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Geotechnical Engineering - Science topic

Geotechnical Engineering
Questions related to Geotechnical Engineering
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Hello everyone. I'm working on reservoir rock mechanical properties. Do you know any conducted study on correlation between rock mechanichanal and thermal properties?
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Thank you Mehdi Razavifar jan.
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Finding the seismic pressure is an important parameter to quantify the damages on structures during large earthquakes. Since soil force equilibrium in wedge approach can be used in site conditions there are no finite methods for laboratory experiments to study the seismic earth pressure behavior. A simple demonstration in this research area would help many students to understand its basic concept with good insight.
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I am in the research and development phase of (integrated doctorate) thesis. My thesis is about Reinforcement of elements exposed to high heat ( I can share the summary information about the project work with the relevant professors who might be interested)
We have done most of the project work, I will carry out my researches and develop the project in Pisa university with a supervisor for one academic year. 
looking for a supervisor support in Materials Engineering, Geotechnical Engineering, Chemical Engineering or similar related professors who might be interested in Reinforcement of elements.
Please kindly support/guide me to find the correct contact.
My contact information is as follows. Thank you,
+90 538 780 0818
Skype: rishadazizi
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Perhaps I can help you. Write more specifically what you need here:
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I want to get information about world-class universities, especially in the fields of geotechnical engineering and tunneling. Therefore, the following questions arise:
Which universities and in what research topics are the best at present?
What are the reasons for choosing them?
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Colorado School of Mines
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I would like to benefit from your academic and research experiences in the field of civil engineering. I would like to study a master's and doctorate degree in geotechnical engineering. Is this specialization recommended for the future from an academic and research point of view, and is there a specialty within the field of civil engineering that is recommended or preferred to study a master’s and a doctorate in it?
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soil structure interaction
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I am trying to model excavation procedure of tunnel (D-shaped) in Abaqus (CAE). I have obtained the RF1 and RF2 from an independent analysis as given in Abaqus example (Abaqus example problem guide/1.1.11 Stress-free element reactivation). Now, my problem is that how to apply those concentrated forces ((2n+1)*2) on corresponding nodes?... Because, in my model total number of nodes (2n+1) on tunnel periphery are 129 (in the abaqus example, there are only 13 nodes). And, its changing with each trial/variation of mesh size.
So, how should I apply the concentrated forces?
i) one by one clicking each node, creating each node a set and then applied the loads from load module ? (it's tedious/repetitive. I don't want to do it) or
ii) Doing some editing in *.inp file? (But, when I tried with following format, ABAQUS is simply neglecting my edited lines:
*CLOAD
node number, direction, magnitude) or
iii) writing ULOAD subroutine?
Please clear my doubts.
Thanks in advance.
Regards,
Dipaloke
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So your input file looks like something like this ? (CLOAD statements for each node ?) :
*CLOAD
node number, direction, magnitude
*CLOAD
node number, direction, magnitude) or
*CLOAD
node number, direction, magnitude) or
...
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i wanted to know the recent trending research interests in the field of Geotechnical engineering
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Hi Shad!
It could be some topic about analysis of off-shore structures foundations and studies of rock fracture in geothermal exploitation.
I hope that it helps you🙂
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I Have A Concrete Retaining Wall Completely Filled with Gravel from one side and half filled with the same gravel (with gamma = 20 kn/m2 and phi = 38) from the other side my problem is i designed the wall when the half side was empty which is supposed to be the worst case but due that iam assuming the wall will deflect to half filled size the Kp of the gravel using manual calculation caused the wall to be unstable which i know it shouldnot i also solved the problem numerically using plaxis 2D but i wanted to verify it manually so how to solve it ?
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thnks very much
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Many open source programs exist in the field of geology with all its specializa (Water resources , hydrology , Hydrogeology, Geostatistics ,Quality water .......etc) that many people are unaware of.
What software do you want to suggest to us ?
Thanks
Reghais Azzeddine
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Here is a list of common software and free alternatives
Software list
Illustrator => Inkscape, Scribus
Photoshop => gimp
Matlab => Python, R, GNU Octave
Anaconda, R studio, Jupyter notebook, Spyder
ArcGIS Pro and ArcGIS Online => QGIS, GRASS, uDig , GEODA, FOSS4G, Leaflet
PowerPoint => Google slides, LibreOffice, FreeOffice
Microsoft Word => LaTex, Google docs, LibreOffice, FreeOffice
Excel => Google sheets, LibreOffice, FreeOffice
Microsoft OS, Mac OS (and older computers) => Linux (Ubuntu, many others)
Others
GitHub, Arduino, Raspberry pi, Audacity, BRL-CAD, freecad, Dia, PDFCreator, Blender, Cinelerra, Bluefish, KeePass, 7-Zip, Psiphon, Clonezilla, VLC, Quanta Plus, NixNote, Overleaf, TeXstudio
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I simulated a pile embedded in sand soil. The pile was subjected to lateral and vertical forces. The model was aborted. I have printed the "Job Diagnostic" to present the causes of the aborted model. The problem occurred because of the nodes at the contact surfaces between the soil and pile. Some nodes were overclosure, and others separated, as presented in the figure below. How can I solve this problem?
