| On the basis of existing studies in the field of seepage of rock mass both at home and abroad, the present dissertation has conducted a broad study in terms of hydraulic and geometric parameters, computing model, basic seepage law, fracture drainage, rockmass' unloading mechanics and its relations with seepage. The paper is written by employing such methods as field observation, model test, theory research and numerical analysis. The main research payoffs are as follows.⑴ Field observations and measurements and relevant statistics show that the NE-NEE and NNW constitute the first and second dominant trends of the discontinuities of the rock mass in the area of the permanent shiplock in the Threee-Gorge Project. Of all the discontinuities, the steep dip takes the absolute lion's share. In this case, drainage through upward hole is obviously advantageous over that through plumb hole. The measured ratio of drainage using the said two ways is rather similar to that of numbers going through the discontinuities (i.e. about 2). Since the underwater level is basically immune to the changes of rainfall, the seepage flow is steady on the whole.⑵ According to the existing studies of the basic law of fracture seepage, there are two sharp contrastive relations between seepage discharge and aperture: super-cubic and sub-cubic. Similarly, there are also two opposite relations between seepage discharge and relative roughness: positive and negative relations. For the first time, this dissertation has analyzed the two relations in a detailful way and proved the existence of the above two relations by means of test of single fracture seepage. The test results reveal that mating fracture trial cubes present a super-cubic and positive relationship and that non-mating fracture a sub-cubic and negative relationship.⑶ By using the aperture curve and roughness curve, the author of the dissertation has put forward the concepts of frequency hydraulic aperture and frequency roughness for the first time. Of the two concepts, the first or frequency hydraulic aperture has got some advantages of its own in the seepage analysis. By analyzing actual cases and simulating finite element of random fracture through computer, the frequency hydraulic aperture falls within 48~50%, i.e. eh=e48~e50.⑷ By doing single fracture drainage experiments, this paper has successfully presented the logarithm function relationship between ratio of drainage discharge through upward and plumb drainage hole and the ratio of their equivalent diameters. The drainage effect will be the best when the included angle between drainage hole and fracture surface is 21~36°. At the same time, experiments also show that the horizontal affecting radius of drainage hole is no more than 11.6 times that of drainage hole radius.⑸ In this dissertation, the author presents a model of transforming element fracture net into element equivalent hydraulic conductivity tensor. This model can effectively reflect the obvious anisotropy and non-homogeneity of fracture rock seepage and makes it easier to simulate the various aperture fissure and display the fundamental characteristics of discrete fissure net. In addition, the model is can also make the best use of the sound theoretic foundation of equivalent continuum model. At the same time, the disscharge balance method developed in the dissertation can specify the exact location of discharge point in an easier and more efficient way. In other words, the new method gets rid of the limitation of the traditional method which fixes the point of discharge at the node alone. Actual computation proves the said new method is both feasible and practical.⑹ Rock mass projects are of different engineering mechanical states including loading, unloading, coexistence of loading and unloading, alternation of loading and unloading. What is suitable in the research of slope works is the unloading rock-mass mechanics. Since the unloading rock-mass mechanics has taken into consideration the dynamic anisotropy, accelerated degradation of t...
|
PDF Full Text Request