| In the dam foundation and underground tunnel of large-scale water conservancy projects,fractures of different scales and trends will be generated inside the rock mass due to the long-term geological processes.The permeability of fracture is much larger than that of rock,so fracture becomes the main channel for seepage inside the rock mass.Studying the morphological structure and seepage characteristics of fractures can provide a reasonable prediction for the safe operation of engineering.In this paper,fracture seepage with different roughness is numerically simulated based on the two-dimensional fracture morphology description method.The interaction between stress and seepage and the effect on roughness are analyzed in combination with the shearing-seepage coupling test of single-fracture radiation flow.Based on the seepage law,a two-dimensional seepage model of single-node cross-fracture was established,which laid a foundation for the study of fracture network seepage model.The main research results of this paper are as follows:(1)When the sampling interval was 2 mm,the relationship between roughness coefficient(JRC)and roughness profile index,relative undulation,effective tooth dip angle,and fractal dimension was derived.A two-dimensional numerical model was established for the straight line and curved fracture profiles of different JRC.The results showed that the flow velocity distribution was greatly affected by the tooth dip angles,and for the same fracture,the flow velocity changed when the order of the fracture tooth dip was changed.In addition,under a certain hydraulic gradient,the larger the gap width was,the smaller the JRC was,and the larger the seepage flow was.(2)Based on the conservations of energy and momentum,a groundwater seepage test with a depth of 80-150 m was designed.The smooth and regular serrated specimens were used to derive the external force and head loss formula at the radiation flow.The test results showed that the seepage pressure was less sensitive to shear stress than the normal stress(3)The seepage flow rates of the two specimens were analyzed.The fitting showed that the seepage flow and the fracture width were in accordance with the power exponential relationship.And the rougher the surface was,the smaller the index was.The roughness of the fracture surface changed after the test.The smooth specimen changed from JRC=0 to about 3 The increase of JRC was positively correlated with the normal stress.The serrated specimen changed from JRC=16.41 to about 12.The reduction of JRC was positively correlated with the shear stress.(4)A two-dimensional radiation flow seepage model was established to analyze the flow velocity distribution of the smooth specimens under the influence of shearing action.The final result showed that the maximum flow velocity value was about 78%higher than the inlet flow velocity at the same seepage pressure.The width of the serrated fractures were undulated and changed during the shearing process.The water flow between the fractures was turbulent,and the range of the generated eddies were related to the fracture width(5)Taking a node of the fracture network as the research object,an X-type single-node cross-fracture network seepage model was established.The calculation results showed that the exit angle was an important factor in determining the dominant channel when the inlet fracture width was constant.At the same time,the maximum flow velocity of the cross-fracture was lower than that of the single fracture under the same boundary conditions. |
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