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Good afternoon! If the model solution stops, it is desirable to check the boundary conditions, it is also possible to increase the size of the computational grid. The pile is usually monolithic and the moment of inertia is evenly distributed.
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Hi there
there are any keys to publish in high Journal's Impact IF of Geotechnical Engineering.
best regards.
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YOU CAN PUBLISH YOUR PAPERS IN SAGE GROUP OR HINDAWI.
MAY BE YOU WILL BE INTERESTED .
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Bit of background… Geotechnical engineering in mining focus on broader classification (RQD, Q, RMR etc). The makeup of rocks grouped in these classifications and other classes like lithology can vary significantly. For example, some data I’ve looked has a range of 40% iron content for an individual lithology. I would expect something like iron influence rock mass strength, an influence which would be masked if not lost, when relating the broader categories to excavation performance.
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All of the points listed above can be applied also to underground mining works with some adaptations to the individual stoping designs and types of mineral deposits
HGD
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My phd work is on alkali soil improvement by adding different agricultural waste material like press mud and rice husk ash.in construction work. To avoid the salinity effect on foundation and building. Related to this topic please send me the SCI journal paper for the reference work. Thanks.
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I would like to suggest International Journal of Geosynthetics and Ground Engineering and Applied and Environmental Soil Science.
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When we apply soil improvement by using rigid columns, like deepsoil mixing, jet grout, stone columns, geopiers..etc., we normally place a load transfer platform by using a granular material. Is there a minimum soil thickness to prevent soil arching to form or does soil arching actually occur?
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Dear Ahmed,
There always exist a shear stress between moving and stationary soil masses due to relative displacement. Localized displacement causes arching. Change of soil strength as well as soil plasticity also the reason of soil arching.
If a statically admissible stress field is
provided support then there will be less failure due to arching.
If the work rate of external load acting on the soil exceeds the rate of internal work rate then arching will not occur.
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Data science is a growing field of technology in present context. There have been notable applications of data science in electronic engineering, nanotechnology, mechanical engineering and artificial intelligence. What kind of future scopes available for data science at civil engineering aspects in the field of structural analysis, structural design, geotechnical engineering, hydrological engineering, environmental engineering and sustainable engineering?
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I simulate a pile embedded in multi-layer soil (Five Layers: 3 layers of clay, and 2 layers of sand ), subjected to earthquake (El-Centro earthquake) as solid elements by using Abaqus. Why the present curve gives a good agreement at the beginning only? How could I improve the model?
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Manar Naser Can you share your Abaqus model (.inp format)?
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Complex graphical sketches are highly involved in Culmann's methods. Therefore, it is highly prone for getting deviations in magnitudes for resultant pressure on retaining wall. I would like to get suggestions from RG colleagues on why Culmann's graphical approach is mostly preferred in many research papers albeit Rankine's method is easy and precise in terms of equations and substitutions. I would welcome answers from both theoretical and practical perspectives.
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Perhaps this is due to the fact that the graphical method makes it possible to "see" the calculation. Psychological factor in choosing a method.
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I am looking to start my Masters' Dissertation in Data Science. with a five months time frame. What interesting topics would you suggest, one in which I would be able to get a dataset from open source and analyse.
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Well, may I suggest my improved version of the least squares regression method? It's new and it has a lot of potential, I believe.
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For example it is common that curve of (v) against (ln p) will be plot. Why don't we use e instead of v?
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The reason is the one described by Pedro Miguel Vaz Ferreira above. The specific volume is linked to total volumes and definition of volumetric strain is then straightforward. No effect on the CSSM parameters, other than that
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Dear all, I have a problem with defining ZeroLenght element.
I want to connect black nodes with 4-dof (soil nodes) with green ones (intermediate nodes) with ZeroLenght element by defining p-y, t-z and q-z materials, and then connect green nodes with yellows (pile nodes with 6-dof) by equalDOF command.
Any idea for doing this correctly? I got this error:
"WARNING ZeroLength::setDomain cannot handle 3dofs at nodes in 4 d problem"
I think the problem is the fourth DOF of soil nodes that contain pore pressure of soil.
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Hi Abolfazl,
If I understand your problem right, I don't think that the number of DOF is the cause of this error. In order to define a ZeroLength element between two nodes, the location of those must be identical. So the location of green and black nodes should be the same. Then you could define p-y, t-z, and q-z materials separately. There is a term of direction in predefined ZeroLength element (-dir), in which you can define a direction for these elements. For example, if you referred to the y-direction as the number of 2, you would write 2 for the elements in the y-direction (-dir 2).
I hope this information can help you in solving the problem.
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I'd like to ask where I can find a free version from Plaxis 3D? or any alternative software
Please, if anyone can help me to provide me the free version I will appreciate that so much
Thank you
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Dear Ahmed B Shaath,
you can download Plaxis 3D 2013, Plaxis 3D connect v20, Plaxis 2D connect v20 here
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I am simulating piled raft foundation subjected to seismic load (earthquake) in ABAQUS. I have modeled soil as solid elements and Mohr-Coulomb parameter. I want to know how can I apply geometric damping (silent boundary) to prevent the reflection of seismic waves?
