The grounding pressure under the action of weight of the vehicle in water and the maximum grounding pressure under the supporting rolls were measured. 28 sensitive soil pressure transducers were evenly embedded in simulated soft seabed sediments 25cm below the crawlers. The results have shown that the measured values of grounding pressure are distributed in the form of hump curve. The maximum grounding pressure, 11.6kPa, occurred at about 3.7m point, which lay under 11th supporting roller. The effects of backward displacement of center of vehicle gravity and nonlinear distribution of grounding specific pressure of vehicle crawlers on the traction force of the vehicle were theoretically calculated. Optimization of grounding specific pressure distribution by varying numbers of support rollers as well as pitch of track plates was carried out to enhance adhesion performance and trafficability of deep seabed vehicle on soft sediments.
Crawlers were made of a series of track plates connected with hinges. The hinges show flexibility so that the crawlers can adapt to the contour of the ground. However, the weight of the vehicle was transmitted to sediments via the supporting rollers to the crawlers. The supporting rollers cause concentrated load, which is called the maximum grounding pressure. The peak pressure occurring under track rollers was twice to thrice as high as nominal grounding pressure, or even higher, and the pressure between supporting rollers can be very low, or even close to zero. Thus, it was obviously inapplicable to use nominal grounding pressure to evaluate effects of vehicle on ground. Tests of Schreiner (Schreiner, 1967) proved that vehicles with same nominal grounding pressure, but different pressure distributions have quite different trafficability performance on soft ground. According to Rowland (1972), average maximum grounding, is used to be a value for evaluation of trafficability of vehicle on soft sediments.
