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However, the frictional sliding or horizontal movement could also be taken into account!
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I assume that the foundations are made of hard and compact rock which can be modeled as an elastic material. In this case, there are almost no differences in the response of the dam (static and/or seismic). Another reason could be related to easier modeling and less computational cost.
Personally, I prefer to model also the foundation layer.
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Please, I am searching for master Thesis topic in Drill engineering : Geomechanic ,, Analyzing and improving technique and/ or technology of HDD for special tasks, and similar research field like Clay for Drilling Fluid.. I will be very glad if somebody could give a link or Idea on any of the above mentioned areas.
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Good day Jalal,
I may suggest, you can try Stochastic model Assessment of clay particles of Geodynamics heat flow for a Reservoir system.
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This topic is created to be a place for sharing reliable open-sources that contain quality free courses, webinars and short educational videos in the field of geotechnical engineering.
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Zew Zealand Geomechanics Society Recorded Webinars.
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In the oil and gas industry, for technical, economic, and similar reasons, well-Log running is done from special intervals. Therefore, to build comprehensive models for field development, we will need more information at different depths. Today, with advances in numerical methods, especially machine learning and deep learning methods, we can use their help to eliminate these data gaps. Of course, there are methods such as rock physics that are very practical. But according to my results, part of which is described below. It is better to combine the rock physics method with the deep learning methods, in which case the results will be amazing. I selected wells from the Poseidon Basin in Australia for testing and got good results. In this study, by combining the rock physics method and deep learning (CNN + GRU), the values ​​of density, porosity, and shear wave slowness were predicted. A comprehensive database of PEF, RHOB, LLD, GR, CGR, NPHI, DTC, DTS, and water saturation logs was prepared and used as training data for the wells. The below figure is the result of a blind well test for Torosa well in the Poseidon Basin, Australia. As you can see, the prediction results are very close to the measured values ​​of shear wave slowness in this well.
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You can use Machine learning algorithm to learn the data trends, where it is available and what parameters the data depend on, then use the algorithm to predict the data where they are missing the relationships learn from the training.
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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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I want to calculate adsorption isotherms from an aqueous solution in zeolites using sorption module. Is there any way to do this or can I just calculate isotherms from molecules in gas state with the pressure variation? 
Which program would be good to do this?
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You can check this study for help
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Petrophysical and seismic data analysis is one of the key technics for reservoir characterization and pore fluids identification. Rock physics is a link between these data and rock properties, such as porosity, lithology, and pore fluids. Quantitative interpretation and risk assessments of data and uncertainties associated with predictions need methods and multidisciplinary tools that use statistical technics and pattern recognition approaches, in addition to deterministic rock physics relations. The statistical rock physics approach is a way for quantifying the uncertainties in different steps of reservoir exploration and management. This approach applies some of the progressive statistical methods such as the Bayesian approach, Monte Carlo simulation, and Information Entropy. In addition to quantifying the associated uncertainties with predictions and evaluations, the statistical rock physics approach is a useful method to identify the most valuable information for predicting the desired properties.
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I'm currently focusing on research, which covers topics such as geomechanics, geophysics, statistics, & numerical modeling techniques.
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One of my challenges in this research is a gap in log well information in some formation intervals.
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Given the time constraints, how can these data gaps be filled with the least amount of uncertainty?
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Hello;
I- In general cases, we can apply many statistical tools and machine learning methods to reconstruct the missing data from other measurements. (Handling missing values in exploratory multivariate data analysis, see for example this link https://husson.github.io/index.html
2- There is a special study branch for data analysis for missing data.
3- It is known that real data may have missing sections due to the acquisition environment or to the lack of measurement. In such cases, rock physicists often proceed to reconstruct the missing data from other measurements.
For this purpose, the Rock physics module provides the following tools:
  • Gardner approximation: based on either an exponential or polynomial approximation, you can reconstruct bulk density from compressional slowness and reconstruct compressional slowness from bulk density
  • Note: Based on the Mavko et al Rock Physics handbook, the maximum polynomial degree used in the approximation is 5.
  • Faust approximation: this method is used to reconstruct compressional slowness from resistivity data.
  • The Gardner approximation provides a synthetic bulk density log reconstructed from a P-waves velocity Vp or compressional slowness log. Two alternative approaches have been implemented for this purpose: the exponential and the polynomial method.
  • The Gardner approximation for the compressional velocity reconstruction Vp from the bulk density RHOB is used to get synthetic compressional velocity and compressional slowness logs.
  • The Faust approximation for the compressional velocity reconstruction Vp from the resistivity Ro is used to get synthetic compressional velocity and compressional slowness logs.
  • Han's empirical Vp and Vs: This method computes compressional and shear velocity based on the empirical relations developed by Eberhart-Phillips (1989) on Han’s data.
  • Display Han's Vp vs Phi : This method generates a parametric cross plot where compressional velocity is displayed versus porosity for the considered depth points. Parametric Han regression lines linking the compressional velocity to porosity are displayed for different clay contents. These lines are based on the work of Eberhart-Phillips (1989).
  • Display Han's Vs vs Phi This method generates a parametric cross plot where shear velocity is displayed versus porosity for the considered depth points. Parametric Han regression lines linking the shear velocity to porosity are displayed for different clay contents. These lines are based on the work of Eberhart-Phillips (1989).
  • Smooth with missing values, corresponds to a Gaussian smoothing in which the missing values are taken into account to calculate the weighted average and impact the calculation of the smoothed value. It is a way to smooth point data as they usually contain a lot of missing values.
  • For example, the K.mod method performs parameter prediction and log reconstruction using multilayer perceptron technology. Dedicated templates enhance usability. Quantitative estimates of the fit quality obtained are provided. Models are stored and applied to other wells.
I hope I have given you some help and good luck.
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I'm working on a simple infiltration simulation(coupled stress and pore analysis), as far as I know, I should run the geostatic analysis as the first step.
