Numerical analysis of the failure mechanisms of sill mats made of cemented backfill

Keita, Alpha Mamoudou Talibe; Jahanbakhshzadeh, Abtin; Li, Li

doi:10.1080/19386362.2021.1962108

Cited by 6 publications

(5 citation statements)

References 28 publications

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“…Considering the likelihood that many undercut CPB sill mats or plugs will be forced into the post-peak regime of their stress-strain response, design based on elastic beam analysis is tenuous. This interpretation is consistent with recent numerical modeling simulations considered in [41][42][43][44], where a reasonable expanse of rock mass was included surrounding the modeled stope to better capture the closure strains induced by excavation. In [43] a parametric study considered sill mats in (sub-) vertical orebodies at depths from 300 to 800 m, corresponding to horizontal stresses of 16-43 MPa.…”

Section: Implications For Mine Backfill Design Using Mitchell's Sill ...supporting

confidence: 89%

“…This interpretation is consistent with recent numerical modeling simulations considered in [41][42][43][44], where a reasonable expanse of rock mass was included surrounding the modeled stope to better capture the closure strains induced by excavation. In [43] a parametric study considered sill mats in (sub-) vertical orebodies at depths from 300 to 800 m, corresponding to horizontal stresses of 16-43 MPa. The CPB's cohesion and Young's modulus were not varied in a consistent way, but instead the modulus was varied from 0.6 to 1.8 GPa and the limiting cohesion for stability was determined.…”

Section: Implications For Mine Backfill Design Using Mitchell's Sill ...supporting

confidence: 89%

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Cemented Paste Backfill (CPB) Material Properties for Undercut Analysis

Grabinsky

Jafari

Pan

2022

Mining

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A longstanding mine backfill design challenge is determining the strength required if the (partially) cured backfill is subsequently undercut. Mitchell (1991) called the undercut backfill a sill mat and proposed an analytical solution that is still often used, at least for preliminary design, and has motivated subsequent empirical design methods. However, fully employing the Mitchell sill mat solution requires knowledge of the backfill material’s Unconfined Compressive Strength (UCS), tangent Young’s modulus (Et), tensile strength (σt), as well as estimates of stope wall closure. Conducting a high-quality UCS test poses challenges but relating the test result to the remaining material parameters is more difficult. Some new material testing data is presented and compared to available published results. Using the parameter mi=UCS/σt the range of available testing data is found to be mi= 3 to 22, however, the most compelling data is obtained when the Mohr’s failure circle in tension is tangential to the corresponding Mohr–Coulomb failure envelope determined from other strength tests. In these cases, the value mi= 4 is found for the materials tested, which is much lower than the value mi= 10 commonly assumed and implies a limiting UCS 60% lower compared to the conventional assumption. It is also found that the relationship between Et and UCS is described by a power function that is close to linear, but the values for the constant and exponent in the power function depend on the material tested. However, for given tailings the power function is found to be independent of void ratio, binder type or concentration, curing time, and water salinity, within the ranges these parameters were investigated. Therefore, when Et is used in the Mitchell sill mat solution it should be correlated with the UCS using the appropriate power function. These correlations are then used with the Mitchell sill mat solution and published measurements of backfill closure strains to estimate the Mitchell solution’s range of applicability based on its underlying assumptions, and a similar analysis is extended to an “empirical design method” motivated by the Mitchell sill mat solution. It is demonstrated that these existing approaches have limited applicability, and more generally a full analysis in support of rational design will require numerical modeling that incorporates the effect of confining stress on the material’s stiffness and mobilized strength.

