On August 4, 1994, about 1405 Pacific daylight time, a Stinson 108-3, N6276M, operated by the owner/pilot, was substantially damaged during a precautionary landing in Bend, Oregon. The private pilot, the sole occupant, received minor injuries. Visual meteorological conditions prevailed and a VFR flight plan was not filed. The personal flight departed from Sunriver, Oregon, and was conducted under 14 CFR 91. According to the pilot during an interview one day after the accident, light and variable winds were reported by the unicom frequency after the pilot requested an airport advisory for landing at the Bend Municipal Airport. The pilot stated that she approached runway 34, touched down, bounced, and decided to execute a go-around. She entered downwind for runway 34 again, and then decided to land on runway 16 instead. She "...overshot the runway" during the approach and executed another go-around. The pilot stated that she raised the flaps during the go-around, but could not remember cutting off the carburetor heat. The pilot stated that the airplane was not climbing and the engine could not generate full power. In a written statement, she stated that she was "scared" at this time, so she performed a precautionary landing in a field. During the landing, the landing gear collapsed as the airplane rolled along rough terrain and was substantially damaged. An examination of the engine (report attached) by an FAA aviation safety inspector from Hillsboro, Oregon, did not reveal any evidence of a pre-impact mechanical malfunction. The examination also revealed that the carburetor heat valve was found in the open position.