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Rock Mechanics - Science topic

Rock mechanics is the theoretical and applied science of the mechanical behaviour of rock and rock masses;also compared to the geology, it is that branch of mechanics concerned with the response of rock and rock masses to the force fields of their physical environment.
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Kindly suggest a recent review paper on developing landslide early warning system in Hard Rock Slopes? It would be great if papers are provided where role of rainfall is considered in rock slope. It is important to mention here that, I require papers where rainfall role in hard rock slopes is considered NOT soil slopes. Kindly suggest recent papers on this topic. Thanks
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Dear Mohammad Azarafza Sir, Thanks for sharing the papers.
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Hello everyone. I'm working on reservoir rock mechanical properties. Do you know any conducted study on correlation between rock mechanichanal and thermal properties?
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Thank you Mehdi Razavifar jan.
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I want to get information about world-class universities, especially in the fields of geotechnical engineering and tunneling. Therefore, the following questions arise:
Which universities and in what research topics are the best at present?
What are the reasons for choosing them?
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Colorado School of Mines
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I am currently focusing on 3D geomechanical modeling. And in the future, I want to extend it to a 4D model. During my recent studies, I realized that most of the 4D geomechanical modeling that has been done has not properly updated the elastic properties such as Young's modulus, bulk modulus, Poisson ratio, etc. If a 3D static model is extended to a dynamic model, or a two-way or one-way coupling is performed, it is necessary to consider all material behaviors in a time-dependent manner. Please share if you have useful information in this regard or if you have a suggestion, I would be grateful if you could comment.
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Hi Erfan Rahimi , in time-dependent 3D geomechanical simulation ("4D" coupled flow and geomechanical simulations) there a many interdependencies between material properties (e.g., elastic properties, strength properties, porosity/ permeability, fluid properties) and simulated fields (stress, strain, pore pressure).
You have to think carefully when including additional interdependencies (or vice versa NOT including these interdependencies), whether they add (i) a lot of additional complexity, (ii) create a lot of additional insight, (iii) create complexity without creating insight, (iv) the error incurred by failing to include the interdependency. As you correctly point out, updating elastic properties in the overburden is NOT commonly for coupled flow and geomechanical modelling. This is one of the cases where you make the simulations a lot more complex, without adding a lot of insight. Elastic properties due to stress/strain changes in the overburden change by less than a percent from their initial value - and updating the elastic properties will affect the simulated stress field by an amount which is insignificant compared to our ability to calibrate the stress field. In your picture, you show a loop which includes updating of velocities for 4D seismic attribute generation. Here updating the velocities (even by less than 1%) results in something we can observe in field data in the form of time-lapse timeshifts. In a similar manner, if permeabilities are stress dependent in a significant manner and neglecting to include this coupling will create a large error, it is customary to include this coupling. Another example of coupling which is sometimes, but not always, used is to use non-linear stress-strain relationships in the reservoir, if significant compaction occurs and the reservoir rock will experience irreversible compaction.
In summary, keep models as simple as possible, and add complexity if there is a good reason. Do not fall into the trap of making models "complex" for the sake of complexity. Complex models are harder to interpret, and don't necessarily provide more insight. There is an unfortunate tendency of assuming that "complex" models are "better" models. They sometimes are, and often are not.
Hope this makes sense, and addresses your question.
Cheers,
Jorg
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Please share the links in your comments.
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Bit of background… Geotechnical engineering in mining focus on broader classification (RQD, Q, RMR etc). The makeup of rocks grouped in these classifications and other classes like lithology can vary significantly. For example, some data I’ve looked has a range of 40% iron content for an individual lithology. I would expect something like iron influence rock mass strength, an influence which would be masked if not lost, when relating the broader categories to excavation performance.
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All of the points listed above can be applied also to underground mining works with some adaptations to the individual stoping designs and types of mineral deposits
HGD
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I am a Ph.D. candidate in Mining Engineering. I was so confused in the selection of a suitable topic for my Ph.D. My areas of interest include Slope Stability, Rock Mechanics, Rock Blasting, Slope Stability, Waste Management, and Environmental Management in Mines. any suggestions would be appreciated.
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Dear Kandi,
I recommended that the following topics can be interested in mining engineers:
- Deep learning application in mining,
- An automated smart system in mining operations and stabilizations,
- IoT monitoring systems in open-pit mines,
- Deep structured learning application in green mining.
Best regards,
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In order to calculate the volume of an in situ block intersected by three joint sets, besides spacings between joints, we also need the intersection angle between joint sets. How can we calculate the intersection angle between joint sets using dip and dip direction data? Can you recommend any methods, software, or papers related to this subject?
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Dear Mehmet,
But you can determine the angle between two joint sets from this method. You can also determine dip and dip direction of the intersection plane.
Best
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The tensile-compressive cyclic tests on metals and alloys are extensively reported. However, the similar tests are rarely reported regarding rocks or concretes due to the difficulties encountered in terms of sample making, installation and the implementation of tensile-compressive loading. Can anyone suggest some literature concerning the tensile-compressive tests on rocks or give some comments on how to effectively perform the tensile-compressive cyclic tests on rocks.
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Our research group has conducted experiments in this field and achieved some results
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I have completed a Master of Engineering in Mining Engineering. I am currently exploring the possibility of pursuing a Ph.D. in the same domain in early 2022 or 2023.
My areas of interest are the following:
- Rock mechanics and ground control
- Backfilling the mined-out area
- Gemstones and their processing
- Open-pit optimization
Any other suggestion beyond this abovementioned is also welcome.
Thank you.
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Dear Ntigurirwa: If I may suggest, I would choose something related to tailings and mine wastes. Tailing ponds slope stability and tailing piles slope stability methods, besides methods of improvement of their stability are topics of interest to many mines. In addition minimization of wastes is another area that deserves attention and is key to any mine development. In this last case developing mine processes that will reduce or eliminate waste generation, and mine wastes recycling may gear attention of many mine groups and, who knows, provide funds for research. I suggest you concentrate your research efforts in these topics and find a case to study. Look for key researchers jn these areas and contact them to see if they can be your advisor in your Ph.D. Probably they will have room for a Ph.D. student to help them develop their research. Good luck
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I am looking for the data from the completed Tunneling projects located all over the Nepal if possible. Data can be geological mapping, Physical features, rock mechanical data if any, tunnel convergence or any deformation related values, etc.
