Post-failure behavior of two mine pillars confined with backfill

Tesarik, D.R.; Seymour, J. B.; Yanske, T.R.

doi:10.1016/s1365-1609(02)00139-9

Cited by 22 publications

(6 citation statements)

References 2 publications

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“…However, if the abutment is confined by backfill, the amount of this dilation could be reduced. Previous NIOSH studies have demonstrated that backfill confinement limits pillar dilation and enhances the ground support characteristics of mine pillars (Seymour et al 1998; Tesarik et al 2003).…”

Section: Long-term Responsementioning

confidence: 99%

Long-Term Stability of a 13.7 × 30.5-m (45 × 100-ft) Undercut Span Beneath Cemented Rockfill at the Turquoise Ridge Mine, Nevada

et al. 2019

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In 2001, researchers from the National Institute for Occupational Safety and Health (NIOSH) installed instruments at the Turquoise Ridge Mine in cooperation with Placer Dome, Inc. to monitor the geomechanical behavior and stability of a cemented rockfill (CRF) sill and the surrounding host rock during test mining of a large undercut span beneath backfill. Six parallel, adjacent drifts were mined and backfilled to construct a CRF sill, approximately 22.9 m (75 ft) wide by 30.5 m (100 ft) long. The sill was then partially undercut, successfully creating a 13.7-m (45-ft) wide by 30.5-m (100-ft) long span beneath the CRF. Only small vertical displacements were measured in the overlying host rock during mining, with most of the movement occurring at shallow depths in the mine roof. Because the back above the CRF sill remained stable, the majority of the mining-induced stress was transferred to the host rock abutments rather than to the backfilled drifts. During retreat mining of the undercut span, the CRF sill and the mine roof remained stable. Most of the measured vertical displacement was caused by separation of the backfill from the overlying host rock, or deflection of the CRF sill, which was comparable to the deflection of a monolithic, elastic plate having similar dimensions, material properties, and undercut spans. The CRF sill moved in mass as a single unit rather than as individual drift segments, and the vertical cold joints between adjacent backfill drifts did not adversely affect their stability. Additional measurements collected from the instruments have shown that the backfill span is still intact and in stable condition more than 16 years after the completion of undercut mining. Displacements in the mine roof and abutments have stabilized, and vertical stress and deformation within the CRF have generally leveled off or decreased. Although only slight mining-induced loads were transferred to the backfilled drifts, the CRF has confined the abutment ribs and mine roof, thereby improving their long-term stability. Results of compressive and tensile strength tests conducted with CRF samples from the test site indicate that the long-term compressive strength gain for CRF is similar to that of concrete, and that the tensile-to-compressive strength ratio for CRF is about 1/6 rather than 1/10. Assuming the in-place CRF gained strength at the same rate as the lab samples, an analytical analysis of the flexural stability of the CRF undercut span shows that the Factor of Safety for the span should have logically increased over time. By providing a better understanding of the long-term strength properties and geomechanical behavior of CRF, these research findings help improve the methods that are used for designing stable, long-term undercut entries beneath cemented backfill.

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Section: Long-term Responsementioning

confidence: 99%

Long-Term Stability of a 13.7 × 30.5-m (45 × 100-ft) Undercut Span Beneath Cemented Rockfill at the Turquoise Ridge Mine, Nevada

et al. 2019

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“…When confinement was 1,000 psi, this coal showed strain-hardening behavior. Tesarik et al [2003] measured stress change and dilation of pillars confined by backfill, with pillars mined sequentially. They calibrated a UTAH3 model to extensometer readings using the elasticperfectly plastic Drucker-Prager constitutive material model.…”

Section: Calibration To Post-peak Strength Behaviormentioning

confidence: 99%

Ground stress in mining (part 2): calibrating and verifying longwall stress models.

