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By Mohamed Sassi, I. Kolo, R. L. Sousa, R. K. Abu Al-Rub, Manhal Sirat

"Fractures induced by folds are pivotal in hydrocarbon exploration, ground water transport and harnessing of geothermal energy. This is because of the need to predict and understand fracture propagation in reservoirs which have folded rock formations. Despite its prominence, there is a lack of reliable numerical models for simulating fractures resulting from rock folding. This is partially due to the difficulty involved in fracture modelling. As a contribution to fold-fracture modelling, this work applies a coupled plasticity-damage model to rock fracturing and anticlinal folds. Parametric studies on a single folded layer give insight into the fold formation and behaviour. The anisotropic continuum damage model which considers both tension and compression is formulated using the power damage evolution law. For ease in formulation, strain equivalence hypothesis is adopted whereby the strain is the same for both damaged and undamaged configurations. Lubliner plasticity yield criterion is adopted for plastic deformation. The model is coded in Abaqus user subroutine UMAT and is applicable to quasi-brittle materials.INTRODUCTIONThe understanding of fractures in the earth’s crust helps in the prediction, evaluation and characterization of fractured reservoirs, whether they are petroleum, geothermal or underground water reservoirs. This is partly because reservoir permeability and stability are dependent on fracture properties (Nelson, 2001). To achieve this, various approaches have been developed to analyze reservoir rock fractures. These could be grouped into (a) discrete approaches – where the rock mass is represented by a finite number of well-defined components and (b) continuum approaches – where the mathematical assumption of an infinitesimal element is made (Jing, 2003). Ivanova (Ivanova, 1998) comprehensively studied fracture systems in nature and highlighted folds as one of the major geologic settings that produce fractures. Naturally occurring folds in reservoirs sometimes compound fracture analysis. It might not be clear whether the fractures formed before, during or after rock folding. Fractures formed during the folding process are expected to show stress orientations related to folding and are thus of primary concern in rock folding simulation. It could be argued that there are no numerical models that as"

Jan 1, 2015

By Kubik K

The objective of this paper was to determine if recent advances in numerical electromagnetic wave propagation modelling techniques could be used to study the propagation of GPS signals over arbitrary terrain. Specifically the effects of diffraction and multipath were to be modelled accurately for propagation over arbitrary terrain surfaces defined by a digital terrain model. Ideally the model was to be in three dimensions and cover an area of a few square kilometres with a simulation height of a few hundred metres. Simulations were to run on current technology PC's with run times less than a few hours. A relatively new technique that involves a numerical solution to the Parabolic Equations can be used to solve for two-dimensional propagation over any type of terrain. The PE provides a direct solution of Maxwell's wave equations by approximating the Helmholtz scalar wave equation. This technique does not rely on the study of individual ray paths as used in the Geometrical Theory of Diffraction (GTD). It was decided to develop a two dimensional Parabolic Equation code, using the Fourier Split/Step method that allowed propagation over arbitrary terrain (; ; ). The model boundary conditions assumed that the satellite transmission was a plane wave, and that the lower boundary was a perfect reflector. Propagation simulations from the model accurately provide the amplitude and phase of the propagated plane wave at all points within the model domain. The PE model was used to study the effects of diffraction and multipath caused by various types of terrain commonly found in an open cut mining environment. The study of diffraction errors was relatively simple, because we are simply concerned with amplitude of the signal as it diffracts about an obstacle. If the amplitude is above the level receivable by a GPS receiver then the diffraction error can be obtained from the geometry of the terrain obstacle. The study of multipath is more complex, as the computed phase from the PE model is ambiguous and the presence of multipath can only be inferred. Thus the absolute magnitude of the nmltipath error is not currently determinable, though the results of some new work is shown here. This paper shows that diffraction effects can cause significant errors in range. It also shows the effects that multipath has on the received amplitude of the signal and the received phase of the signal. A discussion is made of further work that is presently underway that will allow the direct determination of the multipath error by comparing the ambiguous phase with a reference phase.

Jan 1, 1997

By D. J. Reddish

The paper describes a case study where numerical modelling has been applied to predict potential risks associated with inflows of water in active mine workings from an overlying sandstone aquifer. The objective of the modelling was to predict the development of strata fractures and strains as the longwall panels were extracted and investigate their relationship to an sandstone aquifer. The numerical modelling study also included the investigation of the effect of mining on a fault that existed close to the start position of one of the panels. The potential effects of mining on the fault were undertaken by parametric studies adjusting properties for the fault and the relative position of extractions, which allowed the mine planner to position the panel layout accordingly.

