×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Influence of Cement SAND in Pile Capacity

Influence of Cement SAND in Pile Capacity

Influence of Cement SAND in Pile Capacity

(OP)

Hi,

I'm working on pile capacity calculations over on carbonate soil for Container berth terminal construction. We are going to construct 580m length and 56m width berth. Berth have 6 grids with an equal width spacing of 11.5m expect the first grid. Pile diameter is 1.4m.

Each grids line hols 64 pile with centre to centre 9m approx spacing. The dredging level at A grid is - 14.5 which is followed by the slope 1:3 till the 6 grid.

Embedded length of piles in all grids by Calculating pile capacity is 30m. Reference Euro code 7 part-1 and Geotechnical characters have taken reference from Tomlinson 5th edition.

Considering the parameters Phi 38 deg by taking avg N value of 40. Laboratory test show 36 to 38 deg from direct shear. The design safe load is 1200 T for each pile

General Soil strata is 6 m Sand from top level followed by 9m cemented sand again 2.5m Sand followed by 2m cemented sand intermixed with Fragments of Falun which is followed 2m Sand underneath by 2m of cemented sand followed by 25m Sand.

The problem which I'm facing here is 5th & 6th grid pile foundation is placing over the Cemented Sand [Caco3 % varying from 30 to 60 %]. Increasing pile embedded depth will resolve this issue but it will affect over excess cost.

Will carbonate sand influences in reduction of end bearing capacity.

What will be the percentage of reduction will be there in Pile capacity?

Because as of now there is no exact design method for pile foundation in carbonate sand.

Kindly share your valuable feedback on this scenario if possible.

RE: Influence of Cement SAND in Pile Capacity

We found piles in Calcarenite (carbonate sandstone) all the time. I don’t see wha the big issue is? What are you afraid of cemented sand loosing its cohesion? If so, this is not an input in your pile design and if there is some loss of cohesion will it reduce your phi angle? Probably not. the shear box test you have done would have had no cohesion due to remoulding of the sand and as such your phi from your shear box should be somewhat reliable

RE: Influence of Cement SAND in Pile Capacity

(OP)
Carbonate soils differ in many ways from the siliceous sands. An important distinction is that the major constituent of carbonate soils is calcium carbonate which has a low hardness value compared to quartz, the predominant constituent of the silica rich sediments. Susceptibility of carbonate soils to disintegration (crushing) into smaller fractions at relatively low stress levels is partly attributed to this condition. Typically, carbonate soils have large inter-particle and intra-particle porosity resulting high void ratio and low density and hence are more compressible than soils from a silica deposit. A soil matrix which is predominately carbonate is more likely to undergo degradation due to crushing and compressibility of the material than soil which has low carbonate.
I would like to know how these crushability of calcareous sand will impact in reduction of pile capacity.

Vinothkumar S
Geotechnical Engineer

RE: Influence of Cement SAND in Pile Capacity

"Carbonate soils differ in many ways from the siliceous sands. An important distinction is that the major constituent of carbonate soils is calcium carbonate which has a low hardness value compared to quartz, the predominant constituent of the silica rich sediments. Susceptibility of carbonate soils to disintegration (crushing) into smaller fractions at relatively low stress levels is partly attributed to this condition. Typically, carbonate soils have large inter-particle and intra-particle porosity resulting high void ratio and low density and hence are more compressible than soils from a silica deposit. A soil matrix which is predominately carbonate is more likely to undergo degradation due to crushing and compressibility of the material than soil which has low carbonate."

The above seems to be a general comment from published text maybe not applicable to piles.

Get good core samples to check the material parameters as average N=40 is a weak rock/strong soil boundary. Do void ratio lab tests as well. How much stress/acid do you need to disintegrate the sample?

If you are too late and in design stage and if end bearing is a concern, I guess there is reason enough to increase the FoS to say 10 like we do in carbonate rocks if there are dissolution features from geological history. I doubt skin friction will be affected for design life.

If the ground is unstable maybe you need deeper piles/inject grout around piles.

Allow for test piles and loading pre-contract.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Resources

White Paper – Choosing the Right Spring Loaded Connector
In today’s cost-sensitive world, designers are often driven to specify the lowest cost solution for every aspect of their designs to ensure that their solution is competitively priced and their company remains profitable. However, specifying a low-cost, low-quality connector solution can result in premature failure, considerable re-work costs and damage to reputations. Download Now
eBook – Own the Lifecycle: Sustainable Business Transformation
Increasingly, product and services companies are seeking more information and control in the operational lifecycle of their products, including service and use. Better information about the operational lifecycle, and the ability to use that information, requires more than just unstructured data flowing back from products in the field. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close