Your pansies are experiencing frost heave. Their root balls likely were growing in their pots in a soil mix high in organic matter. When they were placed in the ground, there was a strong difference in soil types between their root ball and the surrounding soil. As the ground freezes and thaws, the soil expands and contracts. Differing soil types lead to different rates of expansion and contraction. In the process, the pansies' roots were pushed up and out of the ground. If the expelled root balls haven't dried out, you may be able to save the plants by poking them back into the ground. Of course, the root systems of these root balls are limited, so treat them as brand-new plantings, watering as necessary. To prevent frost heave from happening again, cover the soil with a couple of inches of organic mulch. The insulating effect of the mulch diminishes the effects of rapid temperature changes. Once the ground becomes frozen it will more likely stay frozen beneath the mulch until sustained warm temperatures arrive.