Can anyone direct me to the places or person that can help me in this process.
Thank you!!
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Prabin Acharya I am looking for already constructed or being constructed Tunnel projects. I think DOED does not have such kind of information. Any way thanks for suggestion.
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What are the parameters required for designing open pit mines?
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Bench height.
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Hi everyone!
How we can calculate the stress intensity factor (KI and KII) in numerical software such as FLAC, UDEC or any software except Abacus (I mean Integral J)?
There are some equations for determining KI and KII based on stress in crack tip, but it cannot be calculate the KI and KII because of teta angle in these equations. Does any relationship between KI and KII based on stress in crack tip (for inclined crack)?
Thanks in advance for answering.
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Im interested too , if u can help me sir
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we have some experimental data of mechanical strength of rock material. We compare this data with the estimated strength (calculated using several existing criteria) and also determined the error percentage for each criteria. 
So i want to know that
what is the maximum percentage of error, that is acceptable for rock mechanics purposes, specially when we compare the experimental data with the estimated ones.
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the error for my study (prediction of unconfined compressive strength - 1120 data points) is about 30%
do you have any reference regarding your answer that may help me
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I am a master degree candidate in Mining Engineering. I am interested in rock mechanic and geotechnical area of study in mining, which will be highly in demand in the future. any suggestions would be appreciated.
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The field of rock "bursting" in deep underground mines could use more research.
When this phenomenon occurred about 1.5 km below surface there were no experts to suggest improvements and the mine I used to work for had to be abandoned.
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dear friends from the rock mechanics field
Good day. I have what may seem a minor problem, but I cannot crack it somehow.
I have attached a page from Hoek & Brown (1997) paper, which gives elaborate spreadsheet formulas for simulation of triaxial data and conversion to Mohr-Coulomb parameters, in absence of actual triaxial tests. All the formulas are explained and mutually connected except one.
What is the formula for signt??
It is the normal stress which must be specified in order to calculate the tangent to the Mohr envelope. There is a myriad of formulas involved with the problem and I just don't see the answer. I would greatly appreciate assistance.
Cheers, Hrvoje Vučemilovič
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Hoek Brown criteria helps in determining rock failure conditions, while Mohr Coulomb criteria is related to plasticity of rocks and strength.
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I did my PhD research on slaking rocks or soft sedimentary rocks, respectively. During my literature research in the beginning of my PhD project it was pretty obvious that there is no general defintion of the terms "soft rock", "weak rock" etc.
There are two fundamental views. On the one hand there are the (classic) defintions with respect to the strength of the rocks on the other hand there are defintions relating to the slaking behaviour of rock.
Even in the very recent book "Soft Rock Mechanics and Engineering" most of the reseachers find it necessary to define the term "soft rock" and how it is used in the following chapters indicating that there are still lots of open questions regarding a general definition of this/these group of geomaterial.
What is your opinion on the definition on the term "soft rock", "weak rock", "slaking rock" etc.?
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Building on some of the previous posts, in my mind "weak rock" refers to the rock's strength. Typically, a boundary strength value will be specified to separate "weak" from "strong" for a given context.
"Soft rock" refers to how a rock responds to weathering, or how abradable the rock is (there tends to be a correlation, but they are different processes). A rock that quickly weathers is "soft." Likewise, a rock that is readily abraded, for example when it forms a stream bed, is "soft." Often, but not always, these "soft" rocks will exhibit slaking behavior when they are cycled through wetting and drying. It is a specific form of disintegration in response to weathering and is associated with clay minerals. Slaking can also result from freezing and thawing or the growth of precipitates, like salt.
Low strength, readily weathered/abraded, and prone to slaking are often attributes that are found together (e.g. a claystone). Likewise, high strength, slow to weather, and not being prone to slaking are often found together (e.g. a quartzite). However, there are exceptions. For example, some sandstones can be relatively strong, but weather relatively quickly without exhibiting slaking behavior.
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Dear colleagues!
What is the best method to determine In SItu Block Size Distribution if I have orientation, spacing and persistence data collected from 3D Point Cloud?
I considered using 3DEC but I am not very fluent in the software.
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Hi Friend
I think you use the Rmi classified to detemine Vb.
Thanks
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Hello everyone!
I'm looking for the most recent developments in analytical, numerical and experimental micromechanical modelling of mechanical and flow response of Jointed Rocks.
I would like this space to be open and free also to suggestions of materials, articles and so on.
Thanks a lot!
Augusto Borges
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Hi
What's your project subject? What do you like do?
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I am planning of furthering my career by doing a PhD in Mining engineering, most likely in 2021 or early 2022. My areas of interest are Rock Mechanics and mining geotechnical. I am not too sure about the topic that I chose. Is this topic still interesting enough for now?
or are there any suggestions for other topics that are more interesting?
as well as university recommendations for me to take my doctoral programe ?
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In underground mines the stability aspect of the infrastructure and of the mining process itself will always be relevant. Obtaining methods or techniques of self-support or support through external elements under a minimum cost scheme is one of the fundamental aspects for the technical and economic viability of the exploitation of an underground mining deposit. Mines that have suffered collapse in some of their areas have experienced great losses due to stoppage of their operations, loss of equipment and in some cases of people, therefore it is an issue that continues to be valid. Something similar happens in open pit or surface mines. The equilibrium slope must be maintained to ensure that the slope is stable. A steep slope allows for greater stability, but is too expensive. On the other hand, a slope with a steeper incline is more economical but reduces its safety factor. It is necessary to find the optimal inclination that allows the company to generate maximum profitability without affecting safety. Finally I could tell you that it is a very good topic for your thesis. Cheers
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There are three primary areas of ground movement towards a pressurised TBM: at the face, along the shield skin and at the tail void -(In the attached figure).
Can the maximum surface Settelment of the tunnel Longitudinal Cross section due to the displacement of the tunnel face can be added with the Transverse cross-section surface Settelment and introduced as the final surface Settelment? in 2D model-numerical method.?
