Effects Of Dynamic Loading On The Geomechanical Behaviour Of Cemented Paste Backfill
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Effects Of Dynamic Loading On The Geomechanical Behaviour Of Cemented Paste Backfill
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Author : Gonzalo Hernan Suazo Fuentealba
language : en
Publisher:
Release Date : 2016
Effects Of Dynamic Loading On The Geomechanical Behaviour Of Cemented Paste Backfill written by Gonzalo Hernan Suazo Fuentealba and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
[Truncated] Backfill is any material that is placed underground to fill the voids (stopes) left after the process of extracting minerals from crushed rock. Cemented Paste Backfill (CPB) is one of these materials, which consists of a mixture of full stream tailings, a small percentage of cement and water. Underground space is a dynamic environment that subjects these fills to a series of dynamic loading resulting from blasting and seismic events. Refracted stress waves at the CPB-rock interface can increase the shear and compressive stresses in the fill. As a result, excess pore water pressures may develop and liquefaction can eventually be triggered. Liquefaction might cause the failure of the retaining barricade constructed at the bottom of the stope since total pressure can rise to as high as the full hydrostatic head of the fill. However, the amount of dynamic energy transmitted to the fill as well as the liquefaction risk, greatly diminishes as the fill desaturates and negative water pressures arise in the pore space. In this context, the primarily objective of this thesis is to evaluate the liquefaction susceptibility of CPB at early curing ages due to seismic and blasting stress waves. In addition, the propagation phenomena of compressional waves in CPB, the effects of degree of saturation on stress wave refraction at CPB interfaces and the blast response of a backfilled stopes are explored. Finally, the evolution of unsaturated CPB properties and the mechanism of desaturation of the fill are investigated. This research consisted of in situ and experimental testing, and a numerical modelling component.Direct simple shear (DSS) tests were conducted to study the cyclic undrained shear response of CPB. The effects of confining stress, initial static shear stress and void ratio on the liquefaction resistance of uncemented fine-grained tailings was firstly researched. Then, the cyclic response of cemented tailings prepared at different curing ages, cement contents and initial void ratios, was examined. The material, independently of the degree of cementation, showed a predominantly cyclic mobility type response with large degradation of shear stiffness at advanced numbers of shear cycles. However, no flow type of failure was observed in any of the tests conducted. The overburden stress correction factor was found to decrease with increasing confining stresses in the range 100 to 400 kPa and to gradually increase from 400 kPa onwards, when samples were tested at the same initial void ratio. Similarly, higher cement contents, longer curing periods or higher initial solids contents were found to increase liquefaction resistance. A unconfined compressive strength (UCS) of about 70kPa, which corresponds to a shear wave velocity of 220 m/s, was found to be adequate to resist liquefaction under a large earthquake-induced cyclic stress ratio (CSR).
Advances In Design And Implementation Of Cementitious Backfills Adicb
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Author : Erol Yilmaz
language : en
Publisher: Frontiers Media SA
Release Date : 2022-10-05
Advances In Design And Implementation Of Cementitious Backfills Adicb written by Erol Yilmaz and has been published by Frontiers Media SA this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022-10-05 with Technology & Engineering categories.
Dissertation Abstracts International
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Author :
language : en
Publisher:
Release Date : 2004
Dissertation Abstracts International written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004 with Dissertations, Academic categories.
Bibliography And Index Of Geology
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Author :
language : en
Publisher:
Release Date : 1985
Bibliography And Index Of Geology written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1985 with Geology categories.
Effects Of Transient Hydro Mechanical Cemented Paste Tailings Properties On One Dimensional Deposition Behaviour
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Author : Mohammad Shahsavari Goughari
language : en
Publisher:
Release Date : 2020
Effects Of Transient Hydro Mechanical Cemented Paste Tailings Properties On One Dimensional Deposition Behaviour written by Mohammad Shahsavari Goughari and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020 with categories.
