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Geosynthetics - Science topic

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Dear colleagues
I have a question:
In interface shear studies between sand and structures such as geosynthetics or CFRP , how we can calculate or achieve initial relative density for internal and interface friction angles at critical state?
Based on which ASTM, or through which experiments.
Please let me know if you have an answer about this question.
Thank you for your kind responses.
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It is stress dependent at relativly very low stress level
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Hi,
In ABAQUS,the geosynthetic materials are mostly modelled as membrane elements with only tensile stiffness as the major input parameter. However, geotextiles are not just used as reinforcement, but also for drainage applications . In this sense, simulating the permeability characteristics of the fabric is necessary to simulate the actual behavior of treated ground. How can we do this in ABAQUS?
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Jochen Hack Thank you. But "embedded region" cannot be assigned for certain applications like encasement, where the contact properties govern the behaviour.
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Procedure for it
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For a small scale experiment setup, just fold the longitudinal axis very carefully. In field formwork in needed similar in the case of wraparound walls.
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Geo-Environmental Engineering is concerned with engineering solutions relating to environmental impacts of contaminants within soils, and includes such aspects as understanding the migration, interactions and fate of contaminants, the protection of uncontaminated regions, the remediation or clean up of contaminated sites. It requires an understanding and knowledge of the relevant principles of chemistry, biology and physics, types of contaminants, geosynthetic and other barriers and containment systems, regulatory requirements and site remediation technologies. It entails site investigation, sampling approaches and methods, modelling, assessments, treatment and control strategies.
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I have 3 conference proceedings.
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what is the allowable load (percentage of the elastic limit of the geosynthetic product) that must not be exceeded to produce a tolerable creep strain at the end of the structure's life (typically 100 years) for geosynthetic products in polypropylene and in polyster .
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Typically below 40% of the load at failure (failing load at quasi-static test).
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I am using abaqus to model geosynthetic encased stone column (wished in-place). I am new to abaqus so how should I model geosynthetics in 3D and 2D (solid or shell or wire ) and can I get an idea about what type of interaction should I apply in between soil- geosynthetics and geosynthetic-stone column ( in 2D and 3D ).
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Embedded beam element or shell element
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how to one determine the maximum acceptable load applied to the geosynthetic reinforcement product?
I know that we can use the isochronous curves found from the creep curves for the same material at different loads so I want to know on what basis we choose these different loads ?
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Plaxis model analysis, whenever we use the geosynthetic in soil plaxis is given the interaction factor. I would like to understand the interaction efficacy in stone columns. And how do we quantify the shear resistance between clay - aggregates, aggregates - geosynthetics?
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Don't know the exact answer for stone column but for if geosynthetic is geotextile than, most commonly 0.7-0.75 for soil-geotextile (Rint).
If geogrid than it depends on median grain size to minimum aperture size of geogrid. If D50<dmin, you may assume full interlocking (holtz and lee 2002) based on original work by jewell (1985).
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Hi everyone,
I'm using cable element to represents geosynthetic reinforcement embedded in soil.
I know that it should enhance the settlement, but once using cable element in soil, and assigning the appropriate inputs ( geometry of the cable and grout properties), I don't see any improvement in the settlement profile.
Keep in mind that I can see the shear and axial forces develops correctly in the cable element.
Anyone can help on this issue?
Thanks and best regards,
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Join here the pdf file, Pages 239-247 from pdf (or 251-259 from paper)
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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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I want to perform a slope stability analysis of a river bank. Bank protection materials are 400mm cement concrete cube block and sand filled geobag. I need to know the shear strength parameters such as internal friction angle, cohesion and also I want to know unit weight of these materials. If anyone knows, please share.
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Thanks for your useful information William F. Hansen . Actually, I need an idea. If you use these values ( C, Phi of C. C. Block) in any one of your research work, then, let me know.
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There are many published literature available on modeling of actual shape of geocell in FLAC3D. But there is no paper available on Plaxis 3D. Many people modeled it as a square or circular shape in Plaxis 3D but no one able to model it as the actual curve-linear shape. Is it a limitation of Plaxis 3D, in modeling thin curve shape?
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My pleasure
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I need to compare their performance in minimizing the degradation and deformation characteristics of the railroad track using PLAXIS-2D. but the only parameter of THE GEOGRID dataset in PLAXIS-2D is axial stiffness, EA. so can you please provide me a formula to calculate axial stiffness for geogrid, geocomosite and geotetile and s on.
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hello Professors, I have questions about the project GARDEN
1 - is the geosynthetics put under the three slabs or only under the central slab ?
2- Is the facing foot anchored in the foundation soil where it is placed above a clean concrete ?
3- the facing / slab distance is it calculated from the the back facing of the block ?
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1-about the lateral slab. How did the soil under it resist to a loading of 420 KN ?. i think that the only the soil cann't resist tath great the loading.( is the facing blocked ? )
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I try to model deep mixed column support embankment with geosynthetic by using plaxis. But the settlement result with and without geosynthetic are the same.