But in the transverse two-dimensional method, we cannot get Settlements dou to face pressure induced by tunnel advanc.
I was going to get the Settlements dou to face pressure from the longitudinal 2D model and add it to the other Settlements Caused by other factors
In the longitudinal section of the tunnel, details and geometries and conditions have been implemented so that only the displacement caused by the face pressure is created and that the shield cone and mortar injection and consolidation are not modeled.
so only max surface settelment in longitudinal cross cestion is occurred due to face pressure It is capable of adding with max surface settelment in transverse cross sestion due to injection pressure and shield cone?
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I simulated the shield driven-tunnel by FLAC 2D, in which step of numerical model must be applying the traffic loads of ground surface (20 Kpa)? the traffic loads of ground surface change along day and night
@steps:
1. elastic initial equilibrium.
2. elastic-plastic initial equilibrium.
3. Simultaneous with excavation and pre-installation lining.
*in which step influence the traffic loads is real? (interaction with ground above tunnel)
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I need a large model say 100 x100 m with a mesh size of 0.05m. such a large model cannot be made in version 7. before upgrading to version 8, I need to confirm whether it is working in version 8 or not?
I have also tried trail version 8. it is also not working
if anyone has version 8, I can send you a file to check.
Thanks
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When conducting analysis of foundation on rocks, and the triaxial test results of the rock material is found as c=3 MPa and ϕ= 44 degrees. In analysis, this cohesion value has to be reduced to account for the rock mass, to a value of maybe 50-300 kPa. Is this assumption correct? Or are there some correlations in the literature?
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This is one of the toughest questions in rock mechanics. Many 'answers' may be far from the truth - which we will never know anyway. But here goes: what if 2D UDEC-MC or UDEC-BB are allowed/available. Represent the jointing as sketched by an engineering geologist, digitize, and apply scaled JRC, JCS values using block size scaling. Convert the non-linear BB to MC for the joints if UDEC-BB not available. Try to model with some discontinuous jointing, and use numerically glued joints. Can estimate a lower-bound c for the intact bridges/glued joints from a linear tangent to the tensile and UCS Mohr circles, c =1/2(sigma c x sigma t)E0.5: construct and check, also estimate phi. If a continuum analysis is to be performed with linear MC or non-linear HB be aware that degrading c and mobilizing phi is more correct than the usual addition. If the building is very high and you are under higher stress, the more correct curved envelope for the critical intact bridges is found by moving 1 x UCS along the normal stress axis and drawing the critical state max. shear strength Mohr circle, with radius = UCS, therefore max possible shear strength numerically similar to UCS (Singh et al 2011). Sigma 1 (max) = 3 x UCS for stronger more correct curvature than HB. Note also stress-dependent deformation moduli might be relevant for a high building.
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For saving money, petroleum industry prefer poroelastic equation to calculate minimum horizontal stress rather than direct measurement (e.g. via Leak-off tests). Still, by comparing the value of calculation and measurement, it is showed that the value from calculation always underestimate the one from measurement. This phenomena has been interpreted to be caused by tectonic strain. I determine the tectonic strain. And, I'm trying to find some implication of tectonic strain on petroleum processes, for instance, wellbore stability or sanding production potential.  
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Hi, Uy Vo! The tectonic strain strongly affects the well construction process, including causes such complications as walls collapse, stuck pipe, loss circulation fluid, mobile formations, unconsolidate formations. These are very unpleasant and expensive types accidents and complications and cause great economic damage to oil companies.
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Residual soil is the product of the weathering processes for rocks.
What are the main characteristics of this residual soil?
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Dear Dr. Al-Obaidi:
Residual means it formed in place or in-situ. It is commonly used for ore mineralization be it created by mechanical or chemical weathering on top of a fertile bedrock (parent rock). It can be a placer or a kaolin deposit. In soil sciences it makes little sense because soil is an autochthonous cover on top of different types of parent material from almost organic free oxisols to organic rich ones with well – defined horizons. You should not use this technical term anymore. There is something similar called paleosol which is a soil intercalated into a stratigraphic sequence with all hallmarks of a special modern soil type but subjected to soil-diagenesis so that it comes closer a chemical sediment like silcretes or ferricretes. In this case the transition into sediments is not sharp. There is another type of soil called soil-sediment. It is a former soil which was reworked by water and shows the features of clastic sediments.
For examples and distinction see:
DILL, H.G. (2020) A geological and mineralogical review of clay mineral deposits and phyllosilicate ore guides in Central Europe - A function of geodynamics and climate change.- Ore Geology Reviews 119 (in print)
DILL, H.G. (2017) Residual clay deposits on basement rocks: The impact of climate and the geological setting on supergene argillitization in the Bohemian Massif (Central Europe) and across the globe.- Earth Sciences Reviews 165: 1-58.
DILL, H.G., BUZATU A., and MAFTEI A.E. (2017) Capturing digital data with handheld devices to determine the redox regime, lithology and provenance of siliciclasticsediments and residual deposits - A review and field manual.- Arabian Journal of Geosciences 10: 188-217 (plus supplementary data).
DILL, H.G. (2016) Kaolin: soil, rock and ore From the mineral to the magmatic, sedimentary, and metamorphic environments.- Earth Sciences Reviews 161: 16-129.
Kind regards
H.G.Dill
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Dear colleagues!
What is the best method to determine the spacing of the discontinuities on a digital 3D model of a rock slope obtained with TLS? I am only looking for a manual method since the aim of the Master thesis is to compare manual and semi-automatic methods.
Semi-automatic mapping results were obtained using DSE.
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If you are specifically thinking about fractures, there is a lot of literature on observational methods to quantify spatial attributes, well beyond "spacing". Here are just a few references to get started. These are generic but contain concepts that could be applied to TLS data.
