The paper reviews in summary form the generalised behaviour of soils under nonisothermal and chemically varying conditions. This generalised soil behaviour underlies the performance of a number of ground improvement techniques. The behaviour of frozen soil is examined first showing that some concepts of unsaturated soil mechanics appear to be readily applicable. Afterwards, the observation that volumetric behaviour of saturated and unsaturated soils at high temperature is similar, leads to the proposal of a combined constitutive law employing suction and temperature as additional constitutive variables. The paper closes with a review of the behaviour of soils under chemical actions and with the description of a constitutive model that accounts for the effects of cation exchange in expansive clays.