In the geostatic analysis, I would like to set the specific saturation on the ground surface in the initial, I have been tried a lot of different methods to get a reasonable geostatic outcome that is the Sat, pore, stress is as similar as I sat in initial. But I always cannot do that. I put the information about my method. any suggestion is appreciated.
the way I calculate the value:
- Sat=G*wc/e
- pore pressure from wc by water retention curve
I list the different method I have a try below:
1) set predefined fields of pore pressure(elevation distribution linearly), stress(elevation distribution linearly), void ratio (constant) in initial
2) set predefined fields of pore pressure(elevation distribution linearly), void ratio (constant) in initial
3) set predefined fields of pore pressure(constant on the ground surface & bottom), void ratio (constant) in initial
4) set predefined fields of pore pressure(constant on the ground surface), void ratio (constant) in initial
5) set pore pressure(constant on the ground surface) as BC in step1(geostatic ), set predefined fields of void ratio (constant), by this way I can gain the result I want on the ground surface (but not on the bottom) after geostatic, but it always fails in the next step (transient simulation)
all BC are set: fixed x-axis in lateral, fixed y-axis or fixed y-axis & x-axis in bottom
I attached my cae file here
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That is a good question.
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nowadays, the role of conventional or unconventional well log data is to know Formation evaluation. But other problems can be resolved by taking account other special data logs as an example NMR, Imagery etc..
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Yes, well log analysis can give good results in geomechanical studies, and that results will be more reliable if calibrated with laboratory tests on core samples.
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Hello,
in my research group we would like to evaluate how the asperities of two rough planes deform when we press them together. We would like to use Abaqus, due to its advanced contact mechanics algorithms. It is not clear to us, though, how to model rough surfaces with certain statistics in Abaqus. Anyone knows any CAD software/code that could generate these models and be easily integrated with Abaqus?
Best regards,
Rafael.
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Hello Rafael,
Even I am working on the same problem, please let me know if you have found the solution. It would be a great help.
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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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Migmatites are inadequately considered as gneiss without any other distinction for civil engineering purposes. However, they are hybrid rocks generated by anatexis and composed of a mixture of metamorphic and igneous lithotypes. This feature can induce marked physical and mechanical variability in aggregates' technological properties, affecting the performance and durability of structures constructed using these aggregate rocks. In the last few years, I have been looking for articles or technical reports addressing the physical properties and mechanical behavior of migmatites' components (pelaeosome, leucosome, and melanosome), considering them individually. If you know a document with such an approach, please mention it here. I would appreciate it.
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What type of paper are you seeking?
I mean a conference, journal, etc.
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As a function of dimensions of real projects?
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Feel free to get in touch with me for more explanation.
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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 looking for a way to increase the number of sensors in acoustic emission lab experiments. Fiber optics (DAS) is a natural candidate but the standard resolution is several meters. Is it possible to increase the resolution to cm and use the method on laboratory scale?
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I highly recommend you to dig into the difference between OFDR and OTDR methods. If you want mm gauge length, you might need to make OFDR DAS system, or ask manufacturer like LUNA to customize one for you. OFDR is not recommended for length more than 50 m.
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Hello,
I would like to ask if there is anybody that have worked with an open source software OpenGeoSys to construct 3D static geomechanical model? I would very much like to hear any feedback/opinions/comments on this issue.
Best Regards,
Michal Kruszewski
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Thank you Murat! I will check it out.
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Haimson and Fairhurst (1967) derived equations for the near-wellbore stresses (axial σyy, tangential σθθ, radial σrr...) around a pressurized hole in a porous, permeable "poroelastic" medium considering fluid infiltration from the borehole into the surrounding rock. Their expressions include Biot's constant, A which depends on the Biot poroelastic coefficient, αB.
Should at αB = 1.0 those expressions give the same answer as when using the standard near-wellbore stress equations for linearly elastic media (the Kirsch solutions modified later by Hubbert and Willis to incorporate pp, on pages 170 and 174 in Zoback, 2010)? I was of the impression that the answer will be "yes" but the math seems to prove me wrong.
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Apparently, the approximation Haimson and Fairhurst (1967) used (from Terzaghi) to modify the Hubbert and Willis (1957) expressions to account for fluid infiltration from the wellbore to the porous-permeable surrounding rock does not match the corresponding equations for linearly elastic media.
The discrepancy between the two models increases with (pw - pp) increase and is minimized to zero at pw = pp. This leads to the conclusion (which I should have known) that using αB = 1.0, despite yielding the same effective stress (σij = Sij - αΒδijpp), it will not yield the same wellbore stresses values (namely axial σyy and tangential σθθ). Fig. 7b on my recent JPSE paper (link below) shows that taking account of linear poroelasticity in expressions used to approximate the stress state on the perforation base (intersection of two cylinders of different diameter) yields different results compared to using the corresponding expressions for linear elasticity.
I attached three figures demonstrating that drawn using inputs (Moos, 2012) for a horizontal well drilled parallel to Shmin the Barnett Shale in Texas:
(1) Variation of σyy and σθθ with angle θ for pw = Shmin
(2) Variation of σyy and σθθ with pw at the top of the hole (θ = 0 deg)
(3) Variation of σyy and σθθ with pw at the top of the hole (θ = 90 deg)
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Based on the principles of fracture mechanics, a crack propagates when KI >= KIC, i.e. stress intensity factor is larger than fracture toughness, where KI=σ√(πa) for a central crack. Theoretically, as crack propagates and crack length (a) becomes larger, KI increases too. Therefore, when a crack starts to grow, it never stops! However, it is not the case in many geomechanics applications in underground structures. For example, a propagating crack in a tunnel surface will stop at a distance from the tunnel wall eventually.
In numerical modeling, a stress relaxation method may be used to lower the acting stress on the crack to model crack propagation more realistically. what are other efficient ways to model this phenomenon realistically? Good references are appreciated.
Thanks.