Andrews, B. J., Roberts, J. J., Shipton, Z. K., Bigi, S., Tartarello, M. C., and Johnson, G.: How do we see fractures? Quantifying subjective bias in fracture data collection, Solid Earth, 10, 487–516, https://doi.org/10.5194/se-10-487-2019, 2019
Watkins, H., Bond, C. E., Healy, D., & Butler, R. W. H. (2015). Appraisal of fracture sampling methods and a new workflow to characterise heterogeneous fracture networks at outcrop. Journal of Structural Geology, 72, 67-82. 10.1016/j.jsg.2015.02.001
Sanderson, D. J., & Nixon, C. W. (2015). The use of topology in fracture network characterization. Journal of Structural Geology, 72, 55-66. 10.1016/j.jsg.2015.01.005
Roy, A., Perfect, E., Dunne, W. M., & McKay, L. D. (2014). A technique for revealing scale-dependent patterns in fracture spacing data. Journal of Geophysical Research: Solid Earth, n/a-n/a. 10.1002/2013jb010647
Randall Marrett, Julia F.W. Gale, Leonel A. Gómez, Stephen E. Laubach,
Correlation analysis of fracture arrangement in space, Journal of Structural Geology, Volume 108, 2018, Pages 16-33,
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I want to measure the hardness of particles that are smaller than 120 micrometers. Do you think we can use depth sensing nano indentation method to measure the hardness of this material?
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Yes and there are at least 2 methods used as nanoindentation with atomic force microscopy (AFM), and in situ compression by a force probing holder based on the observation with transmission electron microscopy (TEM).
However, in both cases the results are still under debate for it is not clear how particle size and nanoindentation depth could influence quite puzzling results especially for nanosized particles
see for instance the excellent paper by Dan Guo et al. :
‘’Mechanical properties of nanoparticles: basics and applications’’
Dan Guo, Guoxin Xie and Jianbin Luo
Published 3 December 2013 • © 2014 IOP Publishing Ltd Journal of Physics D: Applied Physics, Volume 47, Number 1
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Can someone provide a manual or a guide of geotechnical investigation procedures for different types of constructions in English? I mean a guide of methodology and standard procedures for transmission towers, bridges, regular houses, etc?
I am interested in a manual which is compatible with Eurocodes or ASTM standards.
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There are so many tunnel excavations, and so many who use either 'observational' (maybe double-shell) NATM or single-shell B + S(fr) selection from Q, or RMR, or less frequently RMi. Many then ask their younger (?) numerical modellers 'in the office' to check for 'plastic zone' size (often using the RocScience Hoek-Brown, GSI, Phase 2 / RS 2 software). We can alternatively use UDEC-MC or UDEC-BB to check for bolt and shotcrete loading. There are no 'plastic zones', just modelled joint adjustments: some joint shearing, joint aperture changes, and deformations. An altogether clearer idea of rock mechanics mechanisms. We can make improvements in bolt spacing or length or shotcrete thickness/strength if needed. Unfortunately it has been known for a long time that one should not add 'c' and sigma n tan(phi), either in linear Mohr-Coulomb or non-linear Hoek-Brown. This applies to the FEM continuum models. The nested equations involving a crudely estimated GSI (from a diagram, not from characterization) and the following opaque equations of c and phi need software as they are so complex. There is also a disturbance number D giving great freedom for the result, and a deformation modulus equation without depth or stress adjustment. Unfortunately the 'plastic zones' that the young modellers produce, though very colourful, may be grossly exaggerated, as found in a formal court case concerning a stable tunnel excavated without the need for shotcrete support. Is it not time to re-think the numerical modelling we are often doing in rock engineering? It is often based on so many a priori assumptions with even the input needing software. Mostly, the empirical methods, though with some inevitable weakness like subjectivity, are at least based on a posteriori principles.
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I believe that the condition of the inner and outer layers of the rock should be taken into account in the discussion of plastic dependence.
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I'm searching for open access and peer reviewed international journal (obviously of high quality and with Impact Factor) to publish research on geology, geomorphology, landslides, geotechnics, soil and rock mechanics.
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I would say Applied Sciences or Geosciences journals by mdpi
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For RMR and SMR classifications, field work is required to obtain information about discontinuity dip, strike and ,.... Are are aware of any resource to learn this field work?
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Please contact Dr. R.V.K.Singh, Liasion Officer, CIMFR, Dhanbad and its branches at Nagpur, Roorkee etc.
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From Wikipedia
”In engineering, a foundation is the element of a structure which connects it to the ground, and transfers loads from the structure to the ground. Foundations are generally considered either shallow or deep. Foundation engineering is the application of soil mechanics and rock mechanics(Geotechnical engineering) in the design of foundation elements of structures.
How future Materials and development of smart structures and new technologies in construction Will Shape the Future of buildings foundations?
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Good question Azm Shaher Al-Homoud .
Type of foundation should be a function of soil conditions and applied load. Recently, we observe also other factors influencing the geotechnical design.
Concerning soil conditions, we may assume that best locations are already occupied and we move our development to "unsuitable places". That is why we should expect further development of deep foundations. It refers also to reinvested lots with remaining of older (demolished) structures. In that case, the reuse of old foundations or debris from demolition works may be an issue imposed by "eco" regulations. I guess that due to political reason (in relatively reach countries, that seem not to have other problems) the last mentioned aspect may also comprise a pressure to develop "low-emission" technologies e.g. substitution of cementous binders with some kind of fly-ash or other materials with neutral carbon footprint. That also imposes a discussion over sustainability of geotechnical technologies and their adequacy for a desired life time of the structure. For now, I have an impression that we tend to provide "immortal" foundations for temporary or short service structures.
Speaking about applied loads, I'd underline the aspect of seismic and climatic impact on tall buildings and structures. That imposes some measures in design of buildings and their foundations, adopted to those conditions. One may notice that the growth of the economy provokes irrational behavior of many investors and designing "original" (tall, deep, shaped in not natural way) structures just for show and fame. That is why so complicated foundation systems must be designed.
Finally, I'd like to point again on the importance of testing. Whenever we observe a progress, we are touching the unknown. In the case of foundations all the risks are multiplied by the consequence factor for the supported structure and the difficulties related to any strengthening or repair methods under the existing structure.
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I was simulated 500 kg TNT on the ground surface to explosion, soil is clayey sand with young modulus E=100 MPa, dimensions of ground crater due to detonation is 70 cm in depth and 200 cm length!!(according to figure)
Are the results of the sizes correct??
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As i see your result is to inaccurate. Check your model based-on an authentic paper and or verify a paper or case study model.
