Study Of Mechanics Of Water Pressure Action In Hard Roof

Strata behaviors of working face of hard roof are violent. The hard roof hangs oneself from a beam in a large area and does not collapse. The roof collapse in a large area often seriously damage the surports, staffs and facilities, even minequakes happen. So, it is important to study and learn hard roof controlling theory and technique. The paper deeply studies mechanics of water pressure action in hard roof by theory analysis and numerical simulation. The main conclusions are drawn as follows:(1) Based on the chemical damage in water-rock interaction, the influence on rock strength of water is analyzed. Water chemical damage model is established. Water effects on strength of rock come down to scale effect and mechanics effect. Given the new criterion under water action, the criterion quantitatively reflects the effect degree of pressure water and fracture strength of rock masses.(2) Using penetration theory and basing on performance equivalence principle, which determine the permeability coefficient of equivalent and continuous dielectric. Based on the theory of fluid-solid coupling, coupling of seepage and stress of rock mass by water-infusion is analyzed, and control equation is established by using the finite element method.(3) The paper mainly applies the theory of fracture mechanics to analyze the mechanism of hydrobreakage to directive stratifications. The caving distance and thickness and pressure of hard roof decrease by directive stratifications.(4) By numerical simulation of water- infusion softening roof, it can approve action of high-pressure water-injection method to hard roof. We can consider water-infusion softening method as an effective method.