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Hi Abolfazl,
Thanks for your interesting question. I think it might be good to consider strains rather than stresses, if you are dealing with brittle and semi-brittle materials. I would, in particular, recommend looking at the critical tensile strain criterion by Fujii and the extension strain criterion by Stacey. I hope you find this useful. Regards, Ebrahim
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I am trying to use the swelling constitutive model in FLAC 8.00, and cannot figure out what the a1, a3, c1, and c3 swelling parameters are.They are only defined as "a soil swelling property" in the manual. I have contacted Itasca and was given some literature indicating that they are determined through triaxial testing, but have not been able to find any other literature on what these parameters specifically are or how they are derived. Does anyone have an idea of what they may be or how they are found?
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I have a similar question regarding the swell model parameters of FLAC. I will be glad to provide me information about these parameters.
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can someone give me a publication about model phase2 near surface use gravity field stress ? I want to know how the deformation vector, and should I use fixed or pinned as the restraints on the surface ?
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Hi, the model follows real geometry when a near surface struture is analysed.
G.S.E. is an auxiliary function. I am attaching in brackets the help online by RocScience web site. Consider that some initial adjustments to displacement can be necessary. In addition chek the boundary conditions also at the upper lateral corners of the model.
"The reason the displacements are upward is rebound. The initial stress due to the gravity loading for a particular element is higher than the body force due to the elements above it. This can be because 1) the unit weight you're using for gravity loading is higher than the material unit weight used for body forces and 2) the ground surface elevation is at the top of the slope. If the initial stress is higher than the weight of the material above a certain element it will expand. This is why the surface moves up and is a common phenomenon when modeling surface excavations. Generally, what people do is use the first stage to get the initial condition correct then look at relative displacements between stages. You can do this through the Data->Stage Settings option in Interpret. Also see: Phase2 Developer's Tip: Setting up the Initial Stress State for Surface Models Also see the Gravity Field Stress topic. The Use Actual Ground Surface option can now be used to obtain a much better estimate of the initial stress field under a non-horizontal ground surface. Previously it was only possible to define a single datum elevation from which to measure the vertical stress."
Regards
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Scientists are holding a lot of experience ,and using scientific methods better than politicians and military personal ,but unfortunately they cannot hold positions,but singapore is good example,
a few times in recent years and been impressed with its wealth and modernity. I was also quite aware of its world-leading programs in mathematics education and naturally noted that one of the candidates for president was Tony Tan, who has a Ph.D. in applied mathematics. Tan won the very close election and joined the government of Prime Minister Lee Hsien Loong, who also has a degree in mathematics.
China has even more scientists in key positions in the government. President Hu Jintao was trained as a hydraulic engineer and Premier Wen Jiabao as a geomechanical engineer. In fact, eight out of the nine top government officials in China have scientific backgrounds. There is a scattering of scientist-politicians in high government positions in other countries as well. German Chancellor Angela Merkel has a doctorate in physical chemistry, so i think PH.d holders are better than bwhat is going on in America now,so how to imply this marriage of science and pollitics?
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If scientists would lead the country, then what would politicians do? Scientists are made to discover new things through research for progress and betterment of humanity, not to lead the country.
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I am working on my master's thesis in geomechanics and I need a database, about 6 months or 1 year of a mine with seismicity induced by mining.
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Hi!
Try https://tcs.ah-epos.eu/ - here you can find many sets of time-correlated geophysical, technological and other relevant geodata that relates comprehensively anthropogenic seismicity to its industrial cause.
It is totally for free!
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How can estimates geomechanical parameters use seismic data ???
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Dear Masoud, the answer is Yes!
If you have only Vp data, you can estimated by the equations the values of the density and the shear-wave.
But remember that you are trying to find the points of the crossplots so far from the linear / math / regression. Therefore, with equations, you will not see the anomalous points.
The relationships are:
1- Vp to density by Gardner´s equation (1974):
ρ=αVβρ=αVβ
where:
ρ = bulk density given in g/cm3,
V = P-wave velocity,
α = 0.31 for V (m/s) and 0.23 for V(ft/s)
β = 0.25.
Although Gardner estimation considered a variety of sedimentary rocks, the model is approximately a mid-line that averaged several lithologies including shale, sandstone, limestone and dolomite. For example, for sandstones, the constant value 0.31 maybe is a little less, say 0.28; and for shales, it is a little higher, say 0.33 for example.
On the other hand:
2-Vp to Vs by Greenberg and Castagna (1992):
have given empirical relations for estimating Vs from Vp in multi mineral and brine saturated rocks based on empirical, polynomial Vp-Vs relations in pure monomineralic lithologies (Castagna et al., 1992).
I recommend to use the classical relationship between Vp and Vs (Castagna, et. al., 1985) and defined as:
Vp= 1.16Vs +1360,
where:
Vp = is the P-wave velocity, (m/s)
Vs = is the S-wave velocity, (m/s)
You should be tested when it is applied to your area of interest. Maybe, a locally generated relationship between Vp and Vs is a similar or other forms exists in your zone of work, for example, due that the a fluid factor.
Please, try to read the paper that I attached, a classic paper in the literature.
Mario
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Without Laboratory experiments, is there any analytical method available to predict/model the stress path for the coal seams, which shall be very much useful in Depletion CBM operations and better long term production simulations w.r.t depeltion. I am pretty sure the conventional method for stress path determination is not going to work for coals.
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Dear Karthikeyan G., I can tell from my experience that under some conditions a stress gradient can be higher than 1 psi/ft. As for the depletion, the question is really insufficiently studied.
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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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In some literature, I find there is a code named BIOT2 from the following reference. Could anyone tell me how to obtain the code? Thank you.
Hsieh, P. A. (1994). Guide to BIOT2: a finite element model to simulate axisymmetric/plane-strain solid deformation and fluid flow in a linearly elastic porous medium. US Geological Survey.
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Try contacting the US Geological Survey, as they developed it. It is probably not widely used software.
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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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What is the actual nature of sand production? Shear or tensile failure? Shear bands? Erosion? or a combination of these criteria?
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What is the correlation between microseismic imaging and Geomechanics?
