Assessment of the compaction effect and operational characteristics of a crawler tractor based on a rheological approach

BACKGROUND: At considering the issues of crawler tractors interaction with soil the determining factor is the time-varying impact of loads on the soil layer, its stressed and strained state, which, in turn, directly depends on its stress-strain properties. The properties assessment should be carried out with a rheological approach, which allows to explain many phenomena and processes and to develop new high technologies in terms of the criterion of minimizing the impact on the soil. AIMS: Studying the compacting ability of a crawler tractor in a configuration in various machine-tractor units, obtaining a curve for the effect of the traction load on the tractor hook, tractor speed and tractor mass redistribution over the lower track wheels on changes in soil compaction due to developing deformations, the coefficient of running resistance and skidding of the crawler-mounted mover. METHODS: The evoluation method for compaction impact of crawler-mounted mover on the soil layer was developed on the base of the previously constructed a general mathematical model for determining ways of reducing the compacting impact of crawler-mounted movers on the bearing surface, computer calculation programmes and the carried out assessment for the deformation development and changes of soil compaction under the crawler track. RESULTS: There are presented the simulation results of the process with an assessment of the developing dependences of the crawler tractor rut depth and its sliding on the travelling speed and on the displacement of the center of pressure at different loads on the hook, that obtained with the developed metod of analysis and the well-known theory of hereditary creep of elastic-visco-plastic materials. At the same time, the development of vertical and shear deformations of the soil layer in the area of lower track wheels impact is separately analyzed. The analysis of the constructed dependencies allows to identify a number of patterns for changes of compacting effect indicators of a crawler tractor on the soil with an assessment of the influence of the main design and technological parameters on them. It is established that taking into account the rheological characteristics of the soil layer and its state parameters permit significantly improve the accuracy of calculations for vertical and shear deformations of the soil layer and its final compaction after successive passes of the crawler lower track wheels. At the same time, the desired indicators behavior is ambiguously at passes of various lower track wheels. CONCLUSION: The conducted studies contribute to the optimal selection of parts for various machine-tractor units based on a specific crawler tractor, which perform the appropriate technological operations in certain conditions of work at specific parameters of the soil state.