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Drop Box Design

Drop Box Design

Drop Box Design


I am looking for references on the design of drop boxes.  Guide lines for diameter depth of pool and erosion issues.

Does anybody have any experience with drop boxes?

RE: Drop Box Design

It has been a bit since I dropped in to look through some of the queries.  Hope this still is timely.

1. What material are you dropping?  Ore, aggregate or binder (types, gradation), slurry (percent solids, grind), liquid?

2. What is your drop height and conduit size/shape?

Since you mention pool, I gather you are dealing with slurry and/or liquid.  Are you after stilling basin layouts and such or tails drop boxes?

There's a lot of mixed terminology these days, thus my questions.

RE: Drop Box Design

Hello Backfill,

The service is a tailings line from a molybdenum flotation circuit.

P80=275 micron
37% solids by weight
SGmixture = 1.37
2300 cu.m/h
approximately 33% fines
Carrier - water

The slurry is pumped from a pump box over a haul road to run along a flat pipe bed.  Once outside of the plant boundaries (elevation 1440 m) the pipe bed slopes down at approximately 1.6% for 500m then 3.5% for another 1000 m to an elevation of 1410m.

From this elevation the slope is 12% down to a starting 1340 m and the crest of the tailings dam where the line feeds a dewatering cyclone.  The crest of the dam will grow over time.

I am considering a series of boxes to dissipate excess head in the system.

The slurry would flow into the top of the box and then exit through a gravity pipe near the bottom of the box.


RE: Drop Box Design

Our background and experience with tails is primarily stability, hydrology, liner systems and subaerial deposition.  My observance has been that drop boxes generally are three to four pipe diameters, with the outlet two to three box diameters above the sill (floor) of the box. The pipe runs themselves should be designed to balance settling and wear. I have seen non-technical references to -1%, but it's wise to run the numbers based on existing or expected settling characteristics.

A good place to start might be at http://www.tailings.info, which is managed by the folks over at Leeds University.  A pertinent text they reference is:
Vick, S. G. (1990). Planning, design, and analysis of tailings dams. Vancouver, BiTech.ISBN: 0921095120.2nd Edition.xi, 369

I see that his work is a primary basis for an EPA document I have used in the past, in disciplines or areas I mentioned at the top of my reply.  On that note, I would encourage looking over the rest of his work.

Hope this helps.  Sorry my own data is anecdotal at best.


Ralph R. Sacrison
Sacrison Engineering

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