ABSTRACT:

This paper is concerned with an experimental investigation about tractive performance of a tracked vehicle on extremely soft soil. A tracked vehicle model with principal dimensions of 0.9m × 0.8m and the weight of 144kg was constructed with a pair of driving chain links driven by two AC-servo motors. The tracks are configured with detachable grousers, of which the span can be varied. Deep seabed was simulated by means of bentonite-water mixture in a soil bin of 6.0 m × 3.7m. Slip of vehicle and torque of motor were measured with respect to experimental variables; grouser span, grouser chevron angle, driving speed, drawbarpull weight, center of gravity and weight. L8 orthogonal table is adopted for DOE(Design Of Experiment). The effects of experiment variables on traction performance are evaluated.

INTRODUCTION

In order to get the basic information for the design of a vehicle running on deep seabed, experiments of a vehicle model were performed on extremely soft and cohesive soil. The shear strength of soil is varying in deep-seabed. The maximum shear strength is about 3.0 - 10 kPa under 10 cm below seabed surface and its sensitivity is about 2.7 in the Clarion- Clipperton Fracture Zone (CCFZ) of the Pacific Ocean (Chi, 1999). Low contact pressure and high tractive force make tracked vehicles to be preferable to the other types for soft soil. There are many studies on tracked vehicle on soft bottom: Dugoff (1966) conducted studies in a water soil bin for a tracked vehicle model to bury cable in the seabed. Muro(1983, 1989) studied on the trafficability of a tracked vehicle on very soft bottom and investigated grouser effects on tractive performance of a bulldozer running on soft marine sediment. Dörfler (1991) performed drawbar pull tests of a tracked vehicle on simulated cohesive soil.

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