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The simplest solution you can use in an Abaqus simulation is to place viscous dampers at the boundaries of your model as described by Lysmer and Kuhlemeyer (1969) and make sure your boundaries are not too close to the structure and foundation. This works well in the presence of a homogeneous soil profile and perpendicular/tangential waves with respect to the sides of your model. The next step would be to look at more advanced approaches such as: infinite elements, absorbing layers (e.g., CALM = Calm Absorbing Layer Method), PML (Perfectly Matched Layers) or even hybrid approaches mixing FEM and BEM formulations. However, I do not know if these methods are available in Abaqus software (perhaps using user-defined elements?) nor the particular problems that may arise when calibrating their parameters, numerical stability, etc.
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I'm willing to prepare a loess ( collapsible) soil in order to test it's collapse potential in accordance to the ASTM Standards.
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Nice question . Why dont you add different proportions of expanding clays ( smectites ) to see the effect ...
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ITASCA PFC uses distinct element method for analysis that is mostly suitable for particulate media such as sand and gravel in geotechnical engineering. My inquiry is, whether we can model the behaviour of soft clay soils with respect to physico-chemical interactions between two clay particles (i.e., Van der waals and double layer forces) and also plate-like shape of clay particles compared to spheres used in PFC3D? Otherwise I may need to utilise a more general Discrete Element method using hexagonal elements.
Will it be also possible to model partially saturated clay soils using PFC?
What do you recommend?
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I recommended FLAC 3D program
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I need to model the weak and surface soil as a perfect elastoplastic material with drucker prager behavior in Abaqus, I don’t know how i can use hardening coefficient.
thanks for helps
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Check Applied soil mechanic with Abaqus application, Sam Helwany, C 2.9 p 61. it has a full description continuing with a good example.
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How can I optimize the positions of sensors (Broadband Accelerometers) around a meter scale experimental site to record the microcosmic signals ???
Simulation of sensors around a source before going into field
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This is a good question.
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Hello Everybody,
My objective is to model the stress-relief mechanism of a clayey meter scale experiment.
Please, share published material and your suggestions for such a small scale experiment.
Thanks  
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This is a good question.
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I would prefer experimental findings, not conclusions such as the fact that it is above 1 and can conservatively be taken as 1.
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This is a good question.
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In Plaxis 3D, I have modelled a quai front consisting of cellular sheet pile walls as a continuous plate with interfaces. How can you find the interlock strength of such a construction? In theory the maximum interlock strength will occur at 67% of its height but this has not occurred where i try to find the results from the output.
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That is a good question.
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I am trying to understand if there is a relationship between the angle of internal friction of soils and the angle at which the stress is distributed within the soil if a vertical force (via a footing) is applied at the surface.
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That is a good question.
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How can I appling non-axisymmetric loads or displacement to an axisymmetric model? I use bilinear asymmetric-axisymmetric elements (CAXA4N), but I also want to impose the asymmetry to the loads. (I'm using ABAQUS)
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CAXA4N are not supported by Abaqus/CAE. You must include them in .inp file. The main limitation is that deformation must be symmetric with respect to the r–z plane at θ=0,π. Look at the sect. Axisymmetric elements with nonlinear, asymmetric deformation: https://abaqus-docs.mit.edu/2017/English/SIMACAEELMRefMap/simaelm-c-dimension.htm#simaelm-c-dimension-t-AxisymmetricElementsWithNonlinearAsymmetricDeformation-sma-topic11__simaelm-c-axisolid-fourier-modes
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Hello there,
I am looking for a geotechnical design software which has the capacity to model FRP composite sheet pile wall for shoreline protection. I would appreciate any suggestion you can provide.
Thank you.
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Hello, find the softwares like PLAXIS3D, FLAC3D and also ABAQUS are useful for simulating your problem..ok all the best in your research..
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I am working with weathered granite laying on hard granite on Plaxis 2D v20. The problem is I used RocLab to get the closest fit to Mohr Coulumb just to make sure of the hoek brown results. What is VERY weird is that mohr coulumb input reach an overall factor of safety of 2 , while hoek brown model is more reinforced and reaches FS= 1.2 ...
Another question on plaxis, in hoek brown model Erm is defined in the manual as modulus of rock mass and you can easilty calculate it. What value E' should I input into plaxis mohr coulumb model? Do I use the same E=Erm?
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Check the stress level you used in RockLab. If the confining stresses in RockLab in the region of interest are different from the stresses in your Plaxis model, the distance from linear M-C shear strength envelope to curved H&B shear strength envelope may be significant, affecting plastification.
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The application of Machine Learning (ML) is rising day by day in all fields of studies. As a geotechnical engineering enthusiast, I want to know what are the most widely used ML algorithms (based on various python libraries and R packages) that can be used to improve the state-of-the-art practices in geotechnical engineering. Moreover, what are (/ can be) some of the most key applications of ML in geotechnical engineering research and application? It would be great if someone can suggest some key skills regarding ML/Deep learning/Programming for a young researcher in geotechnical engineering field. Thank you.
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The machine-learning algorithm could deal with Regression and Classification work. in research of traditional civil engineering, lots of prediction models are established to handle the various problems. Therefore, the machine-learning algorithm or data mining methods provide a new strategy to establish the mentioned above models. for example, the landslide displacement prediction, is also one of my research interests. the inducing factors of the landslide could be regarded as features in ML theory, and the landslide displacement also is regarded as labels. the consequent thing is to use different ML algorithms to train the model and other data to evaluate the accuracy of the prediction model. the svm, bpnn, rf and elm ML algorithms are widely used in Civil Engineering. with the development of Deep Learning, LSTM, CNN and other improve Deep learning algorithms are utilized to handle the prediction issue of big data. the sklearn module of Pythone is the best tool to establish ML models from my view.
by the way, I think that ML is just a tool to solve the problem and the analysis of failure or deformation mechanism is the most important.
