The Tampa Colombia DC-8 operated on a cargo flight to Miami (MIA). The captain stated that during the landing rollout on runway 09R, while the airplane was at a speed of about 100-120 knots, and while the thrust reversers were deployed, the airplane began to lean and veer to the right. He said that he initially thought it may have been due to the crosswind, but he soon realized that the landing gear had collapsed. The captain estimated that when the airplane began to lean and veer it was positioned in the vicinity of taxiway T-2, and the airplane stopped in the vicinity of taxiway U. The flight crew then evacuated the airplane onto the taxiway via the L1 door slide. PROBABLE CAUSE: “Improper torque of a landing gear lockbolt by company maintenance personnel during landing gear installation.”