Larson¹,

Tesarik²,

Johnson³

2020

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The boundary element code MULSIM/NL was modified to accommodate a larger number of elements in the mesh, and a stress-versus-strain material model defined by a piecewise linear function, called the five-point material model, was added and verified. This updated version of MULSIM/NL is named MulsimNL/Large. MulsimNL/Large and FLAC 3D , the latter using an unverified and uncalibrated caving model, calculated gob loading that was in a reasonable range. However, better estimates of gob loading are necessary to proceed further with full model calibration. Detailed pillar models using FLAC 3D suggested that alternatives to the Mark-Bieniawski pillar strength model should be considered, especially for pillars with a width-to-height ratio greater than eight. A Holland-Gaddy equation fit to data from FLAC 3D models consisting of average pillar strength versus pillar width-to-height ratio showed better ability to describe model results than did the Mark-Bieniawski strength equation. Experience with the detailed pillar models also suggests that stratigraphy should be modeled, wherever possible. Borehole pressure cell (BPC) trends and comparison of model-calculated load transfer distance with equivalent load transfer distance determined from measurements of first arrival of mining-induced abutment stress strongly suggest that commonly used yield models were inadequate to describe seam material behavior near the ribs at Mine A. A MulsimNL/Large elastic model with the coal modulus reduced in the outer two rings to 60% and 80% of full value, respectively, provided the best match of "measured" versus model-calculated load transfer distance derived from stress increase at each BPC site. In considering appropriate strength models that might sufficiently simulate this behavior, measurements indicate that ribs are sometimes able to take much more stress than that calculated using most common yield strengths models, suggesting that strain-hardening might be an important part of the coal pillar behavior near pillar ribs. Observations in these two case studies (Mines A and B) suggest that geologic structure changes, not represented in the models, were important for predicting stress and instability of ground. Observations suggest that prior knowledge of structure change and individual structure properties would be necessary to adequately simulate its effect on stresses and failures with a particular mining layout.

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“…The mine design process must include calculations of pillar failure, but the post-failure stress-strain relationship is often unknown. [30] has described the post failure stress-strain relationship for rock fill-confined pillars in the Buick Mine with estimation of rock mass modulus, uniaxial compressive strength, and residual strength etc. They have used data from the calibrated model to show a strain-hardening stressversus-strain relationship.…”

Section: Residual Strength Of Intact Rockmentioning

confidence: 99%

Post-failure fatigue behaviour of intact sandstone from burst prone coal mine in Ostrava-Karvina Coalfield

Bagde¹

2016

Proceedings of the Conference on Recent Advances in Rock Engineering (RARE 2016)

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In the literature, mostly, pre-failure behaviour of the intact rock in static and rarely in cyclic loading is reported. In various earlier publications on the subject by the authors, pre-failure fatigue behaviour of intact rock is discussed. The post-failure behaviour of the intact rock in the laboratory is still a topic of hard discussion and of debate. Many researcher's of the opinion that post-failure behaviour of the intact rock is not of that rock under testing but it is simply of servo-controlled testing machines. However, in the present paper, post-failure fatigue behaviour of intact sandstone rock obtained from the rock burst prone coal mines in Ostrava-Karvina region in the Czech Republic subjected to uni-axial cyclical loading is discussed. From the presented results, the importance of post-failure behaviour in mine pillar and support design is emphasized. This study has practical significance to the behaviour of rock and rock masses within the excavation systems subjected to dynamic cyclic loads, since tested rocks were from the rock burst prone coal mines from the Ostrava-Karvina Coal Basin in the Czech Republic.

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Post-failure behavior of two mine pillars confined with backfill

Cited by 22 publications

References 2 publications

Long-Term Stability of a 13.7 × 30.5-m (45 × 100-ft) Undercut Span Beneath Cemented Rockfill at the Turquoise Ridge Mine, Nevada

Long-Term Stability of a 13.7 × 30.5-m (45 × 100-ft) Undercut Span Beneath Cemented Rockfill at the Turquoise Ridge Mine, Nevada

Ground stress in mining (part 2): calibrating and verifying longwall stress models.

Post-failure fatigue behaviour of intact sandstone from burst prone coal mine in Ostrava-Karvina Coalfield

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