Seismic bearing capacity approach for vehicle mobility problems

Abstract

This thesis introduces a new approach in soil-vehicle interaction analysis for quick determination of vehicle mobility in off-road conditions. Geotechnical analysis for the problems of vehicle-soil interaction is an almost unmentioned subject in literature because of the extraordinariness and the complexity of the situation. Here, the aim is to transform the problem into well-known and more comprehensible geotechnical issue which is bearing capacity of soils. The main argument is that there is a strong mechanical analogy between two distinct problems, namely, the behavior of the soil under seismic activity and the behavior of the soil beneath a mobile vehicle. According to this approach, the tracks or the wheels of an off-road vehicle correspond to the footings of a structure, the traction loads corresponds to horizontal loads of the structure during an earthquake and the seismic degradation of the soil strength under seismic loads corresponds to the difference between bearing capacities of soil of a sloped and soil of a horizontal ground. The decrease in the bearing capacity of the soil on a slope and beneath a mobile vehicle is defined by introducing a mobility reduction factor. This reduction factor covers strength loss of soil due to both tractive force and inclination of the ground. The mobility reduction factors for each component of the bearing capacity equation are derived on the basis of seismic fluidization concept. The whole theoretical works are assambled on a computer program and results for various types of terrains and vehicles are presented.