Pile design in soft rock
Pile design in soft rock
(OP)
Hi All,
I have found a paper by R.K Rowe called "A design method for drilled piers in soft rock" from a Canadian Geotechnical Journal. This paper addressed methods on how to design with low RQD rock and tight settlement criteria (duplicating the conditions that I have), but is based on case studies with static loads.
These piles will be subjected to cyclic loads only.
Will this paper and the suggested design method still apply ?
Any other suggestions and/or papers to address cyclic loads ?
I have found a paper by R.K Rowe called "A design method for drilled piers in soft rock" from a Canadian Geotechnical Journal. This paper addressed methods on how to design with low RQD rock and tight settlement criteria (duplicating the conditions that I have), but is based on case studies with static loads.
These piles will be subjected to cyclic loads only.
Will this paper and the suggested design method still apply ?
Any other suggestions and/or papers to address cyclic loads ?





RE: Pile design in soft rock
I asked my principal engineer what the definition of 'soft rock' was? Thinking about strength and RQD etc etc.
He said 'Bryan Adams and Meatloaf'
Weak Rock,,, always 'weak' rock.
RE: Pile design in soft rock
RE: Pile design in soft rock
you can try the technical report IF-99-025 "Drilled shaft: construction and design methods" published by FHWA or the EM-1110-2908 "Rock Foundations" by the U.S. Army Corp of Engineers.
A comment on always "weak" rock, as in soil clasification there are several methods for instance USCS or AASHTO, in rock classification there is also some guidelines to clasify rocks, I mean, I'm not geologist but if I can remmeber well, in fact the term soft rock already exist and is used to clasify rocks in field according to its hardeness, the criteria is something like
very soft- can be deformed by hand
soft - can be scratched by finger nail
Moderately hard- can be easily scratched with a knife
hard - can be scratched with dificulty with a knife
very hard- can not be scratched with a knife
Now "weak" rock seems to relative for me, for insatnce someone who is only familiar with a region where igneous rocks are the outcropping rocks, is acostum to deal with "strong" rocks or may be heavy or hard rocks? Lets say this rocks have RQD values higher than 90 and compressive strengths higher than 7000 psi, wow! that's a "strong" rock for someone who live in a reagion where sedimentary rocks outcrop, let say shale with RQD values ranging from 30 to 60 and compressive streghts of abouth 2800 psi that seem to a "weak" rock, well to avoid those interpretation clasification methods give the following descrptions
The first rock may be clasified as:
Basalt, dark gray,of excelent quality (based on RQD) slighlty weathered,hard or very hard (based on Hardeness), fine grained, vesicular perhaps, massive I'll say, moderatly to slightly fractured. Perhaphs this rock could be referred as sound or intact rock not as hard or strong rock
The second rock can be calsified as:
Shale, greenish gray, very poor to fair quality (again RQD), maybe moderately to slightly weathered, soft or mederately hard (Hardeness too),very fine grained, medium to thick bedded, highly to moderately fractured, dipping, moderately to highly weathered joints, in this case this rock usaully is referred as weathered, fractured or soft rock
In the other hand, soft sand it is in fact an abomination
RE: Pile design in soft rock
While I'm at it, shale is by definition "very fine grained". Also, it is fissile or very thinly beddded / laminated, so it can not be "medium to thick bedded". Mudrock or claystone might be a better term for this rock.
RE: Pile design in soft rock
Loose - medium dense - dense - very dense - are terms to described the density of granular sediments.
Very weak - weak - moderately weak - moderately strong - strong - very strong - extremely strong are terms used to describe the strength of rocks.
All these classification systems can be empirically determined or determine in the field by simple hand tests with basic tools ie hands, hammers, pegs etc etc. I have worked across the globe (not just the UK) and have found these terms to be the most widely used adopted methods of describing strength / density. They absolutely should not be interchangable. It is my opinion that the terms 'soft' when describing a rock is an older term that has long since lost it's meaning. New Eurocodes (eugh - sorry), which are being adopted in the far east and Australasia define them better than I ever could.
Sorry for the rant, but this is the 21st century - lets all start singing from the same sheet.
RE: Pile design in soft rock
RE: Pile design in soft rock
As part of our remit as professionals I continually try to update contractors to the most recent standards. It's called continual professional development. A competent report will have references, but more importantly appendices describing the fieldworks / and insitu testing undertaken and can even be read as a stand alone document. I know mine are.
The irony being that I kinda agree with you anyway!
RE: Pile design in soft rock
For interest, below find a URL of a guideline document for Soil and Rock logging, that defines "Soft Rock" quite well without making reference to the by Bryan Adams and Meatloaf.
http://www
So if someone can try and answer the question AFTER downloading and reading the pdf and is sure we're talking about the same rock, that would be great.
RE: Pile design in soft rock
Then they're using slightly moist, moist, wet. How is this determined?
We use Standards for a reason. They are called standards for a reason. Lets try to lose the ambiguities as this is where errors creep in.
I'm ranting again now arn't I? Sorry.
I still kinda agree with Patgeotech anyway.
Sorry about all that,,,,what was the question again???