AbstractThe properties of non-planar (cylindrical and spherical) dust-acoustic solitary waves (DA SWs) and double layers (DLs) in an unmagnetised collisionless four-component dusty plasma, whose constituents are positively and negatively charged dust grains, super thermal electrons and Boltzmannian ions are investigated by deriving the modified Gardner (MG) equation. The well known reductive perturbation method is employed to derive the MG equation and solve it numerically to study the nonlinear features of the finite amplitude non-planar DA Gardner solitons (GSs) and DLs, which are shown to exist for κ around its critical value κc (where, κ is the super thermal parameter and κc is the value of κ corresponding to the vanishing of the nonlinear coefficient of the Korteweg-de Vries (K-dV) equation). It is seen that the properties of non-planar DA SWs and DLs are significantly differs in non-planar geometry from planar geometry. It is also found that the magnitude of the amplitude of positive and negative GSs decreases with κ and the width of positive and negative GSs increases with the increase of κ.