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Hi all
Im modeling interaction of soil and reinforcement in abaqus. As you know there are two obtaining parameters for soil-reinforcement interface from direct shear test of soil and reinforcement:
1. Friction coefficient between these surfaces
2. Apparent cohesion (adhesion)
for simulating mentioned interaction in abaqus I used surface to surface contact algorithm.
Friction coefficient can be defined in Tangential behavior >> Penalty method, However I can not find any way to insert apparent cohesion of interface.
It should be mentioned that Intrinsic cohesion of soil inserted as a plastic property of soil in mohr - coulomb plasticity. But apparent cohesion between these two surfaces cannot be defined in mentioned part, because this property is related in both surfaces.(its not the plastic property of one material).
Im wondering to hear any suggestion.
Thanks for your attention beforehand.
Alireza Akbari
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Dear all,
When calculating the earth pressures of a simple retaining wall, Coulomb/Rankine methods are used in the static condition and Mononbe Okabe in the seismic condition.
What about burried structures? Does the same assumption apply as shown in the figure below?
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You should consider the effect of interfaces between the buried structure and peripheral soil on the system interaction.
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Hi
I wanna model interaction between two different material(soil and reinforcement)in abaqus.
As I know when there is no penetration between these two parts, hard contact must be defined in normal behavior however in my simulation reinforcement penetrates in soil due to loading in normal direction so I think soft contact is required in normal behavior. right??
for this purpose linear relation must be defined but I don't have stiffness (coefficient between stress and over closure).
It should be noted I tried some different value for stiffness just to see effect of that, however the analysis didn't convergence at all.
I'm willing to hear your suggestions.
Best Regards
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Hi, Alireza!
I recommend checking out this paper on the use of hard and soft contact implementations through the general finite-element software, Abaqus. You can jump directly into section 7.3, which is related to your concern. Below is the link.
Chapter Contact
I hope this helps. Good luck!
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The seawall made of FRP sheet piles is used for shoreline protection. I want to calculate the deflection of the FRP piles under certain surcharge loading conditions. How to calculate deflection if the FRP piles are tied down or not.
Please refer me to some books or articles to understand deflection-based FRP sheet piling design.
Thank you.
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Dear Arif Alam ,
Have you read the following paper?
Bdeir, Zeid. “Deflection-Based Design of Fiber Glass Polymer (FRP) Composite Sheet Pile Wall in Sandy Soil.” (2001).
If that article is not related to your work, please inform me.
Regards,
Ali
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Hello.
I'm working on my master's degree project and I'm trying to understand the behaviour of the drains to mitigate liquefaction hazard. From literature review, I found the FEQ Drain software by Pestana (1997) and I'd like to compare the results with another software. Until now, I've been thinking in comparing with Plaxis 2D. Is there another software available for this modelling?
Thank you so much.
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Hi everybody
The FLAC software is very capable of Couple analyze liquefaction.
With using Constitutive models:
Finn, UBCSAND, PM4SAND, CycLiq, Wang2D, NTUA-Sand, UBCHYST, Dames & Moore, Dafalias-Manzari
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Please, RG community suggest this subject area (topics).
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Crack, crunch, scrape, swoosh! Seriously - progressive failure of rock slopes - involving (possibly) all four components of strength (and weakness). We have been waiting 50, 100 or more years. So much of what we have done has ignored/failed to match the reality. Start with physical models of partly fractured rock simulants. Progress to modelling the components. Specifically do not use GSI.
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Hi dear researchers
Im trying to model polymeric material, but the elastic module of that is not constant and varies with change in strain, this polymeric strip(membrane element) is embedded in soil as a reinforcement and tensile load will be applied to that, so I wanna know if for my purpose using property >> mechanical >> elastic >>Hyper elastic is suitable or not, because as I know entering stress -strain test data is possible in hyper elastic.
Im wondering if using hyper elastic requires any special conditions or not or any alternative( better) way for my purpose.
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Sujeet Kumar dear sujeet
thanks for your attention, but I have doubt about that, because my purpose is to use stress-strain curve in Elastic phase Not Plastic ,I mean using plasticity option for my goal seems wrong , whats your opinion?
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Hi
I know the procedure of modeling modal analysis to obtain natural frequencies(I mean using Linear perturbation step>>frequency and without defining any other loading....) but the problem is all examples I have seen is just for model made of just one material(most examples for cantilever beam) but my model is consist of two or more material( 2layer soil and layer of polymer between these soil layers), for obtaining natural frequencies in this case, my exact question is: I have to run modal analysis for each material separately or all together?!
I should mention that the polymeric membrane part does not have any type of support and its just in interaction with soil( normal and tangential behaviour), and if I run the modal analysis for this part alone natural frequencies for polymeric membrane is zero. while the soil is fixed at bottom and sides and by running modal analysis once for soil alone and another time soil with polymer,the natural frequencies are the same for both conditions. so i'm willing to know any advise and special point to obtain natural frequencies procedure for model consist of two or more materials in abaqus.
