The first two pictures look like spiderwebbing of the chamber walls, not cracked cake. Either way, you're incinerating the walls of the chamber and yes, you will destroy your pipes if you don't significantly modify how you smoke them.
The pipes appear to be smoked way too hot and possibly too wet. That causes spiderwebbing and if not corrected, will eventually grow into cracks and splits.
Dry your tobacco a lot more. Pack it looser. Smoke slowly, puff to light then just sip. You'll get a hell of a lot more flavor out of what you smoke if you just simmer it rather than cremate it. If the pipe goes out, just relight. Use a soft flame, like a match or a BIC, not a torch. Torhes might be OK for cigars, but they burn pipes.
Don't try to burn every last shred of tobacco. You will do further damage. Toss the dottle out. It mostly tastes like crap anyway.
Or, you can continue on the way you're doing it and destroy your pipes.