Requesting for Settlement criteria of Minerals Stock Pile

[vinothsekar]

Dear all,

We AFCONS Infrastructure Limited has been awarded by Terminal Industrial Polyvalent de San Pedro (TIPSP, the Employer) the EPC contract to construct and expand the dry bulk terminal at the Port of San Pedro in Ivory Coast.

2 berths, revetment, dredging, onshore structures and reclamation are planned in Phase 1 and
Phase 2 of the project. In Phase 1, the terminal will be developed for
1) Berth 1 area
2) Stockpile areas
3) Buildings
4) Truck Parking areas
5) Berth 2 interface and revetment
6) Workshop
7) Rigid pavement on landside and reclamation, and
8) Other areas near workshop

In this connection, limiting settlement criteria(50mm for 50 years for all developements)are proposed by the owners for different developments. Our consultant has come up with a different set of limiting settlement criteria for these units considering the tolerance of these units to differential settlement.

ZONE 3 Structure (Pink) AREA AREA LOAD SETTLEMENT CRITERIA
m² (Ha) (kPa) ER COWI
3A TRUCK PARKING - 1 2160 0.22 25 50 50
3B STOCK PILE 2200 0.22 100 50 300
3C TRUCK PARKING - 2 1020 0.10 25 50 50
3D WORKSHOP AREA 4875 0.49 70 50 50
3E NON-BERTH REVETMENT 13000 1.30 10 50 200
3F RIGID PAVEMENT ON 9460 0.94 25 50 50
3G BERTH-2 INTERFACE 1750 0.18 10 50 200
3H BERTH-2 REVETMENT 1100 0.11 10 50 200
3J OTHER AREAS 980 0.10 10 50 200
3K TRUCK PARKING 1200 0.12 25 50 50
TOTAL 37745 3.78

Average loading details are worked out for each development. Our consultant estimated settlements of founding soil under these loads and recommended rigid inclusion (Controlled modulus column) ground improvement schemes.

I would like to know that what is the global settlement criteria for mineral stock pile over the year. I am requesting to review and advice on the settlement criteria with reference or any code provision to defend my client by saying that proposed criteria by client is very stringent to non sensitive structures like stock pile and revetment.

Thank you in advance for your immediate response to this request.

Vinothkumar S
Geotechnical Engineer

 

[EireChch]

Where do I send my invoice?

 

[oldestguy]

So the stockpile settles. Unless there is a significant shear failure, who will know it settles? Unless there is something nearby that will see damage, I'd say you will meet the specs, but won't be measuring elevations to a movable stock pile.

 

[vinothsekar]

To oldestguy - Based on settlement calculation with reference to geotechnical investigation data, we have computed and measured the total settlement will go up to 850mm and it can be restricted upto 300 mm settlement after ground improvement such as CMC with minimum spacing of 2m with 450 mm column and 15m depth of improvement.

The particular 3B location from my previous attachment, the soil strata follows as +4.0m to -2.0m Medium SAND which underneath by very soft clay (shear strength <20kPa) from -2m to -4m which is followed by fine to medium SAND from -4m to -6m which is followed by Soft clay from -6m to -10 m which is underneath by medium to dense SAND from -10m to -20m.

By practically saying, Its quite difficult for us to limit the settlement within 50 mm for 10m height Magnesium Ores stock pile with dead load of 10 t/m2.

I just want to know that is there any settlement criteria or reference note to address the minerals stock pile to defend my client.

Vinothkumar S
Geotechnical Engineer

 

[oldestguy]

It may not be just settlement you should be concerned with. With weak layer, you may have a significant slip out failure. It may limit you not only to height limit but also side slopes of the pile. A geotechnical investigation and report of that stability (question) may be worth while.

 

[vinothsekar]

We have taken all consideration including slope stability FS>1.5 in the revetment and other structures. we have calculated the possibility of sliding away the soil between consecutive columns – 2 to 3 m of shear failure zone which is okay in the replacement ratio of Controlled modulus column.

