Have we lost our ability to think? Have we learned that we only need to ask questions and not try to solve the problem ourselves?
In linkedin groups for geotechnical engineers and other forums I have seen (and many times replied) to questions for geotechnical problems without even the necessary information. This is poor engineering which we should try to avoid. Many times practicing engineers or students pose questions without even try to find the answer for themselves.
I think it would be much better and more efficient if the Questioner would provide also
his proposal. For example, instead of posting a question like “what type of shear strength parameters can I use to evaluate a soil sliding mass?” it would be much better to post: “I am evaluating a soil sliding mass which has moved xxx(mm) and I think I should use residual friction angle for the sliding surface, what is the group’s opinion?” This type of question includes thinking of the problem and a possible solution which the group can evaluate and reply if it thinks is appropriate or there are other solutions.
We should try hard to promote geotechnical engineering and increase our intelligence and experience of the subject and not try to find the easy way for someone else to solve our problem.
I’ve lost count of the young folks coming to me with a borehole log asking for a K-zero value or a friction angle so they can plug a number in a formula. “What do you think” seems to fall on deaf ears. Just gimme the number, so I can get the job done in the allotted timeslot..
Dear Paul,
you are absolutely right and the worst part is that even if you give them a “space” value of friction angle, lets say 68 they will not even question it!
Hi, I’m also trying to understand the nature of slope failures and what parameters play a role. My question to you is since the mass movement has happened, what is the benefit evaluating the residual friction angel of the surface? Also, is it clear that there is a definite sliding or failure surface or is it internal friction issue of the material?
Dear Hannu,
When a soil mass is sliding on a surface, the shear resistance developed along that surface is constantly reducing until a residual value is reached. This value is the minimum shear strength the material will obtain, but the movement required (displacement needed) to reach this value is not exactly known. A good estimate of the necessary displacement to reach residual shear strength and the value of that strength may be obtained from residual shear strength tests.
Here is a good paper from Stark et al on the subject http://www.geotechpedia.com/Publication/Show/2506/DRAINED-SHEAR-STRENGTH-PARAMETERS-FOR-ANALYSIS-OF-LANDSLIDES
hi, thanks for the opinion.Mass sliding is an interaction of forces to nature.How about if i use the Work Energy equation, and equilibrium equation to analyze how fast and how far the mass
would travel. The total work is equals to the sum of the change in potential energy (P.E) + the change in kinetic energy K.E – work done by frictional force.Work due to frictional force is equals to Ff x S. By rotated axis tan of an angle is equals Ff/ Fn. What is the opinion of the group?thanks.
theres another force, the Fw which is the force due to the weight of the mass or mass x gravity.
I think you have not taken into account the thermal energy produced and how you will evaluate that energy.
In joining techno groups in geology (and other sciences), it is likely that numerous folks are seeking a connection with other individuals who may know much more on the sugject then them.
An approach which encourages open dialogue may be more beneficial in inspiring curiosity than just telling others to use their head before posing a question.
Thwarting open dialogue typically does’nt add much to the equation, kind of like slamming a door in front of someone after a brief introduction.
Food for thought I believe.
Francois, you have a point. But I don’t think it applies to Chrys’ original post. In my view, the ASCE and geotechnical LinkedIn fora are intended for use by knowledgeable individuals, not grad students looking for an easy way to solve their homework problems – or lazy project engineers. I understand that Ralph Peck used to insist that his students prepare a ONE PAGE summary of the problem and their solution in order to get an A on homework assignments. My first boss had a similar policy he referred to as his “two minute drill.” You were given two minutes to present your problem AND solution; if you overstayed your “welcome” or didn’t try to solve the problem, you were unceremoniously dismissed from his office! (This happened to me exactly once.)
Inappropriate questions should be flagged, and open-ended questions should be challenged. We should promote the use of critical thinking skills, not rote memorization or “copying” from others.
If less knowledgeable persons want to participate, they need to try to solve their own problems first. In my view, Chrys is right.
Going to hannu’s post:
hannu posted “…Also, is it clear that there is a definite sliding or failure surface or is it internal friction issue of the material?”
In my experience, there is seldom a definite sliding surface, at least in soils. (Rock behavior can be different.) It’s usually a zone; the greater the movement, the more likely the failure is a zone that could be feet to meters in width, and not particularly well defined.