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Does Eurocode allow use of Robertson chart to determine soil type based on CPT results?

Does Eurocode allow use of Robertson chart to determine soil type based on CPT results?

Does Eurocode allow use of Robertson chart to determine soil type based on CPT results?

It seems that use of the Robertson charts (Robertson, P.K. [1990] " Soil Classification using the cone penetration test" Canadian Geotechnical Journal 27(1), 141-8) to classify soil type based on CPT results is widely accepted practice in the Netherlands. I cannot, however find any prescriptions in the current Eurocode which explicitly allows this. I have checked all relevant standards:

- EN 1997.1
- EN 1997.2
- NEN-EN ISO 22476-1
- ISO 14688-1 and ISO 14688-2

Some of these standards are perhaps not the most recent and others do not contain the national annexes, so perhaps that is my problem. However, I cannot find a clear stipulation which allows or prescribes use of the above charts to actually determine soil type based on CPT results.

Could anyone indicate why this is allowed? Am I missing something in the standard? If it is common practice how does it not contradict the standard?

RE: Does Eurocode allow use of Robertson chart to determine soil type based on CPT results?

BS EN 1997-2:2007 - Section 4.3 provides a detailed discussion on the use of CPT. As you said it doesnt specifically recommend the use of Robertsons Chats, however to my knowledge, his charts are internationally accepted as the method for inferring soil type from CPT data.

I think using CPT data (and any classification method) on its own to assess soil type is not good practice (unless you have a lot of knowledge of the ground conditions). Boreholes, sampling and lab testing as standard is required.

RE: Does Eurocode allow use of Robertson chart to determine soil type based on CPT results?

Hi @EireChch. Thanks a lot for your response. I have also noticed that EN 1997-2 covers use of CPT, it also indicates that CPT should not be the go-to method for soil classification and this concurs with what you are saying. However, I have seen that here and there CPT's are used as additional confirmation for the borehole data.

To perhaps make the question more clear, I have come across the following figure (in addition to the Robertson chart) in my textbook:

As you can see they are claiming that this figure can be found in ISO 22476-1 which BS EN 1997-2 refers to in the CPT section. I could not find this figure anywhere in the standard and nowhere does it say to use this as additional help for soil classification...

Any other ideas? Thanks!

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