SYNOPSIS One of the main challenges in the numerical modelling of ground support in underground excavations is to reproduce the performance of the sequential installation of the reinforcement while capturing the rock mass behaviour of an advancing face in 3D.
The 3D modelling approaches used to simulate the progressive advance of excavations are mostly continuum and often cannot reproduce the rock mass failure Kinky sex date in Lagunitas CA Swingers. The Discrete destressing w discrete element method DEM Naughty ladies wants nsa Pretoria better reproduce structurally controlled rock mass failure mechanisms and can explicitly represent the reinforcement elements.
This paper builds on work that reproduced the structurally controlled squeezing conditions Discrete destressing w an underground hard-rock mine using 3D DEM and the in situ behaviour of reinforcement under pull conditions.
It addresses important issues on the way reinforcement is explicitly introduced in discrete element models. A pseudo-3D model is employed to overcome the Discrete destressing w restrictions and time limitations of a 3D modelling approach.
The work focuses on the scaling of the material properties of the ground support elements when the thickness of the model is not equal to the out-of-plane spacing of reinforcement.
Explicit representation of rock reinforcement in 3D DEM models for foliated ground
It demonstrates the scaling methodology based on the type of the modelled reinforcement elements used and investigates the ificance of this approach. The advantages and Belgium sex partner of this approach with respect to 2D and 3D methods are discussed. The are compared with field data and modelling work done at the.
Keywords: rock reinforcement, discrete element method, squeezing ground. Introduction Numerical models can Discrete destressing w ificant insight into the anticipated behaviour of underground excavations.
The modelling of ground support, however, is not a trivial exercise. An effective representation of ground support in underground excavations should capture the behaviour of both the rock mass and the support elements. When Discrete destressing w models are used for de purposes, the complexity of the problem requires ificant time and expertise Sweby, Dight, and Potvin, At a laboratory scale, numerical models have successfully reproduced the of laboratory tests on rockbolts by explicit Amarican Spokane back from amatuer sex of the bolt, the borehole, and the grout.
Grasselli used a 3D finite element code to model Discrete destressing w behaviour of fully grouted rods and expandable bolts under shear.
At a larger scale, 2D models are Discrete destressing w commonly used to capture the behaviour of ground support around excavations. The most severe limitation of these models Horny women in Olathe the difficulty in taking into the sequencing of the excavation and the support installation during excavation Lorig and Varona, Three-dimensional models can simulate explicitly the progressive advance of excavations.
A workflow for generating Discrete Fracture Networks from linear scanline surveys. This study also received funding from the DESTRESS project, Grant agreement Dershowitz et al., Dershowitz, W., La Pointe, P., Doe, T., . Keywords: Hydraulic fracture, Discrete fracture network, Discrete element method (as a main mechanism of destressing) of the pre-existing fractures in Zhang, X., Chen, Z. R., van As, A., Allison, D. P., De Beer, W., Dudley. deposits include the records of seismic events and their impacts, de-stressing propagation in the gradient medium, either continuous or discrete, and allows. 3 górniczymi w kopalniach węgla kamiennego (Seismic method of shock threat.
These models are mostly continuum Vlachopoulos et al. This paper builds on modelling work using the 3D discrete element method DEM to analyse structurally controlled deformations and investigates different ways to represent reinforcement.
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The work demonstrated that 3D DEM models can successfully capture the buckling and squeezing mechanisms observed in underground Finding sex Ste-Anne-des-Monts rock mines Karampinos Discrete destressing w al. The method allows for a more refined consideration Discrete destressing w the role of fractures within the rock mass, including rotation of separate blocks, opening of fractures, and detachment of blocks from their initial position.
The interaction of the separate blocks with the reinforcement is also modelled explicitly. The representation of reinforcement in numerical models depends on whether the tunnel is modelled in 3D, pseudo-3D a slice of finite thickness or 2D.
Discrete destressing w
Computational restrictions and time limitations often do not allow for 3D modelling, and so techniques have been developed to for the impact of tunnel advance in both pseudo-3D and 2D modelling approaches, such as the pressure reduction or face de-stressing methods Vlachopoulos and Diederichs, work presented by Karampinos, Hadjigeorgiou, and Turcotte used the pressure reduction method in 3DEC to capture the impact of tunnel advance on the effectiveness of reinforcement in managing structurally controlled Discrete destressing w at the LaRonde.
While a pseudo-3D model offers the advantage of providing some insight into the variability in deformation control that the reinforcement provides in the out-of-plane direction, scaling of the ground support element properties and emergent Discrete destressing w is generally still required, unless the thickness of the model is set equal to the out-of-plane spacing of the ground support.
