Formation mechanism and deformation characteristics of stratified cemented tailings backfill under noncontinuous filling system

Abstract

This study aimed to explore the formation mechanism and deformation characteristics of stratified cemented tailings backfill (SCTB) under noncontinuous filling system. Accordingly, SCTB samples with filling interval time of 0 min, 20 min, 40 min, 80 min, 120 min, and 200 min were prepared. The cement-to-tailings ratio were 1: 4, 1: 6, and 1: 8, and the solid content were 68%, 70%, and 72%, respectively. The initial width variation of the stratified surfaces was investigated using scanning electron microscopy test. The mechanical properties and deformation characteristics of SCTB samples were investigated using unconfined compression test based on digital image correlation method. Our results demonstrate the following points: (1) The initial width of the stratified surfaces increases exponentially and approaches a fixed value when the filling interval time increases. The stratified surfaces are formed due to the difference in hydration reaction between the two parts of the backfill. (2) The elastic modulus of the sample decreases significantly at a certain filling time when the filling interval time increases. The effects of cement-to-tailings ratio and solid content on the elastic modulus of samples are greater than that of filling interval time. (3) The unconfined compression strength (UCS) of SCTB decreases significantly at a certain filling interval time when the filling interval time increases. The certain filling interval time reduces with the increase in cement-to-tailings ratio and solid content. The effects of filling interval time on the deformation characteristics of the sample are far greater than that on the strength characteristics. (4) The existence of stratified surfaces significantly affects the axial deformation of specimens. With the increase in filling interval time, the strain difference between the stratified surface and the average strain increases, and the difference has a sharp increase at a certain filling interval time. The certain filling interval time reduces with the increase in cement-to-tailings ratio and solid content. As the filling interval time further increases, the strain difference no longer changes significantly.