| The structural plane is an important component of rock mass and plays a major role in controlling the engineering characteristics of rock mass.The shear strength of structural planes is a key parameter for stability analysis and reinforcement design of engineering rock mass.Therefore,the research on the shear strength of structural planes is the basic work for stability evaluation of engineering rock mass.Through direct shear test of structural plane,N.R.Barton showed that the strength of wall rock and surface morphology of structural plane were the main factors determining the shear strength,and proposed the famous JRC-JCS empirical estimation model.In recent years,many scholars at home and abroad have done a lot of research on the shear properties of structural planes,but most of the tests are aimed at studying the strength properties of structural planes or measuring the strength parameters of structural planes.There are few studies on the influence of structural plane morphology on shear deformation and the hierarchical analysis of structural plane morphology.Therefore,through numerical simulation and laboratory direct shear test,this paper studies the influence of structural surface morphology characteristics on the shear strength of structural surface.The main contents involved in the paper are as follows:(1)The surface morphology of the rock mass has an important influence on the strength of the structural plane.In order to quantify the influence of structural surface morphology on the shear performance of structural surface,many classical theoretical models have been established by using regular sawtooth instead of real structural surface morphology.In this paper,discrete element software(UDEC)is used to construct the rock mass model of a single regular sawtooth structure plane and one with multiple tooth-attached structure planes,and direct shear tests under different normal stresses are carried out.The influence of normal stress,tooth height and tooth number on shear characteristics of structural surface is discussed by changing tooth height and tooth number,and the concise formula of Barton straight edge method is modified by response surface theory;(2)The surface topography of natural rock mass discontinuities is complex,and the traditional methods are usually artificial to classify the surface topography characteristics of discontinuities due to their inability to accurately separate the geometric features of discontinuities.In order to overcome the problem that the surface topography of rock mass discontinuities cannot be quantified and thus can not be accurately decomposed and reconstructed,this paper proposes a method of surface topography decomposition of rock mass discontinuities based on wavelet transform,and uses 3D printing technology to make structural surface molds.On the one hand,this method solves the problem of multi-level quantitative description of the surface fluctuation morphology of the structural plane,and significantly improves the accuracy of the surface topography description of the structural plane.On the other hand,the use of 3D printing technology to produce mold in line with the test requirements,save the time of mold making,reduce the cost of mold production;(3)In order to carry out the pouring test smoothly,this paper refers to the research done by some scholars to determine the rock similar materials and mix ratio,and uses the structural plane die produced by 3D printing technology to pour the structural plane rock material samples of different decomposition levels;The 3d laser scanner was used to compare the structural surface of the pouring sample with the morphology of the mould of the structural surface,and the coincidence degree reached 98%,which verified the validity of the pouring sample of the structural surface.Through unconfined uniaxial compression test,the uniaxial compressive strength of the rock-like test block are 66.74MPa;(4)GCTS direct shear apparatus was used to conduct direct shear tests on the poured samples of A0?A8 with a total of 9 levels of structural surface under a series of normal stresses,calculate the contribution coefficient of shear strength of each level of structural surface,and determine the degree of contribution of each level of structure to the shear strength of the original structural surface;The total variance of the roughness contour curves of all levels of structural surfaces was calculated,and combined with the direct shear test results,the critical point of the main structural surface topography characteristics with the decomposition grade of A6 at the sixth level was obtained.Under the same normal stress,the shear loss of the structural plane decreases with the increase of the decomposition level of the structural plane.With the increase of normal stress,the shear loss area and the failure depth of the structural plane of the same decomposition grade increase,and the shear loss area of the structural plane is mainly concentrated in the convex part of the structural plane. |
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