## Design of a plate with Impact Load from a Rock

## Design of a plate with Impact Load from a Rock

(OP)

Hi,

Here is my scenario; I have a rock bin (a bin made of rock for rocks, yes it is in an underground mine) with a hopper and chute at the bottom discharging to a conveyor.

We want to install a plate at the bottom of the bin to block any rock entry in the chute.

I am using a worst-case scenario for the impact caused by a falling rock on the protective plate. (max height, max size, maximum impact in the normal axe)

What I know : rock size and max velocity at impact.

What I do not know : Modulus of Elasticity of rock

Assumption; rock will absorb 0 energy

Here are the formulas and steps I am using to design the plate:

1. I am calculating the

https://www.engineersedge.com/calculators/uniform_...

2. With the

https://www.engineersedge.com/calculators/uniform_...

3. With the Impact Load Formula, subbing the

If the

Is my thinking correct? Am I over-simplifying?

I have read a couple of threads on the subject (84200, 74498, 36240 & 77905) but I have not found the steps to be a 100% clear to my linking. I am thinking, hopper, chute and bin’s engineers must do those calculations often, and a straightforward process to achieve those designs must exist. Please let me know if I have to take out my pink glasses.

Also, please note that I am limited resource wise with Mark’s Standard Handbook for Mechanical Engineers, Handbook of Steel Construction (CISC) and google search. So please do not send me a reference of a book I have to purchase and me trying for hours to find a bypass to acquire the said book

Thanks!

Here is my scenario; I have a rock bin (a bin made of rock for rocks, yes it is in an underground mine) with a hopper and chute at the bottom discharging to a conveyor.

We want to install a plate at the bottom of the bin to block any rock entry in the chute.

I am using a worst-case scenario for the impact caused by a falling rock on the protective plate. (max height, max size, maximum impact in the normal axe)

What I know : rock size and max velocity at impact.

What I do not know : Modulus of Elasticity of rock

Assumption; rock will absorb 0 energy

Here are the formulas and steps I am using to design the plate:

1. I am calculating the

*maximum allowable Force*from the Impact using stress on a plate formula and the*Steel Yield Strength*:https://www.engineersedge.com/calculators/uniform_...

2. With the

*Max Allowable Force*found in step 1, I calculate the*deflection*:https://www.engineersedge.com/calculators/uniform_...

3. With the Impact Load Formula, subbing the

*deflection*found from step 2 as the*travelling distance*, I calculate a*theoretical impact load*.If the

*theoretical impact load*calculated in step 3 is higher than the*allowable force*calculated in step 1, I re-iterate the steps with a thicker plate until I achieve a*theoretical impact load*with security factor lower than the*allowable force*. (Next steps is to optimized with stiffeners, but I am not quite there yet)Is my thinking correct? Am I over-simplifying?

I have read a couple of threads on the subject (84200, 74498, 36240 & 77905) but I have not found the steps to be a 100% clear to my linking. I am thinking, hopper, chute and bin’s engineers must do those calculations often, and a straightforward process to achieve those designs must exist. Please let me know if I have to take out my pink glasses.

Also, please note that I am limited resource wise with Mark’s Standard Handbook for Mechanical Engineers, Handbook of Steel Construction (CISC) and google search. So please do not send me a reference of a book I have to purchase and me trying for hours to find a bypass to acquire the said book

Thanks!

## RE: Design of a plate with Impact Load from a Rock

## RE: Design of a plate with Impact Load from a Rock

## RE: Design of a plate with Impact Load from a Rock

## RE: Design of a plate with Impact Load from a Rock

BTW, I think Miningman's comments are just you need.

## RE: Design of a plate with Impact Load from a Rock

After you get x then the maximum instantaneous force is

Now you can calculate the stresses using the max allowable stress formula.

Using the same set of formulae you have used

But keep in mind, the stiffness may be higher if point of impact is closer to the edges. Also details of plate support should tally with the model considered.

Engineers, think what we have done to the environment !https://www.linkedin.com/in/goutam-das-59743b30/

## RE: Design of a plate with Impact Load from a Rock

Can you explain? Is this reinforcing or material added for wear resistance? I've not heard the term before. Thanks...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

## RE: Design of a plate with Impact Load from a Rock

## RE: Design of a plate with Impact Load from a Rock

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

## RE: Design of a plate with Impact Load from a Rock

@Miningman,

The bin is a 40ft height in verticality (not true verticality, as 25years of ops tends to shape a wall).

The bin constricts at the end (the hopper) to fit the chute, which feeds the conveyor. Only the hopper and the chute is lined, the vertical walls is straight on rocks with fragments on what use to be ground support rods (rebars). Problem is we have to empty the bin if we want to install a protective plate and protect any rocks from entering the chute.

The big idea here, and as you work in the mining field you might have another option to propose, is to secure the discharge chute to be able to change the liners. We use to completely empty and clean the bin, sending workers with the jackhammer and the high-pressure hose, but rising safety concerns put a stop to that.

Other alternative:

Shortcrete is a month shutdown of the bin, and does not last from shutdown to shutdown.

Liner Handlers: I am testing the water with suppliers

Head Cover : contractors use them for ore bins but that's not what they were design for.

@Goutam Freelance

Thank you very much for the information! I will explore with those.

## RE: Design of a plate with Impact Load from a Rock

## RE: Design of a plate with Impact Load from a Rock

Dear IGSAM , I did not look in detail to the previous responds and am not in a position being offensive to any of the responders however, with procedure you want to follow , you may get undesirable plate thickness. If the theoretical impact load calculated in step 3 is higher than the allowable force calculated in step 1 , you will increase the plate thick. and you will get higher impact load than the previous iteration. I will not suggest to follow... I did not look in detail the previous responds , but apparently the applicable impact load based on energy approach is not mentioned.

Let me explain some concepts;

-If the drop object and the supporting ( beam, rod , in this case plate) fully elastic and no energy dissipation, the dynamic load is a function of static deflection

Pdyn = W ( 1 + SQRT (1+2h/ Δst) W = weight falling from a height h. Δst = is the static deflection for the weight W.

- The following snap from the Roark’s Formulas for Stress and Strain based on the above formula..

di and σi are deformation and stress for the impact loading.

- In your case, restitution for natural rock and friction with the surface reduces the impact stress. With a conservative assumption , spherical rock striking to elastic surface ;

The above is a snap from the book Formulas for mechanical and structural shock and impact by Szuladzinski .

You may provide more detail to get better responds. Getting a thicker plate is not always the solution.

Good Luck..

## RE: Design of a plate with Impact Load from a Rock

How is the rock flow to conveyor controlled during operations? I assume either a vibrating feeder or is the conveyor a belt feeder?

## RE: Design of a plate with Impact Load from a Rock

all impact calc devolve to answering the question "how long is the impact (time interval) ?" "how long does it take for the falling/moving object to come to rest ?"

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