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I simulated one tunnel in the soil medium, I going to study on the ground surface settelment due to excavation tunnels
Which Constitutive model of the soils (SC-GC) is better? and why?
1. Mohr coulumb (MC)
2. Soft soil
3. Softening strain (SS)
4. Hardening soil (HS)
5.Hardening soil small-stiffness (HS-SS)
6. CY-Soil
7.CH-Soil
8. Druker-prager
9. cam-clay
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Difficult to say. I would suggest that you start with an elastic model, and then move your way down your suggested ladder until you meet a good match. However, ideally, your stress strain curve from lab results should be able to help in deciding your final selection.
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I have a rock specimen and a soil specimen. During my mechanical measurements I observed that the rock reacts much faster on stress rate changes (observable by a sharp kink in the deformation curve) than a soil (no such kink). What is the explanation? Where can I find a publication dealing with this phenomenon?
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The first thought is that elastic waves propagation takes place. Corresponding velocities are proportional to sqrt of elastic moduli. See, for example, https://petrowiki.org/Compressional_and_shear_velocities
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What is the uniaxial compressive strength of westerly granite?
References would be appreciated.
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The conventional triaxial compression for Westerly granite test indicates: CP = 100 MPa, USC = 201 MPa, reference: Haimson and Chang (2000).
you can find more in the following reference:
Strength criterion for rocks under compressive-tensile stresses and its application, Journal of Rock Mechanics and Geotechnical Engineering, Volume 7, Issue 4, August 2015, Pages 434-439, https://doi.org/10.1016/j.jrmge.2015.05.002
You can find it from the following link:
I hope it is helpful for you.
All the best.
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dilemmas in rock mechanics..
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Many sophsticated suggestions already. We could also return simply to 'the shear strength of rock masses' (a 50-60 years-old dilemma since Muller-Brace) - and ask why progressive failure (and the possibility of monitoring prior to eventual failure) often occurs. This should tell us to be aware that Mohr Coulomb and Hoek Brown - if used as 'intended' to add 'c' and 'sigma n tan phi' - need to be used sparingly to say the least. It is not just 'c' then 'sigma n tan phi' (degrading cohesion and mobilizing friction, and then post peak) but actually several components: CCSS - 'crack, crunch, scrape, swoosh' as intact rock bridges (if present) fail, then the new fractures are immediately sheared, then 'capable' joints (the 'scrape') then the clay-filled discontinuities/faults (the 'swoosh'). How can we put this together - degrading strength at successively larger shear strains/shear displacements?
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Dear RG users,
I am wondering if there are good research topics related with industries need on “Wastewater threatment facilities” and “Solid waste landfills” considering only Geotechnical aspects.
I am looking forward for your messages.
Best Regards
Bekir S.F.
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It is very important topic and really we and our planet is in need of such importance researches
Best Regards
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We're trying to develop a portable tribometer to measure friction coefficient of rock surfaces. There are more than about 240 designs of tribometers which are developed to measure friction coefficient of different surfaces under various conditions, But non of theme were applied to rock mechanics.
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In our past investigation (which are not published yet) we found that the residual friction coefficients obtained from rock to rock point contacts (by shearing prepared cone shape rock sample with very small contact area on other rock plane surface) and plate contacts (conventional DST) under same normal stress and shear rate conditions are almost equal. Therefore now we're aiming to find a cheap and easy way to measure basic frictional properties of rock surfaces during field investigation stage.
Thank you very much for your encouragement
Mehrishal
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The most important current and future research to tackle problems related to industrial application in the field in soil and rock mechanics?
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One must distinguish between "hottest" and "most important" topics.
As for “hot” topics – look at the Universities. New tools (powerful hardware and software) make it possible for developing more and more sophisticated geotechnical research (calculations). Scientists publish more and more “indexed” but “unread” research papers without any influence on contemporary world. There are some key words in this “parallel universe” (sponsored by public institutions) like: green, eco-, sustainability that replaced former leaders: risk, reliability etc. The scientific world does even not pretend to address their findings to the current needs.
As for “important” topics – just look at the current situation in the developing countries. There is a big need for “infrastructure”, “food” and “energy” for the growing populations. The clue point is that development of Asian, African and South American countries does not demand for high-tech technologies or methods. The real world needs simple, cheap and robust geotechnical technologies to be applied in large infrastructural projects (roads, railways, dams, hydro-energy, flood protection, water supply for people and agriculture. �.
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I am trying to model the strain-softening behavior of rock mass using UMAT subroutine. And, I am applying the 'static Riks method'. My model is running fine in abaqus under small loading. However, when comparatively large loading is applied the analysis is being aborted after 18% load application with an error msg, 'THE SOLUTION APPEARS TO BE DIVERGING. CONVERGENCE IS JUDGED UNLIKELY'.
I have checked the .msg file, .log file and the UMAT subroutine file, but could not find any thing helpful.
Kindly give me some suggestions for solving this problem.
Regards, Dipaloke
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Can you select arc length method in ABAQUS?
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I am currently working on the effects of rock boulders upon a structure and I would like to simulate the dynamic impact force using Plaxis 2D. Since the duration of the impact is between 0-0,2 sec , how could I calibrate precisely a table of Impact Dynamic Force avoiding excessive Globar Error, and Log Info ''Accuracy condition not reached in last step''? Briefly, I'd like to mention that I tried to perform the analysis defining as accurately as possible a figure of Force domain.
Thank you in advance,
Paschalis M.
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You could design your impact load with very small time step in table load. then the PLAXIS will select an appropriate time step automatically or you could change the time step of the analysis to manual type and insert a very small time step by using number of steps close to 400 steps according to your case.
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We are trying to decipher origin of magnetite-apatite ores from Evate deposit, Mozambique. I would like to know if someone observed textures like that illustrated in the attached figure, showing oval baddeleyite crystal decorated by euhedral spinels, all enclosed in magnetite with geikielite exsolution lamellae. Note that smaller euhedral spinels are regularly distributed in the magnetite, except for spinel free-zone around the baddeleyite grain. In our opinion, this may indicate the spinel growth controlled by the Ostwald ripening, i.e. dissolution of small crystals and their redeposition on the surfaces of larger crystals and nucleation centers. This interpretation is supported by the intersection of some spinel grains by geikielite exsolution lamellae, thus suggesting the spinel growth taking place in Fe-oxide melt. I would be grateful for some alternative interpretations (solid state diffusion?), including references to published works describing similar phenomenon.
