Cemented Paste Backfill 1-D Consolidation Results Interpreted in the Context of Ground Reaction Curves

Jafari, Mousa; Shahsavari, Mohammad; Grabinsky, Murray

doi:10.1007/s00603-020-02173-5

Cited by 20 publications

(13 citation statements)

References 17 publications

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“…It is not possible to provide ranges of the potential spikes of pressure at this point in time as the effects are data limited. However, as noted in Jafari et al (2020), the amount of stress within the backfill of a stope, due to a seismic event, will be dependent on the closure and the modulus of the backfill. When backfill has a low modulus (low strength at early stages of cure) the increase in stress due to closure is low compared to when the backfill has a higher modulus (final strength).…”

Section: Discussionmentioning

confidence: 99%

In situ backfilll monitoring database

Oke¹,

Hashemi²

2021

Paste 2021: 24th International Conference on Paste, Thickened and Filtered Tailings

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The history of backfilling underground mined-out voids dates back to the beginning of mining several centuries ago using rockfill. Currently, there are three major types of backfill: rock, hydraulic, and paste fill. When backfill is required to be exposed from mining beside or underneath, cement binder is added. Cemented hydraulic fill is the most commonly used backfill as it has existed for over 80 years. 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.

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Section: Discussionmentioning

confidence: 99%

In situ backfilll monitoring database

Oke¹,

Hashemi²

2021

Paste 2021: 24th International Conference on Paste, Thickened and Filtered Tailings

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“…e previous studies showed that the mechanical properties of CPB depend on its physical and chemical characteristics of the binder type, particle size, water content, and tailings' mineralogy [3,10,14,16,19,20]. ese mechanical properties vary significantly with the binder content and curing time.…”

Section: Methodsmentioning

confidence: 99%

Shear Properties of Cemented Paste Backfill under Low Confining Stress

Pan

Grabinsky

Guo

2021

Advances in Civil Engineering

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Cemented paste backfill (CPB) plays an important role in the mining industry due to safety, cost efficiency, and environmental benefits. Studies on CPB have improved the design and application of paste backfill in underground mines. Direct shear is one of the most fundamental parameters for assessing backfill strength. This study harnesses direct shear tests to explore the low confining stress behavior of CPB. We perform all the tests in a standard apparatus on the combination of three binder contents of 4.2%, 6.9%, and 9.7% CPB with four curing times of 3, 7, 14, and 28 days, respectively. The applied confining stress levels vary in a range according to the in situ regime. Results are presented by strength envelope, stress-strain property, and shear strength with curing time and binder content. The data suggest that the shear strength follows the Mohr–Coulomb envelope in which the shear strength and behavior are time and binder content dependent. In addition, the results show that shear strength is strongly related to the binder content than the curing time, namely, the higher the degree of binder hydration, the higher the cementation binding force between CPBs.

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“…Uniaxial compressive strength (UCS) of CPB has been studied quite extensively (e.g., Kesimal et al (2005); Klein and Simon (2006); Orejarena and Fall (2010); Yi et al (2015); Gorakhki and Bareither (2017); and Xu et al (2018)), in part because it is the least resource intensive, but also because there are many limit equilibrium design methods that depend on UCS as a key input (e.g., Mitchell et al (1982) and Potvin et al (2005)). Less attention has been paid to tests that study mechanical properties and effects of cemented bond breakage on the behavior of cured CPB under more complex loading conditions (Pierce et al 1998;Yilmaz et al 2010;Yilmaz et al 2015;Fang and Fall 2020;Jafari et al 2020a;Jafari et al 2020b). Therefore, new information about CPB's response to high confining pressures is needed.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, new information about CPB's response to high confining pressures is needed. Jafari et al (2020a) showed how laboratory oedometer test results could be used to understand the backfill-rock mass interaction for tabular ore bodies undergoing predominantly one-dimensional compression. In this work a similar approach is used to understand how backfill in massive orebodies would respond to predominantly isotropic loading.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, in the current work a range of binder contents and cure times is considered representative of practical mining conditions. Previous work (Jafari et al 2020a) showed that the Unconfined Compressive Strength (UCS) can be determined as a function of binder content and cure time, and so it is also desired to relate the isotropic compression response to the UCS test results if possible, as the UCS is more conventional and readily carried out. Although the calibrated test results will be specific to the materials tested, it is desired that a framework be demonstrated by which other mine's materials can be similarly tested in a more efficient way with fewer resource-intensive tests.…”

Section: Introductionmentioning

confidence: 99%

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Predicting the Isotropic Volumetric Compression Response of Hydrating Cemented Paste Backfill (CPB)

Jafari

Grabinsky

2021

Preprint

Self Cite

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Deep and high-stress mining results in stress transfers onto the previously placed backfill, and mines have recorded several MPa induced backfill stress. Understanding the backfill-rock mass interaction is therefore critical. Previous work considered tabular ore bodies undergoing primarily one-dimensional compression and showed how the backfill reaction curves could be estimated from oedometer laboratory test results. This work considers massive orebodies and develops a similar approach based on isotropic compression curves. Isotropic compression tests exceeding 6 MPa are carried out on samples with 3.0–11.1% binder content, tested at 1-day cure time to 28-day cure time. The compression curve is characterized in three stages: initial elastic compression up to a yield point, followed by a transition stage to the start of a final stage with a linear post-yield compression line in \({\epsilon }_{v}-\text{l}\text{o}\text{g}\left({p}^{\text{'}}\right)\) space. Because these isotropic compression tests are rare (the reported results are the first for Cemented Paste Backfill), attempts are made to relate the isotropic compression test parameters to parameters from the more commonly used Unconfined Compression Strength (UCS) tests. Unifying equations as functions of binder content and cure time are found to determine the initial yield stress and the peak strength from UCS tests. These are then related to the corresponding parameters in isotropic compression. Finally, the slope of the post-yield compression line is found as a function of UCS, thereby enabling complete reconstruction of the isotropic compression response based on parameters from carefully controlled UCS tests, as functions of binder content and cure time. Although the calibrated parameters are specific to the studied mine’s materials, the framework is general and applicable to other mines’ CPBs.

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Cemented Paste Backfill 1-D Consolidation Results Interpreted in the Context of Ground Reaction Curves

Cited by 20 publications

References 17 publications

In situ backfilll monitoring database

In situ backfilll monitoring database

Shear Properties of Cemented Paste Backfill under Low Confining Stress

Predicting the Isotropic Volumetric Compression Response of Hydrating Cemented Paste Backfill (CPB)

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