I assume that you know that any pad left on the ground will grow into another cactus. Thus, you must get it ALL.
How are you planning on proceeding? What kind of ground do you have? Rocky or dirt?
You can get a excellent kill on pear using herbicide.. it just takes a while for it to become obvious that you got it and for it to wilt down into the ground. Several passes a couple of months apart after you can tell which plants are hit and which are still healthy will get you there... 3 years later, it'll all be melted into the ground.
Me, I'd spray unless I needed it physically removed quickly.
Then, I'd do the job with two people, one on a tractor, the other with a long tine pichfork to pick up all the pads and pile them immediately into a flat bed trailer. If in dirt, I'd use FEL to slice just below ground level and get the cactus, roots and all. If in rocky ground, I'd use a toothbar on the FEL.
Herbicide actually works better on plants that have been physically damaged. Thus, you could do the physical removal, then spray the remains, plant by plant.
I've sprayed for cactus, never tried to do wholesale removal physically, except by hand labor and a grubbing hoe... an approach recommended only for the younger generation seeking exercise to lose weight. Best to do this in winter when the rattle snakes are not as active.
