Experimental Study On Static And Dynamic Mechanical Properties Of Rough Jointed Rock Specimens Based On 3D Printing

There are a large number of complex and variable rock masses in nature.Due to their formation conditions,formation processes,and the influences of different geological processes and climate alternation in later stages,the effects of cracks,bedding and joints are formed inside the rock masses.The joints,as an important structural plane of rock masses,plays a leading role in the deformation and failure of rock masses because they makes the mechanical properties of rock masses more complex.Nevertheless,the structural plane of jointed rock masses in practical engineering is often rough.However,in the past,when scholars carried out experimental studies on the mechanical properties of jointed rock masses,they usually assuming that the structural plane is smooth or linear,which is far from the deformation and failure in actual engineering.(1)The roughness coefficient of the joint surface was quantitatively analyzed,the irregular surface was transformed into a regular sawtooth surface,and the three-dimensional digital model of the rough joint surface was established and sliced by reverse engineering modeling software.Five rock samples with different joint angles(ɑ=0°,30°,45°,60°,90°)and five rock samples with different joint roughness(JRC=0,5,10,15,20)were made by 3D printing technology and similar materials.(2)Ultrasonic detector was used to measure the longitudinal wave velocity of rock samples with weak filling joints of different joint angles and different joint roughness,and to study its variation law.The experimental results show that the wave velocity of the joint specimen increases with the increase of the joint inclination angles,and the attenuation degree becomes smaller and smaller.When the joint inclination angles are same,the wave velocity of the joint sample decreases gradually with the increase of JRC.(3)The static uniaxial compression test shows that the static uniaxial compressive strength of the joint sample decreases first and then increases with the increase of the joint inclination angle,and the compressive strength of the joint sample with a inclination angle of 60° is the lowest.When the joint inclination angles are the same,for the joint inclination angles of 0° and 90°,no matter how the JRC changes,the compressive strength is maintained in a certain range,and the difference is very small.For the other three inclination angles,with the increase of JRC,the roughness of the joint surface increases,and the compressive strength of the joint sample shows an increasing trend.The failure modes of rough joints under static uniaxial compression are mainly divided into three types: axial splitting failure,slip shear failure and split shear mixed failure.(4)The Hopkinson bar(SHPB)test system was used to carry out dynamic impact compression tests on rock samples with weak filling rough joints,and the changes of joint inclination angle and joint roughness coefficient(JRC)on deformation,dynamic compressive strength and failure characteristics of rock samples.The results show that the dynamic compressive strength of the joint specimens increases gradually with the increase of JRC.Under the same JRC condition,with the increase of joint inclination angle,the boundary of 45° shows a trend of decreasing first and then increasing.When the inclination angle is 45°,the upper and lower plates of the main failure characteristic joints slip,shear,and break along the direction of the joint plane.When the JRC increases to 20,the failure mode of the sample changes from shear failure to tensile shear composite failure.Figure [34] Table [3] Reference [92]...