scholarly journals Impact of draw velocity profile on footprint definition for primary rock

2021 ◽  
Vol 2 (1) ◽  
pp. 28-35
Author(s):  
J. Contreras ◽  
Y. Marulanda ◽  
J. Valdivieso
Keyword(s):  
Rock Mass ◽  
Velocity Profile ◽  
Dynamic Response ◽  
Extraction Capacity ◽  
Study Case ◽  
Mass Rock ◽  
Column Extraction ◽  
Economic Objective ◽  
Level Height ◽  
Selection Of

In block/panel caving mines the footprint geometry and the undercut level height are key planning elements that have a bearing on the project final value. Selection of these parameters obviously depends on the economic objective, but it is also strongly influenced by rock mass characteristics that define column extraction capacity from draw points. This paper presents a simple methodology that allows defining the footprint and the best height of draw (BHOD) based on column extraction velocities, which are defined with the aim of controlling mass rock dynamic response while caving is propagated.  The proposed methodology can be used by industry because of the ease of application. A study case is presented for a block model which is evaluated by both the proposed methodology and nominal profit estimation.

scholarly journals Weightage Effect during Back-Calculation of Rock-Mass Quality from the Installed Tunnel Support in Rock-Mass Rating and Tunneling Quality Index System

2019 ◽  
Vol 9 (10) ◽  
pp. 2065 ◽  
Author(s):  
Jonguk Kim ◽  
Hafeezur Rehman ◽  
Wahid Ali ◽  
Abdul Muntaqim Naji ◽  
Hankyu Yoo
Keyword(s):  
Rock Mass ◽  
Quality Index ◽  
Rock Bolt ◽  
Rock Mass Rating ◽  
Rock Mass Quality ◽  
Back Calculation ◽  
The Difference ◽  
Bolt Spacing ◽  
Q System ◽  
Selection Of

In extensively used empirical rock-mass classification systems, the rock-mass rating (RMR) and tunneling quality index (Q) system, rock-mass quality, and tunnel span are used for the selection of rock bolt length and spacing and shotcrete thickness. In both systems, the rock bolt spacing and shotcrete thickness selection are based on the same principle, which is used for the back-calculation of the rock-mass quality. For back-calculation, there is no criterion for the selection of rock-bolt-spacing-based rock-mass quality weightage and shotcrete thickness along with tunnel-span-based rock-mass quality weightage. To determine this weightage effect during the back-calculation, five weightage cases are selected, explained through example, and applied using published data. In the RMR system, the weightage effect is expressed in terms of the difference between the calculated and back-calculated rock-mass quality in the two versions of RMR. In the Q system, the weightage effect is presented in plots of stress reduction factor versus relative block size. The results show that the weightage effect during back-calculation not only depends on the difference in rock-bolt-spacing-based rock-mass quality and shotcrete along with tunnel-span-based rock-mass quality, but also on their corresponding values.

Instrumentation on Impact Shock Study of Polymers and Possibility of Non-Equilibrium Shock Hugoniot

2010 ◽  
Vol 638-642 ◽  
pp. 1059-1064
Author(s):  
Kunihito Nagayama ◽  
Yasuhito Mori
Keyword(s):  
Carbon Fiber ◽  
Velocity Profile ◽  
Dynamic Response ◽  
Particle Velocity ◽  
Energetic Materials ◽  
Polymer Materials ◽  
Space Applications ◽  
Shock Response ◽  
Shock Hugoniot ◽  
Relaxation Structure

Polymer materials have widespread applications in various situations for structural materials by themselves as well as by combining with other materials such as carbon fiber. Some of them are also candidates for energetic materials in space applications.[1] Due to their general use, shock response of them has attracted attention for many researchers.[2-4] One of the striking characteristics of the dynamic response of them is that stress and/or particle velocity profile has a relaxation structure of s range.[5, 6]

scholarly journals Numerical Modeling for Engineering Analysis and Designing of Optimum Support Systems for Headrace Tunnel

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Sajjad Hussain ◽  
Zahid Ur Rehman ◽  
Noor Mohammad ◽  
Muhammad Tahir ◽  
Khan Shahzada ◽  
...  
Keyword(s):  
Rock Mass ◽  
Support Systems ◽  
Research Work ◽  
Strength Properties ◽  
Efficient Design ◽  
Headrace Tunnel ◽  
And Performance ◽  
Selection Of

The empirical and numerical design approaches are considered very important in the viable and efficient design of support systems, stability analysis for tunnel, and underground excavations. In the present research work, the rock mass rating (RMR) and tunneling quality index (Q-system) were used as empirical methods for characterization of rock mass based on real-time geological and site geotechnical data and physical and strength properties of rock samples collected from the alignment of tunnel. The rock mass along the tunnel axis was classified into three geotechnical units (GU-1, GU-2, and GU-3). The support systems for each geotechnical unit were designed. The 2D elastoplastic finite-element method (FEM) was used for the analysis of rock mass behavior, in situ and redistribution stresses, plastic thickness around the tunnel, and performance of the design supports for the selection of optimum support system among RMR and Q supports for each geotechnical unit of tunnel. Based on results, Q support systems were found more effective for GU-1 and GU-2 as compared to RMR support systems and RMR support systems for GU-3 as compared to Q support systems.

