Tensile strength of cemented paste backfill for lead–zinc mill tailings: lab and in situ scenarios

Cemented paste backfilling (CPB) in underground mines is a widely accepted backfilling technique. It has plenty of scope for application in Indian underground mines. Both the uniaxial compressive strength (UCS) and tensile strength (TS) are the essential CPB design parameters. During adjacent stope extraction, minor principal stresses in the backfill mass increase; to overcome these minor principal stresses, the CPB should have sufficient TS. There are limited studies reported in literature about TS of CPB both in lab and in situ conditions, correlation between TS and UCS of CPB and tensile strength prediction models. In this article, the tensile strength development in CPB prepared using lead–zinc mill tailings with different binders (cement, fly ash, and slag) was investigated and statistical tensile strength prediction models were developed. Moreover, the correlation between TS and UCS of CPB was statistically determined with a developed correlation model. Further, the in situ strength of paste backfill specimens was determined and compared with the lab-determined strength. The in situ backfill specimens showed a shrunk of 28-day UCS and TS by 9% and 7%, respectively, as compared to lab-prepared specimens. The findings of this study would help in bulk environment-friendly tailings disposal in underground mines, better backfill strength design, and further excavation processes in lead–zinc underground mines.