A Study On Mechanical Characteristics Of Flawed Rock Mass Specimens Based On CT Scanning And 3D Printing Technology

Rock mass is an important engineering medium with complex inner structure and containing a variety of structural surfaces,and its strength and mechanical characteristics is affected by the common effect of structural surfaces existing in the rock mass.Many studies have shown that the failure of rock mass is caused by cracks further propagation and coalescence,which dues to the interactions between original structure surfaces and cracks produced under external force.While in the previous studies on mechanical characteristics and coalescence processes of rock mass,the complex internal structure of rock cannot be restored and specimens with absolutely identical internal structure cannot be obtained massively and quickly,and thus lead to some test error.This paper combined the CT scanning technology and 3D image processing technology to build the three-dimensional digital models which have the same internal structure with natural sandstone specimens,based on that,corresponding three dimensional solid models were built with proper printing material by 3D printing technology,and then the mechanical properties and crack propagation characteristics of flawed rock mass were explored under uniaxial compression.Besides,this paper has made the numerical simulation of models under uniaxial compression by using general finite element analysis software ABAQUS,and then the results were compared and validated with those by laboratory tests.The main works and research results of this paper are as follows:(1)This paper introduced the printing procedures,printing materials and forming processes of 3D printing technology,analyzed the its advantages and limitations Compared with traditional manufacturing methods,and also introduced the application situation of this technique in geotechnical engineering and rock mechanical laboratory tests.(2)The digital models obtained by CT scanning and three dimensional reconstruction can reconstruct the realistic structure information of natural sandstone specimens like internal “weak areas”,then 3D printed specimens which have the same inner structure characteristics with natural sandstone specimens can be obtained by using the different printing processes of 3D printing technology.(3)The comparative experiments showed that the specimens printed with furan resin and sand powder in rational composition as printing material were relatively closed to the natural sandstone specimens in the density,uniaxial compressive strength,uniaxial tensile strength,elastic modulus and other indicators of physical and mechanical properties,which can be used in the laboratory experiments and researches of sandstone.(4)Under uniaxial compression,the failure patterns of 3D printed specimens having prefabricated flaws with different incline angles mainly include tension failure,shear failure and tensile-shear mixture failure.The peak compressive strength of specimens presented "V" type trend,which decreases firstly and then increases along with increase of incline angles.(5)With the finite element calculation of three dimensional reconstructed models by using numerical simulation software ABAQUS,the crack propagation laws of specimens under uniaxial loading were analyzed,and compared with the laboratory experimental results,the results were relatively close.