May 1, 2003

By C. V. Deutsch, O. Babak, J. G. Manchuk

High levels of geological heterogeneity occurring over relatively short distances pose a challenge to the unconventional open-pit techniques used in oil sands mining. There is strong motivation to mine selectively and minimize dilution and loss; however, the large equipment and high mining rate used to meet production targets tend to reduce selectivity. A numerical model is developed to account for geological complexity, mining equipment, regulatory criteria, and other operational parameters. This framework is used for more accurate forecasts, optimization of equipment, and other operational decisions. An example demonstrates the approach in light of Alberta Energy Regulator criteria.

Jan 1, 2014

This paper discusses support requirements for the proposed monorail system to be used in decline development. The monorail drilling and loading systems are systems that move on the rail (monorail) installed in the roof of the decline and supported by roof bolts, suspension chains and steel supports. However, due to the weight of the components of the two systems, it is imperative that the force in each roof bolt, suspension chain and steel support capable of suspending the weight of the heaviest component is determined. Numerical models that relate the weight of the monorail drilling and loading components to the required strength in the support system have been developed. Using these developed models, numerical values of the forces in each roof bolt, suspension chain and steel support, required to suspend the weight of the heaviest component of the monorail drilling and loading systems are determined.

Dec 6, 2010

By S. P. Lin

The numerical models of nonlinear piles for deep foundations are studied in this paper. The purpose of these is to clarify the mechanical behaviour of deep foundation nonlinear piles subjected to axial and lateral loadings. Based on the site data of p-y curve as well as t-z curve of foundation soils, it is possible to evaluate pile performance under above mentioned loads by means of combined FEM/FDM models. Numerical examples are presented in tall building and offshore jacket for illustrating the technique, it show high efficiency of these models. Some information to be interested by design engineers are given, especially for those who pay very concerns on the interaction behaviours of structure and its pile foundation.

Jan 1, 2010

By Andrzej Walentek

This paper presents the results of numerical modeling of the fractured zone around longwall gateroads. The numerical computations have been based on the results of underground measurements of the fractured zone around longwall gateroads, which were performed for various geological and mining conditions and measured with the use of the endoscopic method with a digital camera. Having results of the underground investigations, trials of duplicating them by the Finite Element Method using software PHASE and the Hoek-Brown failure criterion were performed. In order that the fractured zone predicted by the model-based computations closely simulate that measured underground, some selected parameters in the Hoek-Brown failure criterion were modified based on the earlier determined relations used for prediction of the roof-to-floor convergence in longwall gateroads. As a result, the model-based computations produce results very close to those obtained from the underground measurements. Determination of the fractured-rock zone around the mine roads is of great importance to mining practice, especially in planning and designing supports for longwall gateroads. The influence of the front abutment pressure causes the fractured rock zone around the roads to increase and results in an increase of support load. Moreover, proper determination of the fractured rock zone is one of basic elements in the process of planning roof bolting for mine workings.

Jan 1, 2009

By Andrzej Walentek

This paper presents the results of numerical modeling of the fractured zone around longwall gateroads. The numerical computations have been based on the results of underground measurements of the fractured zone around longwall gateroads, which were performed for various geological and mining conditions and measured with the use of the endoscopic method with a digital camera. Having results of the underground investigations, trials of duplicating them by the Finite Element Method using software PHASE and the Hoek-Brown failure criterion were performed. In order that the fractured zone predicted by the model-based computations closely simulate that measured underground, some selected parameters in the Hoek-Brown failure criterion were modified based on the earlier determined relations used for prediction of the roof-to-floor convergence in longwall gateroads. As a result, the model-based computations produce results very close to those obtained from the underground measurements. Determination of the fractured-rock zone around the mine roads is of great importance to mining practice, especially in planning and designing supports for longwall gateroads. The influence of the front abutment pressure causes the fractured rock zone around the roads to increase and results in an increase of support load. Moreover, proper determination of the fractured rock zone is one of basic elements in the process of planning roof bolting for mine workings.

