| The intact rock has the characteristics of high strength and small permeability coefficient.However,the natural rock mass contain joint fracture,and the occurrence of joint fracture makes the characteristics of the rock mass different from the intact rock.Under the same stress environment,the shear strength of the rock mass is small;the joint fracture constitute the flow channel of the seepage water,thus the rock mass has greater permeability than intact rock.In engineering,almost all hydraulic structures involve the stability of rock slopes.It is of great value to study the influence of joint fracture on engineering safety.The research of this subject needs to start from the characteristics of single fractures.Based on the existing research results,the mechanics,seepage and fluid-solid coupling characteristics of single fractures are studied by hydraulic test,theoretical derivation and numerical simulation.The main conclusions are as follows:(1)Based on the shear test data under three-dimensional topography,a new peak shear strength formula is established.The formula conforms to the evolution of the dilatancy angle with the normal stress and reflects the influence of the maximum contact area and the schistosity structure on the peak strength.The new formula has higher prediction accuracy than the existing formula.(2)The evolution of JRC values with different statistical parameters is summarized.In general,there are certain errors in the prediction results of diff’erent statistical parameters for JRC values between 6 and 12.(3)The cubic law of radial flow is deduced in detail,and its applicable conditions are summarized:the firacture structure surface satisfies the smooth parallel plate structure;the fracture flow belongs to the Darcy flow;the water flow can enter the weak inertial band with negligible ine rtia force d uring the radiatio n pro cess.For the neglige nce of inertial force,the discriminant formula is derived and verified by hydraulic test.(4)When the shear test was carried out at water pressure of 0.2 to 0.6 MPa,the flow rate of the parallel plate test specimen was maintained substantially unchanged,and the linear Darcy flow was satisfied.However,the flow rate of the regular tooth te st specimen does not satisfy the linear flow and there is a sudden change in the flow rate during the shearing process.The nonlinear characteristic of the water flow before the sudden change point is greater than the sudden change point.Both the shear and the decrease in the osmotic water pressure result in a decrease in the proportion of nonlinearity. |
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