A one-dimensional model for premixed gas combustion in a rough tube (or in an inert porous matrix) accounting for the hydraulic resistance and molecular transport is considered. It is shown that the hydraulic resistance causes a gradual precompression and preheating of the unburned gas adjacent to the advancing deflagration which leads (after an extended induction period) to a localized thermal explosion triggering an abrupt transition from deflagration to detonation. The paper is an extension of a previous study of the problem, based on a reaction-diffusion-acoustics model, over a fully nonlinear formulation allowing for steepening of compression waves and formation of the shocks.