Rock anchored bolt

[joseiochoam]

Dear John,

I would like to know if it is possible to simulate the anchoring of a bolt nailed into a rock. The rock would be at the bottom of the sea to anchor a 10 m boat, and since the bolt has been torn off after a storm (it has no deformations), the idea is to determine the maximum force that the assembly can support without the bolt sliding out (they forgot to put resin). In the hole drilled into the rock, I understand that we must of course apply friction, but I don't know if it is possible.

What type of analysis would be appropriate? In the drilled hole (bolt diameter is 16.1 mm) should there be some clearance between the rock and the bolt?

Please find below some images.

Many thanks!

[John_Holtz]

Hi @joseiochoam 

I suggest that you forget about trying an analysis with friction because:

• the initial conditions are unlikely to be known with any accuracy. What size is the hole (to the nearest 0.1 mm)? How straight is the hole? How straight is the bolt? What is holding the bolt in place if there was no resin? A minor change in any of those factors will change the answer. Thus, you need to do N analyses to get a range of answers.
• Perhaps you know how much force was required to put the bolt into the hole. Would the force to remove the bolt be the same?
• You can include friction in an analysis, but it makes the analysis 3 to 10 times more difficult. The way to get the answer with friction is to do the analysis to calculate only the normal contact force. Based on the normal force, you calculate the friction force by hand (= friction coefficient*normal force). N simple analyses (for all the variables) done in minutes instead of N complex analyses, each of which takes hours to complete.

John

[joseiochoam]

Dear John, as always, many thaks for your great help, and it is clear.

Regarding data 316L bolt is 16,1 mm diameter, bolt has 260 mm length, and drill hole in rock is 150 mm. For rock we consider calcita material.

As you said, I will calculate manually normal force 

Best regards

Jose