When underground mining voids are filled with Cemented Paste Backfill (CPB) a dynamic interaction occurs between the hydrating CPB's engineering properties (hydraulic conductivity, stiffness and strength) and the fill rise rate, drainage conditions, and underground atmospheric conditions. These interactions are particularly important in the first 24 hours after a fill layer's placement in order to support continuous filling. Unfortunately, most previous studies started taking measurements at one day or more, missing this critical initial period. The work presented in this thesis obtains representative material properties at curing times as soon as 30 minutes. Four stages of hydraulic conductivity evolution are linked to corresponding stages of binder hydration at times from 30 minutes to 5 days, and it is shown conventional measurement methods could under-estimate initial hydraulic conductivity by an order of magnitude. Consolidation tests with virtually continuous loading rates simulated effective stress development onsets between 4 and 48 hours, at rates between 5 and 20 kPa/hr and final level of 400 kPa. In virtually continuous loading it is impossible to deconvolve the parameters controlling the ultimately achieved void ratio and stiffness, but a graphical technique is developed to aid preliminary design and determine likely void ratios that should be used in other laboratory tests for engineering properties. The hydraulic conductivity and consolidation element test results are then used to interpret results from four mesoscale laboratory experiments that simulate continuous backfilling. These tests demonstrate the importance of properly simulating the underground atmospheric conditions, and in placing the fill in the most continuous manner possible. For placement conditions that most closely simulate the actual placement conditions at the studied mine, it is found that virtually no self-weight consolidation occurs and thus the void ratios in the field and in the meso-scale experiments are essentially identical. Therefore, the effective stress path realized in the field will not lead to significant self-weight consolidation and the attendant strength gains that might otherwise occur.
In Situ Properties And Liquefaction Potential Of Cemented Paste Backfill Microform
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Author : Kim-Anne Le Roux
language : en
Publisher: National Library of Canada = Bibliothèque nationale du Canada
Release Date : 2004
In Situ Properties And Liquefaction Potential Of Cemented Paste Backfill Microform written by Kim-Anne Le Roux and has been published by National Library of Canada = Bibliothèque nationale du Canada this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004 with categories.
Mercury intrusion porosimetry as well as semi-qualitative image analysis techniques such as scanning electron microscopy, microCT and visual analysis software were used to develop an understanding of the structure developed in field CPB in both the macro and micro scale. Standard oedometer consolidation testing with a modified loading rate was used to investigate the interrelationship of loading rate, which simulates rate of paste accumulation in a stope and the hydration of binder of the paste. The results show that the structure that develops is sensitive to both the binder content of the CPB and the rate of paste accumulation. Cemented paste backfill (CPB) has gained increasing popularity in the last 5 to 10 years and is used routinely in several mines. However, most of the CPB designs are based on laboratory prepared CPB material properties and there is growing awareness that the field CPB may be different from the laboratory prepared material. A field based investigation quantified the extent to which the field material differs from laboratory material. Not only is the field material more heterogeneous than expected, but on average it has a higher void ratio and a lower degree of saturation. These differences impact the performance of the field material. Numerical analysis using FLAC 3D was undertaken to show the influence of the field condition on the stability of the CPB. This research provides practical recommendations for industrial application and provides a framework for further investigation of CPB. Several research projects arising from this initial work are already underway through the Lassonde Institute at the University of Toronto, and several more are at the proposal stage. Static and dynamic liquefaction testing of early age CPB showed that liquefaction due to self-weight alone is unlikely but that blasting too close to the CPB can mobilize the material. Practical recommendations such as limiting blasting in proximity to early age CPB and cordoning off vulnerable areas during the critical initial 24 hr period that the paste is vulnerable to dynamic liquefaction. The cyclic liquefaction results are believed to be the first reported for cemented paste backfill.
Testing And Multiphysics Modelling Of The Shear Behaviour Of Rock Cemented Paste Backfill Interface
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Author : Kun Fang
language : en
Publisher:
Release Date : 2021
Testing And Multiphysics Modelling Of The Shear Behaviour Of Rock Cemented Paste Backfill Interface written by Kun Fang and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021 with categories.