The Selection of the Linearized Natural Frequency for the Second-Order Normal Form Method

2011 ◽  
Author(s):  
Zhenfang Xin ◽  
S. A. Neild ◽  
D. J. Wagg
Keyword(s):  
Normal Form ◽  
Dynamic Response ◽  
Natural Frequency ◽  
Nonlinear Dynamic ◽  
Equations Of Motion ◽  
Second Order ◽  
Nonlinear Dynamic Response ◽  
Weakly Nonlinear ◽  
Selection Of ◽  
Normal Form Technique

The normal form technique is an established method for analysing weakly nonlinear vibrating systems. It involves applying a simplifying nonlinear transform to the first-order representation of the equations of motion. In this paper we consider the normal form technique applied to a forced nonlinear system with the equations of motion expressed in second-order form. Specifically we consider the selection of the linearised natural frequencies on the accuracy of the normal form prediction of sub- and superharmonic responses. Using the second-order formulation offers specific advantages in terms of modeling lightly damped nonlinear dynamic response. In the second-order version of the normal form, one of the approximations made during the process is to assume that the linear natural frequency for each mode may be replaced with the response frequencies. Here we will show that this step, far from reducing the accuracy of the technique, does not affect the accuracy of the predicted response at the forcing frequency and actually improves the predictions of sub and superharmonic responses. To gain insight into why this is the case, we consider the Duffing oscillator. The results show that the second-order approach gives an intuitive model of the nonlinear dynamic response which can be applied to engineering applications with weakly nonlinear characteristics.

Dynamic response of rock mass induced by the transient release of in-situ stress

2012 ◽  
Vol 53 ◽  
pp. 129-141 ◽  
Author(s):  
Wenbo Lu ◽  
Jianhua Yang ◽  
Peng Yan ◽  
Ming Chen ◽  
Chuangbing Zhou ◽  
...  
Keyword(s):  
Rock Mass ◽  
Dynamic Response ◽  
In Situ Stress

scholarly journals Towards more realistic values of elastic moduli for volcano modelling

2020 ◽  
Author(s):  
Michael Heap ◽  
Marlène Villeneuve ◽  
Fabien Albino ◽  
Jamie Farquharson ◽  
Elodie Brothelande ◽  
...  
Keyword(s):  
Rock Mass ◽  
Shear Modulus ◽  
Bulk Modulus ◽  
Volcanic Rock ◽  
Elastic Moduli ◽  
Numerical Models ◽  
Laboratory Data ◽  
Volcanic Rocks ◽  
Published Data ◽  
Selection Of

<p>The accuracy of elastic analytical solutions and numerical models, widely used in volcanology to interpret surface ground deformation, depends heavily on the Young’s modulus chosen to represent the medium. The paucity of laboratory studies that provide Young’s moduli for volcanic rocks, and studies that tackle the topic of upscaling these values to the relevant lengthscale, has left volcano modellers ill-equipped to select appropriate Young’s moduli for their models. Here we present a wealth of laboratory data and suggest tools, widely used in geotechnics but adapted here to better suit volcanic rocks, to upscale these values to the scale of a volcanic rock mass. We provide the means to estimate upscaled values of Young’s modulus, Poisson’s ratio, shear modulus, and bulk modulus for a volcanic rock mass that can be improved with laboratory measurements and/or structural assessments of the studied area, but do not rely on them. In the absence of information, we estimate upscaled values of Young’s modulus, Poisson’s ratio, shear modulus, and bulk modulus for volcanic rock with an average porosity and an average fracture density/quality to be 5.4 GPa, 0.3, 2.1 GPa, and 4.5 GPa, respectively. The proposed Young’s modulus for a typical volcanic rock mass of 5.4 GPa is much lower than the values typically used in volcano modelling. We also offer two methods to estimate depth-dependent rock mass Young’s moduli, and provide two examples, using published data from boreholes within Kīlauea volcano (USA) and Mt. Unzen (Japan), to demonstrate how to apply our approach to real datasets. It is our hope that our data and analysis will assist in the selection of elastic moduli for volcano modelling. To this end, our new publication (Heap et al., 2019), which outlines our approach in detail, also provides a Microsoft Excel© spreadsheet containing the data and necessary equations to calculate rock mass elastic moduli that can be updated when new data become available. The selection of the most appropriate elastic moduli will provide the most accurate model predictions and therefore the most reliable information regarding the unrest of a particular volcano or volcanic terrain.</p><p>Heap, M.J., Villeneuve, M., Albino, F., Farquharson, J.I., Brothelande, E., Amelung, F., Got, J.L. and Baud, P., 2019. Towards more realistic values of elastic moduli for volcano modelling. Journal of Volcanology and Geothermal Research, https://doi.org/10.1016/j.jvolgeores.2019.106684.</p>

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