Estimation of Labworks by using field results

[taylanba]

Dear All,

I am new at the forum. And since I am not native English speaker, please forgive me if I write wrong things. I continue to confession, I am not good at geotechnical issues. So, I don't understand the abbreviations. Because of this, could you please answer the question like to tell to the idiot

First I need to explain my situation: Our subcontractor is the responsible for the performing both field works and lab works. We have one site engineer at site. We are sure that all of the field works, i.e. SPT, sampling etc have been done correct. However, we are not sure that whether he performs lab works correct or not. Is there any way to estimate the lab engineering lab works. Direct Shear, UU Compression, CU compression results. I don't want to learn very precise results. But I need to learn the results whether 1 or 100. I know that site is totaly fine grained, i.e. silty clay, clayey silt, sandy silty clay etc.

I found somethings from internet but I couldn't understand which test results they talking about. For example, can the test results coming from direct shear, UU compression test and CU compression test be 0.2, 0.9 and 0.6 respectively for cohession?

I would be very improving if I can find any help

Thank you.

T.

 

[oldestguy]

Taylanba

You can help us if you describe what type of construction project these tests are to be used for and the qualifications of the person (engineer) to use them. Is there another company in your area that you can go to for professional help? If you are inexperienced in use of the data, you may be tackling something that a more experienced person should be involved.

 

[taylanba]

Dear Oldestguy,

This is road construction Geotechnical Investigation. We are the contractor of Client and responsible for the designer. Designer decides which site works and lab works should be performed. Addition of this, the road axis has 2 big landslides. We are responsible for the write and submit factual report. We don't need to give any oppinion for the site or works that would be done. During this stage, as I said before, we should deal with the site and lab works. We are sure site works but not lab works.

The geotechnical engineer has good qualification to help a designer. He is good at that subject. Our company works generally undeveloped countries, so we haven't any chance to find another company to help us.

Actually I am not charged with to examine the data. I, myself want to check these test results whether they are logical or not.

I hope these infos may help you.

Thanks.

T.

 

[oldestguy]

While getting a dependable detailed answer to your question probably is not likely, it would seem that you should have sufficient knowledge of the lab operations that you feel comfortable in saying the tests were done according to a known standard test procedure, such as ASTM or (if there is no ASTM test method), that another authority, such as the US Bureau of Reclamation, procedure was followed.

If the geotechnical engineer is well experienced,he (she)should be able to judge the dependability or expected results of the lab work done, by just what you bring up, using field data as a start in his review of the lab data. If you can assist him (her)fine, but I'd be careful with any comments like "Seems OK" or "I question this", since that extra work may not be what you were expected to do. You may comment, however, on sample condition. Sometimes it is difficult to get good samples and the lab has to work with what they are given.

This may not help, but documenting the test procedure used, in reference to some known standard, should be a standard part of your reports.

If that geotech engineer was "doing his job" correctly, it would seem that he would have specified that to begin with.

 

[taylanba]

Dear Oldguy,

Actually we are getting started to obtain UU comprssion test and direct shear test results also. In site we have different two kinds of formations which are CH and CL. According to phi angle and cohession values, the UU test and direct shear test results are different. Can there be any relationship between the phi and C values coming from CU UU and DS test results at the same depth of samples coming from same borehole locations?

Thanks.

T.

 

[oldestguy]

Since the test results will go to an engineer who will use them, if this were my job, I would want to be there when samples are extruded from samplers and when they are prepared for testing. Then any differences in data obtained (as you may be finding) would be something I would want to evaluate. The person running the tests should be in on this evaluation.

Under your apparent circumstance,all you can do is run the tests and comment, if necessary, on apparent disturbance or other factors that may have influenced the results.

When the final user of the data is not present or aware of all testing factors, that can lead to questions as you now have. I think the best you can do is call that person or group with your observations, and as they say "put it in their court" before you organize and prepare your report.

 

[L0k]

Hi Tan
It is a bit difficult to compare the insitu test and the lab test, both of them are having disturbance especially when you take an undisturbed sample depending on your technique to taking samples either push or using piston sampler etc. When you extrude the sample there is another disturbance. SPT is depending on how to drop the 63.5kg hammer using pulley or automatic hammer.
So, there is no correlation accurately and your engineering judgement is required.

I am not sure whether the landslide in your terminology means the ordinary slope failure?