Herein is developed a fundamental solution to the problem of the expansion of a cylindrical cavity in a dilatant soil which exhibits effects of large strains. A result of some importance to geomechanics concerns the development of a shear stress‐strain curve for the tested soil by using the measured pressure‐cavity wall displacement response. It is shown that in order to develop the desired stress‐strain relationship for a dilatant soil it is necessary to introduce a kinematic constraint which relates the finite volumetric strain in the soil to the components of the Lagrangian strain matrix. Particular results are developed for the case where the volumetric strains vary linearly with the radial and circumferential Lagrangian strain components.