An investigation of thermo-osmosis in a saturated and chemically active rock such as shale is presented. The model presented is based on an existing coupled thermal, hydraulic and mechanical model (THM) for unsaturated soils. A simplified form of a coupled THM model for saturated porous medium is developed which considers the effect of solid-fluid thermal expansion and the effects of thermal osmosis in hydraulic behaviour. An example problem dealing with pore water pressure development in saturated shale rock surrounding the bentonite buffer installed around high-level nuclear waste canister emitting heat is presented. It is demonstrated that the heat input from the waste canister can affect the pore water pressure evolution in the shale. In particular, under the conditions considered, it is shown that thermally driven liquid water flow due to thermal osmosis contributes to the convective transport of dissolved species.