On March 31, 1998, at 1444 central standard time, a Cessna 310J, N3020L, received substantial damage following a loss of directional control during a planned aborted takeoff on runway 31 (7,001'x100') at the Hutchinson Municipal Airport, Hutchinson, Kansas. The instructional flight was being operated under 14 CFR Part 91. Neither the certified flight instructor (CFI) or the airline transport rated pilot (student) were injured. Visual meteorological conditions prevailed and no flight plan was filed. The flight was originating at the time of the accident. The CFI reported that they had planned to practice an aborted takeoff following a simulated failure of the right engine. He reported that the student was briefed on the procedure and was told which engine would be "failed." The CFI reported that the student initiated the takeoff, and at an airspeed of approximately 50 mph, the CFI pulled back the mixture on the right engine to simulate the engine failure. He continued to report, "[the student] appeared to initiate the correct aborted takeoff procedure by retarding the throttles to idle...." The CFI reported that when he saw the airplane tracking correctly he advanced the mixture for the right engine at which time the right engine "caught" veering the airplane off the left side of the runway. The CFI reported that he was unaware that the student had not reduced the throttle setting for the right engine during the aborted takeoff procedure. The airplane traveled into a soft grass area where the nose gear collapsed, damaging the firewall, and the airplane slid to a stop.