Bolt design in a mine..........Roof bolt

[Chen1]

Hello i am working on a project. i need to design a roof bolt for a coal mine. inside a mine, after removing the coal, the immediate roof will sag and break. the immediate roof is a layer of rock such as sandstone. so in the model we have coal which is overlain by sandstone and shale. I will use a pretension bolt. the length of this bolt is usually 6-8 ft.

the model is 3D, first i will remove some elements to simulate an excavation (cutting coal), the bolt should be deactivated at this stage, then i will activate the bolt. is it right? please correct me if i am wrong.

the problem is the mine is so big and i need to install roof bolt in that big area, and the model is 3D. i am thinking of running a global model then run a sub-model to focus only on a small area of the mine.

Hence, i need some tips about how to simulate that roof bolt and if whether you think that sub-model is a good idea or not to overcome the size of that big problem.

Thanks.

 

[Chen1]

any advice.

 

[mrgoldthorpe]

Chen,
Do a simpler 2D plane strain model first to sort out the issues and get some numbers for comparison. Then proceed to more complex 3D.

 

[mrgoldthorpe]

edit .... do an axiymmetric (2D) model

 

[Chen1]

Hell Mrgoldthorpe

Can i use Fastener instead of a bolt? You know i am still thinking how can i simulate that problem.

let me give you more details about my problem, when we mine a coal (this is an underground mine), the immediate roof which is a layer of rock such as shale breaks and fails, we use a steel bolt of length 8 or 6 ft, so we can hang or attach that layer (failed layer) to the upper strong layer.

i need to model different lengths and diameters of that roof bolt.

Again, is it ok if i use fastener. or i should use only bolt.

i am still reading in the manual, but your advice is highly appreciated.

Thanks a lot.