Analysis on Strength of Fractured Rock Mass under Seepage Pressure

Abstract

According to the rapture mechanics, model of fractured rock mass under crevice water pressure is established to deduce the formula of stress intensity factor at the cracks tip under mutual effect of remote stress and seepage pressure by superposition principle based on which the mutual effect of adjacent cracks is further studied. The result shows that, the mutual effect of cracks have large effect on the stress field of crack tip if the intervals of cracks are small. There are two effect zones after different superposition of stress fields, that is, reinforcing zone and receding zone of stress intensity. When adjacent cracks’ tips are located in reinforcing zone, the stress intensity factor of the crack will grow or reduce if opposite. The mutual effect of cracks is concerned with the interval between, as the interval grows, the intensity factor tents to a constant which is considered as intensity factor of single crack without mutual effect of cracks. Therefore, when the interval is larger than the length of cracks, mutual effect of adjacent cracks can be ignored. Meanwhile, the seepage pressure effect the stress field at the tip of cracks obviously. The KI of each crack tip grow while the seepage pressure grows (-KI reduce), this demonstrates that seepage pressure counterbalanced part of the normal stress at the crack surface, which provides theoretical basis of establishing Rupture instability mechanism of fractured rock mess under seepage pressure.