<p>In this typical image of rock fracturing, why do the joints / fissures occur where they do, as opposed to, say, along the line drawn in blue on the image?  More specifically, what characteristics of the rock grains on the separated joint surfaces result in a (relatively) planar joint surface?</p>
<p><a href="https://i.sstatic.net/DkLTw.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/DkLTw.jpg" alt="enter image description here" /></a></p>

CC BY-SA 4.0
2022-04-05T00:41:51.043Z
perhaps getting closer... "microfractures form in a process zone ahead of a propagating macrofracture."  So basically a large fracture forms by connecting smaller cracks in the rock ahead of it.  But again, why in such a regularly linear/planar fashion?  This would seem to imply that all the microfractures are magically lined up in a plane originally.
charlie_sar
CC BY-SA 4.0
2022-04-05T14:29:15.967Z
Reg your comment: no, same alignated fracture may occur also in metal materials, micro fracture can be randomly oriented.
For example, if you generate voids inside the materials, then you still get a planar/linear fracture:
https://www.researchgate.net/profile/Shakir-Gatea/publication/319937742/figure/fig1/AS:549392810561536@1507996861298/Schematic-of-nucleation-growth-and-coalescence-of-voids.png
EarlGrey
CC BY-SA 4.0
2022-04-11T14:35:39.567Z
"No" what?  the graphic you cite illustrates my hypothesis; the voids that develop are pre-aligned in a linear / planar fashion (from the very first step), then the fracture propagates along that plane.
charlie_sar
CC BY-SA 4.0
2022-04-11T15:02:52.187Z
no to "microfractures are magically aligned in a plane". They are distributed in the media, most likely with no dominant orientation, but their cumulative effect may results in the creation of empty volumes which are then "oriented" due to the interaction with the load acting on the rock at that time.
What you are asking can be explained with fracture mechanics, therefore by a specialist with knowledge which is acquired at PhD level... and on top of that you need very good skills at teaching and condensing it in an answer of readable size: sorry I am only 2/3 up to the task :)
EarlGrey
CC BY-SA 4.0
2022-04-11T15:04:40.933Z
please take all I wrote as "empty volumes" and "oriented" as broad approximation of reality, there is no exact knowledge in those wordings.
EarlGrey
<rocks>
Why does fracturing occur along a specific plane or region of the rock?
charlie_sar
# Why does fracturing occur along a specific plane or region of the rock?

(Asked by: username_0 on 2022-04-05)

In this typical image of rock fracturing, why do the joints / fissures occur where they do, as opposed to, say, along the line drawn in blue on the image? More specifically, what characteristics of the rock grains on the separated joint surfaces result in a (relatively) planar joint surface?

[![enter image description here](https://i.sstatic.net/DkLTw.jpg)](https://i.sstatic.net/DkLTw.jpg)

**Tags:** rocks

> **Comments:**
> **username_0**: perhaps getting closer... "microfractures form in a process zone ahead of a propagating macrofracture."  So basically a large fracture forms by connecting smaller cracks in the rock ahead of it.  But again, why in such a regularly linear/planar fashion?  This would seem to imply that all the microfractures are magically lined up in a plane originally.  
> **username_1**: Reg your comment: no, same alignated fracture may occur also in metal materials, micro fracture can be randomly oriented. For example, if you generate voids inside the materials, then you still get a planar/linear fracture: https://www.researchgate.net/profile/Shakir-Gatea/publication/319937742/figure/fig1/AS:549392810561536@1507996861298/Schematic-of-nucleation-growth-and-coalescence-of-voids.png  
> **username_0**: "No" what?  the graphic you cite illustrates my hypothesis; the voids that develop are pre-aligned in a linear / planar fashion (from the very first step), then the fracture propagates along that plane.  
> **username_1**: no to "microfractures are magically aligned in a plane". They are distributed in the media, most likely with no dominant orientation, but their cumulative effect may results in the creation of empty volumes which are then "oriented" due to the interaction with the load acting on the rock at that time. What you are asking can be explained with fracture mechanics, therefore by a specialist with knowledge which is acquired at PhD level... and on top of that you need very good skills at teaching and condensing it in an answer of readable size: sorry I am only 2/3 up to the task :)  
> **username_1**: please take all I wrote as "empty volumes" and "oriented" as broad approximation of reality, there is no exact knowledge in those wordings.  

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## 0 answers