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There has been many laboratory experiments, field and numerical studies in an effort to bridge this gap. To name a few authors who have done some work in this regard:
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I 'm about to start a new project which will last 6 months , the topic will be : hydrocarbons recovery optimization , using geomechanical reservoir parameters changes ?
I would like to ask you if you know any oil and gas society who would work on such a topic ?? thank you
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Please clarify the question. In raw form , as porosity and rock compresibility (the change of porosity triggered by change of effective stress) is a geomech property, I would classify "recovery methods using changes in mech properties" in 1. conventional depletion (change of porosity without substantial permeability change), 2. unconventional depletion (change of porosity with substantial permeability change, including Cold Heavy Oil Production with Sand, dilation occuring during SAGD, chalk, etc.) and 3. all methods related to fracking (the trendy engineered tight gas or oil fracking or the more conventional thermal fracking in injection wells, fracking associated with acidizing, etc). When you think along those lines all companies in the Oil & Gas industry tackle 1. Most tackle 3 these days fairly extensively. Looking into 2 is done in all majors and many others companies.
I would suggest you clarify your question.
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I cannot speak to the entire discipline of Geophysics, but in the seismic world for E&P (design, acquisition, processing, interpretation, reservoir characterization) which are for your opinion the three most important problems that strike us as important?
Let me share some issues:
Rock Physics and seismic elastic inversion?
Geomechanics and anisotropy for unconventional reservoir?
Discrimination between lithology and fluid content?
Thank you very much for your answers, I will try to put a synthesis with your best knowlegde and point of view.
Mario E. Sigismondi
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Thank you very much for your answers.
Mario
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I am currently investigating the load-carrying mechanism of a driven pile (hollow bar) and trying to install strain gauge on the pile for measurement of stress distribution.  I have tried to install the strain gauges on both outer and inner surface of the pile with sealant and protective tape on but they all fail due to the large driving force applying on the pile. Most of the gauges broke at the lead wire connections. Is there a way to install the gauges that can withstand large driving force?
Regards, Philip
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I am also working with strain gauges pasting it on circumference of the hollow circular pile. I am currently grooving the outside the layer of pile with the thickness of the gauge length of the strain gauges. The wires soldered to the strain gauges were sent from the holes made on the pile above the strain gauges and the strain gauges are then protected with the protective layer given by the HBM. Thus, driving the pile by hammering does not affect the strain gauges and the wires attached to it.
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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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For instance, Rayhani and El Naggar (2008) posited that the said distance ought to be greater than five times of the superstructure width.
Rayhani, M. H., & El Naggar, M. H. (2008). Numerical modeling of seismic response of rigid foundation on soft soil. International Journal of Geomechanics, 8(6), 336-346.
Have you got any other references, covering the question of interest?
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check the attached paragraph from "Geo technical modeling", David Muir Wood-2004
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I am trying to make a geomechanical simulation in Ansys 17. I need to change the element type to CPT 216. So far I have inputed
et, matid, 216
r,matid,5000000 !(for 5 MPa pore pressure)
in the APDL command script.
I know this is incorrect, but I have two general questions:
1. Do I need to do this for every node? I have a 5m x 5m x 1m slab of shale I want to simulate.
2. What am I missing in my code? Do I need more parameters?
Any advice or help is greatly appreciated.
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Dear Jarrett,
You need not to change the element first, then if you know the boundary at which pore pressure is acting. Then, assign the known pore pressure value to those nodes which are covering on the boundary. You can use any continuum element for simulating the model and assign material properties. Please collect some ansys based literature related to your interest of work and ansys manual for doing it in correct manner. All the best..
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Experience in using the method of discrete elements in solving problems of geomechanics.
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There are some commercial software like PFC and some open source like LAMMPS and LIGGGHTS. They all use very simplified particles, such as disk for 2d and sphere for 3d, they are not suitable to simulate practical problem. Because the particles used in numerical model is up-scaled and too rounded. If you are doing numerical experiments or games, they are fine. But if you want to use it to investigate practical problems, FDM based FLAC, FEM based ABAQUS/ANSYS and combined FEM-DEM based ELFEN will work.
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Any idea/suggestion about using molecular dynamics simulation about transport and geomechanical fate of proppants?
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LAMMPS is a good MD code for materials research.
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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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I am wondering how to tie the seismic data and well log information to build a geomechanic model...
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Engineers prefer to use the Poisson's Ratio and Young's Modulus instead of using velocities and impedances. It is important to say that E&P Geomechanics is younger than Engineering Geomechanics, and because of its nature, has followed a direction based far more on Physics, Analysis and Field observations than on laboratory testing and empirical models.
Geomechanics are related with Geophysics, Structural Geology and Enginnering sciences.
Because I am Geophysicist, I prefer to use the seismic velocities and impedances. So, if I am talking about seismic impedances, I need to talk about seismic inversion in prestack domain, e.g. elastic or AVO inversion; I need to talk about AVO attributes, inversion theory, Zoeppritz equations, and so on.
Note that all these properties can be derived from 1) wells that have full-wave sonic (P and S) and density logs. 2) seimic inversion that estimates P/S impedances and density. The wells are critical to calibrate with seismic data, but the real thing I think is a major application, is when you can derivate or estimate the geomechanical properties from seismic, due that you can predict the mechanics state for hydraulic fracturing, a critical point in E&P.
It is critical the best knowledge of Geomechanical properties of subsurface rocks from wells and seismic, to a best comprenhension of the sustentability of oil and gas resources, economical viability optimization of E&P projects; avoiding demages in the geological formations, horizontal well-planning, and so on.
I try to write to you not only a synthetic answering, but also thinking about this questions:
When do we need to integrate Geomechanics into Reservoir Simulation? How can we improve the seismic data to use it for derivate geomechanical properties?
I suggest the books:
"Petroleum Related Rock Mechanics", by E. Fjaer, Holt, Horsrud, Raaen and Risnes.
