Soil Test

[owillis28]

Does anybody have any notes or example problems dealing with standard penetration tests? I am also looking for information on boring logs and soil test results.

My geotech reference materials are not very good. Sorry about being so vague.

Any help would be greatly appreciated.

owillis28

 

[RIP - VTEnviro]

What kinda info?

I've done this sort of work a number of times (am schedule to do so again tomorow!), so I've picked up knowledge on the job.

 

[owillis28]

Here is a list of items that I eluded to in my first email. I was trying to recall some problems that I had come across during my studies of geotech problems that I was unable to understand. Just thought I would use this for to obtain additional information.

1. Anything that explains information contained on a boring log. (i.e. calculating the N-value from a certain soil at a given depth, Corrected N-value)

2. How to interpret results from a standard penetration test (SPT).

3. Standard soil tests information (i.e. When to use given a soil type and trying to find a particular soil property, )

 

[Hockeyfan960]

http://www.dot.state.fl.us/structures/Manuals/SFH.pdf

This link was on another post, but anyways, the manual has a lot of soil testing information.

http://www.dot.state.fl.us/MapsAndPublicat...wnload-list.htm

I also used the Coduto - Geotechnical Engineering book on the test as it had a lot of the soil testing equations and definations. (SP)

http://www.vulcanhammer.net/download/gener...l_mechanics.php

Replaces NAVFAC DM 7.01 or DM 7.1, 1 September 1986. This book also has a good deal of Soil Testing information.

Let me know if you need anything else.

 

[Guest]

1. Anything that explains information contained on a boring log. (i.e. calculating the N-value from a certain soil at a given depth, Corrected N-value)

Somebody posted a link to a geotechnical investigation manual (PDF) some time ago on this board. As I recall, it was a publications produced by a state agency and looked pretty good and included boring log investigation details.

I will take some time to see if I can find that link.

As far as looking at the boring log with respect to N-values, the only notable feature will be the blow counts. There are a number of formulae available for calculating N or corrected-N from the blow counts. I use Braja M. Das' text - Fundamentals of Geotechnical Engineering. I believe his other texts would be suitable for this purpose as well. The NAVFAC Manual may also provide some guidance as well - try 7.01 or 7.02. If you haven't downloaded those and skimmed the material, there are some nice chart, figures, and tables in those references for geotechnical investigations/design.

Question for you - are you only interested in SPT results from the boring log? Are you concerned with any other aspects of interpreting the boring log?

2. How to interpret results from a standard penetration test (SPT).

The test is used by different practioners in different ways. The test is essentially measuring the relative density for in-situ (undisturbed) soils. A number of correlations have been developed in the literature to look at the values of the SPT and other engineering properties of the soil to look at soil strength, bearing capacity, sheart strength, friction angle, etc. I think it really depends on the type of investigation you are conducting and the results that you need.

3. Standard soil tests information (i.e. When to use given a soil type and trying to find a particular soil property, )

You might have need to give more details for this one. I work in groundwater/soil remediation field - the investigative work I conduct/review with respect to standards soil tests is much different than say .. a structural engineer. If you provide some applications, I might be able to point you in the right direction.

JR

 

[Guest]

^^^ I found the reference for Geotechnical Investigations, it is published by the FHWA

Publication No. FHWA NHI-01-031

I think this will help with many of your questions.

JR

 

[Old as Dirt Geo]

Here is a list of items that I eluded to in my first email. I was trying to recall some problems that I had come across during my studies of geotech problems that I was unable to understand. Just thought I would use this for to obtain additional information.
1. Anything that explains information contained on a boring log. (i.e. calculating the N-value from a certain soil at a given depth, Corrected N-value)

2. How to interpret results from a standard penetration test (SPT).

3. Standard soil tests information (i.e. When to use given a soil type and trying to find a particular soil property, )

I will try to give you the short and sweet answers to your questions. Remember that a large part of interperting boring logs is experience and the lab testing is based on knowing what information you need to preform a certain type of analysis, i.e. pile analysis, settment analysis, determination of bearing capacity.

In general the number of hammer blows required to advance the 24-inch spoon in 6-inch increments (four increments in all) are recorded. The number of blows required to penetrate the middle two increments (6 to 18 inches) is known as the Standard Penetration Resistance (N-Value). If you are using an 18-inch spoon you will have 3 6-inch increments and the number of blows required to penetrate the last two increments is the N-Value. As for corrections there are a number of corrections that can be applied to the N-Values, such as hammer efficiency, borehole diameter, sampler type and length of rods. The most common correction is for depth of sample. When correcting for the depth of the sample remember that this correction will adjust the N-Value to a standard 1 tsf of overburden pressure. This means that the correction will increase the N-values when the overburden pressure is less that 1 tsf and decrease the N-Value when the overburden is greater than 1 tsf. So most geotechs will only correct when the overburden pressure is greater than 1 tsf, which is usually between 10 and 15 ft depth, depending on the unit weight of the soil at the top of the boring.

To interpret the results of the SPT test, in general the lower the N-value the weaker the soil. This means the soil has a lower shear strenght, lower unit weight, etc.

As for standard tests, in general you perform labs tests to assist in classify the soil and to determine engineering properties for the specific type of analysis you will be performing.

I hope is helps.

Old as Dirt Geo

 

[mikdrago]

Hello all,

I am a college senior that is in the last semester of civil engineering program. I am working on an assignment that requires calculating the N values for a given boring log. I know that you ignore the first 6 inches and then use the next two sets of data of the next foot to get the N value, but how do you begin the N table? Do I record the N value at 6" or at 1 foot? I am starting from ground level and test goes to 102 ft. I am assuming that I would take the value for 6" to 18" and enter it for a depth of 6". Then my next depth would be 3' and and would enter the data at 2', using the blow counts from 2' to 3', continuing to the end. If anyone can help clarify this that would be great. Thank you very much. I will attach a copy of the first page of the boring log we are using. I have circled the data that I am assuming I should use. I had to crop it down to fit the 500 k upload size.

Michael Drago

Engineering Student