The use of cemented paste backfill (CPB) is becoming increasingly more common at underground mines worldwide. Part of any CPB design includes the specification of the (typically) shotcrete barricades that retain the CPB within the stope during filling. Newmonts Tanami Operations (NTO) has started an in situ barricade stress monitoring program. The data from this program will provide a basis for comparison of several models that can be used to model the capacity of these barricades. These models vary in complexity from analytical solutions to 3D numerical models. Part of the comparison will include a discussion detailing the required material inputs and how these inputs were obtained. Analysis of this comparison will provide additional understanding on what parameters affect the ultimate capacity of a shotcrete barricade.
This bulletin provides references to publications written up until 1989 on tailings dams. It divides the references into the following categories: Tailings Sources; Deposition and Disposal Techniques; Safety and Failures; Stability of Tailings Embankments including Seismic Aspects; Material Properties and Evaluation; Legal Aspects; Site Selection and Investigation; Tailings Transportation; Drainage, Seepage and Groundwater; Decants, Water Management; Pollution Control and Environmental Aspects; Closure and Rehabilitation:Monitoring; Instrumentation; Vegetation; Reworking Existing Deposits; General.
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.
The perceived need for accurate and reliable methods of measuring suspension rheology in real time arises from the greater demands being placed on mineral processing operations. To extend mine life and reduce TSF footprint the adoption of finer grinds, higher solids concentration and high clay ores result in complex multiphase suspensions that need close monitoring to optimise thickener performance, pipeline transport and tailings deposition. Often the control of the processing or transport of these suspensions can be related to its rheology. However, due to the involved nature of rheological measurement for suspensions and the nuanced interpretation of data necessary to produce useful decisions, rheometry has only seen limited application in process monitoring. A robust unit that can measure, analyse and interpret the rheology of a process stream continuously and unattended is needed. The CSIRO has developed an online rheometer to address this problem. This paper describes the process prior to the deployment of the online rheometer to an Australian goldfield site, comparing online rheological measurement to benchmark laboratory values.
Cemented paste backfill (CPB) has become known as a superior secondary ground support technique and mine tailings storage method for stoping. Extensive scientific research has been conducted by the authors on CPB to provide the Red Lake operation (RLO) of Evolution Mining with an optimised backfill placement process. Due to these complex factors and interactions, a rational CPB material design process was assessed to demonstrate the safety aspects related to a continuous pour. For this purpose, an extensive field monitoring program was required to quantify the CPB performance and characteristics. There are two different ways of optimising the CPB design to maximise placement rate: (i) optimising the type and amount of binder added to the system, and (ii) optimising the CPB placement process underground. Optimisation of binder type and dosage is relatively easy as the required backfill stand-up strength is based on block dimensions, stope stability, and extraction sequencing. Four stopes were instrumented with total earth pressure cells (TEPCs) and piezometers to capture the pressures acting on the fill fence structures and the strengthening response of the CPB plug within the stopes. This paper summarises the results of each of the tests performed. Based on the results obtained from this study, it was concluded that RLO can safely conduct continuous CPB pours with appropriate safeguards and protocols in place. It is important to note that this paper is a summary of the CPB performance and characteristics in RLO longhole stopes and does not reflect site-specific safety procedures, protocols, and critical controls required for a more aggressive pouring regime.
One of the earliest attempts at field measurement within hydraulically placed cemented backfill occurred over 20 years ago. Recently, Thompson et al. (2014a) published their findings on capturing thermal expansion within cemented paste backfill (CPB) and cemented hydraulic backfill (CHB). They discovered that the total earth pressure within the CPB following placement is likely to increase at a rate of 30 kPa/°C (i.e. for an 11°C temperature increase). However, Thompson and his co-authors' research did not elaborate on the subsequent effects of thermal dissipation (or thermal contraction) in backfill. A comprehensive literature study concluded with no clear evidence of thermal dissipation phenomenon and its effects in backfill. It is hypothesised by the authors that if thermal expansion can occur, then thermal dissipation or contraction is also likely to occur. Red Lake operation (RLO) of Evolution Mining conducted a field program to capture the characteristics of the CPB during a transition from a plugcuremain pour strategy to a more aggressive pour strategy (i.e. continuous pour operation). During this investigation, strong evidence of thermal contraction was observed in three of the four instrumented stopes. This paper presents detailed findings of two of the instrumented stopes.
Mining facilities store process water or paste slurry. Lateral and vertical water percolation may create major problems concerning dam safety and environmental impact. Means for monitoring the saturated zone is widely used, but none concerning the unsaturated zone (vadose zone). A novel Vadose Zone Monitoring System (VMS) was developed at Ben Gurion University in Israel. VMS units include a set of advanced water and pressure sensors along with sampling ports. The units are mounted on a flexible sleeve which is installed through dedicated uncased small diameter boreholes. Through a control panel on the surface, data is transmitted via a cloud-based server directly to the clients dedicated application. Over the past decade, the VMS was successfully installed in a variety of scientific and commercial projects on water infiltration and contaminant transport from land surface to the groundwater in a variety of geological and hydrological setups. Recently, fertilizers producer in Israel (ICL), installed several VMS stations under phosphogypsum waste lagoons for monitoring the potential leaks from the bottom of lagoons to the subsurface, and one system in in an earthen dam for monitoring its safety status. The case study deals with contamination that was discovered in the aquifer. Continuous monitoring of water percolation beneath the ponds indicated that the levels of water percolation and pollution potential from these ponds are relatively low and therefore environmentally safe. These findings were accepted by the environmental authorities and the client wrote: "The VMS already had an important use, in proving the authorities that the contamination is from another source and not from our cell. We couldn't have done it any other way". Implementing of the VMS systems at the above case and other cases produced real time information which has proved to be critical for maintaining long term safe operation of tailing sites.
Topics include the physics of remote sensing, data sources, image processing, and preparation of data for inclusion in a geographic information system (GIS) for further analyses. A summary of former and current Denver Office remote sensing studies is appended to show the variety of possible topics.