Ground Improvement - Science topic

Respected sir,

Can you recommend any paper regarding CO2 emissions during the production of Xanthangum

Zew Zealand Geomechanics Society Recorded Webinars.

Embedded beam element or shell element

Hello. I am lecturer of FLAC 3D and other Itasca Software.

Ask me your questions in LINKEDIN.

Dear Haibat Ali

The following webpage might help you:

Dear Ivan Marquez,

For weathered rock, you can use the triple fluid system (water jet surrounded by an air jet, with a separate grout port).

Good luck!

Go for PLAXIS and ABAQUS.

Geotechnical enginnering is iportant area of research

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..

Yes definitely, see for example a comprehensive study

and

Dear Sharmila Pant

You asked a short question that require a detailed (and "conditional") answer ;-)

Some "conditions" must be defined before answering your question.

1. What is the range and character of loads that must be transferred to the ground?

2. What are the requirements concerning settlements of supported structure?

3. Are there any environmental limitations for applied foundation technology?

Vibro Replacement Columns (VRC) have a double function:

- create a vertical drain within cohesive soil and fasten the consolidation,

- form a rigid inclusion (stone column) that increases the stiffness of the soil body.

So, answering your question, I'd give some recommendations:

- You may use VRC if no restrictions are established for the vibrations.

- Due to limited internal capacity, VRC cannot substitute concrete piles when large loads are applied. The application of VRC in very soft soils (and in peat) is also limited for the same reason.

- Limited capacities may result with large size of capping slabs (decrease of load for a singular column).

- Consolidation takes some time and imposes settlements. Relatively long time of construction or slow increase of loads is recommended. Otherwise, supported structure should be somehow "adjustable".

- The good thing is that in the case of large infrastructural projects, when the loads are distributed over large areas and increase slowly, VRC are very beneficial. Not only because of lower cost compare to concrete piles, but also because of long-term improvement of surrounding soil layers.

Best regards

Depending on how many observations and variables for each one you have, you can train a model to predict the "risk degree" of different cases or possible scenarios.

I have studied a bit about artificial intelligence, but actually I have not applied it to real data, nevertheless, despite my short expertise in that field, I think that it is highly possible to estimate the "risk degree" for sinkholes if your data is robust enough.

Best regards,

Dear Jayatheja Muktinutalapati

The stiffness of the wall, its ability to move and deflect, play a crucial role in soil pressure envelope in uniform soil. In the case of real soil profiles, it may happen that the increased soil internal friction or appearing cohesion provokes the decrease of soil pressure despite of higher vertical stress.

If you consider various methods of vertical soil support calculations (especially for flexible structures) , the soil pressure envelopes are often modified to take into account this phenomena.

From my experience. Usually the total active pressure is corresponding to the theoretical value but its position may vary depending on the above mentioned factors.

Best regards

Can u try about " Standard Test Methods for One-Dimensional Consolidation Properties of Soils Using Incremental Loading (ASTM D2435/D2435M)" about consolidation ? Sir.

You can find out about Prof. Indraratna or Dr. Begardo , they have done on VCM work.

Hi Mohsen, thanks for your answer. However, I'm not using large displacements mode (actually if I apply this mode, the code stops because the geometry is invalide after a few thousands of steps).

I still have this problem, at first I thought it was a problem of the parameters so I tried almost everything.

The weird thing is that if I apply equilibrium to the whole system (all the materials at the same time) then I dont have (for some cases) these grid points exaggerated displacements... But if I want to add the upper layer in different stages (keeping the same parameters for everything) then I have the weird behavior again...

I realized that I had a mistake with the initilization of the CYSoil parameters; I havent initialized the current shear and bulk moduli for each zone depending on the isotropic pressure. Now I have corrected this thing but the problem persist...

Yes, this is online sharing only as said. When I get author`s copy, I will share the same

You can model the geogrid using the geogrid structural element available in PLAXIS. Input parameter required is EA.

Dear Mohamad,

I suggest to find Brazilian publications. Is common to us use fine soils to build reinforced walls.

Dr. Karaman has suggested an interesting instrumented GRS. In the sequence are others that you can read.

Regarding your questions, I do not reccomend to use strips in fine soils because of the interface shear strenght. I also do no reccomend to use vertical face walls (84° or 10V:1H is recommended).

- BENJAMIM, C. V. S. ; ZORNBERG, Jorge Gabriel ; BUENO, B. S. . Field monotoring evaluation of gotextile-reinforced soil-retaining walls. Geosynthetics International, New York, v. 14, p. 100-118, 2007.

- RICCIO, MARIO ; EHRLICH, MAURICIO ; DIAS, DANIEL . Field monitoring and analyses of the response of a block-faced geogrid wall using fine-grained tropical soils. Geotextiles and Geomembranes, v. 42, p. 127-138, 2014.

- SANTOS, EDER C.G. ; Palmeira, Ennio M. ; BATHURST, RICHARD J. . Behaviour of a geogrid reinforced wall built with recycled construction and demolition waste backfill on a collapsible foundation. Geotextiles and Geomembranes, v. 39, p. 9-19, 2013.

- GOMES, R. C. ; PALMEIRA, E. M. ; LANZ, D. . Failure And Deformation Mechanisms In Model Reinforced Walls Subjected To Different Loading Conditions. Geosynthetics International, London: Thomas Telford Publ., v. 1, n.1, p. 45-65, 1994.

