| The structural plane widely exists in natural rock mass,which plays a crucial control role in the deformation and failure of rock mass.The instability of related rock mass is mostly caused by the failure of structural plane.As a common means of geotechnical engineering reinforcement,anchorage technology is widely used in mines,tunnels,slopes and dam foundations and other major projects,which is used to control the development and penetration of structural planes.Therefore,it is of great engineering significance to study the shear failure characteristics of anchorage structural planes.In order to explore the shear mechanical properties of anchoring rough structure planes,a three-dimensional digital model of typical Barton standard JRC curve was constructed.The rough joint mold was prepared by 3D printing technology.The rock samples of full-length and two-end anchoring rough structure surface were prepared for direct shear test,acoustic emission test and digital speckle test.The main research contents of this paper are as follows :(1)Based on the gray-level matrix image processing technology of matlab,four representative contour lines of 0-2,6-8,12-14 and 18-20 in the typical Barton standard JRC curve are selected for digital processing.The coordinate points of the contour line are extracted,and the2-dimensional graphics are drawn by CAD.Then the three-dimensional model of the rough structure surface is imported into 3DMAX.Finally,the resin mold is prepared by 3D printing technology.The anchor inclination angles are set to 30°,45°,60° and 90°,respectively,and the anchorage modes are divided into full-length bonding type and expanded-end type anchors.(2)The full-length bonded anchorage structure surface is simulated by using the rough structure surface directly embedded in the bolt during the pouring of the sample.Direct shear tests were carried out under normal stress of 2MPa,3MPa,4MPa and 5MPa.The typical yield-shear curves have obvious elastic stage,yield stage,failure stage and residual stage.The shear test results show that the optimal anchorage angle of the full-length bonded anchorage structure plane is between 45° and 60°.The failure modes are mainly sliding failure along the structural plane and shear failure of the asperity.With the increase of normal stress,the failure mode becomes more and more complex.(3)The rough structure plane sample with expanded head at both ends of the prefabricated anchor is used to carried out primary and secondary shear tests under normal stress of 2MPa,3MPa,4MPa and5 MPa.The primary shear strength of the 30°-anchorage structural plane and 45°-anchorage structural plane is relatively large.The shear stiffness of the secondary shear specimen is greater than that of the primary shear specimen,and the shear stress-displacement curve shows a sharp point.After the shear stress reaches the peak,it drops rapidly to the residual strength.The peak stress of the secondary shear failure specimen is slightly higher than that of the residual strength of the primary shear failure specimen,but the residual strengths of the two specimens are the same.The broken area of anchor and structural plane is obvious,and the anchor at the structural plane has ’ S ’ deformation.(4)Acoustic emission technology is used to record the acoustic emission signal characteristics of structural plane shear under different normal stress.The AE ringing count,cumulative ringing count and value of acoustic emission technology are used to analyze the crack propagation in the process of event shear failure.At the same time,the digital speckle correlation method is used to analyze and explain the changes of the strain field in the x direction and the displacement field perpendicular to the shear direction in the shear failure process of the specimen to the internal cracks of the specimen.The existence of anchor can adjust the change between the surface and bottom of the sample structure,change the position of strain expansion,and prolong the time of shear expansion effect. |
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