Piles on slope ( weathered rock)in marine area

[Useeeer]

Hi Engineers,
I'm a marine Structural Engineer. Currently, we are designing a platform for loading cargo onto ships. Open piled structure, located at approx. 1km into sea. Ground slope is very steep 1 in 1. For most depths, weathered calcarenite is observed. Area is near coral reefs. Currently, the piles are founded at an average depth of 7 m into sea bed levels. Geotech engineers have computed toe levels based on compression on pile. When asked about lateral capacity, they provided a calculation wherein the lateral capacity is more than the lateral force at bed levels, However, the overturning moment capacity based on the socket length assumed is lower than the bending moment at the piles at sea bed levels. When enquired about this, we're being informed that before reaching that BM, the piles will fail by compression (I couldn't agree on this because the piles are designed to withstand that BM structurally). We're bothered about the first two piles at shallowest bed level as attached here, since they are already on slope, not sure soil strength will offer the capacities quoted by engineers. Sorry about the sketch. Length shown are free length of piles. I would like to know more about the theory being told by geotech engineers and if it's not that case, some reference to check the socket lengths properly.

 

[HTURKAK]

You do not supply a lot of info here.
I will suggest two options ;

- Consider batter pile slope could be 1/15
- Consider rock anchor at the bottom.

The use of both options together will be better..





He is like a man building a house, who dug deep and laid the foundation on the rock. And when the flood arose, the stream beat vehemently against that house, and could not shake it, for it was founded on the rock..

Luke 6:48

 

[Useeeer]

Hi HTURKAK

Actually, I posted this in another thread and got responses as well. Thought of linking but the thread seems deleted.
Anyway, Thanks for your response.

Batter pile construction is ruled out siting difficulties in positioning and driving.

Rock anchor may be provided, depends on the pile test results (understand that rock anchor will be provided, if the presented toe level couldn't be reached).

One of the points looked at is, while driving itself some soil mass may be lost due to impact driving. According to my understanding, the moment at bed level should be balanced by the rotational capacity considering the socket length (which is not seen in present calculation)