Geomechanics - Science topic

Yes, it is possible to estimate horizontal in-situ stresses' directions and magnitudes from seismic data using AI methods. By preprocessing seismic data, extracting relevant seismic attributes, and integrating well logs and geomechanical models, machine learning algorithms can be trained to recognize patterns indicative of stress conditions. AI models, particularly those using supervised learning, can accurately predict stress magnitudes and directions, leveraging the complex, non-linear relationships between seismic data and subsurface stresses. This approach enhances efficiency, accuracy, and automation in geophysical analysis, although it relies heavily on data quality and requires careful validation to ensure generalizability and interpretability.

Weathered sandstone may have "rock like behavior" or "soil like behavior", varying from compact sand to weakly bonded rock.

Some data may be found in the document below. It is in portuguese, but you will find data that may be interesting searching for "arenito" = sandstone.

Good Luck!

Ahmed Merzoug

Thank you Dr. Ahmed

regards

EL-Mahdy

well each system includes different parameters, for RMR system you have 5 parameters and the sixth is the oraintion correction, for RMR it counts the effect of strength, RQD, spacing between discontinuity, the impact of water, and condition of discontinuity as well as for Q-system it also takes 6 parameters RQD, Jn joint set numbers, Ja joint alteration, Jr joint roughness number and effect of water Jw and SRF stress. each system gives a different rating and support system option the Q- system shows more details about discontinuities when the rock is poor or too weak in a better way than RMR. hope that helps there are many articles you can find related to this. good luck and regards

Yes

Hi dear Brian P. J. Stevens,

You're right. But the researchers themselves must be sure of the correctness of the equations to a great extent because they develop their research based on these equations.

Barton Q system?

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.

Hello dear Jalal Al Hatoum,

You can follow the topics below:

1- Mathematical modeling of information on the drilling line for dynamic simulation of Gas Kick Detection

2- Creating graphic output of dynamic well waste profile based on trend-line information of Mudlogging system

3- Predicting the type and probability of drilling string in real-time based on the output information of the Mudlogging system for display on the drilling panel

4- Dimensional analysis of solid particles of complementary fluid in the well to achieve minimal formation damage

5-Case study of RSS tool drilling in drilling common field overdraft projects

6- Evaluation of the optimal performance of PDC drills in drilling operations using the RSS system

7- Providing mechanical solutions to minimize pressure fluctuations during the performance of the complementary string pressure test operation.

Good luck!

Zew Zealand Geomechanics Society Recorded Webinars.

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.

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

You can check this study for help

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:

I hope I have given you some help and good luck.

That is a good question.

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.

Im interested too , if u can help me sir

Dear Emilio Velloso Barroso

What type of paper are you seeking?

I mean a conference, journal, etc.

Feel free to get in touch with me for more explanation.

Hi

What's your project subject? What do you like do?

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.

Thank you Murat! I will check it out.

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 (p_w - p_p) increase and is minimized to zero at p_w = p_p. This leads to the conclusion (which I should have known) that using α_B = 1.0, despite yielding the same effective stress (σ_ij = S_ij - α_Βδ_ijp_p), it will not yield the same wellbore stresses values (namely axial σ_yy and tangential σ_θθ). 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 S_hmin the Barnett Shale in Texas:

(1) Variation of σ_yy and σ_θθ with angle θ for p_w = S_hmin

(2) Variation of σ_yy and σ_θθ with p_w at the top of the hole (θ = 0 deg)

(3) Variation of σ_yy and σ_θθ with p_w at the top of the hole (θ = 90 deg)

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

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.

Regards

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.

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!

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)

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

I recommend the ITASCA software such as (UDEC, PFC, 3DEC). They are designed specifically to anaylze the behavior of discontinuous media such as rock masses Bekir Salih Firincioglu

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.

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.

Try contacting the US Geological Survey, as they developed it. It is probably not widely used software.

Dear Dr. @Mohammad Hossein Shahsavari@

Greating!

The following links may be useful to answer

With best wishes.

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:

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.

Thank you very much for your answers.

Mario

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.

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.

check the attached paragraph from "Geo technical modeling", David Muir Wood-2004

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..

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.

LAMMPS is a good MD code for materials research.

@ Rouhollah Basirat

Hi Dear Rouhollah

Both methods

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.

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.

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.

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

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).

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.

Dear Peter,

congratulations for the hard work! If possible, I would like a copy of your article. Thank you!

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

Thanks Dr. Luca Schiavinato and Vipin Kumar!

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. 

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.

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.  

Dear Ali，

We usually introduced the Barcelona Basic Model in PLAXIS to represent the swelling behavior of clay with "swelling coefficient ".

I found the mistake so thank you all for your great help! I apologize for my late response!

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.

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.

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.

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

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.

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.

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

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

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

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

Yes, It has an essential role. For example, the angle of discontinuity in rock can be increase or decrease the UCS and elastic modulus.

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

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.

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.

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 .