Back analysis of grouted rock bolt pullout strength parameters from field tests

Li, Bin; Qi, Taiyue; Wang, Zhengzheng; Yang, Longwei

doi:10.1016/j.tust.2011.11.004

Cited by 24 publications

(8 citation statements)

References 7 publications

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“…It should be noted that, as illustrated in Equation 7(St John & Van Dillen 1983), the grout friction angle in the numerical modelling was not considered. Some corrections have since been made by Bin et al (2012) to the cohesive strength and friction angle for numerical purposes. Without these corrections, the model responds as expected according to experience in static conditions.…”

Section: Resultsmentioning

confidence: 99%

Numerical modelling of dynamic testing for rock reinforcement used in underground excavations

Marambio¹,

Vallejos²,

Burgos³

et al. 2018

Proceedings of the Fourth International Symposium on Block and Sublevel Caving

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As mines have expanded due to increased depth, new challenges have appeared for mining engineers. High-stress environments, where there are rockburst events caused by energy release, have become especially interesting in terms of geomechanics and have prompted changes in conventional designs, demanding more research into how underground excavations absorb dynamic impacts.For these underground excavations, the development of new reinforcement elements capable of both resisting dynamic loads and yielding in the process without failing has advanced in the last 30 years due to studies and testing programs carried out by recognised institutions. However, executing these testing programs implies a high cost in time and validation. Hence, a limited number of these have been completed. In this context, numerical modelling to represent the performance of the process and enhance laboratory testing has become increasingly necessary and relevant.In this paper, a numerical modelling methodology based on the finite difference method has been applied in order to predict the behaviour of threadbar, commonly used in Chilean mining as reinforcement in underground excavations, in dynamic load testing. Accordingly, a comparison and calibration of the numerical model with laboratory-scale dynamic tests from previous research is presented.

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Section: Resultsmentioning

confidence: 99%

Numerical modelling of dynamic testing for rock reinforcement used in underground excavations

Marambio¹,

Vallejos²,

Burgos³

et al. 2018

Proceedings of the Fourth International Symposium on Block and Sublevel Caving

View full text Add to dashboard Cite

show abstract

“…The numerical model described in the following sections represents the operating mechanism of the Chilean facility in hopes that it could serve as a complement for the tests to be carried out in the near future. This mechanism was selected considering that some authors have questioned the effect of the other modes of dynamic loading on rock reinforcement elements [8,9,18,42]. The threadbar was selected (known also as rebar or gewibar) as the reinforcement element to be modeled due to its wide use and range of success in Chilean underground mining along with the necessity to improve this element given its possible globalization.…”

Section: Problem Assessmentmentioning

confidence: 99%

Explicit Numerical Study on Dynamic Behavior of Threadbar under Impact Loading

Marulanda,

Vallejos,

Velásquez

2024

Preprint

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Due to the continued deepening of today’s mining projects, there is a need to develop new or improved rockbolts that are strong and yielding and have high energy absorption when exposed to dynamic loading. Impact tests can provide useful information about the dynamic response of rockbolts but most laboratory tests involve high costs in preparation and result validation. Numerical modeling is an alternative that, in addition to complementing laboratory results, can be used to represent the process of deformation and energy absorption of support elements. In this paper the implementation and results obtained from a finite difference (FDM) numerical model are presented. The model functions as a simulation tool to illuminate all the elements that conform the large-scale (1:1) impact test and their behavior and influence on the dynamic response of a threadbar bolt (22 mm nominal diameter). The model was calibrated using published results and based on these results as well as parametric analysis, the response of each component (steel tube, grout, and bolt) could be identified and its behavior in terms of absorbed energy and displacement could be observed. Results show the model can provide important preliminary information to make design decisions about support elements design.

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“…However, the parameters controlling the behaviour of the spring-slider system cannot be directly derived from the bolt or grout properties. The she2012ar spring parameters which control the axial behaviour of the pile have been calibrated using data from in-situ pull tests (Bin et al 2012;Nemcik et al 2014). Calibration for normal spring parameters which control the bending and shear behaviour of piles has only been done using laboratory shear tests (Tulu et al ).…”

Section: Numerical Modellingmentioning

confidence: 99%

“…The stiffness of the spring represents the deformability of the interface and the cohesion and friction angle control the strength of the interface. The parameters for the shear spring can be obtained using the load-displacement plot from in-situ pull testing of the rock bolt (Bin, Taiyue et al 2012, Nemcik, Ma et al 2014. Calibration of the normal spring parameters which control the shear behaviour of the pile element requires load-displacement data from an insitu shear test of the rock bolt.…”

Section: Calibration Of Pile Element Parametersmentioning

confidence: 99%

Improving the Numerical Modelling of In-Situ Rock Bolts Using Axial and Bending Strain Data from Instrumented Bolts

2022

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Numerical modelling has become an important tool in the underground rock bolt reinforcement designing process. Numerical modelling provides the advantage of easily and quickly simulating complex underground geometries and mechanisms with sensitivity analyses. However, a numerical model needs to be calibrated using mathematical solutions, lab testing or with actual in-situ observations and measurements (which is the preferred method) before its results can be quantitatively applied to reinforcement design. Instrumented rock bolts provide a useful data source for calibrating in-situ rock bolt models. In this work, procedures have been presented to identify and determine the orientation of structures in the rock mass based on the strains on the instrumented rock bolts. A method to calibrate the rock bolt model with in-situ data is also presented. The results of the presented procedures have been validated with laboratory tests and numerical modelling. The procedures have been applied to create and calibrate an in-situ rock bolt model in FLAC3D and the results are validated using in-situ data.

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Back analysis of grouted rock bolt pullout strength parameters from field tests

Cited by 24 publications

References 7 publications

Numerical modelling of dynamic testing for rock reinforcement used in underground excavations

Numerical modelling of dynamic testing for rock reinforcement used in underground excavations

Explicit Numerical Study on Dynamic Behavior of Threadbar under Impact Loading

Improving the Numerical Modelling of In-Situ Rock Bolts Using Axial and Bending Strain Data from Instrumented Bolts

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