Cemented paste backfill (CPB) is an innovative technology developed in the mining industry during the last few decades. It has been adopted worldwide by many underground mines for its tremendous advantages: (1) mining space is stabilized by pumping cemented paste backfill into the underground cavities created by mining activity, which is critical to the safety of mine workers; (2) the consumption of tailings (which is stored at the ground surface and is a major source of acid mine drainage (AMD)) is beneficial for environmental protection and community safety; (3) due to the supporting effect of the CPB structure on underground cavities, the recovery ratio is significantly increased; and (4) CPB structures can also carry heavy equipment when mining the adjacent orebody, facilitating mining operations. How to design a safe and cost-effective CPB structure is a key task or challenge for mining engineers and researchers. Mechanical stability is one of the most important design criteria. This stability is mainly a function of the uniaxial compressive strength (UCS) of CPB body and the shear strength/behaviour of the CPB-rock interface. Given the lower friction angle and adhesion of the CPB-rock interface (in comparison with the friction angle and cohesion of CPB body), a thorough understanding of the shear strength/behaviour of the interface is critical for a cost-effective geotechnical design of underground CPB structures. However, only limited studies have been conducted to date on the shear performance of the CPB-rock interface, and no studies have taken into consideration the effects of different factors (e.g., temperature, sulphate ions, self-weight or surface morphology) on the shear behaviour of the CPB-rock interface. Moreover, no multiphysics interface model is currently available that incorporates the aforementioned factors to describe and predict the CPB-rock interface shear behaviour. This research gap was therefore addressed in this PhD study. In this PhD research, a series of laboratory tests were conducted assessing the effects of sulphate content, temperature, curing stress, drainage condition and interface roughness on the shear strength/behaviour of the interface between CPB and rock. The results obtained so far indicated that sulphate and temperature can either positively or negatively affect the shear strength of the CPB-rock interface, depending on the initial sulphate contents and curing time. In terms of the effect of temperature, the shear strength and shear strength properties generally increased with temperature. However, high temperature (≥ 35°C) resulted in an adverse effect on the shear strength because of the crossover effect. In addition, higher curing stress benefitted to the shear strength acquisition of the interface and, due to the increased effective stress and matrix suction, the drained condition increased shear strength as well. As for the effect of surface morphology, the shear strength of the CPB-rock interface rose with surface roughness. Furthermore, chemo-elastic as well as coupled thermo-chemo-mechanical cohesive zone models (CZMs), which take the sulphate attack and temperature-induced acceleration in the cement hydration into consideration, are also developed to simulate the shear strength and behaviour of the CPB-rock interface. The proposed models can well capture the shear behaviour of the interface under different loading conditions. Besides, they also numerically attest to the importance of the shear resistance of the CPB-rock interface in controlling stress distribution in CPB structures. The results obtained from experimental tests, numerical modelling and simulations concerning the shear behaviour of the CPB-rock interface under different multiphysics conditions provided useful information for understanding and more effectively assessing the shear strength and behaviour of the interface between a CPB structure and rock mass, which is critical for the design of safer and more cost-effective CPB structures.
Strength And Deformation Behaviour Of Cemented Paste Backfill In Sub Zero Environment
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Author : Shuang Chang
language : en
Publisher:
Release Date : 2016
Strength And Deformation Behaviour Of Cemented Paste Backfill In Sub Zero Environment written by Shuang Chang and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
Cemented Paste Backfill
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Author : Yong Wang
language : en
Publisher: Elsevier
Release Date : 2024-05-19
Cemented Paste Backfill written by Yong Wang and has been published by Elsevier this book supported file pdf, txt, epub, kindle and other format this book has been release on 2024-05-19 with Science categories.
In view of the demand for the research on the transport resistance characteristics and mechanical properties of CPB under the influence of temperature effect, the book comprehensively describes the studies on rheological and mechanical properties of CPB materials used in underground metal mines. This book covers a wide range of topics, including a new definition of CPB, past participation and flow-induced corrosion of pipeline under the constant temperature condition, multiphysics processes in CPB and the associated consolidation process, the variation of rheological parameters and transport resistance, prediction model for rheological properties, mechanical behavior and properties of CPB and fiber-reinforced CPB, and control technology to reduce the adverse effect of temperature. Therefore, an academic framework for the transport resistance characteristics and mechanical properties under the temperature effect was established in this book. - Investigates rheological properties and multiphysics processes in CPB materials around the world - Looks into systematic studies on pipe transport and mechanical properties of CPB under temperature effects - Focuses mainly on the effect of temperature on paste transport and mechanical properties under the temperature effect, which provides a theoretical basis for safe and efficient filling operation and associated future research in this field - Offer in-depth insights into the evolution of the rheological and mechanical properties of CPB under the effect of temperatures
Geotechnical Characterization Of Cemented Paste Backfill
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Author : Erol Yilmaz
language : en
Publisher: LAP Lambert Academic Publishing
Release Date : 2015-02-10
Geotechnical Characterization Of Cemented Paste Backfill written by Erol Yilmaz and has been published by LAP Lambert Academic Publishing this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015-02-10 with categories.
Cemented paste backfill (CPB) technology is now widely utilized by most modern underground hard rock mines in Canada, Australia, the United States, South Africa and Turkey. CPB is a cementitious material produced with three ingredients: filtered wet tailings, hydraulic binders, and mixing water to ensure the paste's flowability in pipeline for final deposition. This book investigates CPB technology using a recently designed lab apparatus called CUAPS (curing under applied pressure system) that estimates in situ CPB conditions. The CUAPS apparatus has been demonstrated as a practical and cost-effective tool that effectively replaces the traditional approach using non-perforated plastic moulds. The results obtained with the CUAPS apparatus will contribute to improve the safety of mines and miners and provide a better understanding of paste backfill. Each section of this book represents an original contribution to the science and engineering of paste backfill. This book provides some theoretical and experimental bases for designing paste backfill mixtures in terms of cost savings and safety and for incorporating in situ backfill behaviour and properties.