In situ backfilll monitoring database

The history of backfilling underground mined-out voids dates back to the beginning of mining several centuries ago using rockfill. Currently, there are three major types of backfill: rock, hydraulic, and paste fill. When backfill is required to be exposed from mining beside or underneath, cement binder is added. Cemented hydraulic fill is the most commonly used backfill as it has existed for over 80 years. In the early 1960s, a series of field instrumentations were initiated by the US Bureau of Mines on hydraulic fill. These studies were conducted in order to better understand the characteristics of hydraulic backfill. Cemented paste backfill (CPB) has gained wider acceptance in the mining industry and the number of operations utilising CPB has expanded significantly. One of the earliest attempts at field measurement in CPB occurred over 20 years ago. Since then, extensive scientific research has been conducted on CPB material in order to provide mines with a rational design process; however, there has been limited published instrumentation programs. The authors’ affiliated company has been involved with in-stope backfill instrumentation programs at numerous operations. Because of the data collection and field experience, the authors have a better understanding of how in situ backfill behaves, and how operations can use this information to safely improve the efficiency of their backfilling operation. In order to improve the safety and efficiencies of backfilling for other mines and other practitioners, a collection of published data along with additional case studies are provided. This paper summarises both hydraulic and CPB instrumentation results focusing on the important mechanical properties of backfill: time to onset of effective stresses and hydrostatic loading (i.e. fluid backfill to soil‐like material), influences of flushes, thermal expansion and contraction, and influences of seismic and blast events.