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Interesting
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Hi researchers
Im trying to model dense sand which has peak friction angle and constant volume friction angle . As you k now if we plot shear stress - shear displacement(strain) of dense sand till reaching specific displacement curve ascends to the peak point(peak friction angle)and after that with slight reduction becomes constant(constant volume or residual friction angle). I wanna model the behaviour of soil accurately so my purpose is to define friction angle as a function of shear displacement. I searched and understood using SUBROUTINE (specially USDFLD) may help me but I have not work with subroutines at all and this is my first time however I linked vs code and intel R with abaqus and its completely ready for working.
I will be thankful to hear your helps and advises.
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U can refer to the ABAQUS user guide about the details of user defined field.
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We are trying to get the best compression and consolidation in making Compressed Earth Blocks. Any suggestions on how to optimise the soil composition to get best packing density will be most appreciated.
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Clay loam soil. Theoretically, for maximum compaction there should be an equal proportion of sand, silt and clay fraction, i.e. 33 per cent each. But in nature, it hardly happens. Therefore, try to have proportion within 10 per cent deviation among these fractions to have maximum compaction. Yes type of clay particularly, swelling type is also the factor which determine maximum compaction at given moisture content. Proctor moisture shall be used for achieving highest compaction. May contact further on vkphogat@gmail.com. thanks
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The purpose of this discussion is to find out if the AI and ML techniques are being used practically in geotechnical projects or their applications are still limited to academic studies. If they have been accepted as reliable design approaches, has any standard been developed for systematic application of these techniques?
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Muhammad Nouman Amjad Raja Thanks for your helpful contribution to the discussion.
That's right, one of the major challenges in this area is the lack of reliable data in large scale. However, from my industry engagement experience, I can say that the data is available but the main issue is the lack of effective collaboration/communicate between universities and industry to use these value databases for AI/ML studies/analyses, which by itself could be another important topic for discussion.
I believe the Geotech industry should be well educated through simplified manuals and design methods to learn how to use AI and ML approaches in practice and also be able to review/verify the designs that have been done based on these techniques.
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Dear All Researchers and Engineers,
We are organizing an International Symposium on Construction Resources for Environmentally Sustainable Technologies (CREST) during 10-12 March, 2020. On behalf of the chairman Prof. Hemanta Hazarika, we would like to invite all those interested in participating in the event. Please send your abstracts and papers, which will be published by Springer.
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Hi dear Divyesh.
Today, the growing need of society for buildings and housing, the need to use new building systems and materials to increase the speed of construction, lightening, increase useful life and earthquake resistance of buildings has become more and more. In this regard, upgrading the scientific and professional level of the engineering community and familiarity with new systems and building materials in order to apply these systems, is inevitable. Solving problems such as long construction time, low useful life or high cost of construction of buildings in the housing sector requires the provision of solutions for practical use of new building systems and new building materials to reduce weight, reduce construction time, more durability and ultimately reduce costs. Is run. These measures are considered essential for sustainable development. Also, in the long run, these efforts will reduce the waste of construction materials and consequently meet environmental needs, optimize construction, increase housing production and achieve optimal operating conditions. On the other hand, such developments will lead to the expansion of infrastructure investments in the housing sector, especially by the private sector, which will help governments achieve their housing goals.
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Hi
Im modeling test which first phase of that is displacement control (adding constant rate of displacement) and the next phase is load control (adding cycling load) ,more precisely after reaching specified load by constant rate of displacement cycling load must be applied,however something seems wrong.cycling load doesn’t being applied correctly, and in plot stress ,stress stays constant (stress at the end of first phase)in cyclic phase. so I deactivated the displacement control in following step(cyclic phase) but in this situation stress drops to zero, and for the last attempt I activated that again but I modified it too and made the displacement in following step zero but it didn’t help and stress decreased slowly, it must be mentioned I modeled cycling load alone in first step to see if the problem related to that but everything was correct and cyclic load applied correctly in this situation I will be thankful for your help.
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Simon Smith Thank you so much for your explanation 🙏
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Can I find a book or research that involves this topic?
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Best advice is to ask the technician and lab manager of the accredited test authority you use. Text books are needed too, but there are limitations on what can be expected from standard tests.
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I use COMSOL Multiphysics 5.2 and I face these issues when I build the mesh :
1- Edge is much shorter than the specified minimum element size.
2- Face is (or has a narrow region that is) much smaller than the specified minimum element size.
I hope someone can help me to solve this issues
Thank you in advance
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I think the geometry has very small species or small spaces, check the geometry specially the regions in alert massage. if their dimensions are wrong, fix them or if it is possible, change them.
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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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Hey guys,
I am attempting to model the installation of a helical pile into sand using Abaqus CAE (explicit). I am using a CEL model with a rigid pile and Eulerian sand part.
Every time I run the job, the sand part 'explodes' and has very large deformations. I have attempted to rectify this problem via the following trials:
-assigning cohesion to the sand;
-applying a pressure to the sand;
-beginning the installation with the pile already penetrated into the sand part.
Through an exhaustive trial-and-error process, I found that I have solved the exploding sand problem by changing the 'hard' normal contact interaction to a 'linear' contact interaction. However now, the history outputs show no plasticity/plastic deformation! This is kindof important as I am interested in finding the installation disturbance effects of screw-pile installation.
