Abstract: Hydraulic fracturing caused by high confined water is the root cause of water inrush in roadway. The discrete element fluid-solid coupling algorithm was improved， and the action mode of fluid channel length and water pressure on particles was updated. The interaction between the hydro-splitting fractures (HFs) and the weak planes (WPs) was simulated. Five different modes were obtained and the critical pressure values were calculated. The displacement， contact force of the specimen and the various of the stress at a specific point were analyzed. The research shows that: 1) with a constant injection pressure， the pressure value is the largest at the initial crack， then gradually decreases along the crack. 2) the displacement response are different under five interaction modes. The normal contact force has obvious vertical dominant surface in its contact direction， and the shear contact force generates four vertical dominant distribution directions. 3) the stress at Mc1 changes dramatically during the initiation stage， and the maxmium principal is always compressive. Stress response in Mc2 is relatively hysteretic. The diversity of principal stress is fundamentally determined by the interaction mode between HFs and WPs.

Key words: particle flow code(PFC); fluid-solid coupling; hydraulic fracturing; displacement response; maximum principal stress