Geotechnical report recommenation for CIDH (drilled Shaft)

[abds]

We have to prepare geotechnical report for Cast-in-Drilled Hole pile foundation is recommended for the supporting deck with nominal load on 2H:1V slope. What are the typical geotechnical parameter do we need to recommend for Structural Design.

 

[Ron]

I'm surprised that you are asking such a question in a forum. This is a question that experienced people in your organization should be involved in answering. You have not given adequate information for an informed answer in a forum.

If you do not have sufficient geotechnical experience to properly design an investigation, evaluation and recommendations for such, please get local help.

 

[abds]

Ron;
We are very happy to talk about theory but some time practical world is little weird new person to figure out the boundary of different engineering fields. You are absolutely right, i may not have "sufficient" experience, therefore, seeking help to be smart in front of Superviser.

I have seen variety of reports but I just want to stay on the side of geotechnical side. Not want to spend time of structural part. I just want to know what geo recommend and structural engineer expect ?

 

[oldestguy]

I don't wish to be insulting, but, from your question, it appears that you are getting into an area of engineering where you have not been before. While getting into new areas may be good for expanding the firm, you may be risking your reputation and finances. In any venture into new work, there can be risks. However, in your case are you prepared for a legal law suit for a serious mistake that a more experienced person would not make?
Take the firm I was with some 19 years. We had a great deal of experience in many geotechnical aspects. However, on one large project, the same field as what we had worked on before on a small scale, we didn't want to take a chance of a mistake. We hired a nationally recognized expert and asked that he look over what we were planning to do. The result was he pointed out a few details, while they didn't change things much, they made our client appreciate the niceities that this expert added to the job. We probably could have gotten along without him, but we didn't feel totally at ease with this job. We learned from this outside help, and didn't have to learn the hard way. None of us are too smart not to now and then need outside help.

If you are not totally confident in what you are doing, hiring an expert for a one time association may really put you into the field you are looking at with more confidence and less risk. You can't get that advice at this forum.

 

[fattdad]

you need to state nature of the bearing layer, soil type, design parameters and design values that led to your settlement forecast. You need to provide unit end resistance and to what extent you recommend any contribution of shaft friction. You'd need to provide ultimate values and factored values. There should be some consideration for horizontal loading. The structural engineer may want to know p-y relations, but that'd be hard to do if the structural engineer hasn't yet figured out the reinforcement.

You'd need to give some construction considerations related to the geologic conditions. Is ground water an issue? How to confirm that the bearing surface is adequate or concrete placemnt (i.e. if it's rock, do you want a pilot hole and a scraper down the hole to "feel" for discontinuties or vugs/voids?

If this is a roadway job, you'd need to consider LRFD requirements. If this is a design-build job (well at least in Virginia), you'd need to complete a reliability assessment to clearly define the reliability of your data set.

You should help the structural engineer on matters to plumb - i.e., what's acceptable plumbness?

I guess you'd need to read up on these things, but those are few items that jump to mind. . .

f-d

¡papá gordo ain’t no madre flaca!

 

[abds]

I was expecting simple answer; typical "write up" in recommendation portion. Some report presents only pile load capacity and depth of pile and some report presents soil value like Cohesion, Angle of internal friction, Total unit weight, Relative density, Strain at 50 percent of maximum stress, Skin friction,Allowable bearing pressure,Young’s modulus of soil. I just want to know the presentation; not asking vague portion of analysis.

Oldetsguy; thank you for your suggestion i am not completely unaware about technical and legal issues. "Insulting" is not professional word. I just want to learn more and i expect advise originating from "Positive Mind'.

 

[jayrod12]

The soils reports that we generally receive in our office are specific recommendations as to pile type based on site conditions. If friction piles are the way to go then we are given skin friction values, minimum and maximum depths, frost protection(if required), spacings and group factors. If end-bearing is the better option then they give bearing pressures (In 99% of the end-bearing jobs we do at our office, end bearing is on Canadian Shield bedrock and therefore there is no settlement type numbers given).

Hopefully that helps.

 

[oldestguy]

This is simple, but probably will not satisfy you.

"Pile tip elevation at xxx elevation will have a capacity of yyy Kg."

Without all the data in now your hands and not provided here, how can any of us answer your question correctly? That's why my recommendation is get help from an expert in your area. Maybe ask your employer on this one. We all are learning and the boss should recognize that.