Surge load tests to ASTM D3966 1

[dijam]

Reviewing a previous specification on load tests to piles, I have noted that this calls for "surge loading in accordance with paragraphs 6.4.1 and 6.4.3 of ASTM 3966. This shall consist of loading and unloading the piles to a load of 4 tons (lateral load design capacity), for a total of fifty (50) loading cycles. Only lateral movements of the piles shall be monitored during surge loading" I cannot see the reason for including this test in this particular instance, but as this is from a clients previous specification on the same site, he is uncomfortable in dropping the test. The site comprises loose sand (1-3m thick) on friable limestone (1-3m thick) on loose to medium dense to dense sand (6-10m thick) on dense sand. Can anyone help me by clarifying the need or benefit of carrying out such lateral load tests?

 

[Focht3]

Please describe the site and proposed structure in more detail. Where is the site? What is the structure?

What changes, if any, have been made between the previous and current foundation systems?



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[dijam]

The site is at the coast in Kuwait. The site is very large with a variety of structures. The proposed contract is for a design and build project with ourselves fixing the design concepts. The foundations are envisaged as being piled using pre-cast concrete piles.

 

[Focht3]

Who is your geotechnical consultant? You are describing a pretty significant project in difficult soil / rock conditions. What does your consultant say?



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[dijam]

Our geotechnical consultant is in-house. We have carried out the basic foundation design and written the specification. You will see that our query relates to the fact that we do not consider it necessary to carry out any surge tests. Please refer to the original query.

 

[Focht3]

I spent two months at the al Ju'aymah LNG export terminal (on the Kuwait side of the Ras Tanurah refinery) while it was under construction. As a result, I have some personal experience with the calcareous sands common to the area, as well as my years of experience with the design and construction of laterally loaded piles and piers.

I assume that the original specification has to do with earthquake loads. The Kuwaitis and Saudis have done a good bit of study of the behavior of the calcareous soils, since those materials do not behave like the "normal" soils described in the majority of the geotechnical literature. You should check with the local universities for advice. In "normal" soils, permanent cavities will only form adjacent to piers/piles that have been subject to "significant" lateral loads. In "normal" soils, the cavities caused by "small" loads will generally heal over time; sometimes the healing occurs almost immediately. However, this does not happen in those calcareous soils where particle crushing occurs, and in general the healing process is delayed in calcareous materials. The principal reason appears to be the general lack of shrink/swell behavior in these materials.

The formation of permanent cavities along the piles will significantly affect the dynamic performance of the pile foundation system. This is a very big deal if you are constructing an oil/gas facility, or a refinery.



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[dijam]

Thank you for your reply and apologies for the delay in responding to you.

The soils on the site are considered to behave as siliceous soils, however we have decided to clarify the scope of the EPC contractors geo-technical investigation to include the comprehensive sampling and testing, physical and chemical, to classify the physical nature and mineralogy of the soils, including calcium sulphate and carbonate content and also to determine the susceptibility of soils to weaken under repeated cyclic loads.