"Reservoir Geomechanics: Earth Stress and rock mechanics applied to Exploration, Production and Wellbore Stability by Mark D. Zoback, Department of Geophysics, Standford University, 2006.
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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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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).
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Please, I am searching for master Thesis topic in petroleum engineering(Drilling) : Geomechanic ,, wellbore stability in deviated and horizontal well,,optimum orientation well path , and similar research field.. I will be very glad if somebody could give a link or Idea on any of the above mentioned areas.
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There are lots of research areas you can work on in drilling engineering. It just depends on your interest. Some of the relevant topics are:
1.      Drilling technology and heat transfer technique for Geothermal energy wells.
2.      Analysis of wellbore instability for shale/tight oil/gas wells.
3.      Sand control methods, optimization and design for deepwater wells.
4.      Prediction of frictional pressure drop gradient for complex drilling fluid systems.
5.      Modeling and simulation of dynamic surge pressure.
6.      Effects of drillstring eccentricity and rotation on circulating pressure drop.
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I am researching on hydro-mechanical processes in deeper fractured crystalline (basement) rocks up to 2000 m depth below surface. For my research I compile hydraulic data (permeability and hydraulic conductivity data) from different sources (e.g. hydraulic/pneumatic packer testing, tracer testing). Especially data from 1000-2000 m below surface and from schistose rocks (from upper greenschist metamorphic facies/contact metamorphic equivalent and higher) are sparse. I have already a compilation of data stemming from publications of radioactive waste research in US, Canada and Europe. If you have references to other published data sets please let me know.
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Dear Peter,
congratulations for the hard work! If possible, I would like a copy of your article. Thank you!
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a question
Someone has experience in the duration of split sets over time
With water with neutral pH or without water.
Using splitsets in tasks that last 10 years.
or slightly alkaline?
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Information can be collected on the technical brochures provided by the producer. The durability depends on the steel thickness of the bolt , stress level acting and chemical local conditions. References available also at
Regards
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Dear all,
I am modeling a slope with discontinuities in UDEC. 
According to UDEC manual, the vertical stresses are usually equal to gρz. However, when I assign the insitu stress by this way, some joints will slip or separate when the model is brought to an equilibrated state.
I am wondering if researchers could suggest me about this case.
Thank you in advance!
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Thanks Dr. Luca Schiavinato and Vipin Kumar!
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Title 1: High speed train X2000 on soft organic clay - measurements in Sweden. Proceeds of the 12th European conference on soil mechanics and geotechnical engineering
Title 2: High speed lines on soft ground: soil behaviour. laboratory test results. Ledsgard and Peppared at Vaskusrbanan
Kindly share them or forward them to 15197832@sun.ac.za
Your assistance will be highly appreciated
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Suppose in a basin we have a dam and we want to naturalize the flow at the outlet of the basin. What are the ways for naturalization of streamflow, so that the dam effect can be neglected. I have a long series of streamflow record prior to the dam construction.
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This has everything to do with the design of the outflow channel.  The channel must be shaped and dimensioned to mimic natural outflows corresponding to precipitation events.  Factors such as the nature of the inflow channel and incident precipitation directly on the reservoir surface will alter the flow regime and must be accounted for.  While you can mimic the flow, there will be a delay imposed by the reservoir.  The out flow rate will be driven by the levels in the reservoir and the configuration of the outflow channel.  Depending on the size of the reservoir and associated watershed, creating an effective discharge structure to mimic flows that would have occurred without the presence of the reservoir can be quite challenging. 
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Hello everyone, I'm trying to experimentally study the effect of Cd movement through a heterogenous soil column simulating a pumping aquifer. Can anyone help me in how we can find experimentally, the link between one dimensional flow and solute movement ?
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  • You need to determine the delay in Cd breakthrough relative to a "non-adsorbing" tracer. The Retardation coefficient you derive thereof contains the Kd-value.
  • As to flow velocity under pumping if you know the gradient (drawdown) and know the conductivity you may simply apply Darcy's law
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I am reporting on shale unconfined compressive strength (UCS) values for a petroleum audience. Some laboratory data I received from CoreLabs and TerraTek report in psi, however I have seen academic and professional publications reporting in MPa and psi.  Have you seen a trend of preferred units for the various industries for UCS and/or Young's Modulus? 
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MPa is very convenient in (at least) rock mechanics, as the typical range of the frequently quoted compressive strength of  rocks is say 2 to 200 MPa - i.e. conveniently 'small' numbers. Deformation modulus of rock masses, and Young's modulus for intact rock in GPa is also very convenient, typically 1 to 100 GPa. As 'psi' too many zero's. Re more personal usage, as an English researcher, but moving to Europe after student days, since the early1970's have never used psi in publications. (But maybe when in TerraTek, USA for four years, had to revert to both systems: in early 1980's.) We can live with both but much much prefer MPa, GPa, MPa/mm etc etc: they are perfect for rock mechanics.
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Generally, we know that EDEM and PFC3d have perform the same functionality in DEM.
However, after a long search I have found that most of railway ballast modelling that are used in academic research have been modeled by PFC3d.
However, I like the functionality and ease of EDEM even there are limited academic researches about railway ballast used EDEM.
What are the key differences between PFC3D and EDEM for Discrete Element modelling for ballast railway track applications? Which one is more appropriate to be used in my research area?
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I would recommend EDEM if it is available due to its simplicity and pre-defined functions. However, you may also try Rocky, but for academic purposes, EDEM is your best choice even though they don't have an academic license for students.  
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I am a graduate student of civil engineering. I have recently done my undergraduate thesis on "Numerical analysis of swelling behavior of Shale with PLAXIS Software". Therefore I am just interested to know about your current research work. 
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Dear Ali,
We usually introduced the Barcelona Basic Model in PLAXIS to represent the swelling behavior of clay with "swelling coefficient ".
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this happens before and after i insert the water
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I found the mistake so thank you all for your great help! I apologize for my late response!
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I want to study the effect of spatial variability of rock mass properties on the stope stability using FLAC. I therefore need to write a FISH functions that will spatially assign the rock material properties into the FLAC model.