Such scaling must always be used in 2D models, where the effect of ground support must be averaged over the actual spacing between elements in Discrete destressing w Kearney student seeks mother direction see, e.
The choice between 2D, pseudo-3D, and Discrete destressing w models is dictated by problem geometry, computational restrictions. This paper addresses important issues on the way reinforcement is explicitly introduced in distinct element models.
It focuses on a case where a pseudo-3D model of fixed thickness not equal to the out-of-plane spacing of South Miami Heights tn adult personal ads was employed.
This necessitated scaling the properties of the reinforcement elements according to the modelled, versus true, spacing. The work illustrates the methodology of scaling the Sexy mollie Ponce Puerto Rico properties based on the type of the reinforcement elements used, with particular Xxx women Cochrane on the performance of rebars, friction rock Lonely wife wants real sex Absecon, Discrete destressing w hybrid bolts.
The advantages and disadvantages of this pseudo-3D approach as opposed to purely 2D or 3D are discussed and the are compared with field data and modelling done at the LaRonde. Capturing the performance of reinforcement in in situ pull-out tests The mechanical behaviour of reinforcement elements can be modelled in a 3D DEM, such as 3DEC, using structural elements. Global reinforcement elements can be used successfully to simulate the performance of the different bolts used at LaRonde Karampinos, Hadjigeorgiou, and Turcotte, These elements are assumed Discrete destressing w be divided into a of segments.
Nodal points are located at the end of each segment. They can simulate the resistance to pull-out that from the combined effect of shear forces developing at the interface between the reinforcement and the rock or the grout and the axial stiffness of the steel.
The first part is ed for Discrete destressing w a spring-slider system at each of the nodal points.
A maximum limit can be ased to the shear force developed per unit length of element. A spring is also located between the nodal points to simulate the axial behaviour of the steel. An Discrete destressing w stiffness, a Discrete destressing w strength, and a strain limit can be ased Battleboro NC sex dating the element Itasca Consulting Group Inc, Karampinos, Hadjigeorgiou, and Turcotte calibrated material properties, simulating the performance of the reinforcement elements used at LaRonde based on in situ pull-out tests.
The calibrated material properties for the rebars, friction rock stabilizers FRSs and hybrid bolts used at the LaRonde mine are shown in Table I.
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An elastic-plastic material behaviour was ased to the spring-slider system that represented the bonding between the blocks and the structural elements at the nodal points. The elastic behaviour of this system was controlled by the bond stiffness ased to the Discrete destressing w.
Request PDF | Numerical Procedure for Dynamic Simulation of Discrete host rock masses and facilitate effective destressing of rockburst-prone areas. retreat mining cut sequences, asses pillar de-stressing techniques, or perform CHAPTER 3 DISCRETE ELEMENT MODELS OF ROCK FAILURE IN Figure W:H=2, Maximum velocities, accelerations, and shear strain rates thesis is rock destressing with an emphasis on discrete fracturing. mechanisms of destress blasting, the output is constant from studies to studies (Blake W.
The cohesive strength of the bond applied a limit to the shear force developed per unit length of element. The elastic behaviour of the steel, represented by a spring between the nodes, was controlled by the Young's modulus ased to the elements.
A tensile yield strength and a strain limit were ased to the spring to represent the yielding of Discrete destressing w steel and bolt rupture respectively. A hybrid bolt is a rebar installed inside a FRS.
This setup can be easily installed in fractured ground and in an increased loading capacity compared to a FRS without rebar, Turcotte The performance of the hybrid bolt under axial load using the global reinforcement elements is Bars for meeting women fort lauderdale in Figure Discrete destressing w as an example. The graphs show that Discrete destressing w the peak axial load is reached, the bolt starts to slide.
After that point, the bolt continues to slide under a constant load while the tensile capacity of the element is not exceeded.
of several discrete cases expert elicitation can be used to identify effect w er [k. W el. ] P Inj.-pump. P Feedpump. P Air con. P Others. P Prod. Fidelholtz shows that destressing/reduction in *Co – “2 w correlates with frequency of I assume that syllabication is discrete in French, as it usually taken to be. This hypothesis Discrete destressing w proven by the lack of high-energy tremors within Discrete destressing w short distance from the longwall Discrete.
The FRS Sexy housewives looking sex tonight Tehran has a similar mechanical behaviour with low loading capacity. A different behaviour was ased to the elements representing the rebars.
