SM or Better?

[fattdad]

BigH's thread on "free draining" get's me on my pet peeve. If you want something, take the time to specify it correctly.

The term "SM or Better" is such an ambiguity. Where do you go to find out what soil types are "better" than SM? Sure, folks reference ASTM D-2487 (or 88) but the ASTM doesn't say which soils are better than others. The implication is that SC is worse? Would a fine- to coarse-grained clayey sand (CL fines) really be worse than a fine SM with elastic silt fines? Don't think so.

There, it's off my chest.

Carry on. . .

f-d

¡papá gordo ain’t no madre flaca!

 

[emmgjld]

"SM or Better" I love the thought.
Like a Geotech goes to a table and specifies a backfill,
similar to picking a Versa-Lam Beam and everyone knows exactly what we are saying.

 

[dgillette]

I think it's like going into a restaurant and saying "Bring me the grilled salmon or better."

 

[BigH]

The sorry thing is that the waitress doesn't know what a "better" is . . .

 

[dgillette]

From her perspective, "better" probably means "15 percent of more expensive."

 

[Ron]

Agree...in my business (construction/structural forensics) I see so many bad specifications. I see poor compaction requirements, improper foundation prep requirements, concrete specs that don't make sense, structural steel with no welder qualifications or inspection criteria, improper fastening for wood/rough framing, bad waterproofing and sealant specs, roofing specs that are incompatible with the roofing intent, yada yada yada.....yet it is almost impossible to find an architect who will give an opinion against another architect on standard of care. Engineers do it routinely. If one engineer screws up, other engineers have no hesitation to explain why and how it should have been done better/differently.

Why is that?

 

[fattdad]

I'm working on a case right now where the geotechncial consultant was not asked to provide recommendations on finished slopes and issued a report that gave recommendations for bearing pressure and subgrade preparation. The structural engineer used the geotechnical recommendations in their design. The civil engineer had nothing to go on and just designed the embankment for 3H:1V slopes. The slope failed.

Can't blame the geotech, he wasn't brought to the dance. Civil engineer seems to be standing alone, but fails to recognize any issue at all, "Act of God" type response. (Almost like, we always spec and design this way and never a problem until this oddball project - can't be our fault.) It's frustrating, but understandable, I guess. . .

I remember when Masterspec came out. I reviewed the overall template (for my company) and found so many areas of confusion in the earthwork spec, that I offerred my comments to the editors. It was like talking to a vacuum. The committee was done - I mean where's continuous improvement?

f-d

¡papá gordo ain’t no madre flaca!

 

[BigH]

fattdad - you hit a point with me, too. I found some obvious typo errors in some AASTHO specifications. One had the yield stress for rebar on the tensile strength line and had the tensile strength on the elongation line (elongation line was a header for the elongations for the bars) - also they had dropped a zero in another location. I told them about it and I got a snarky reply about ". . . and experienced engineer would know . . ." - I asked how that would help me if I was on the witness stand and was asked the question about tensile strength - saying, well, and the lawyer says "What does it say on paper?" I have engineers specifying A53 steel pipe for railings - and when the mill certs come in, the don't include Vn etc. So I reject it - then the designer comes back and says - "Oh, we don't care about the chemical composition - just the strength." - so why don't they say this in the spec (oh, and they don't identify if Grade A or Grade B). Sorry, all, I'm in an 'arrrgggg' mood at present.

 

[dgillette]

The case fattdad cites is the opposite of (I think) Ben Franklin's proverb along the lines of "Better to keep one's mouth shut and be thought a fool, than to open it and have that proven." Rewrite that as "Better to ask the question and be thought a fool, than not to ask it and have that proven."

Whenever I'm on the spot to provide answers and I haven't got them, I just start asking questions about the geology, relevant or not. It buys time and people usually think you have a good intelligent reason for the questions. Plus, it makes the geologist feel good.

I have to ask though, what sort of material was involved in instability of a 3:1 slope?

 

[fattdad]

20 ft below the slope there is an interface between natural sand and a stiff fissured clay. The added burden of the earthwork changed the state of stress on the interface and failure occurred - a wedge failure. Today, movement occurs during the winter when the water table rises as the slope is at a safety factor of unity. Don't know whether another prominent relief will occur or not, but we have slope inclinometers in place to further document the extent of movement.

f-d

¡papá gordo ain’t no madre flaca!