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Hi,
Fortunately, There are urand and grand function in flac 7. so you can write a fish function to produce random variables in uniform and normal distributions and then assign them by fish zone variables such as cohesion (i,j) etc.
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Assume that we drill a vertical well, but when we get a survey of borehole trajectory we find that there is some deviated angle and azimuth. Some people say that, because of the weight of an anticline core, the but does as a plummet and get a deviation to crest of anticline. But I want to know the effects of stresses and rock strength independently from bed layering. Is it true that a well makes a deviation to low stress concentration?
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Hi,
As you mentioned, a well tends to be oriented towards minimal stress. But usually due to stress balance, the impact of structural parameters are much more in deviation process.
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Currently I'm working on a COMSOL project on geomechanics and  that have two physics models of solid mechanics. And i am changing geometry by making holes in horizontal direction (representing Tunnel Excavation).
Here my problem is to change the geometry in each step, and the values in the previous step(i.e.t0-1) also must be used in another new step (t0) and so on. 
If anyone could give me some suggestions on this, it would be highly appreciated!! Thanks in advance.
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As in the case of geometry you would have to change the parameters manually as you want..I think there is no option to change the dimensions parameters auto, it would be manually every time.
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I try to correlate the stress regimes from the world stress map with hydraulic measurements. I am able to connect the single sites of hydraulic measurements to sites of stress estimations but what puzzles me is up to which distance this correlation makes sense (horizontally and vertically)? I know stress regimes may change dramatically within short distances and therefore I doubt there is an universal answer but maybe you can provide some thumb rules? Thank you!
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Hi Peter
I think I'd add a word of caution about the influence of structures.  If the stress measurements are close to major structures in competent rocks then I don't think it appropriate to assume "smoothed" stress-fields.  Have a look at  the stress conditions around Fracture 2 at the URL (Martin and Chandler, 1993) . Florian Amman and ISC also has some nice results from GTS now!  Its really only in the URLs or detailed site investigations ( e.g Aspo,  or Forsmark or Mizunami) that you can see these influences.
Cheers
Bill
Martin, C. D., & Chandler, N. (1993). Stress heterogeneity and geological structures. International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, 30(7), 993–999. http://doi.org/10.1016/0148-9062(93)90059-M
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It is a pebble found in alluvium deposits.
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Again thank's to Professor Kamenov the pertrographic expertise has shown that this spicement is actually - slight metamorphosed Biotite Granite. Prime minerals are Quartz,  Potasium Feldspar and Orthoclase.  Accessory minerals are Magnetite, Titanite, Zirconium, Anatase.
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Hi everyone!
The safety factor is a factor for checking the results. How much is the safety factor for different slopes based on different standards or guidelines such as UIC, British standard, and etc.? Is it different for rock slope or soil slope in different conditions such as static or dynamic conditions (ODE/MDE/MCE)? Should it be considered based on special projects like high speed railway or other projects?
Thanks in advance for sharing your experience!
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Safety factors differ for soils and rocks. Also, they are different for static loading and earthquake loading conditions. Most of the times, every project has a specific requirement, based on spatial variability of rock/soil properties. I am involved in the slope stability analysis of Himalayan rock slopes for Chenab Railway Bridge project. The factors of safety under static, design basis earthquake and maximum credible earthquake set for this project are 1.5, 1.2 and 1.0 respectively. Also, it's not just the factor of safety, but the maximum allowed deformations along the slope, that govern the design most of the times.
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Hi everyone!
Some researchers believe that in the depth (more than 15 meters) there is no liquefaction potential for sand layers. Is it true? Is there any example and reference? And is there any sensitive for surface structures in this area (I mean a sand layer is located in the depth more than 15 meters) if an earthquake happen? Do you introduce new relationship for checking the liquefaction potential and its potential relationship with depth?
Thanks in advance for sharing your experience!
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In natural soil deposits there is generally no need to assess liquefaction below 15-18 meters if you have shallow foundations. There are some reasons for this:
- if you have 11-12-13 meters of non-liquefied layers the settlement of the liquefiable deep layers would not result in subsidence close to the surface
- the thickness of the holocene sediments (that are usually succeptuble to liquefaction) is rarely above this range). 
- natural deposits at greater depth are usually densified (that is why neogene sediments are not liquafiable)
However in man-made fills, and embankments such as dams, dikes and levees liquefaction is possible if the sandy soils are not well compacted. Also in most upstream tailings dams where the rate of filling is up to 3 meters/year you may have low density sands in greater depths such as 30 meters. If you have water you may have liquefaction or at least strain softening and cyclic mobility
For me the criteria stated by Prof. Jonathan D. Bray (UCB) give very good envelope of possible liquefaction, see this video: https://www.youtube.com/watch?v=mO7LAZgtdoI
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Metamorphic minerals such as garnet, andalusite, sillimanite, kyanite and staurolite
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Fourmaintraux (1976) proposed an approach for estimation of p wave velocity of all intact rocks based on their mineral composition. It can be helpful for you. refer to 2nd chapter of  this book:
Introduction to rock mechanics, RE Goodman - 1989 - Wiley New York
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.
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Mr. Sangsefidi
Ion exchange usually yields secondary calcite during Na-activation of bentonites (smectite rich clays) at industrial scale. The same process may easily occur in nature when Na-rich pore waters flow through Ca-bentonites in saline/alkaline environments. Similarly ion exchange between smectites and zeolites may retain K in the system which during diagenesis may facilitate illitization (see the attached paper). On the other hand one should not confuse ion exchange with specific adsorption due to fundamental differences (stoichiometric vs non-stoiciometric process).
On the other hand, multi-valence cations such as REE do not easily exchange in clay minerals, but may be specifically adsorbed on the clay edges at non-permanent charge sites especially at relatively low pH below the pzc of the edges. Bearing in mind that REE are usually bound in trace heavy minerals, sometimes reported to have formed diagenetically by authigenic processes (e.g. monazite-see the attached paper), it is expected that specific adsorption of REE of clay minerals may restrain authigenesis of such REE minerals.