Jan 1, 2009

By J. A. Jankowski

The situation in the raw material market has brought into consideration the commercial exploitation of the mineral deposits on the deep sea bed and in particular the manganese nodules. They occur generally in depths of 4000-5000 m, partially covered or buried in bottom sediments. The deposits and their potential recovery have been intensively explored and researched during the past twenty years (Bischoff 1979, Halbach 1988, Padan 1990). Although the present market situation limits the rentability of deep sea mining on an industrial scale, the mining technology is being further developed in many countries. The stagnation phase in the deep mining issue allows sufficient time for conducting research on the precautionary protection of the deep sea environment and for consultation in the development of technologies with the least possible impact on it. The subject has gained in importance since autumn 1994, when the United Nations International Law of the Sea was signed. This also regulates human activities in international waters from the environmental point of view. As fields tests have shown in the past, even with the most modern technologies, mining of the manganese nodules will inevitably be accompanied by a resuspension of some bottom sediments. The generated sediment plumes will be further transported with the ocean currents and in the worst case form stable turbidity layers in different depths (Ozturgut 1981a, Baturin 1991). One of the problems of the environmental impact assessment is the estimation of the plume persistence before it eventually dilutes to approximately the ambient concentration level or settles at the bottom (Lavelle 1981a, Lavelle 1981b, Lavelle 1982, Thiel 1991a, Thiel 1991b). The aim of the research is to develop a numerical sediment transport model in connection with potential manganese nodule mining in a reference area located in the southeastern equatorial Pacific Ocean off Peru (Peru Basin, Discol Experimental Area). In this region, a German mining claim is registered and interdisciplinary field works of the TUSCH (German: TiefseeUmweltSCHutz, deep sea environmental protection) research group are carried out in order to obtain the required scientific background for evaluating of the deep sea mining impacts and to provide the necessary supporting data for the modelling (Thiel 1991a, Thiel 1991h).

Jan 1, 1995

By J. H. Curran

In this paper, a numerical model for determining the stress and displacement fields around a crack of arbitrary geometry in a linear elastic medium is described. Accuracy and computational speed were the main considerations in selecting the numerical method and Propagation criteria used to model the growing crack. Some results regarding the stresses and displacements around a two-dimensional crack of arbitrary geometry are discussed.

Jan 1, 1984

Following a short review of selected literature, a back analysis of stress measurements of stress regeneration in a closed mini-longwall is shown. The agreement is good, lending confidence to the parameters used in the proposed numerical model. Foundation yielding was modelled in the absence of total stope closure. A ?Prandtl? wedge was formed, coinciding with the yield point of the pillar/foundation system. Some theoretical work is used as a starting point for the formulation of a new design methodology for strike or dip stabilizing pillar/foundation systems in deep level goldmines. The existing guideline for the stability of foundations (APS< 2.5UCS) is critically examined. Finally, the advantages of the new approach, and the work required to substantiate the proposed new design methodology, are outlined.

Jan 1, 1998

By D. F. Malan

Considerable practical knowledge and effective use of empirical evidence is required in the design of tunnel support systems. In many instances, it is unclear how individual support elements interact with fractured rock and which elements of the support system are critical in controlling and containing the movement of material proximate to the excavation. The present paper outlines a displacement discontinuity approach that allows the coupling of surface constraints, in the form of liner or mesh material, to an explicit representation of time-dependent rock discontinuity creep movements. The method is illustrated for a simple square-shaped tunnel profile in which the fracture zone is mobilized by an imposed stress field. A crucial aspect of the model is the computational treatment of the coupling between the liner material and there presentation of the fractured rock mass. This allows the response of the liner material to be assessed quantitatively in terms of the possible reduction of movement in the rock mass. The importance of installing the liner timeously after the excavation is formed is illustrated in a specific example. A number of computational difficulties in simulating liner-rock interaction mechanisms are identified.

Jan 1, 2008

By J W. Lee, E Baafi, N Aziz

Ground subsidence due to mining is a common dilemma confronting the underground coal mining industry. The effects of underground longwall mining on river valleys have come under scrutiny, especially when mining is located underneath catchment areas. As public awareness of mining impacts on the environment increases, there is the need to develop damage mitigation strategies. Results of numerical modelling show that river valley response to underground longwall mining can be simulated and evaluated.

Jan 1, 2005

By Horst Peter Wölfel

The goal of biodynamic models is to simulate the vibration behaviour of the human body. In combination with experimental studies biodynamical models can be a powerful tool for the analysis of the effects of vibration exposure on health [1] and comfort. This paper gives an overview of the state of the art of biodynamic whole-body vibration models of humans, addressing both numerical models and hardware dummies. Method Two approaches are distinguished, the phenomenological and the anatomical, as illustrated in Figure 1. [ ] Phenomenological models aim to reproduce the vibration behaviour of humans with respect to particular physical quantities, chiefly the driving-point impedance at the interface to the seat, and partly with respect to other transfer functions. Discrete systems of masses, springs, and dampers with several degrees of freedom whose topology and parameters are determined by structure- and parameter identification methods are used in the sense that the functions derived from measurements are reproduced as well as possible. This paper provides an evaluation of this methodology and defines its range of application as well as its limits.

