How does a drain line disconnect from where it goes into the ground?

Break in line??
A physical force is involved to move that force. Mass verses weight and speed the "For every action there is an equal and opposite reaction" I'm not trying to be smart but the question is missing a lot and if not above is the answer.
Old clay pipe belled shifted/moved/sunk in ground.
Big truck crushed line in ground.
Please need better info! What actually is the problem you are having so I can help and give you a good answer The "HOW' needs to be HAVE a etc
Signed 21 boat

21boat is correct. This also happens very often in areas with seismic activities.