This article tries to impart some idea on the control and contingency issues of the LHC beam. For example:
The complexity means that repairs of any damaged equipment will take a long time. For example, it will take about 30 days to change a superconducting magnet. Then there is the question of damage if systems go wrong. The energy stored in the beams and magnets is more than twice the levels of other machines. That accumulated in the beam could, for example, melt 500 kg of copper. All of this means that the LHC machine must be protected at all costs. If an incident occurs during operation, it is critical that it is possible to determine what has happened and trace the cause. Moreover, operation should not resume if the machine is not back in a good working state.
So this is not case where you can just simply pull the switch if something goes wrong. They have to make sure they dump the beam properly without causing damage to all the components along the ring.
This is, of course, a common issue at large particle accelerator facilities, including the Tevatron. I am still at awed at some of the things they are able to do, and at the scale that they are doing in. I some time wish the most of the general public has some clue on the level of complexity and the accomplishments at just being able to run such an experiment.