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The geosynthetic element will not work if you want to model a deep mixed column. What you could do is following...
1) If you use plaxis 3d you should define column elements as volume fe.
2) If you use plaxis 2d it is more difficult but you could use a smeared region with improved soil simulating the region with deep mixed columns with spacing. In this case you must put more effort to define this soil parameters for which some correlation curves do exist.
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I am looking for software that could be used in 3D modeling geosynthetic encased stone columns.
Thank you.
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I feel both PLAXIS3D and FLAC3D is good in simulating your problem but PLAXIS3D is very easy to use as compared to FLAC3D. PLAXIS3D based literature related to your problem is available, so i recommend you to collect those paper and use effectively in your work..All the best in your research..
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We are very interested in the interface shear of different geosynthetic interlayer products installed with their recommended amount of tack oil. We believe the grid only products and the products with very light carrier nonwoven geotextiles may not give as high of a shear resistance as the full weight nonwoven paving fabrics. Some products recommend no tack and some recommend as little as 0.10 gallon/square yard. Full AASHTO M 288 paving fabric Type II uses 0.25 gallon/square yard. We also fear that the grid products with the very small aperture size of 12.5mm may not interact well with the adjacent pavements and may introduce a shear plane. Please comment and share research on these issues. We may be interested in sponsoring more research.
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The shear bonding between geogrid and pavement is depends on aperture size of the grid is true. I feel you need to conduct shear test with varying aperture size of grid with pavement material and find out which one is giving better response. You even vary the aperture size and also various geosynthetic material can be used for the test. all the best..
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The modulus of elasticity differs in various conditions of foundation soil. I am struggling with defining modulus of elasticity of geosynthetic reinforced sand foundation beneath a shallow strip footing.
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Your question is actually not clear. Are you struggling with finding the modulus of elasticity of sand or struggling with inputting these values in plaxis? You usually need bulk modulus, shear modulus, cohesion (if any), density, friction angle, dilation angle etc. of sand and elastic modulus of geosynthetic, its poisson ratio. You may also need the interface parameters, such as stiffness per unit area, soil-geosynthetic interface friction angle, etc. Typical values for these parameters are available in the literature and if you are simulating the real problems, then you have to carry out tests to obtain these parameters.
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Dear Friends, I am currently working on the topic of geosynthetic encased stone column. The execution of the granular column in the site specifically involves a term called activation widening of the geosynthetics. I need a clear definition of the same in the aspect of during and post construction of granular columns. The design methods with respect to BS and EBGEO codes. In specific the calculation of load capacity of the encased granular columns using the above mentioned codes.   
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The activation starts at the moment when what you call "bulging" is large enough. It could start immediately after load application, radial pre-compression iz zero, see above. The point is: activation starts at the moment when diameter of granular fill reaches the nominal diameter of geosynthetic encasemnt as produced, e.g. 70 cm or whatever. Is this a proper answer? In a homogenious soft soils the largest bulging occurs in the upperst part down to a depth in the range of 2 to 3 D.In layered soils it can start in the softest soil layer in depth.
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Dear all,
I need to give properties of geosynthetic material in ABAQUS. Right now, I am giving as linear elastic material. Is it the correct way to give as linear elastic?, If it is appropriate to give as linear elastic, what way of deriving the properties is realistic. I have wide width tensile test results with me. Suggestions would be really helpful.
Regards
Prasanthi
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Hi Prashanthi
Linear elastic model is fine. Be careful about choosing the elastic modulus. The strain range should not exceed the elastic limit from your tension test. Poisson's ratio can be generally taken in the range of 0.3-0.4.
Madhavi
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Is the technique of geosynthetic-encased stone columns in soft clay applicable really? And is it possible to make geosynthetic around a stone column technically?
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Please have a look at the following articles:
1.Almeida, M.S.S., Hosseinpour, I., Riccio, M., and Alexiew, D. (2015). “Behavior of Geotextile-Encased Granular Columns Supporting Test Embankment on Soft Deposit.” Journal of Geotechnical and Geoenvironmental Engineering, 141(3), 04014116.
2.Mohapatra, S.R., Rajagopal, K., and Sharma, J. S. (2016). “Large direct shear load test on geosynthetic encased granular columns.” Geotextiles and Geomembranes 44(3), 396-405.
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I am trying to analyze the strains developed in nonwoven geosynthetic during wide width tensile test using Geo-PIV RG. After successful  completion of analysis only displacement contours are accessible . I am unable to get the strain values. I am using leapfrog mode of analysis and pixel based matrix.
The following errors are displayed while generating strain contours.
??? Undefined function or method 'scatteredInterpolant' for input arguments of type 'double'.
Error in ==> D:\GEO_PIV\Subroutines\geoPLOTSTRAIN_RG.p>straincontours at 184
Error in ==> D:\GEO_PIV\Subroutines\geoPLOTSTRAIN_RG.p>geoPLOTSTRAIN_RG at 120
 I am also attaching the screenshot of my matlab GUI.
