Abstract: Flow through fissures in rock mass applies simultaneously the normal hydrostatic seepage pressure and the tangent hauling force (the dynamic seepage pressure) on fissure walls. The equations for the hydrostatic seepage pressure and the hauling force and are proposed under three cases of single fissure without fillings, single fissure with fillings and water-filling flow. A computation example is also given to analyze quantitatively the double mechanical effects of fissure flow. It can be shown that both the hydrostatic seepage pressure and the hauling force make the stress components in rock mass bigger, and double mechanical effects of fissure flow should be taken into account in computing the stress in rock mass.

Key words: fissure flow, hydrostatic seepage pressure, hauling force, double mechanical effects