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Operations involving excavation of bedrock in large-scale civil engineering projects, or quarrying works for limestone or crushed rock can be broadly divided into two methods: blasting, and excavation using mechanical power. Ripping operation using bulldozers is typical example of the second method, and this method is superior because it is safe and does not cause pollutions. For this reason, its applicable range is being expanded including areas where the blasting method was being used. However, ripping operation using bulldozers demands a high level of training from the operator, and in addition to this, shoe slippage causes premature wear of the undercarriage and low fuel economy. The shoe slip control system that we have developed carries out sensing of the acceleration of the machine in forward and reverse directions, and sensing of the input / output speed of the torque converter, and in this way it always knows the traction and the slip ratio of the machine.

The users of construction machinery demand higher quality. It is especially difficult to satisfy them with large-size bulldozers designed according to conventional design concepts that is, a new design concept is required now. Komatsu is putting the D475A, built by fully redesigning the D455A bulldozer, on the market. When developing this model, its power-train system, undercarriage, frame, etc., were redesigned under a new concept that emphasized moving large amounts of soil effectively, and new structures were developed as a result. In this paper, the design concept of the D475A and the structure that attained that concept will be outlined.