Is anyone aware of what I can do to accurately/realistically model the installation disturbance effects of a screw-pile being installed into sand? I am happy to provide any more information as needed.
Thanks!
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Dear @Harrison stamoudis,
You can assume a cohesion of 0.01kPa for sand as an aparent cohesion.
Feel free to get in touch with me.
Cheers,
Ali Ahmadi
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in most of the MICP text now they use the term Sporosarcina pasteurii. but in older research text it was called Bacillus pasteurii. Are they two different bacteria if not why to change the name?
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They refer to the same bacterial species.
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Hi dear researchers
I connected a rigid body into the part of my structure by tie constraint and then I added displacement to rigid body, in static general step every thing is fine and these two part are connected during displacement but when i run this model in dynamic explicit step , tie constraint does not work properly and rigid body and structure become separate from each other during displacement at the beginning time of this step,could anyone help?
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Glad I can help, regarding why the error does not appear using Abaqus standard, I can't tell without checking the model. From what I understand, this particular type of error should appear regardless of the type of solver/step definition. If you're interested in pursuing this further, make a copy of your model with the explicit step (the one without the error) and replace the step with a general static step. If the error persists, refer to the manual.
Good luck!
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Hi researchers
I wanna model tensile test on geogrid in abaqus, so I added displacement to one side of geogrid and the other side of geogrid is constrained completely, everything seems normal but i want to see rupture in geogrid after run in visualization(deformed shape) but rupture doesn’t happen,I even made the displacement of geogrid really big(10 meters and more!) but rupture doesn’t happen and just elongation happend in deformed shape,I defined elastic and plastic part for property of geogrid .
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Thanks dear Pavan for your help,there are list of damage definitions in mechanical part of property,you mean that part? if yes, choosing which one of these damages type is suitable for geogrid?
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Is there any software that helps us in the calculating Safe bearing capacity of the soil, permissible loads on the foundation without actually going the same calculations again and again?
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1. ALP99
2. PLAXIS 2D + 3D
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Dear colleagues!
What is the best method to determine In SItu Block Size Distribution if I have orientation, spacing and persistence data collected from 3D Point Cloud?
I considered using 3DEC but I am not very fluent in the software.
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Hi Friend
I think you use the Rmi classified to detemine Vb.
Thanks
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I am trying to model a geosynthetic reinforced soil structure with segmental blocks facing in PLAXIS 2D. The blocks are modeled with the linear elastic model (specific weight equal to 21.8kN / m³; Poisson's coefficient equal to 0.15 and E = 100MPa) and the interfaces with the Mohr-Coulomb model (interface friction angle equal to 37 °, adhesion equal to 1kPa and Rinter = 1.0). The facing is free to move in all directions. However, the simulations are slow, the displacements increase with constant Mstage and I cannot reach a load of 200 kPa.
Could anyone suggest some parameters that I can change and solve the problem?
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Thanks for the guidance! I'll check it out.
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Do we have any laboratory tests to determine the undrained residual strength parameters ? We use reversal direct shear test or ring shear test to determine residual strength, but in general both of these tests give drained strength parameters. Can we use a ring shear test to determine undrained residual strength parameters?
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I think possible. But the triaxial test will be preferable.
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When calculating consolidation settlement under structure loads, it is recommended to use the net foundation stress (net foundation stress= stress of the structure - the stress of the excavated soil). For a normally consolidated soil, how is this assumption correct?
For example, if the structure loads are around 300 kPa, considering the excavated soils, the net stress is around 40 kPa. The settlement caused by 40 kPa is not significant.
My concern is, the excavated area consisted of soil materials, the newly introduced elements are different from soil materials and thus, settlement should be calculated by ignoring the excavated portions. Unless, the soil profile changes, which in that case, settlement will be evaluated considering the existing condition.
#consolidation #geotechnical #settlement
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You said " Now you are applying structural load. So any settlement that happens is predominantly because of the structural load alone even though you back fill it with excavated soil" this means that, after considering the soil as NC, the structural load will be the one causing the settlements , ignoring the weight of the excavated soil, right?
Your explanations are good. Thank you.
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Is there a maximum recommended retaining wall height, in the building codes?
Even if a counterfort retaining wall is constructed, is there a height limit?
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Thank you Hani Alharbi
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I tested several non-traditional soil stabilizers (e.g. ligninsulfonate, biopolymers) with two different concentrations. The standard Proctor test showed that the additives reduced the OMC and increased the MDD of the soil. Further, the data indicated that an increase in concentration reduced and increased the MDD, respectively, decreased and increased the OMC. How can this behaviour be explained?
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The increase in density is expected since u adding new material to the soil and that material filled the pores. Water was reduced because this material u added reduced somehow the affinity of the soil water. For example if the soil has clay, something is going pin on mice-scale. for example the available surface area was decreased therefore a decrease in action exchange capacity is expected. this less affinity for water.
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There are three primary areas of ground movement towards a pressurised TBM: at the face, along the shield skin and at the tail void -(In the attached figure).
Can the maximum surface Settelment of the tunnel Longitudinal Cross section due to the displacement of the tunnel face can be added with the Transverse cross-section surface Settelment and introduced as the final surface Settelment? in 2D model-numerical method.?