- Fonseca, E. C. A. ; PALMEIRA, E. M. ; Santos, E.C.G. . Numerical Analysis of a Geogrid Reinforced Retaining Wall Built with Non-Conventional Backfill Material. In: 10th International Conference on Geosynthetics, 2014, Berlin. Proceedings. Essen: Deutsche Gesellschaft für Geotechnik e.V., 2014. v. 1. p. 1-8.

- MIRMORADI, S. H. ; EHRLICH, M. . Numerical Evaluation of the Behavior of GRS Walls with Segmental Block Facing under Working Stress Conditions. Journal of Geotechnical and Geoenvironmental Engineering, v. 141, p. 04014109, 2015.

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Dear sir,

pl find attachment.

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.

You will need to check your cost function and or criterion as well as your algorithm.

To my knowledge, one of the measures to determine the workability is slump testing which is often used prior to the concreting of diaphragm wall or superstructure. By the slump testing, you will be able to see whether the concrete adopted can flow far enough.

Thanks Erion for the help. I agree with your opinion.

I think it is the limitation of manual calculations and the assumption to consider the adjacent building's load as the surcharge loading of infinite extent is merely for simplification purposes. And the design, in this case, would be on the conservative side.

Any suggestion for the speed of centrifugation that I need to use to remove the cell debris?

Good recommendations have been made. You can also determine Modulus of rupture and strength of penetration.

Cam Clay model simulates volumetric strain behavior of cohesive soil better than Drucker-Prager model.

is the last reply sent properly.

Re=sent:

its not distinguishing between or handling effective stress and total stress properly somewhere, possibly in equilibrium eqnnot an unusual problem.  Not an unusual problem.

If the initial condition has no seepage, just use eefective density if below WT.  This will simulate WT effect.

Good luck.

sorry sir , but link is not working properly

Positive aspects of water:

1) One more comment on bentonite usage as mentioned by Prof. Adamcova. Bentonite slurry (bentonite mixed with water) is commonly used in deep foundation works. It stabilizes deep and narrow excavations before filling them with concrete through tremie pipe. This technology is used during pile formation or execution of slurry walls.

2) Regarding strictly to usage of water in ground improvement techniques, there is a technique called vibroflotation. It is a kind of loose soil compaction by means of a vibrating probe immersed in loose sand with water jet (see e.g. http://www.vibroflotation.com/Vibro/vibroflotation_fr.nsf/site/Vibro-Compaction.Effects-and-Test).

3) Jet-grouting - injection of mortar, mixing it with soil to form cemented soil column. Apart of high pressure injection of mortar, two additional streams may be used to improve efficiency: air and water.

You can find many papers on jet grouting and vibroflotation.

For such a large DS test, the shear displacement may be large, so the area correction is needed.

You have several methods. One is the one Keller recommends for computing the equivalent overall mechanical parameters using Priebe's method. You can find it here: http://www.getec-ac.de/download/en/pdf/GT07-13E.pdf

Another way is to use any FEM analysis and consider the stone columns as such, with proper interaction with the adjacent soil.

A third method, if you intend to have a gradual change of mechanical parameters from the column axis to the soil, is to use the thermal dependence trick, namely consider a homogeonous medium with parameters variable with temperature so that a 0 degrees you have soil parameters and at 1 degree you have the stone column parameters.  You control the linear variation in the zones with temperatures between 0 and 1, you have the columns in the zones with 1 degree and the rest of the soil remains at 0. If you want to pursue this path I can give you additional info.

In fact the hydraulic conductivity in fractured media is function of the hydraulic head. If the head is lowered, the neutral stresses decrease, the effective stresses increase, the fractures close and consequently the hydraulic conductivity decreases. You can check this reasoning in my Ph.D. thesis at Colorado School of Mines, 1971.

for direct shear test you may have a look:

ASTM D3080 / D3080M - 11

Standard Test Method for Direct Shear Test of Soils Under Consolidated Drained Conditions, you will also find the similar information for Indian standard if you inetrested... I am not sure your sample is fully saturated or dry, , how about shape or gradation, depending on the volume of the container (where) you will place the sand and lever arm length and the calibrated ratio you need to calculate the "seating load", i am not sure your machine is digital or hand operated, calibration process may change, i will recommend you to have a look the ASTM standard and manual of the machine(if you have), then calibrate it before testing

One of the possible methods is to enlarge your boundary horizontally until you have no rotation in principle stresses at the edge of your boundary.

Dear Tabchouche Seifeddine

At the moment there is no scientific means of determining the influence of

material dilation angle on the behavior of soils reinforced with stone columns. This can only be done using properly instrumented laboratory test. You can make it your research focus for publication in a high impact journal.

However, it is necessary to understand the principles involved. Let sai =dilation angle. phi_p = peak friction angle; phi_c = critical friction angle.

sai = phi_p - phi_c

The deviator stress versus axial strain diagram for dense granular material (gravel) will rise to a peak at a certain material dependent strain and thereafter diminishes until it approaches the critical friction angle for the material.

Stone columns are provided beneath columns to increase the bearing capacity of soft soil.

The question in the design is what friction angle do you ascribe to the granular material in order to design the combined system under the superstructure load-Phi_p or phi_c or some intermediate value. This depends on how much the stone column-surrounded by the soft soil- strains horizontally under the applied foundation load. Intuitively this strain will depend on the relative stiffnesses of the stone column and the insitu soft soil.

With the above you can plan your laboratory tests to capture the parameters that influence the friction angle of the stone column as it interacts with the surrounding soft soil under loading.

I wish you luck!