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Section: Implications For Mine Backfill Design Using Mitchell's Sill ...supporting

confidence: 89%

Section: Implications For Mine Backfill Design Using Mitchell's Sill ...supporting

confidence: 89%

Cemented Paste Backfill (CPB) Material Properties for Undercut Analysis

Grabinsky

Jafari

Pan

2022

Mining

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“…However, almost all publications on mining backfill have focused on the behaviour of a single type of backfill, including the extensive works conducted by Li and co-workers over the past two decades (Aubertin et al 2003;Béket Dalcé et al 2019;El Mkadmi et al 2014;Jaouhar et al 2018;Jaouhar & Li 2019;Keita et al 2021aKeita et al , 2021bLi et al 2003;Li et al 2005;Li & Aubertin 2012;Li 2014aLi , 2014bLiu et al 2017aLiu et al , 2017bLiu et al , 2018Pagé et al 2019;Qin et al 2021aQin et al , 2021bWang et al 2021aWang et al , 2021bWang & Li 2022;Yang et al 2017Yang et al , 2018Zhai et al 2021;Zheng et al 2019Zheng et al , 2020aZheng et al , 2020bZheng et al , 2020c. Research on the natural mixing behaviour between the waste rocks and paste backfill is absent in the literature.…”

Section: Introductionmentioning

confidence: 99%

Natural mixing behaviour of waste rocks poured in a paste backfill

Zhang¹,

Li²

2023

Paste 2023: 25th International Conference on Paste, Thickened and Filtered Tailings

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In underground mines, large quantities of waste rock can be produced during development in order to access ore bodies. The waste rock is typically hoisted to the surface and transported to a specific place to make a structure called a waste rock pile. This practice requires energy consumption and generates additional operating costs for transporting waste rock from underground to the surface. Alternatively, the waste rock can be poured directly into underground mine stopes filled with paste backfill. As a result, energy consumption and additional operating costs for transporting the waste rock from underground to the surface are avoided or significantly reduced. However, the natural mixing behaviour of waste rocks poured in paste backfill has never been studied. The fill mass generated by this practice can fail and collapse upon a side-exposure associated with the excavation of an adjacent stope if a poor mixture between the cohesionless waste rocks and cemented paste backfill takes place around the exposed face. Thus, it is critical to understand the mixing behaviour of waste rocks poured in paste backfill. To this end, a series of physical model tests have been performed in the laboratory. The results, in part, are presented and discussed in this paper.

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“…The strength and stability of CPB are crucial to its engineering applications [6,7]. The ability of CPB to withstand tensile forces is essential for the stability of the backfilled stopes, particularly in areas with high stress or deformation [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

“…The direct tensile measurement of CPB has been a longstanding challenge [16]. The tensile strength of CPB is typically assumed based on unconfined compressive strength (UCS), having a ratio equal to UCS/10 or UCS/12 [1,7,11].…”

Section: Introductionmentioning

confidence: 99%

Direct Tensile Measurement for Cemented Paste Backfill

Pan,

Grabinsky

2023

Minerals

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Tensile strength is a crucial parameter involved in the design and analysis of cemented paste backfill (CPB). The ability of CPB to withstand tensile forces is essential for the stability of the backfilled stopes, particularly in areas with high stress or deformation. The tensile strength is a critical design parameter used in sill mats to perform underhand cut-and-fill operations. This study presents a novel technique that utilizes rectangular dog-bone specimens and compression to tensile load converters to perform the direct determination of tensile strength. This study indicates that the prevailing assumption regarding the ratio of unconfined compressive strength (UCS) to tensile strength (i.e., 10:1 or 12:1) underestimates the strength. The results suggest a ratio closer to 3:1 or 4:1. The findings indicate that the ratio varies with the curing interval. Specifically, the tensile-to-compressive strength ratios were higher in early-age specimens, as tensile strength values do not increase at the same rate as those of compressive strength. This disparity has notable implications, as underestimating tensile strength via traditional UCS-to-tensile strength ratios could potentially inflate binder consumption. Our study underscores the importance of using direct tensile strength measurements to optimize mining operations.

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Numerical analysis of the failure mechanisms of sill mats made of cemented backfill

Cited by 6 publications

References 28 publications

Cemented Paste Backfill (CPB) Material Properties for Undercut Analysis

Cemented Paste Backfill (CPB) Material Properties for Undercut Analysis

Natural mixing behaviour of waste rocks poured in a paste backfill

Direct Tensile Measurement for Cemented Paste Backfill

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