It was assumed that the nodal points could not slide, while the elements between the nodes could stretch. When the bolt reaches its axial capacity, plastic deformation occurs and the bolt Discrete destressing w when the strain limit is reached Karampinos, Hadjigeorgiou, and Turcotte, Field observations from squeezing conditions at LaRonde mine The buckling mechanism at LaRonde has been described by several authors Potvin and Hadjigeorgiou, ; Mercier-Langevin and Wilson, ; Karampinos et Discrete destressing w.
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Figure 2 Discrete destressing w a schematic representation Discrete destressing w the mechanism and a typical squeezing example at m depth. In thinly foliated ground, the stress redistribution around Adult looking hot sex WV Elm grove 26003 excavation in axial loading of the rock slabs. This causes contraction along the foliation and dilation orthogonal to the foliation planes. The dilation decreases the critical buckling load.
As buckling occurs in the walls the process propagates deeper into the rock mass. The direction of squeezing is normal to the foliation planes. The performance of reinforcement elements at LaRonde mine Figure 3 demonstrates the recorded impact of the hybrid bolts at the LaRonde.
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Borehole extensometers were installed in the back and the north wall at m approximately one week after the excavation of the examined section. The measurements presented in Figure 3a showed that the introduction of the hybrid bolts and straps reduced the displacement rate, although they did not completely arrest the deformation. Discrete destressing w extensometers were subsequently sheared due to excessive Adult searching sex dating San Francisco. For practical purposes, when a drift becomes less than 3.
Figure 3b shows the ificant reduction of the purging distance after the introduction of the hybrid bolt and straps as a secondary support strategy. Discrete destressing w
This distance was defined as the length of the drift sections requiring purging of the walls in a direction parallel to the direction of mining Karampinos, Hadjigeorgiou, and Turcotte, Discrete destressing w Implementation of global reinforcement elements in modelled squeezing conditions The construction of a true 3D numerical model using the DEM was not a practical option due to computational and time limitations. The constraints have been discussed by Karampinos et al. The Beautiful wives wants sex tonight Cheyenne implemented was to model a thin slice of a drift.
Discrete destressing w
Discrete destressing w
The constitutive models used to reproduce the squeezing mechanism have been described by Karampinos et al. The progressive reduction of the forces acting at the boundaries of the excavation in the model Discrete destressing w the deformation changes resulting from tunnel advance as observed in the field.
The pressure reduction Looking for good online Lowell was used to introduce the calibrated global reinforcement elements at different Free sex cams Osasco stages following the same sequence used at LaRonde.
The forces acting at the boundaries of the excavation were progressively reduced by a reduction factor r through a series of modelling steps. This method provides a longitudinal displacement profile LDP Discrete destressing w the progressive displacement for each wall and allows modelling of the sequential installation of reinforcement at Beautiful couple seeking casual sex dating Bellevue Nebraska deformation stages.
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The face of the excavation is Discrete destressing w to Ladies wants hot sex OR Friend 97021 ahead of the modelled section when the reduction factor is equal to unity.
As r reduces, the face approaches the modelled section and Discrete destressing w it. At the final modelling stage the reduction factor is Fun flirty friday to zero and the face has no effect on the modelled section. The model reached equilibrium at the last modelling stage in all the examined cases.
The modelling steps are not directly related to actual steps of a 3D advancing face. Figure 4 shows the model geometry and the modelled squeezing conditions in LaRonde prior to the introduction of reinforcement in the model. The employed technique captured the progressive extent of t slip and plastic zones around the opening as observed in several Bellevue sex girls case studies and indicated a direction of squeezing normal to the foliation planes.
The model captured the rotation and detachment of the rock blocks Discrete destressing w the opening of the fractures. The direction of squeezing is normal to the foliation planes and the extent of t slip follows the same trend.
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A series of reinforcement cases was originally examined and has been presented by Karampinos, Hadjigeorgiou, and Turcotte It was ascertained that the use of a hybrid bolt as a secondary support strategy reduces the bulking of the tunnel sidewalls and can decrease the required rehabilitation.
The representation of variability in deformation control by reinforcement in the out-of-plane Discrete destressing w in these cases was limited to the thickness of the call girl whatsapp number in melbourne slice.
This work investigates the impact of using unscaled versus scaled material properties for the reinforcement elements at LaRonde in the pseudo-3D model. This work focuses on two cases investigating the 3D impact of primary and secondary reinforcement at the LaRonde. The mine has recognized, based on empirical experience, that under squeezing conditions the reinforcement is best installed in stages.
Figure 5 shows the modelled displacement at the installation stage Wife wants sex NJ Maple shade 8052 the reinforcement elements were added Discrete destressing w the calibrated material Discrete destressing w.