Regards
G. E. Christidis
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Dear colleagues,
I am currently working on a multi-material arbitrary Lagrangian-Eulerian (ALE) method for applications in geomechanics and geotechnical engineering. In most multi-material ALE methods, a typical calculational cycle is divided into (i) a Lagrangian step where the motions of the material and the computational mesh coincide, and (ii) a remap step in which the mesh is rezoned (relaxed) and the variables are transferred to the rezoned mesh; see reviews in [1, 2]. In multi-material Eulerian formulations the mesh after the Lagrangian step is moved to its original configuration, so that it appears to be fixed throughout the calculation.
Depending on how the mesh is rezoned, so-called multi-material elements may arise which contain a mixture of materials separated by interfaces. The mixture is treated as an effective single-phase material on the element level by using some kind of mixing rules (mixture theory). Free surfaces are modeled by multi-material elements containing "void material" with (nearly) zero stiffness and mass density. Interfaces resp. free surfaces are typically reconstructed and propagated element by element using Volume of Fluid (VOF) or related techniques.
Almost all ALE or Eulerian methods use explicit time integration schemes in both the Lagrangian and remap steps. The range of application of such "hydrocodes" is therefore limited to dynamic problems having a relatively short-time duration. Reference [3] is the only one I know which deals with implicit integration in the Lagrangian step. Can somebody provide other references? Thanks in advance.
Regards,
Daniel
[1] D. J. Benson. Computational methods in Lagrangian and Eulerian hydrocodes. Computer Methods in Applied Mechanics and Engineering, 99:235-394, 1992
[2] H. U. Mair. Review: Hydrocodes for structural response to underwater explosions. Shock and Vibration, 6:81-96, 1999.
[3] D. J. Benson. An implicit multi-material Eulerian formulation. International Journal for Numerical Methods in Engineering, 48:475-499, 2000
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Hello Hassan,
I am not sure I got your point. The originality of ALE, in my opinion, is that the same mesh in terms of element-node connectivity (topology) can be used throughout the calculation. The mesh nodes can be relocated independent of the material to retain an acceptable mesh quality, either to handle large deformations or to increase the critical time step in explicit calculations (both are related). Complete remeshing is not necessary at all, although I know that in the literature remeshing is sometimes associated with ALE.
Dear colleagues,
To make my point clear, consider a Eulerian or ALE numerical model based on the Lagrange-remap strategy to analyze free surface flow of a geomaterial (e.g. landslide, debris flow). The problem might start out with only elements of pure geomaterial and pure atmosphere. At some stage in the calculation, material deformations may become so large that nodes have to be relocated to allow the calculation to continue. If after such a rezone the free surface is aligned with element edges (so-called simplified or single-material ALE), elements still contain pure material or pure atmosphere. In general, however, the free surface cuts the mesh, resulting in mixed resp. multi-material elements along the material boundary which contain a mixture of geomaterial and atmosphere as well as a portion of the free surface (interface between geomaterial and atmosphere). Methods that handle such mixed elements are called "multi-material" ALE methods; see my first posting above.
The problem with implicit time integration in the Lagrangian step is that a stiffness matrix has to be computed and inverted. Elements which are completely filled or contain a large fraction of atmosphere (or "void material") have almost zero stiffness, thus need special treatment in implicit multi-material ALE (or Eulerian) methods. An example of such treatment is proposed in reference [3] above. I believe that this is not the only published source for implicit multi-material methods...
Regards
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[ Studying rock samples with different patterns and structure]
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Yes, It has an essential role. For example, the angle of discontinuity in rock can be increase or decrease the UCS and elastic modulus.
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I read the ASTM D 1883. In this Code only the duration of the soaking is proposed. There are other papers in which a controlled temperature for this test is introduced. Is there any idea regarding the temperature and chemical composition of the water. Is is a distilled water or tap water or anything else?
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Dear Ebrahim
The quality of water or in general the water type is not so important in CBR tests. However, it is the best practice to use river or well water located in the area of study.
All the best
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Is the technique of geosynthetic-encased stone columns in soft clay applicable really? And is it possible to make geosynthetic around a stone column technically?
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Please have a look at the following articles:
1.Almeida, M.S.S., Hosseinpour, I., Riccio, M., and Alexiew, D. (2015). “Behavior of Geotextile-Encased Granular Columns Supporting Test Embankment on Soft Deposit.” Journal of Geotechnical and Geoenvironmental Engineering, 141(3), 04014116.
2.Mohapatra, S.R., Rajagopal, K., and Sharma, J. S. (2016). “Large direct shear load test on geosynthetic encased granular columns.” Geotextiles and Geomembranes 44(3), 396-405.
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As we all know, rock mass is weaker than intact rock, so how can we modify the strength parameter of intact rock to match the strength parameter of rock mass in continuum numerical modelling?
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The intact strentgh cannot be used directly in analyses. To obtain rock mass strentgh you can use several approaches. On is to combine rock mass classification methods and correlation between rock mass modulus of deformation with RMR, Q, GSI or other system. iI believe that you are familiar with free software Rocklab from the site rocscience.com. There, intact strentgh is combined with Geological Strentgh Index (GSI) and based son empirical Hoek_Brown criteria you can estimate rock mass parameters. To see the effecr, you can compare input intact strentgh balue with rock mass strentgh. For example, use as an input parameter uniaxial sterntgh of intact rock UCS=50MPa and GSI from 30 to 50 and you will see what balue of rock mass strentgh you will obtain. Other approach is to use combined large scale deformability tests and to combine them with refraction seismic tests. This is a so-called statical dynamical combined methodolougy. Any how, this is one of the key questions in Rock Mechanics and if necessary I can reccomend some articles. For a start,   try something with Roclab sowtware. In Rocscience products almost all softwarestwares give possibilities in input to put the value of intact strentgh and GSI, and the other rock mass parameters are calculated.
