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Soil Mechanics - Science topic
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Questions related to Soil Mechanics
I need to know what tillage systems out there cause the least soil compaction. It'd be great if there were references I could cite. I want to compare tillage systems and how much soil compaction they cause (if that would be possible).
The application of numerical models in the simulation of rock/soil cutting process and at the same time the wear on the cutting tool.
Soil curing is one of the effective methods for stabilization and improving soil, and it has received wide acceptance from many researchers in the world in the field of soil and its stabilization, but there are those who use the method of placing it in a container, and others at room temperature, now, what are the criteria for choosing each of them and which one gives effectiveness and better accuracy?
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 ?
However, the frictional sliding or horizontal movement could also be taken into account!
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?
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?
This topic is created to be a place for sharing reliable open-sources that contain quality free courses, webinars and short educational videos in the field of geotechnical engineering.
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.
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?
The sieve analysis of a given sample of soil gave information that 57% of the particles passed through IS 75 micron sieve. The liquid and plastic limits of the soil were 62 and 28%, respectively. Classify the soil in accordance to AASHTO and the USC systems.
For example it is common that curve of (v) against (ln p) will be plot. Why don't we use e instead of v?
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?
.How to calculate the shear strain in a multilayer soil profile based on a half-space under a seismic action?
how we can find poisson's ratio using resonant coulmn (detail procedure )..??
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.
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.
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.
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?
The modulus of subgrade reaction is widely used in the Winkler beam method on an elastic foundation. The most reliable estimation is given by Bowles  as it takes into account the dimensions of the foundation as 40*qu (for around 2.5cm). This subgrade modulus value is it the same for static and seismic conditions?
As far as I understand, since qu is the ultimate bearing capacity, the subgrade value is equal in both states (static and seismic).
What are your views regarding these?
Greeting dear researchers,
I'm doing some application on soil structure interaction and I want to calculate the shear modulus of the soil using the wave velocity given in the Algerian seismic code.
The Algerian code (RPA99V2003) classifies the soil into for types according to the share wave velocity, unfortunately the code dose not give further parameters.
Any information will be of great help.
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.
I'm trying to evaluate the effect of initial void ratio (e0) on the settlement of the material in Mohr Coulomb model in Flac3D. To do so, I'm trying to find a relation between e0 and stiffness parameters in MC model ( K and G). I found a simple relation as in the attached picture based on critical soil mechanics. However, e0 is in the numerator of the equation, meaning that if we increase e0, stiffness of the material will increase, thus, settlement will decrease, which I think is not logical.
I've also run models with several values of e0 using this relation, and indeed the higher value of e0, the lower value of settlement. So I don't know what is the problem or I shouldn't use this relation this relation or do I need to change something in Flac as well for this model.
Any recommendation is highly appreciated.
I'm working on a geotechnical problem of a submerged foundation from a total stress analysis point of view. Since I need to calculate the rate of work of all external forces conjugated to my problem, does it make sense to adopt Archimede's principle of buoyant forces as an external force of the problem?
I'm aware that the effective stress principle is in total agreement with Archimede's principle, so if I adopt the buoyancy force for the total stress analysis, in an effective stress analysis can I disregard it?
Thanks in advance,
As a function of dimensions of real projects?
Certain Casagrande piezometers or Vibrating Wire piezometers have a high air entry filter made of porous ceramic. The reason for using a high air entry filter, typically 1 to 3 bars is to prevent gas pressure present in some soil to penetrate through the filter, so that only water pressure will be measured.
So, I’m looking at a formula to convert the air entry value of the ceramic, say 1 bar, to an equivalent Darcy coefficient of permeability in cm/sec?
I did my PhD research on slaking rocks or soft sedimentary rocks, respectively. During my literature research in the beginning of my PhD project it was pretty obvious that there is no general defintion of the terms "soft rock", "weak rock" etc.
There are two fundamental views. On the one hand there are the (classic) defintions with respect to the strength of the rocks on the other hand there are defintions relating to the slaking behaviour of rock.
Even in the very recent book "Soft Rock Mechanics and Engineering" most of the reseachers find it necessary to define the term "soft rock" and how it is used in the following chapters indicating that there are still lots of open questions regarding a general definition of this/these group of geomaterial.
