Most ornamental grasses will bounce back easily and even thrive when they are dug, divided and replanted. Excavation of large, established grass clumps is the most challenging aspect of this process, but it can be accomplished if you maintain patience and spend plenty of time digging. Divide grasses in the spring or early fall to reduce the stress on the plants.
Excavate the soil around the root ball of your clump of grass with a shovel. Your goal is to limit the damage to the roots of the plant. Start digging outside of the drip line of the grass clump. If you see numerous or large roots move a little farther away from the center of the grass clump and dig there.
Dig straight down until you can get under the main root mass or taproot of the grass and then begin to dig under the clump to free it. Lift the clump up and out of the excavation hole using your shovel as a gentle lever. Set the ball on flat stable soil or surface where you can easily operate on it. Inspect for any roots that were badly damaged in the excavation process.
Using a garden knife or a spade make vertical cuts down through the grass tops and roots to divide the clump into smaller plants. Each new plant must include healthy top foliage and healthy roots. Divide the clumps into plugs of a few inches wide up to a foot wide for larger grass clumps, depending on how wide an area you want to spread the new plants over.
Replant each new smaller clump in loose, well-tilled soil immediately so the roots don't dry out. Maintain the same planting depth in the soil at which the clump had been growing. Tamp soil around each clump to secure the grass in an upright position and make good soil to root contact.
Water each transplanted clump deeply at planting and then water lightly every other day for a week. This will help reduce stress on the grass. Resume your usual watering schedule thereafter.