There is no constrains to do construction except the settlement criteria to limit with 50mm. I can achieve only 300mm for stock pile after CMC improvement. I really looking for reference of mineral stock pile settlement criteria.

Vinothkumar S
Geotechnical Engineer

 

[r13]

Excavate a deep stockpile pit down to an elevation that will produce tolerable settlement.

 

[vinothsekar]

Soft clay is situated in the deeper depth. So excavation is not a good solution to limit the settlement.

Vinothkumar S
Geotechnical Engineer

 

[r13]

I think dummy soil theory shall work. Also, the settlement will be underground, nothing to damage, who will notice/care?

 

[oldestguy]

Quote:

I would like to know that what is the global settlement criteria for mineral stock pile over the year. I am requesting to review and advice on the settlement criteria with reference or any code provision to defend my client by saying that proposed criteria by client is very stringent to non sensitive structures like stock pile and revetment.


I have been in geotechnical engineering since 1956 or so and active until 5 years ago. In all that time I have never been requested to be involved with such as question about settlement due to a stockpile. I suggest you go to the client and explain this is a totally unusual requirement as to limiting settlement for a stock pile. Someone there is totally inexperienced and that tells me I would walk away from this potential job They are likely to cause all sorts o9f unneeded expense in the future. Tell them "good bye".

 

[SlideRuleEra]

I just want to know that is there any settlement criteria or reference note to address the minerals stock pile to defend my client.

I know nothing about magnesium ore stockpiles, but do have experience with large coal stockpiles at our electric generating stations.
A coal stockpile is not static, material is added and removed continuously. When the stockpile is being used to it's limits (say, during a railroad or mine strike), there must be provisions to keep a mix of soil/coal from being recovered. To do this, we have a significant sacrificial layer of (low grade) coal which is never (intentionally) recovered. This sacrificial layer is, if I remember correctly, about 300 mm thick.

My point is, if a sacrificial layer is used with magnesium ore, perhaps the thickness of this layer could be considered as acceptable settlement. Maybe you can find out.

http://www.SlideRuleEra.net

 

[vinothsekar]

To - Oldestguy
Thanks for your straight forward reply towards my request. Since there are many consultant and client are just limit their criteria during the tender without having enough Geotechnical information. We have awarded this EPC project by underestimating the ground improvement activities. I am appreciating for your valuable time toward my request. Thank you. I am looking forward your guidance in my future.

TO - Sliderule era

I have hinted with same information from our ground improvement vendor stating that maximum settlement (300mm) volume of mineral ore will be consider as sacrificial quantity and even we can convince client by paying back the total volume of mineral ore which is going to settle in future as per design calculation in per cubic meter. Thanks for your valuable suggestion.

Vinothkumar S
Geotechnical Engineer

 

[oldestguy]

If you really wish to know the volume of sacrificial material do this. Before placing the mineral material place a few settlement platforms. Such a thing can be a simple plate of plywood at least one meter square. Attach a threaded pipe flat fitting to the plywood and thread into this a pipe of say 5 cm internal diameter. Keep track of pipe length and periodically measure the elevation of the pipe. As the pile gets higher add known lengths f pipe. With this record you can see how much settlement you have.

 

[vinothsekar]

Oldest Guy - Thanks for your suggestion. In my reclamation yard we have installed settlement platform 1m*1m steel plate at bottom and connected with 3cm pipe to certain elevation to measure the total settlement due to 4.5m height reclamation sand fill on the backyard area. The maximum settlement we have observed is 57mm. Please see the attached of preloading in the back yard area.

Vinothkumar S
Geotechnical Engineer

 

[vinothsekar]

Retired13

Could please share the link for dummy soil theory.

Vinothkumar S
Geotechnical Engineer

 

[r13]

The name sounds elegant, actually the theory is just a simple fact - due to weight, there is overburden stress at any depth below grade. If we excavate to the point of interest at a depth, and replace with equal weight material within a short duration, the soil will not know the change. I think this phenomenon can help you to increase the volume of the stockpile without adverse effect, though may not be cheap.