The present study investigates the behaviour of sand under generalised compression loading. A stress path architecture is devised featuring the repetition of loading and unloading at constant η = q/p′ for a sequence of increasing ασ′1 and b = sin2ασ′1; where ασ′1 is the principal direction of stress, and b = \(\frac{{\left( {\sigma{\prime} 2 - \sigma{\prime} 3} \right)}}{{\left( {\sigma{\prime} 1 - \sigma{\prime} 3} \right)}}\) is the intermediate principal stress ratio. Irrecoverable volumetric and shear strains develop under compression with the former being considerably lower than the latter, exhibiting weaker variations with η and ασ′1. It is shown that the compression of pre-loaded sand at the same η but different ασ′1 induces non-coaxiality uncorrelated to excessive plastic contraction. The volumetric and shear strains increase when one of the planes of maximum stress obliquity aligns with the horizontal bedding plane. Furthermore, the compressibility, dεvol/dp′, oscillates with the increase in ασ′1 at constant η. The dilatancy, D = dεvol/dεq, varies from very large values to zero depending on the stress path and stress history. It is also shown that the variable dεq/dp′ normalises effectively both the non-coaxiality angle, ξ = αdε1-ασ′1, and the dilatancy, D. Specifically, a unique curve describes the relationship between ξ and dεq/dp′ for a given ασ′1 irrespective of η, p′, and ψ (state parameter). On the other hand, a unique curve describes the relationship between D and dεq/dp′ irrespective of the value of the variables η, ασ′1, b, p′, and ψ, and of the pre-shearing and pre-loading. This inverse proportion relationship indicates the decoupling of the incremental volumetric strains from the incremental shear strains in the compression mode.