What is your opinion on the definition on the term "soft rock", "weak rock", "slaking rock" etc.?
what is (are) the benefit(s) of drawing the zero air voids with the compaction curve(s) ?
When calculating Gmax of soils by ρ*Vs^2. Does this value reduce or increase if the soil is below or above water table?
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
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?
What topics can be chosen for research in soil mechanics and foundations engineering?
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?
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
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)
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.
Dear scientists and researchers,
Finally, we were able to obtain distributions for individual soil mechanical parameters in order to be able to answer geotechnical questions not only with deterministic but also with probabilistic approaches. Now the validation of the observed distributions is more difficult than initially expected.In the literature there are only isolated references to observed distributions [e.g. Lumb (1974), Lee et al. (1984), Benson (1993), Lacasse and Nadim (1996), Baecher & Christian (2003)] and the normal distributions described therein, among others, provide physically illogical results in further simulations due to their value range below zero.
Which distributions do you use to model soil mechanical parameters, such as the void ratio, the dry and saturation weights, the hydraulic conductivity or the shear strength?
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?
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.
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.
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?
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.
- 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.
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?
What is the effect of the Gypsum percentage on the collapse potential of the soil?
The collapse potential (CP) of the soil can be calculated by the Single Oedometer Test or Double Oedometer Test.
Would you please let me know if the following is accurate as an answer to the question:
Suppose we have sensors which measure the volumetric soil water content of a soil layer for a long period (more than 6 months) and also high temporal resolution (half-hourly). Could I assign the maximum in this dataset to the saturation point?
I understand that we do need to have a lengthy rainfall event, how long the event should be so that the above proposal works?
And if there is any other way that I can get to the saturation point of a soil layer from the volumetric soil water content data/sensors, please let me know.
Mostly focused on the topsoil and preferably only using the dataset.
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.
What is the effect of non-associated flow rule on bearing capacity of a strip footing using finite element method?
In classical soil mechanics, one of the simplest problems is the bearing capacity of a strip footing on a frictional soil obeying Mohr-Coulomb failure criterion. The analytical solutions to determine the ultimate bearing capacity make use of upper bound/lower bound theorems of limit analysis where the fundamental assumption is the associated flow rule i.e. the dilation angle is equal to the friction angle.
However, it is known that soils usually have a dilatancy angle less than the friction angle. This leads to a non-associated flow rule and the analytical solutions are no longer valid.
I want to use finite element method to determine the ultimate bearing capacity of a footing on a frictional soil obeying Mohr-Coulomb failure criterion with a non-associated flow rule.
BUT I find in the literature that there is not a unique ultimate bearing capacity when a non-associated flow rule is used. As you can see in the attached pages from Varn Baars (2018) and Loukidis et al. (2008), the load-displacement curve starts to oscillate and it does not converge to a unique value. The oscillations become more significant as the difference between friction angle and dilatancy angle increases.
I came across theories of bifurcation /strain localization, ….regularization… but none have helped me to understand how I can calculate the bearing capacity of a strip footing using a non-associated flow rule. Does it physically exist? What is the effect of the level of non-associativity on the ultimate bearing capacity?
Loukidis, D., Chakraborty, T., and Salgado, R. (2008) Bearing capacity of strip footings on purely frictional soil under eccentric and inclined loads, Canadian Geotechnical Journal 45, pp 768-787
S Van Baars, 2018 - 100 YEARS OF PRANDTL'S WEDGE.
When conducting analysis of foundation on rocks, and the triaxial test results of the rock material is found as c=3 MPa and ϕ= 44 degrees. In analysis, this cohesion value has to be reduced to account for the rock mass, to a value of maybe 50-300 kPa. Is this assumption correct? Or are there some correlations in the literature?
I am building a database of fall-cone test penetration depth vs water content. The database has 120 soils approx. Looking for published and unpublished results to increase the number of entries.
I was wondering if there are any attempts of creating artificial soil, so that can be used as a benchmark for different custom tests and constitutive models. Especially interested if cohesive soils can be created (I imagine that cohesionless soils are fairly easy to create ).
Can someone provide a manual or a guide of geotechnical investigation procedures for different types of constructions in English? I mean a guide of methodology and standard procedures for transmission towers, bridges, regular houses, etc?
