Terramechanics

Terramechanics is the branch of soil mechanics that studies the interaction between mechanical vehicles and deformable terrain, with emphasis on granular soils such as sand, clay, and regolith. It aims to predict mobility, tractive performance, sinkage, and terrain response for wheeled and tracked platforms, informing vehicle design, control, and mission planning in off-road and extraterrestrial environments.

Key concepts include soil properties (density, moisture content, cohesion, internal friction angle), the distribution of contact pressure under wheels or tracks, and the formation of deformation and shear zones during motion. Frameworks such as Bekker's terramechanics relate pressure to sinkage and define shear strength criteria for soil under dynamic loading. Extensions address dynamic effects, cyclic loading, varying moisture, and scale effects. Mobility is governed by the balance between tractive effort and resistance from slip and sinkage.

Methods combine laboratory tests (direct shear, triaxial tests, controlled soil-bin experiments) with full-scale trials and numerical models, including finite element and discrete element methods. Empirical correlations and simulation tools are used to estimate maximum tractive effort, permissible slip, and expected sinkage for given wheel/track geometry and soil conditions.

Applications include the design and assessment of off-road military and civilian vehicles, heavy equipment, and planetary rovers. Terramechanics informs ground preparation, tire and tread design, track dynamics, and mobility strategies for operations on soft or uncertain terrain.

History and scope: the field originated in mid-20th century with work by M. G. Bekker and collaborators, expanding to modern computational approaches and space exploration challenges. Contemporary terramechanics integrates soil physics, vehicle dynamics, robotics, and planetary geology.