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In order to classify a rock mass foundation of a gravity dam to obtain its strength and deformability parameters using the Geological Strength Index (GSI), is the Ground Penetrating Radar (GPR) an adequate geophysical method to do it?
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The answer depends on the depth of target. As you know very well depth penetration of GPR method is very limited. Besides, deriving the fractures within rocks based on GPS is very hard. Therefore, classification of rock type beneath a site have to be done using other geophysical methods.
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Hello everyone,
  • What type of failure mechanism do you expect to occur in a slope composed of fissured clays?
  • Does the fissure properties influence the overall behavior?
  • Can you expect it to act similar to a disintegrated rock mass?
  • What type of numerical method would you choose to simulate the behavior?
I am particularly interested in fissures in the soil mass and not on the surface such as shrinkage or tension cracks. Also, you can see an example photograph attached.
Thank you for your interest.
Regards,
Bekir SF
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Thank you for your interest Samuel J. Abbey , Which constitutive model do you recommend?
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The current attention in improving the efficiency of mining energy minerals from the earth has encouraged concern in advances, difficulties and likely forthcoming development directions in numerical modeling for rock mechanics and rock engineering. Such modeling is necessary for studying the essential methods occurring in rock, for considering the anticipated and actual performance of structures built on and in rock masses, and hence for supporting rock engineering design. 
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Mr. Niaz, first thing you should keep in mind before starting to learn either FLAC3D or 3DEC that it not practically possible to learn the entire software at one go. Therefore, the beginning of learning of software should be problem specific. For example, if you have to design a pillar, knowledge of brick mesh generation would be sufficient, and you should control one’s temptation to learn not waste you time on other types. Furthermore, if you have griddle or Kubrix available with you, you should learn designing of shape using Rhino, meshing using Kubrix or Griddle and not invest your time on manual meshing; thereby, you can skip ‘Grid Generation’ section given in manual.
You may start with getting started section of the manual. Examples are given to make you comfortable with interface; you copy and paste the examples in text (or data) file to run the commands interactively through file driven mode. Command and plot windows can be opened simultaneously and text files can be called to develop an understanding of each keyword. If you want to see the how a keyword functions, you can insert comma before other lines to make them read as comments. Even after this if you are confident with any keyword, you may search it in command reference which describes every keyword in detail. After developing confidence with software interface, you may read ‘Problem Solving with FLAC3D or 3DEC’ section to develop an understanding on selection of material, meshing, stress initialization etc. After all these you will have a solid foundation to take up any problem for simulation. For project specific case, you may find a similar example in ‘Example Applications’ or ‘Verification Problems’ section.
After following above steps, you will have sufficient understanding and confidence to play with the commands or keywords to get any desired outcome.
I hope you find above suggestions helpful. Best of luck with your project.
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Would be reliable computing a finite element analysis of a dam-foundation system, using the rock mass parameters obtained through the GSI system, in order to evaluate the displacements in the rock mass, if you are using a software that not allow include information about the characteristics of discontinuities, only the rock mass stiffness?
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No certainly it is not reliable, rock discontinuities is a major item in determine both structural and seepage behavior of rock mass. if you don't have a detailed geological study, you may use geological maps to get the main faults locations and widths and from the RMR ( you may assume the worst for safety) you can estimate the width and spacing of minor discontinuities.
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Hey, I'm looking for a FEM analysis software to evaluate the displacements in a rock mass due to a presence of a specific gravity dam. I already have the strength and deformation properties of the rock mass and the dam.
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Dear Konstantinos,
The best software for analysing the stability of your problem is PLAXIS or FLAC..these two software is well established software for geotechnical engineering problem..among these two software PLAXIS is finite element based and FLAC is finite difference based software.. You will find lot of literature related to your topics ..the simulation of material properties in the analysis is very important..you will find rock joint rock model based Hoek and Brown method is available in PLAXIS..ABAQUS is basically developed for mechanical engineering and now civil engineers also using this software for various analysis..you choose the software as per your requirements and limitations of the software..ok all the best in your research..
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Hello RG users,
The rocks are recrystallized limestones and dolomites and physically in various conditions such as in some areas the outcrop is fresh and intact, in some areas it is lightly or highly decomposed and weathered, even somewhere there are residual soils. Also, some areas contain discontinuities and some not.
Assume that I have the plain 3D geometry. I simply cannot assume that the whole area is homogeneous and has same characteristics.
My question is How can I efficiently represent such varying conditions (heterogeneity) in a 3D model based on FEM, DEM, FDEM etc. ? Is there any software capable of doing it?
Thank you!
Best Regards,
Bekir SF
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Dear Bakir,
You have distinct weathering zones in your bench slope. So, you can define these zones in your model as a starting point. You can use GSI for estimating material properties of these zones. Since you do not have any defined joint sets, as you said, you can apply RS2 or RS3, both are FEM analysis program. Your slope dimension seems greather than REV size of your rock mass. Therefore, you can model your slope using continuum approach. Your bench slope is more prone to circular or non-circular failure mechanisms rather than discontunity controlled slip failures, such as plane, wedge or toppling.
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Hello RG users,
I was wondering how can I determine the exact location of expected wedge, planar or toppling falures in rock slopes. Assume that I have already done kinematical analyses and results indicate such possible failure mechanisms. In this case, How can I possible know the location of the wedges etc. to prevent such an instability?
Thank you
Best Regards
Bekir SF
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I don't think using a probabilistic approach is the right thing to do. The most dangerous and statistically processed direction of cracks is not the same. The safety factor is very sensitive to the orientation of the cracks and changing the orientation by 5-10 degrees can change the safety factor several times. Enough odnogo adverse combination that basically the ledge collapsed. The analysis of field measurements of cracks and the choice of the most critical combinations is necessary. Also, it is possible to analyze already accomplished collapses (on what systems of cracks they occurred).