I am interested in a manual which is compatible with Eurocodes or ASTM standards.
I am looking for a reliable method to measure creep in the lab for cohesionless, drained soils. All literature ive observed as far seems to skirt over drained soils. Any ideas?
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.
During casting of Interlocking tapered mud bricks, It was observed that samples casted with pure mud+ water ( moisture content 10-20 %) produces shrinkage crack after 24 hour when it starts drying. When Husk and Straw were added with mud and samples were prepared, no cracks were seen. One reason is husk/ straw work like reinforcement inside the soil.
Why in case of pure sample cracks appears?
Does geometry of bricks have role in producing this cracks or it is general behavior of clay to induce shrinkage crack when water evaporates?
If that is so, why this cracks does not continuous till complete drying of sample ? It only produces in 1st 3 to 4 days after casting
Hi Hi I conducted direct shear test for the. Now I want to obtain Young's modulus from the reading I got. Is there a method to calculate it? Thank you
Could you introduce a good book or article on the topic of upper bound limit analysis in soil mechanics?
Question to active researchers in the field of Geotechnical Engineering role wide: Kindly advise on your availability to work jointly on funded Research projects? Please identify your specific research area(s) in geotechnical engineering?
the soil sample which we test in the lab ( disturbed or undisturbed) provide index and engineering properties. how can we predict entire ground behaviour by conducting lab tests?
- even field tests and FE analysis provide results, but with some shortcomings.
- how to relate lab, field and FE test results to predict accurate ground behaviour?
Geotechnical Engineering is a branch of Civil Engineering that deals with the behavior of earthen materials and how they interact with man-made elements such as foundations, and infrastructure.
The practice of forensic geotechnical engineering is the application of geotechnical engineering to answer questions pertaining to a conflict in the legal system.
Geotechnical engineers must apply science and engineering within the rules
and practice of the legal system In order for their work to be effective in representing reality.
Forensic Geotechnical Engineering involves analysis of a project, site conditions, or construction from a geotechnical standpoint. Analyses of failures connected with geotechnical and geological origin to improve professional practice, codes of analysis and design as well as practice. These analyses are performed to check the calculations and engineering assumptions during and/or after the construction of a project to provide quality assurance or address issues that arise during or after construction.
Common issues that may arise that a forensic geotechnical analysis can help with include:
- Expansive Soils Related problems
- Collapsible Soils related problems
- Settlement of Shallow and Deep Compacted Fill Soils
- Pavement excessive Settlement and Failures
- Slope Stability Failures
- Embankment Failure
- Foundation Failures
- Excavation Failures
For more readings on forensic geotechnical engineering:
The observational method is a framework wherein construction and design procedures and details of a geotechnical engineering project are adjusted based upon observations and measurements made as construction proceeds.
It is always useful to learn from others experiences they encountered in solving challenging Real world problems, and to learn from their past successes and failures. Experience is the best teacher in life.
i can share with you my solution To one for the challenging geotechnical Engineering problems in gulf:
Technical Report Doctoring the Ground: Major Geotechnical Engineering Lessons...
Geotechnical Engineering Researchers: Do you have publications of research involving assessment of accuracy of prediction models by comparison to measured field data ?
I did various indoor experiments on sinkhole occurence due to leakage in underground pipelines in various soil profiles.
I got data for all the experiments and now i want to apply neural networking for risk prediction of sinkhole due to leakage in various subsurface soil conditions.
If any one can share their experiences, views, articles, experties, or advices.
Thank you in advance.
”In engineering, a foundation is the element of a structure which connects it to the ground, and transfers loads from the structure to the ground. Foundations are generally considered either shallow or deep. Foundation engineering is the application of soil mechanics and rock mechanics(Geotechnical engineering) in the design of foundation elements of structures.
How future Materials and development of smart structures and new technologies in construction Will Shape the Future of buildings foundations?
Dear scientists and researchers,
There's a standpipe casing which has so many displacement throughout its alignment (bended or misaligned) in the ground. It made the reading impossible since the probe stuck in the displaced section. What's your idea to still receive data from these piezometers?
There's an idea which I want you to check out:
How about adding water to fill up the tube then calculate the amount of water which was there by subtracting total volume from the volume added.