But in the transverse two-dimensional method, we cannot get Settlements dou to face pressure induced by tunnel advanc.
I was going to get the Settlements dou to face pressure from the longitudinal 2D model and add it to the other Settlements Caused by other factors
In the longitudinal section of the tunnel, details and geometries and conditions have been implemented so that only the displacement caused by the face pressure is created and that the shield cone and mortar injection and consolidation are not modeled.
so only max surface settelment in longitudinal cross cestion is occurred due to face pressure It is capable of adding with max surface settelment in transverse cross sestion due to injection pressure and shield cone?
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I simulated the shield driven-tunnel by FLAC 2D, in which step of numerical model must be applying the traffic loads of ground surface (20 Kpa)? the traffic loads of ground surface change along day and night
@steps:
1. elastic initial equilibrium.
2. elastic-plastic initial equilibrium.
3. Simultaneous with excavation and pre-installation lining.
*in which step influence the traffic loads is real? (interaction with ground above tunnel)
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I modeled a shallow tunnels in urban environments . Which method is suitable for considering the presence of water in the model?
1. specify pore pressures with the INITIAL pp command or WATER table command (in non CONFIG gw mode)
2. specify pore pressures with the INITIAL pp command (in CONFIG gw mode)
In each of the above two conditions which density must be defined?
Dry density or wet density or saturation density
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I have found the hyperbolic parameters (K and n) according to Duncan and Chang model. However, I have no idea how to fit a hyperbolic model into a failure envelope to get the friction angle.
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Hello,
some suggestions can be found at the link:
Take into account that strength parameters should be selected according to the applied stress path, resulting from the loading sequence.
Regards
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Dear RG Community,
As we are aware that there are almost 5-6 FEM softwares available for modelling and analysis, say, PLAXIS, FLAC, GeoSlope, Abaqus etc. related Geotechnical Engineering. I am confused which one is more comprehensive and suits best for Geotechnical Engineering students.
Thank you.
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The choice of finite element software mainly depends on the specifications and the type of project or problem. If your project is industrial, Plaxis and Geoslope are the best software (specially in retaining wall and soil nail modeling). If your project is an academic problem, Abaqus and FLAC are suitable and comprehensive ( FLAC is based on DEM and contains various type of constitutive model). Best regards,
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I am trying to make Bearing Capacity Mapping of certain district and points are limited. But i want to cover whole district. If anyone have any idea please explain step by step.
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When you are using tool IDW or kriging
after the input layer, z value click on environment
- environment setting window will open then select processing extent and select as your study area boundary
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Dear all,
When conducting plaxis analysis the elastic modulus of soils is used as an input in Mohr Coulomb and Hardning Soil models, E´and E50 in drained conditions, respectively. The pressuremeter tests conducted in the fields gives us the Menard modulus of deformatio. Can these values be used as E´ and E50?
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Dear Ahmed Hussein Olat
The pressuremeter modulus has been related empirically to the elastic modulus of the soil as EM/E = α, in which  α  is termed by Menard as the rheological coefficient and has a value between 0 and 1.
For more details, please refer directly to :
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As we have seen over the years many new trends were developed in the field of geotechnical engineering. May that be regarding Geo-Environmental Engineering, Sustainable Geotechnical Engineering or Ground improvement techniques. My query is what are the new emerging trends in the said field.
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Geotechnical enginnering is iportant area of research
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There are various methods for determination of slope stability via Limit Equilibrium Method i.e. Ordinary Method, Spenser Method, US Cops Method, Morgenstern Price Method and so on. The results obtained form theses methods are almost similar but I would like to know the best method among these for the calculation of slope stability.
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Nowadays, the most important advances in the LEM world is the search methods to find the most critical slip surface used together with the LEM approaches. These methods are Metahueristic methods such as Cuckoo Search, Particle Swarm, Simulated annealing from other fields brought to the geotechnical applications. The value of the LEM methods to be combined with the new search methods becomes more important (these are all non-circular methods). Our studies showed that, for complicated models, simplified Bishop method cannot give good results. Janbu method gives the lower-bound for the factor of safety. The best methods that give similar answer to even FEM analysis are Spencer and Morgenstern Price methods. I hope that helps.
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Dear RG Community,
I intend to ask you that what are some classical examples of Geotechnical Engineering related problems, for example differential settlement in Leaning Tower of Pisa was/is considered one of the fine problem. Also if you could help me with some of the case studies which you consider will be helpful in understanding the fundamentals and core of Geotechnical Engineering.
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Mr.Muneeb,
I feel the main important one in all over the world is population increase and no space available for developing infrastructure relative to increase in population. so the construction activities have taken place as closer to an existing structure. In view of this, the stability analysis of existing structure adjacent to new construction in terms of excavation, embankment, tunneling or pile driving is a serious problem. As a geotechnical engineer we need to come out with design idea to protect the existing structure due to the effect of new construction.
Another important issue is we don't have excellent supporting ground for the new construction. So, in this case we need to develop economical ground improvement technique to support the load. Ground improvement technique alternate to conventional method is catching up among researcher . ok all the best in your research..
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Hi colleagues,
Because of the complexity of modelling geogrid layers and their interfaces which can cause convergence problem in FE analyses, I have seen in practice they model the whole MSE wall system (eg a block 6m long and 5m high) with very dense or elastic material.