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Dear RG members,
In rock mechanics and engineering geology, the orientation of a geological discontinuity can be described using 'Dip direction/Dip angle', and I understand what is 'Dip direction/Dip angle'. However, I saw many literatures that use 'Trend/Plunge' to represent the orientation of discontinuities.
What is the meaning of 'Trend/plunge'? what is the difference between 'Trend/Plunge' and 'Dip direction/Dip angle'?
Kind regards!
TC Yin
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Strike and dip are measurements specific to planar surfaces as the other say. Plunge refers to the downward angle and direction of a linear structure. Most commonly it is used to measure the direction and angle of plunge of a fold axis or hinge. The attached photo 'Strathconon' exemplifies what is meant; the stick is pointing down the plunge of the fold. The second photo 'fold 22' shows a recumbent fold in which the fold hinge (marked by the point in the fold where the rocks have split) dips gently into the hillside, i.e. plunges.
Trend is not a term of specific measurement as plunge is, or for that matter strike & dip. It is a general descriptive term for the direction in which certain structures lie. For example, a dyke or vertical fault exposed at the surface can be described as 'trending NW/SE or E/W. Hope that helps
George Strachan
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Hello to all RG users,
I am currently searching for softwares to anaylze the behavior of discontinuous media such as rock masses. It would be a lot better if they are especially developed for Geotechnical Engineering applications. I am also aware that discrete element solutions such as UDEC and 3DEC would do the work. Are there any other softwares for the particular field? I am interested in Discrete Element Method (DEM) and Discontinuous Deformation Analysis (DDA) but I am also open to any other methodologies and softwares. Please keep in mind that they should be used on Geotechniques.
Thank you
Regards
Bekir SF
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Dear RG members,
How to numerically conduct a uniaxial compression test of jointed rock mass in 3DEC (Three-dimensional Distinct Element Code)? Can anyone give a example?
Regards!
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You're right...
I gave the general scheme and forget you did uniaxial compression test.
You will see if the lateral boundaries need particular attention after your first test.
Good luck !
Nathanaël
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Dear All,
I would like to learn if the cut and cover tunnels have special joints between their segments such as immersed tunnels. For example, immersed tunnels have special gasket joints (gina, horn ,stirn, etc.), omega seals and shear keys. Is there any kind of joints for cut and cover tunnels? And anyone has longitudinal sketch of these tunnels showing connection details?
Thank you very much in advance.
Best regards,
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Dear RG members,
Why shear fracturing occurs in the rock compression test where no shear stress is applied?
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In the case of uniaxial compression/tension the shear stresses exist in any plane which is not orthogonal (or parallel) to the load direction.
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Based on earthquake data, how we can define the type of rocks and minerals within the earth?
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Lots of earthquake stations today, therefore, lots of data to study using the velocity of the waves. Scientists know a lot more information than previously and there is more to study. The data displayed in the lecture suggested by Dr. @ Borko Bulajic are amazing!
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Dear RG members,
A three-dimensional DFN (Discrete Fracture Network) can be established using PFC 3d 5.0 (Particle Flow Code), and two-dimensional ourcrops can be mimicked within such a DFN model. My question is: how can I output the information of the fractures observed in this outcrop (including fracture dip, dip direction, diameter, position (x,y,z) and trace lenght)?
Kind regards!
TC Yin
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Thanks a lot dear Dr. Gong for your constructive comments!
Regards!
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Dear RG members,
As shown in the attached picture, If the study objects are not rod-shapped, will cracks and fractures occur under gravity?
If crack appear, how to decribe it? how to determine the location of fracture face? and which yiled criteria is applicable in this case?
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only one way, enhance the craked location. make it stronger. such as reinforcing rib.
it will happened at the farthest point from the section center.
for my opinion, the third and fourth theory are both OK for your object. maximum distortional strain energy is more suitable.
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Hello,
I would appreciate it, if someone explain to me how I could estimate parameters of stoneley waves (such as arrival time, corresponding to the stoneley waves frequency or range of frequencies, velocity and so on...) that propagate in rock sample - limestone.
I've used ultrasonic pulser/receiver and oscilloscope for measurements and got this results ( please find attached ), but not sure what should be the next steps.
How I could differentiate where are P-wave, S-wave or Stoneley-wave moment of arrival and if there are any at all?
Never deal with this topic before, therefore would be grateful for guidance or advice on literature that I should read first.
Thank you.
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Some how you don't get my reply
Ori Yeheskel
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I am working on roughness influence on shear strength of rock. I am facing problems regarding roughness of the upper block as I asked in the question. I am looking forward to the answer. 
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I do not remember such a phenomenon from our 130 natural joint samples. On the contrary, JRC reduced due to highly-stressed damage 'islands'.
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Dear fellow researchers
In rock mechanics there are several methods to up-scale lab results to the field results (especially for Young's modulus) as it most of the times make a significant difference in analysis of tunnels, caverns, etc. However, in petroleum geomechanics the structure in question is a wellbore with a very small diameter (mostly less than 10 in.). I was wondering how much scale effect may be inflict in such a problem? Since the opening is almost as the size of the plugged core samples, is there any significant difference between lab mechanical properties and in-situ properties?
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Many good answers - but back to the scale of Abolfazl's question. Already the surrounding diameter(s) around the wellbore have increased the scale by an order of magnitude in relation to the cored plugs, and it is in the early phase of scaling that we see the biggest scale effects. The P-wave velocity, with appropriate stress-dependence in relation to depth, will show a reduced magnitude from plug size to 2-3 wellbore diameter sizes, due e.g. to JCS and JRC scale effects, if/because, jointing/bedding may be involved (i.e. down-hole velocity relative to lab plug). Modulus can be scaled via Vp, using the increased Vp at depth, which however brings the surround rock mass (20-30 inches scale?) closer to the confined plug modulus. So maybe strength falls faster than modulus with plug-to-surrounds scaling, due to the effect of confinement. UDEC-BB can give some indicators of the scaling using the Ln/Lo (small) block-size scaling. But suggest JCS replaced by confined strength due to the depth and absence of weathering.
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Problem with 10 node tetrahedral on RS3.