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Thank you for your suggestion. The code we are using is a .p file in matlab which we cannot view or change. Hence the presence of scatteredInterpolant function is unsure. Kindly suggest any other method to overcome the problem.
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Hello all.. I need to model an interface between geosynthetic material and asphalt. To model the interface, I have created cohesive elements of thickness 10e-4 and constitutive behaviour is given using traction separation law. After assigning the material properties, I have created a orphan mesh part and I made the thickness of cohesive elements as zero. Now, this orphan mesh part is  an instance in the assembly with zero thickness. I need to give the constraints between this zero thickness cohesive elements and asphalt(bottom), Geosynthetic (Top). I used tie constraints in both the cases. In both the cases, I have given cohesive nodes as slave nodes. Error is over constrain of cohesive nodes. Now my doubt is, Is there any other way of giving interaction between cohesive elements and other part of model??Thanks in advance.
Regards
Prasanthi
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you may create surface to surface cohesive interaction without creating mesh part.
i hope it helps
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Hello all,
I need to model a beam which contains geosynthetic material at some depth. To model the interface between two materials, I have used cohesive elements and cohesive surface behaviour. The results obtained from cohesive elements are reliable. But the results from cohesive surface behaviour are highly deviating. I have given the same properties in both the methods. What might be creating issue?? suggestions will be really helpful.
Regards
Prashanthi
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Cohesive surface is a surface. Cohesive element may be a line element.
please check the properties given for surface. the surface properties are different from those of the bulk material.
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I want to model Geosynthetic Retaining walls in flac and I have friction angle between soil and Geosynthetic. but I don’t know anything about “initial apparent friction coefficient” and “minimum apparent friction coefficient”. please help me.
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Read this report 
It gives complete information on geogrid modeling in reinforced walls.
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Is there something mentioned in the Euro-code, AASHTO or anywhere else?
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FHWA (2009) Design and Construction of Mechanically Stabilized Earth Walls and Reinforced Soil Slopes – Volume I, and Volume II.
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Hi,
Does tensile strength of the fibers affect the shear strength parameters of fiber reinforced sand?
If yes please attach some supportive literature.
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Orientation of fibres mainly governs the strength improvement than the tensile strength of the fibres. Attached file gives more details on this aspect. However, dense sands tend to impose higher tensile stresses on fibres, which leads to higher confinement and strength improvement. If the fibres cannot withstand the tension, they break and hence could not achieve the improvement effect.
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What is the range for strain which will differentiate the these two types? or How will you assured that present consolidation is large strain or small strain?
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Small strain - or small displacement - refers  to the case where we assume that changes after a displacement is so small that the geometry is virtually unchanged. Large displacements would invalidate assumptions like the famous "linear-elastic deformation" one. In cases of small strain, we are indeed talking about linear equations governing the relation between force and displacements. And we take the viewpoint that the material is not deformed once the stress has been removed.
Large strain/displacement is, basically, everything else, but common to them are that they lead to a permanent deformation of the material (that is, deformations that remain after the stresses are removed).
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Madhavalatha et.al 2010 observed that in case of soft sub grade and unpaved roads gecells perform better than geogrid. In the case of moderate/firm sub grades and paved roads which pavement reinforcement solution is better geogrid or geocell? 
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Geogrids and geocells are not alternatives to each other in all situations. The choice of the reinforcement depends on the subgrade modulus as well as the design traffic (msa). Geogrids are cheaper than geocells and easy to lay, but if the required improvement in strength and modulus is very high, you need multiple layers of geogrids placed at regular intervals over considerable depth below the pavement, whereas a layer of geocells filled with aggregate works out to be economical. Geocells are the speedy solution over emergencies, whereas geogrids though simple and easy to install, are not applicable over softer subgrades. Moreover, geocells provide higher lateral confinement and beam effect, thus reducing the thickness of pavement significantly. For many geotechnical problems, savings in time and assured performance of the solution play vital role than economical aspects. 
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We are currently working on a landfill closure concept in Vietnam in a region with a total annual precipitation of 1900 mm. Does anyone have experience with the applicability of the HELP model in this kind of climate? Are alternative landfill covers in this kind of climates ever recommended?
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Thanks for the information. Do you have experience with that model ? does it apply also for landfill covers ? I think we will have to continue with a catchment model.
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Provide information of asphalt sealant type, temperature and rate indicated when using geogrid or geogrid composite.
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This is valuable information Jan. Thank you. In Brazil, we also specify cationic bitumen emulsions for geogrids (instead of asphalt cement), in the rate of 0.4 - 0.6 l/m² (residual). However, the rate specification is still very empirical, as well as the specification of the geogrid type (polymeric or fiber glass, composite or not, tensile properties...). See attached the Brazilian specification (in Portuguese).