Research On Seepage-stress Coupling Test Of Fractured Maokou Limestone

Fractured rock mass widely exists in the nature, which has hidden damage. The exist and change of seepage field is one of important reasons for the instability of ock masses engineering. Even leads to large-scale geological disasters. At present, laboratory experimental is a indispensable important study technical mean for esearch of the fractured rock mass permeability properties,The research for seepage-stress coupling experiment is based on Maokou limestone in this paper. Test samples were cored from Hunan Ningxiang coal dam, and they were all rocessed into Φ50×100mm according to the rock mechanics recommended standards. First of all, Fractured Maokou limestone samples were obtained by split test of the ntact rock on RYL-600 shear rheometer, and then some of them were used to onducted the cycling loading and unloading test. Second, some of fractured samples vere performed for seepage-stress coupling experiment on the MTS815 rock nechanics test system, test characteristics were studied under the test. Based on the ibove experimental study and got the following conclusions:(1)The cycling loading and unloading test under the action of same normal stress vere completed at first. Results show that the fracture normal closure increased as pading cycles, but the final fracture is not closed completely, and there are certain racture, this is the so-called crack residual closure.(2) The same fracture rock sample was performed for seepage and stress oupling test under same axial compression and different confining pressure. The esults showed:1) the permeability coefficient decreases continuously under the ame axial compression effect and the increase of confining pressure. Volume stress, permeability coefficient and pore pressure meet the exponential law relationship petter.2) The greater the fracture apertures, the greater the permeability coefficient. ) The fissure flow of Maokou limestone does not meet the Darcy flow, having non )arcy effect. Under the condition of constant axial pressure, non Darcy effect ncreased as the increase of confining pressure.4) The permeability of non Darcy low is higher than Darcy flow under the same load.5) Circumferential displacement ind pore pressure has positive correlation relationship in the process of rock seepage. Pore pressure changed greatly, so does the circumferential displacement.6) Fissure flow of Maokou limestone meet groove model. Test data consistent with the heoretical calculation data. MATLAB software, and compared with seepage test results, the results show that under the same crack width, bigger fractal dimension has higher permeability coefficient.