Results from using 4 node tetrahedral are similar to 6 node triangle on RS2 (and to analitical calculations) , but results with 10 node tetrahedral are very different, and not logical. Time calculation for 3d model of tunnel with 4 node tetrahedral is 20 minutes, and for 10 node tetrahedral is 16 hours.
What could be the problem with my model?
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Hi
I do not understand how i should change the data in the metric quality to improve my mesh. Please explain?
what would happen if i change either values in the tables
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Sawai et al., 2012 summarized in the appendix the different approaches in these cases like the intercept method. What do you think is the best way to approach this experimental problem?
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Dear Stefano
Teflon can be an expensive matter with time.
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It is known that igenous (and may be other) rocks exhibit viscoelastic properties. Has anyone any experience or insight on whether it is possible to measure either viscosity-only of a given rock sample, or, it's elastic-only (Elasticity modulus) properties. It should be noted that I do not wish that the two properties, that is, viscosity and elasticity to interfere with each other's measurement. I am actually looking for an independent verification. Fortunately, I also have access to Griggs apparatus.
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Elastic deformation is by definition completely recoverable. Elastoplastic deformation tends to begin with an elastic phase, this early elastic component is completely recoverable. Reduce the stress and the elastic strain component ‘bouces’ back. A Griggs rig should be able to record that.
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Hi
We're going to calculate the shear mode of rock specimen.
Thanks
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@ Rouhollah Basirat
Hi Dear Rouhollah
Both methods
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Hello
How to make crude oil by combining different materials, such as gasoline?
Also, can i determine API gravity (American Petroleum Institute) for this Crude oil?
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Hi Sajad
Your question is quite complex. I recommend you start designing the crude starting from a mixture of products that have high content of saturated and aromatic fractions, and then subjecting this mixture to thermal cracking reactions in Batch type reactors and an inert atmosphere between 250-500 psig of Nitrogen. You should create a training matrix so that you can vary the temperature and residence time conditions, since they are the variables that affect the quality and performance of thermal conversion products. Also I present one of my articles to have a better idea about this type of process (thermal cracking) and characterization and see if you can apply, this in my profile. Construction of a formation matrix for the production of anode-grade petroleum tar pitch by thermal cracking. Once you obtain a viscous product you can use ASTM D287 - 12b Standard Test Method for API Gravity of Crude Petroleum and Petroleum Products (Hydrometer Method)
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Hello,
Is it possible to compare classification results of GSI, RMR, and Q-system for flysch grounds?
Or, it's better to work just with GSI classification?
Thanks.
Rafik.
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Piotr!
You are making some serious mistakes concerning the development of the Q-system! The 212 case records dating from 1973 or before were 60% from Scandinavia, and both here and in all the other case records from outside this region there were a lot of different rock types (50 different types - please see some back-ground on Q so as not to spread, no doubt unintended, but nevertheless incorrect opinions). You might be interested to know that in the approx. 100km x 200km of land-area mostly to the south of today's Oslo - where the Q-system was developed, also using local non-hard-rock exposures as examples, there are 10 to 12 named collapsed caldera. Tunnel and cavern case records constructed in your assumed 'hard igneous rocks' would only have been of interest in shear zones and clay-bearing faulted 'hard' rock....we needed B+S(mr) cases, not 'no support needed'. The Q-system does a very good job of characterization, matching tunnelling observation very accurately, at least down to 4 to 9 MPa chalk marl, and of course must be pushed into (< 1 MPa) saprolites on occasion, where Q is usually <0.01.
Back to the flysch- and the sketches of Marinos. What would be the resultant anisotropic properties (?) from H-B/GSI application? Remember please the lack of an SRF equivalent in RMR and GSI - weak rock is not a limitation when you have a stress/strength term activated because needed.
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such as homogeneity particle size index.
Especially for sandstone and limestone.
And how they can be calculated (With math calculations).
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sajad
grain size , arrangement and cementation and matrix, diagnises , fossils.
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Hello all.
According to the AFTES guide, schisitosity is a type of discontinuity.
However, this schisitosity may not be an interruption of the continuity of the rock matrix but rather a rearrangement of minerals (with certainly a weak zone where detachment is easier).
For the geomechanical classification of a shist (eg. RMR), what is the rating to take for spacing discontinuities?
it will always be the lowest rating?
Rock mechanics
Tunnel engineering
Engineering geology
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Hi Rafik Hebib,I would like to advise you that not always, in the problems of foundation and in any case of compressive stresses on schist rocks, can be considered as favorable, it depends on the orientation of the schistosity with respect to that of the solicitation. Regarding the use of classification indexes I suggest you use the GSI and consider an equivalent continuous rock mass. However, if you want to use RMR, you should calculate the compressive strength parameter, either in the laboratory or with the Point Load test, taking into account the orientation of the load with respect to the position of the schistosity.
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are the GSI estimation formulas from (RMR) and (Q-system) still valid? (GSI = RMRbasic-5) and (GSI = 9log [(RQD / Jn) (Jr / Ja)] + 44)
are there new formulas.
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Hi Rafik,
1. The first formula you have shown should be written as (see Hoek and Brown 1997):
GSI = RMR'89 - 5 (for GSI>=18 or RMR>=23)
where RMR'89 = P1+P2+P3+P4+15+0 (evaluation for groundwater = 15 and for joint adjusment = 0)
(GSI = 9log [(RQD / Jn) (Jr / Ja)] + 44) is valid for GSI<18
2. Another quantification of GSI is given in the attached material.
Regards
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Hello all.
The identification of the squeezing potential of the ground is mainly based on the rock UCS, and on the height of overburden.
Is there a direct relationship between the deformation modulus of rocks and the potential of squeezing?
Thanks.
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In no manner any expert on squeezing, but the following observation might be of relevance. In the integrated Qc versus P-wave velocity versus static deformation modulus model that has appeared several times since Barton, 2002, (Figure 4) it is found that a fourth 'parameter' viz. the required support pressure Pr from Barton et al. 1974 is inversely related to the deformation modulus. So very low velocity, and very low modulus correlate with very high support pressure needs (sounds and is logical?), and very high velocity, and very high moduli correlate with the need for negligible support pressure (also logical).