The effect of tyres and a rubber track at high axle loads on soil compaction: part 3: comparison of virgin compression line approaches

Alternative approaches for deriving virgin compression line (VCL) parameters, and their suitability to predict soil displacement from part I and II of this paper series (Ansorge and Godwin, 2007 and Ansorge and Godwin, 2008) using the critical state soil mechanics model COMPSOIL, are presented. In particular, the in situ approach to determine a VCL from readily available tyre and soil data ( Ansorge & Godwin, 2008) was compared to triaxial cell test results. The results showed that a VCL was not a unique line with respect to mean normal pressure. The VCL was dependent on the relationship of minor and major principle stresses. Hence a triaxially derived VCL could only be successfully employed to predict the soil displacement if the relationship of minor and major principle stresses in the triaxial cell test represented those occurring in the field from the passage of a tyre. Subsequently the in situ approach was successfully employed using small scale plate sinkage tests further validating the entire approach and demonstrating the potential of a simple laboratory test to derive VCLs. Applying the in situ approach to soil displacement data from a rubber track showed that rubber tracks have different compaction behaviour than tyres. The rut depth of a rubber track was successfully predicted when the track roller body was modelled with tyres representing the pressure profile occurring underneath a track employing the in situ VCL derived from tyre only data. However, soil displacement at depth was significantly overestimated.