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Mining Publication: Cemented Paste Backfill Geomechanics at a Narrow-Vein Underhand Cut-and-Fill Mine
Keywords: Cut and fill stoping Stopes
Original creation date: December 2019
Authors: M Raffaldi, J Seymour, J Richardson, E Zahl, M Board
Peer Reviewed Journal Article - December 2019
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NIOSHTIC2 Number: 20056207
Rock Mech Rock Eng 2019 Dec; 52(12):4925-4940
Underhand cut-and-fill mining has allowed for the safe extraction of ore in many mines operating in weak rock or highly stressed, rockburst-prone ground conditions. However, the design of safe backfill undercuts is typically based on historical experience at mine operations and on the strength requirements derived from analytical beam equations. In situ measurements in backfill are not commonplace, largely due to challenges associated with instrumenting harsh mining environments. In deep, narrow-vein mines, large deformations and induced stresses fracture the cemented fill, often damaging the instruments and preventing long-term measurements. Hecla Mining Company and the Spokane Mining Research Division of the National Institute for Occupational Safety and Health (NIOSH) have worked collaboratively for several years to better quantify the geomechanics of cemented paste backfill (CPB), thereby improving safety in underhand stopes. A significant focus of this work has been an extensive in situ backfill instrumentation program to monitor long-term stope closure and induced backfill stress. Rugged and durable custom-designed closure meters were developed, allowing measurements to be taken for up to five successive undercuts and measuring closures of more than 50 cm and horizontal fill pressures up to 5.5 MPa. These large stope closures require the stress–strain response of the fill to be considered in design, rather than to rely solely on traditional methods of backfill span design based on intact fill strength. Furthermore, long-term instrument response shows a change in behavior after 13–14% strain, indicating a transition from shear yielding of the intact, cemented material to compaction of the porosity between sand grains, typical of uncemented sand fills. This strain-hardening behavior is important for mine design purposes, particularly for the use of numerical models to simulate regional rock support and stress redistribution. These quantitative measurements help justify long-standing assumptions regarding the role of backfill in ground support and will be useful for other mines operating under similar conditions.
First page of Cemented Paste Backfill Geomechanics at a Narrow-Vein Underhand Cut-and-Fill MinePeer Reviewed Journal Article - December 2019
Go to Web Page
NIOSHTIC2 Number: 20056207
Rock Mech Rock Eng 2019 Dec; 52(12):4925-4940
See Also
Deep Metal Mine Fatality Raises Questions on Use of Cemented Fill
Environmental Impacts of Cemented Mine Waste Backfill
Geophysical Methods to Detect Stress in Underground Mines
In Situ Stress at the Lucky Friday Mine (In Four Parts): 2. Analysis of Overcore Measurement From 5300 Level
Long-Term Stability of a 13.7 x 30.5-m (45 x 100-ft) Undercut Span Beneath Cemented Rockfill at the Turquoise Ridge Mine, Nevada
Numerical Modeling of Paste Sills in Underhand Cut & Fill Stopes
Rock Mechanics Investigations at the Lucky Friday Mine (In Three Parts): 2. Evaluation of Underhand Backfill Practice for Rock Burst Control
Role of Fault Slip on Mechanisms of Rock Burst Damage, Lucky Friday Mine, Idaho, USA
Technology News 436 - Stope Leaching Reduces Surface Environmental Impacts From Underground Mining
Underhand Cut and Fill Mining as Practiced in Three Deep Hard Rock Mines in the United States
Page last reviewed: March 16, 2020
Page last updated: March 16, 2020
Content source: National Institute for Occupational Safety and Health, Mining Program
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