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Please consider a specimen that is compacted in Optimum Moisture Content (OMC). I want to increase the moisture in this specimen so that the moisture distribute throughout of the specimen uniformly. For example, imagine that the OMC is equal to 10% and I want to increase the amount of moisture in this specimen after compaction to 15%
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Ebrahim,
Here is the procedure of increasing water content after compaction:
-Find an appropriate mold (maybe plastic pipe for cylinder or wood made for cubic)
-Start with an initial water content which matches with saturation ratio and  dry density target .
- Compact your sample till calculated height (still you are not on your targeted water content)
- Calculate target water content on the wet side of optimum density and matches with saturation ratio-dry density and pour half of it on the top. let it be isolated for 1-3 days depending on your soil type. ours was cohesive clay and we kept it for 2.5 days.
- Reverse the sample and pour other half of water on the bottom. Keep it isolated for the same time.
- Now your sample is almost homogeneous in water content percentages. 
-Run a water content test from top, bottom and middle of every sample after you ran your test as a report.
* you may see some error according to change in height, expansion, non homogeneous distribution and ...  You have to verify them with measuring height after reaching water content as well as water content tests.
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A normal-sense shear zone has a true thickness of 7km. It dips 30º on average. The longitudinal strain-rate is on the order of 10-11 s-1. The duration of extensional movement is around 2-3 m.y.
What may be the total slip along the dip of the shear zone?
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Hello Nirmalya Chatterjee,
interesting question! Attached I have you an interesting literature for the reconstruction of shear zones. It proposes to go the opposite way and first determine the total slip. Here one could exploit the properties of existing long-lived radionuclides. The specified strain rate of (10-11) 10-2 s-1  does not appear to me realistic. In the literature, for the example of reconstruction was determined a shear rate of about 1 cm/a. The shear rate is determines out of the total slip and the determined time duration (in your example 2-3 m.y.). The sum of the shear rates (here cm/a or ε*L/t) results in the total slip, wherein the shear rate (strain rate) over time is not constant.
[The shear rate means the movement in the shear surface. Maybe should the vector of shear rate be divided in part-vectors.]
Look forward and good luck
Michael Lersow
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Hi All,
I want to derive an analytical solution of a boundary value problem for wellbore plugging. Let us assume, a soil mass is placed in a cylindrical container with full of fluid (water or oil) and fluid will enter to the soil mass. Therefore, soil mass will swell.
Field Problem:
Hydraulic fracture or well bore plugging using bentonite pellet. Fracture initiation process, fluid enter to the rock mass (soil mass) and they swell Or in plugging bentonite pellet absorb fluid and swell.
I used following references, but still not clear how to cope up the solution.
  1. Detournay, E. and A. H.-D. Cheng (1993). Fundamentals of Poroelasticity. Comprehensive Rock Engineering: Principles, Practice and Projects, Vol. II, Analysis and Design Method. C. Fairhurst, Pergamon Press: 113-171.
  2. Detournay, E. and A. H.-D. Cheng (1988). "Poroelastic Responses of a Borehole in a Non-hydrostatic Stress Field." International Journal of Rock Mechanics and Mining Sciences & Geomechanics 25(3): 171-182.
  3. Charlez, P. A. (1991). Thermoporoelastoplasticity General Theory and Application. Rock Mechanics, Volume 1 - Theoretical Fundamentals, Editions Technip: 183-238.
It is noted that I know geotechnical or geomechancis issue but in Petroleum or Minning totally new. At present, I am not considering thermal diffusion part. Most probably the problem is related to the coupled diffusion-deformation process. Any co-operation will be appreciable.
Regards,
Mohammad Nurul Islam
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Dear Mohammed Ismael,
Thank you very much for sending the reference. The approach is little bit different . In referred paper, main focus is the solution of stress and deformation. However, I need to incorporate coupled diffusion which will cause swelling. In Tunnel, when fluid diffused in the rock or soil mass, identical problem develop.
Regards,
Mohammad Nurul Islam
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We collected gravity data on a slope in Avcılar where near the  North Anatolian Fault Zone (NAFZ) . We think that, we can study or collected gravity data on any slope (there is a slope stability problem) and gravity value are affected  by on that. However, we worry that why does the gravity change on the same measurement point in 7 days. The increasing value is approximately 38 mgal near to  (NAFZ) in Turkey? The measurements were conducted with the CG-5 Scientrex device. The stress is increasing sharlpy or not? We asked it to you.? For the earhtquake prediction, Is these increasing is normal or not?
Sincerly.
Dr. Savas KARABULUT (Istanbul University)
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As all above have stated, tides, elevation, and groundwater are all part of the total gravity measurement at any point in the world.  Since these can all change over time, they could be contributing to the change you are observing.
Having said that, I have not personally used the Scintrex CG-5 gravimeter.  In looking at the manufacturer's brochure, I see that it is claiming all sorts of automated corrections.  I would therefore be very suspicious of either operator or instrument error in this matter.  I am supposing that the instrument reports the values used for all those automatic corrections.  I would look very closely at all of them.  I suspect that you might find a clue among them.  I would especially look at the elevation that was used on the two different days.
Another question that arises based on the claimed precision of the instrument.  I am wondering if there is a chance that you mean 35 milligals (mgals) or 35 microgals?  A change of 35 microgals would be much easier to explain, and so much more likely.
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Like our colleagues above mention, physical test are carried out in samples of rock known as cores. SCAL is very common because it gives most of the fluid and matrix properties but it does not do the mechanical properties. Dedicated, special test are carried out for the mechanical properties depending on what you might need. The most common one is for rock strength (unconfined or confined) but in some cases Vp & Vs can be also measured. Mr. Kalani indicated the other way to indirectly get mechanical properties and that is through the use of well logs. A current practice is to reconcile both values (from logs and from cores) and use them for any application as required, I hope it helps
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Would you describe to me, in a short way, the different stages of this relationship by using FEM
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Thanks a lot Mr.Ahidashti