Jan 6, 2006

Floor heave events in underground mining often happen suddenly and cause risk to workers and equipment. Reducing the risk of floor heave must be addressed in mining layout design. To improve that design one must understand the significant parameters that are correlated to the occurrence of floor heave. To accomplish that goal, researchers from the National Institute for Occupational Safety and Health (NIOSH) completed a numerical study using FLAC3D, taking advantage of its strain softening and ubiquitous joint capabilities to better simulate the floor heave and caving mechanisms involved at an actual mine site.

Jan 7, 2020

By R. I. Jeffery, J. W. Summers

An account is given of the verification and calibration of a numerical modelling technique that has been developed for the prediction of subsurface strata deformation following the extraction of coal by longwall mining methods.

Jan 4, 1992

By G. D. Schena, M Zanin

A numerical approach is presented for predicting the liberation of phases during comminution, with direct calculation of a liberation spectrum giving the fraction of the particulate system in each narrow size-composition class. The numerical model uses a Poisson flat process for stochastic generation of the non-convex three-dimensional Poisson polyhedral textures and the system of fractures that give rise to convex fragments. With this numerical approach, there is no need to assume random uniform isotopic fracture (lack of selective liberation); only computational geometry primitives are exploited for the derivation. The agreement with relationships obtained previously under the random uniform isotopic fracture hypothesis demonstrates that the approach is capable of deriving full liberation spectra directly. Both volumetric and superficial composition can be calculated

Jun 21, 1905

By Hongbo Yang, Tongbo Zhang, Ting Huang, Jingshe Li, Fangfang Song

"Liquid core length is a very important parameter of the process of continuous casting, which directly reflects the cooling status in secondary cooling zone and solidification rate of the slab. In this paper, the billet caster in some steel plant in China was chosen as the prototype of simulating. A numerical simulating model for calculating the liquid core length of continuous casting billet was built by ProCAST software, which was verified reasonable and accurate by pin-shooting technique. Based on the model, the relationships between casting speed, casting temperature and liquid core length of casting billet were found, which was very practically useful for the workers on sit to improve casting billet quality. IntroductionContinuous casting process developed very rapidly because of the high metal yield, energy saving, and low-cost 111• And the quality requirements of continuous casting billet for customers became higher and higher with the fast development of economic121• Internal defect usually is the major quality problem for continuous casting billet[3•61 , which is influenced by the solidification process of casting billet, especially the solidification process of liquid core17•81 • So it is very important to study on the relationship between casting parameters and the liquid core length which means the distance between the crystallizer meniscus and the casting billet solidification end-point. In practical production process, the workers usually control the quality of casting billet according to the liquid core length."

Jan 1, 2013

By S. B. Johnson

Keywords: Spray, Aluminum, Simulation A stochastic, droplet-resolved model has been developed to describe the behavior of a binary aluminum alloy spray during the spray-rolling process. In this process, a molten aluminum alloy is atomized and the resulting spray is deposited on the rolls of a twin-roll caster to produce aluminum strip. The one-way coupled spray model allows the prediction of spray characteristics such as enthalpy and solid fraction, and their distribution between the nozzle and the deposition surface. This paper outlines the model development and compares the predicted spray dynamics to PDI measurements performed in a controlled configuration. Predicted and measured droplet velocity and size distributions are presented for two points along the spray centerline along with predicted spray averaged specific enthalpy and solid fraction curves.

Jan 1, 2005

By F. Liu, H. A. Meier, D. M. Valiveti, P. A. Gordon

Hydraulic fracture is a frequently used technique in the Oil and Gas industry to create high permeability pathways for extraction of hydrocarbons. Numerical simulation of this method poses challenges such as representation of 3D fractures, propagation of randomly oriented fractures in 3D media, enabling fluid leak-off from fracture to poro-elastic medium. We have developed a numerical model using the Generalized Finite Element Method (GFEM) to simulate fluid driven fracture in a poro-elastic medium that addresses these challenges. In the GFEM framework, special enrichment functions are used to augment the solution space in the displacement and pore-pressure fields in order to accurately capture the response in the vicinity of the fracture. Adaptive refinement of the finite element mesh is also employed to facilitate accurate and efficient solution of the model. Our model fully couples fluid flow in the fracture, represented with the lubrication approximation, to the geo-mechanical behavior of the bulk poroelastic rock, comprised of an elastic rock skeleton saturated with fluid. Fracturing fluid exerts traction on the fracture surface and is also allowed to leak-off into the poroelastic medium using a transfer function approach. Stress intensity factors (SIFs) are evaluated based on the Contour Integral Method, accounting for the fluid pressure on the fracture surface. The SIFs are used to govern a full 3-D evolution of the fracture. Verification of the model is performed for known behaviors for the poroelastic response and fluid flow in the fracture.

Jan 1, 2015