I couldn't pinpoint this in the literature or in guidelines and standards.
Do you know any reference that suggests this?
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Thank you Ahmed Hussein Olat !
That's an interesting piece of work.
However, what I am interested in particularly is the MSE walls.
There are complications in the response of the geogrid interface to the soil and the block in dynamic analyses.
Because of that, I haven't seen research that investigates the dynamic response of an MSE wall.
In industry, I've seen people modelling the whole MSE block (without modelling geogrid and interfaces) using an overly stiff material that at the end would act as an elastic block because of how stiff it is.
I was just wondering if there is anything in guidelines or research that address or recommend this approach.
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Dear All,
When designing structures using computer programs such as CSI SAP2000 or ETABS or any other equivalent software, generally, we input the subgrade modulus in the form of kN/m3. This value can be obtained from the famous Bowles (1996) equation of 40*ultimate bearing capacity. This value corresponds to an allowable settlement of 2.5 cm. However, nowadays, even though soil structure cannot be directly integrated, e.g. using PLAXIS+ETABS or PLAXIS+SAP2000, is it possible to;
  • obtain all the loads from the structure and apply it on a constitutive soil model in plaxis, then convert the loads to equivalent pressure (All loads/Foundation area) and divide this value by the surface settlement, then go back to either ETABS or SAP2000 and apply the obtained subgrade modulus, to observe the difference in settlement values.
The main disadvantage might be the increase of settlements with depth, this leads to, as per the assumption above, several subgrade modulus. I also think softwares like PLAXIS 2D/3D can be really helpful in these situations rather than depending on the assumption of bowles.
Note:
  • The assumption here is, during the absence of adequate field data.
  • This idea might seem a little bit, amateur, please bare with me, as I am trying to learn in this long journey.
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Bowles' equation is one of the most misunderstood equation as also mistakenly recommended above by Mr. Salem for clays. The two pages in Bowles explains itself. He wanted to give a simple equation based on the settlement based bearing capacity equations for sands. For example, Burland and Burbridge. Those equations calculate the load that corresponds to 25 mm settlement in sand.
Simple rules to follow: (if you can convince your client)
  • Forget the 40 x qult equation. Please do.
  • Subgrade reaction is load (as pressure) / settlement. So, calculate the settlement using any method you like. If you want to give only one subgrade reaction, divide average pressure to average settlement.
  • If someone says the calculated subgrade reaction is very low, ask them "compared to what?" The tables presented in Bowles or any other resources based on the soil type are FOR ONLY PLATE LOADING. In that case, B=0.3.
  • Subgrade reaction is E/(B*(1-v*v)) in its simpest form. So, it depends on the B. If Bowles' table says 100.000 for dense sand, it is only for plate loading. For a raft with B=20m, your subgrade modulus will be 5000!
  • Don't use 40 x qult.
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I'm simulating a simple field loading, rigid (1.1*1.1*0.8 m3) footing on Clay (Bothkennar site) and am trying to figure the best soil model for the site via simulating the test, load was applied up to max BC 140 kpa that resulted in 0.2 m settlement. I tried many combinations and using stress control Vs stress control. Also varying soil models, MC worked quite well but HS model gave weaker trend and stiffness though many authors reported its suitability,
I need to check the model because i am so confused figuring what's wrong
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Mr.Fayrouz,
It is better verify soil parameters used to define all these model used in the simulation because results not matching closely with Jardine results except one i.e. PLAXIS - HS model some what nearer to Jardine results. So better verify material properties of the footing, soil, mesh density & size influence and also interface properties b/w soil and footing..ok all the best in your research..
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If we have the results of a direct shear test on a sandy CLAY (CS) sample. The Mohr-Coulomb effective stress failure criteria given from the test results are an effective friction angle of 23 degrees and an effective cohesion of 27 kPa. Are these results are reasonable?
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Whether your results are reasonable or not will typically depend on a No. of factors:
1. Percentage of Clay and Sand in the sample, more clay implies more cohesion and more sand shall mean a higher friction angle value.
2. Moisture content also has a significant influence on the development of Mohr-Coulumb failure envelope and on the behavior of soil under shear.
3. Testing conditions also have an impact on the results. Often laboratory testing equipments aren't properly calibrated or the lab assistants lack expertise to conduct such tests, these factors have a significant bearing on test outcome.
4. Supervision: A year ago, i conducted DST tests on somewhat similar soil samples having varying proportions of sand and clay, and i found out that the Cohesion and Angle of internal friction values were considerably on the higher side rather unusally. Then my supervisor suggested Triaxial tests to check out influence of capillarity & drainage on results, then i did Consolidated Undrained Triaxial tests to work out the variations between these parameters. The parameters from Triaxial tests showed around 15-20 percent decrease in values when compared with DST values, so it's advised to conduct triaxial tests for better precision. However, if you don't have that much resource availability, you can conduct a No. of trials, work out the variations a
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I need a large model say 100 x100 m with a mesh size of 0.05m. such a large model cannot be made in version 7. before upgrading to version 8, I need to confirm whether it is working in version 8 or not?
I have also tried trail version 8. it is also not working
if anyone has version 8, I can send you a file to check.
Thanks
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