I'd be appreciate it if you would share your ideas.
do you any one have this reference
Soil Mechanics in Engineering Practice" by Terzaghi & Peck (1958)
i need some information from it
I am looking for a numerical model, equation or law, which supports the ground subsidence due leakage in underground water pipelines or interaction of water and subsurface soil.
I simulated one tunnel in the soil medium, I going to study on the ground surface settelment due to excavation tunnels
Which Constitutive model of the soils (SC-GC) is better? and why?
1. Mohr coulumb (MC)
2. Soft soil
3. Softening strain (SS)
4. Hardening soil (HS)
5.Hardening soil small-stiffness (HS-SS)
Theoretically, pressure envelops are linear and maximum earth pressure occurs at the bottom (3H/4 - 1H) of the structure. But in field monitoring with pressure sensors, earth pressure envelops are non - linear and maximum earth pressures are maximum at H/2 - 2H/3 of the wall.
why standard theories are underpredicting or over predicting the field values?
i am giving sinusoidal displacement to a plate anchor in soil by giving periodic amplitude .which step should i take static general ,dynamic implicit or direct cyclic.whether increment size play role in results how to decide proper increment size.
As we know, the formulas of the natural frequencies and their corresponding mode shapes for the uniform linear elastic soil (without damping) on the rigid bed are as follows :
f_n = (2n - 1)vs / (4H)
vs = sqrt(G/ρ)
φ_n = sin((2n - 1)πz / (2H))
where f_n is the natural frequency of the corresponding mode in Hertz, φ_n is the mode shape of the corresponding mode, n is the mode number, H is the depth of the soil column, vs is shear wave speed, and z is the height from the rigid bed.
I create the finite element model (FEM) of soil using the commercial finite element (FE) program Abaqus/CAE 6.14-2 x64. The soil was modeled according to the geometric properties using the C3D8. It has a depth of over 50 meters and a horizontal distance of over 100 meters. The soil element size is 2 meters. The total model consisted of 62500 soil elements. Fig. 1 shows the 3D of the soil model. The unit weight of soil is taken 15 kN/m^3, Young’s modulus is 1000 kN/m^2, Poisson’s ratio is 0.35, Cohesion is 5 kN/m^2.
In order to closely match the theoretical solution, some assumptions have been made for the modeled soil. The soil rests on the rigid bed, modeled as boundary conditions restraining the bottom against translations and rotations at all directions. Further, the outer nodes of the model at the same level (Y equal) are tied using the MPC-Tie constraint to move together.
According to the theoretical formulas mentioned above, the first and second natural frequencies of soil column are obtained 0.0786 Hz and 0.2357 Hz, respectively. Nevertheless, the FE results do not conform to this order as the mode number. The first twenty-two natural frequencies of the soil FEM are shown in Fig. 2. The selected 3D mode shapes of the soil FEM are illustrated in Fig. 3. As can be seen in Fig. 1 and Fig. 2, the 1st frequency of the model occurs at mode numbers 1 and 2 and in two horizontal directions perpendicular to each other. This result is consistent with the theoretical results. However, the 2nd mode shape as the model occurs in modes 11 and 12, which is contrary to the theoretical results. Interestingly, the behavior of other mode shapes of the soil model is also strange.
Why do the order of the fundamental mode shapes and their frequencies of the soil FEM differ with theoretical values? Should further assumptions be made to fully simulate the FEM with the theoretical soil model?
The figures and the Abaqus/CAE FEM file are attached.
Thanks a lot in advance.
 Steven L. Kramer. Geotechnical Earthquake Engineering. Pearson Prentice Hall, 1 edition, 1996.
I have a rock specimen and a soil specimen. During my mechanical measurements I observed that the rock reacts much faster on stress rate changes (observable by a sharp kink in the deformation curve) than a soil (no such kink). What is the explanation? Where can I find a publication dealing with this phenomenon?
I am working on sand with fine content such as 35%-45% of silt. I aim to find maximum void ratio for 35% silt of mixture(silt&sand)However it became so difficult becuse of silt properties. For emax lab. test ,do you have an information any practical methods for silt?
Thanks for your help
I´m working with Geo-PIV program to evaluate displacement vector and Shear strain distribution in reinforced soil. How can I calculate correlation coefficients of obtained PIV result?