Tensile Strength of Cemented Paste Backfill

Pan, Andrew; Grabinsky, Murray

doi:10.1520/gtj20200206

Cited by 11 publications

(20 citation statements)

References 21 publications

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“…This hardening resulted in an increased value of the critical stress to break the sample. The result was consistent with the studies of direct shear by Nasir and Fall (2008), and Koupouli et al (2016), and the tensile by Pan and Grabinsky (2021) in which the shear strengths were related to the binder content and the curing time [4,5,12].…”

Section: Strength Propertiessupporting

confidence: 91%

“…The numerical simulation was performed by RS2 v9.0 FEA software to determine the stress distribution. The CPB strength parameters were based on direct shear, unconfined compression strength (UCS), and direct tensile tests [6,12,23]. The parameters in the finite element simulations are as follows.…”

Section: Numerical Simulationmentioning

confidence: 99%

“…Indeed, CPB must remain stable during the extraction of the adjacent stopes to ensure the safety of the mine operations. Significant progress has been made in understanding the mechanical properties of CPB including failure mechanism under direct shear [4][5][6], uniaxial compression [7], triaxial [8][9][10], and tensile failure [11][12][13]. Nevertheless, the shear resistances under tensile stress-particularly those controlling the sprawling and caving-are not well understood due to limited testing techniques.…”

Section: Introductionmentioning

confidence: 99%

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Hybrid Failure of Cemented Paste Backfill

et al. 2021

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The hybrid failure is a coupled failure mechanism under the action of tensile and shear stresses. The failure is critical in cemented paste backfill (CPB) since there are no visible signs prior to the failure. Few studies have been conducted on the coupled stress response of CPB. This is most likely due to a lack of suitable laboratory equipment and test procedures. This paper presents a new punching shear apparatus to evaluate the hybrid failure of CPB. We harness two-dimensional finite element analysis (FEA) for supplementing experimental study in providing stress transformation, deformation, and possible failure mechanisms. Our study suggests that the coupled stress is a combination of tensile and shear strength in function of the angle of the frustum. The strengths measured by the coupled stress are comparable to those measured by direct shear and tensile strength tests, in which the strength properties of CPB are curing time and binder content dependent. The FEA results substantiate the effectiveness of proposed model for predicting the hybrid failure of CPB.

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Section: Strength Propertiessupporting

confidence: 91%

Section: Numerical Simulationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Hybrid Failure of Cemented Paste Backfill

et al. 2021

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“…More recently, Pan et al [30,31] developed a direct tension test based on a compressionto-tension load conversion method, and compared the measured Williams CPB tensile strengths to the UCS and also to direct shear test results from samples with corresponding mix designs. Importantly, all tested samples were cured in virtually saturated conditions and the UCS and direct shear tests were carried out with the samples submerged to prevent suction development associated with sample dilation.…”

Section: Correlating σ T and Ucsmentioning

confidence: 99%

“…The differences may be due to the relatively soft nature of CPB as opposed to intact rock. Macassa CPB was tested using the same direct tension device as [30,31]. For 10% binder content and testing at 3, 7, and 14 days the strength ratios varied from m i = 5 to 3.…”

Section: Correlating σ T and Ucsmentioning

confidence: 99%

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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Consideration of the Accuracy of Empirical and Indirect Laboratory Methods for the Characterisation of Tension Strength

Sainsbury,

McDonald

2024

Geotech Geol Eng

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This research explores the results of the most common laboratory based indirect tension strength methods over the range of UCS strengths 0.1 MPa (cemented paste backfill) to 100 MPa (concrete). The accuracy of each of the methods is considered through a comparison with direct strength measurements completed on the same material. The results of 241 individual tests suggest that the use of indirect tension methods to determine tension strength for all geo-material strength ranges may provide misleading results unless a correction-factor is applied. Correction factors that relate splitting and flexure results to direct tension results are provided. The correction factors are based on the characteristic UCS of the material. A comparison of the traditional empirical relationship to derive tension from UCS is presented and an updated relationship is proposed that is relevant over the UCS strength range 0.1–100 MPa.

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Tensile Strength of Cemented Paste Backfill

Cited by 11 publications

References 21 publications

Hybrid Failure of Cemented Paste Backfill

Hybrid Failure of Cemented Paste Backfill

Cemented Paste Backfill (CPB) Material Properties for Undercut Analysis

Consideration of the Accuracy of Empirical and Indirect Laboratory Methods for the Characterisation of Tension Strength

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