I got answer from IS code 2911 for standered penitration test. It says that SPT is to be done in a bore hole of dia 100 to 150 mm. If N value is taken in a 500 mm dia bore hole, it is not standard. The results may vary. This was submitted to the consultants and they accepted it.
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Alex Thomas R.Eng, C.Eng, M.ASCE
Senior Site Engineer
Geo Structurals Pvt Ltd
CochinAlexThomasR.Eng, C.Eng, M.ASCEIndia
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Original Message:
Sent: 05-31-2023 06:23 PM
From: Alex Thomas
Subject: Is there any IS or research paper saying minimum N value for friction piles?
We designed a pile foundation for carrying a load of 40 T in Kochi. The sub soil is clayey. N value is very low up to 60m. We designed the pile as friction pile and the cut off was fixed at 35 m. As per geotechnical report the load carrying capacity of 500 mm pile was 60 T, with out considering end bearing. We provided 4 piles (500mm). The total load carrying capacity of the group is 240 T. Where as the load of transformer is 40 T only. The client is asking now to check the SPT value of each pile. We checked. We got N value of 24 at - 35 m in the 1st pile. In the 2nd pile N value was 16 only. 3rd pile even lesser value. IS THERE ANY RELEVANCE IN CHECKING SPT VALUE FOR A FRICTION Pile. If so, how much should be the minimum N value? Why did tge N value get reduced in the 2nd & 3rd hole. Is it acceptable. Is there any IS or research paper saying minimum N value for friction piles?
#Other
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Alex Thomas R.Eng, C.Eng, M.ASCE
Senior Site Engineer
Geo Structurals Pvt Ltd
CochinAlexThomasR.Eng, C.Eng, M.ASCEIndia
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