, using a splitting mold with a vacuum device for membrane stretching. Two solids content were used for specimen preparation resulting in relative densities around 30% and 60%. Maximum back pressure of 450 kPa was enough to get B-values higher than 96%. Altogether five CIU and one CID triaxial tests were performed at effective stress of 50 kPa. Results have shown consistency regarding stress-paths and stress-strain behaviors. Similarly specimen preparation was also undertaken for one-dimensional consolidation test using incremental load. 70 mm diameter and 30 mm high specimens were produced by the slurry deposition method, resulti
Palavras-chave: Specimen Reconstitution Method; Slurry Deposition; Silty Sand