Effect of Filling Interval Time on Mechanical Characteristics of Cemented Tailing Backfill

[Image: see text] In order to study the strength reduction caused by delamination, single-gap and double-gap specimens were made, and a uniaxial compressive strength (UCS) test was used to analyze the relationship between filling interval time (FIT) and UCS of single and double-spacing specimens. Based on the cement hydration reaction theory and damage mechanics, the influence mechanism of the FIT on backfill strength was studied. The test results show that the UCS of double-interval backfill is affected by two filling intervals at the same time, and the lower clearance has a greater influence on the strength of the backfill than the upper clearance. With the increase of FIT, the UCS of the filling body decreases gradually. The cementation effect of single and double fillings is negatively correlated with the FIT. Filling within 0–12 h has little effect on the strength of the filling body. On this basis, a mathematical model between damage increment and damage dissipated energy is established. Under the same stress condition, the larger the damage variable (D), the smaller the dissipated energy (G) required by the damage expansion of unit filling body. This study provides a reasonable reference for the design of the filling interval in mine fractional filling.