During the landing roll at a private airstrip, the airplane struck a sink hole and bounced 10 to 15 feet in the air. The pilot added power to cushion the next touchdown and the airplane drifted to the left. The airplane settled to the side of the runway. The pilot decided to land and reduced engine power. The airplane entered tall grass on the side of the runway and the landing gear was broken off. The airplane slid approximately 150 feet before coming to a stop on its belly. The pilot said he did not see the pot hole. The composite bulkhead around the landing gear was split. A postaccident examination of the airplane revealed no anomalies.