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Title: Small-Scale Mobility Tests in Fine-Grained Layered Soils
Authors: Swanson, Gary D., 1960-
Patin, Thomas R.
Mobility and Environmental Systems Laboratory (U.S.)
Keywords: Trafficability
Publisher: U.S. Army Engineer Waterways Experiment Station
Series/Report no.: Technial Report (U.S. Army Engineer Waterways Experiment Station);no. M-75-1
Abstract: Laboratory single-wheel tests were conducted with a 2.50-4 tire on uniform fine-grained soil and on two conditions of thick-layered, fine-grained soils: condition I in which a soft layer was placed over a firm layer, and condition II in which a firm layer was placed over a soft one. In both cases, the smallest ratio of layer thickness to tire width tested was 0.33. The results of the baseline tests on uniform soil showed that the WES numeric prediction system, which had not hitherto been used for such a small tire, will predict the performance of the small tire as accurately as it predicts the performance of a large tire. The system also can be used in predictions for layered-soil systems, if the soil strength of the top layer is used in the numeric and as long as the lower layer is relatively strong in relation to tire loading. When the soft upper layer becomes thin, the primary phenomenon is lubrication of the firm lower layer by the soft upper layer, and a different mechanism is involved. When a relatively thick soft layer overlies a hard one, the change in pull performance increases as tire deflection is decreased for a given top-layer thickness and wheel load. As values of the clay mobility number increase, the critical thickness of the top soil layer decreases and the change in pull performance decreases. Torque performance does not change with the ratio of top-layer thickness to tire section width. When a hard layer overlies a soft one, pull and torque performance show slight tendencies to decrease with thickness of the top layer. Torque requirements increase when the tire breaks through the hard layer into the underlying soft layer. Generally, it is suggested that efforts be directed toward investigations of thin-layered soil systems instead of pursuing further the problem of thick-layered soil systems.
Description: Technical Report
Gov't Doc #: Technical Report M-75-1
Rights: Approved for public release; distribution is unlimited
Size: 80 pages / 7.323Mb
Types of Materials: PDF/A
Appears in Collections:Technical Report

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