Study On Shear Strength Of Rock-like Structural Planes Based On 3D Printing Technology

Rock mass is ubiquitous in nature,and it is an important component of many geological structures.Rock mass is considered to have structural characteristics in rock mass mechanics of mines.Rock blocks(structural bodies)and structural planes together constitute rock mass.Structural planes in mine rock mass engineering are mainly faults,bedding,joints and so on.Structural plane has an important influence on the mechanical properties of rock mass.Therefore,it is of great significance to study the characteristics of structural plane and its mechanical properties for rock mass engineering.Firstly,aiming at the non-repeatability of mechanical test of rock specimens,threedimensional scanning technology was used to obtain the morphological data of rock structural planes.Based on the obtained morphological data,a batch of structural plane dies with the same morphological characteristics were produced by using three-dimensional printing technology.A batch of gypsum structural interviews with the size of 10 cm x 10 cm x 10 cm were poured into the prepared steel mould.Three-dimensional scanning and three-dimensional printing technology have realized shear mechanics tests of structural surfaces with the same appearance characteristics under different normal stresses and directions.Then,anisotropic shear mechanics tests of gypsum structural planes were carried out in the laboratory.The shear mechanics tests of 16 identical structural planes in four directions(0,90,180 and 270 degrees)were carried out.The normal forces in each direction were divided into four grades,which were 0.3 MPa,0.4 MPa,0.5 MPa and 0.6 MPa,respectively.The test results show that the peak shear strength increases with the increase of normal stress,and the shear strength in different directions is different.The shear strength in 90 and 180 degrees directions is greater than that in 0 and 270 degrees,while the shear strength in this direction is larger than that in the lower wall of the shear direction when the shear direction is "climbing",and vice versa.It is fully explained that the roughness of structural plane has an important influence on its shear mechanical properties.Extension shows that the shear strength of the structural plane in all directions is related to the inclination angle of the structural plane in all directions and the shear direction(the direction of movement of the loading upper/lower plate).It is fully explained that the roughness of structural plane has an important influence on its shear mechanical properties.In order to further analyze the anisotropic characteristics of shear strength of rock discontinuities,numerical simulation tests of anisotropic shear mechanics of rock discontinuities were carried out by using PFC numerical test software.Based on the mechanical parameters of gypsum specimens with the same material and ratio,the meso-parameters of PFC numerical test were calibrated.Then five curves were extracted at equal intervals in each direction for the above-mentioned structural planes,and the elevation data of the five curves were averaged.A new contour was obtained as the contour of the simulated structural planes.The results of PFC numerical simulation were in good agreement with the experimental results.This research is a new exploration of anisotropic shear mechanics test of rock discontinuities,and provides a new method for further understanding the anisotropic mechanical properties of rock discontinuities.