Study On Mechanical Properties Of 3D Printed Rock Samples After Temperature Treatment

Rock mass exists in the complex geological environment.As the development of practical engineering to deeper underground,the effects of high temperature environment on the physical and mechanical properties of rock mass and the damaging fracture modes must be considered..The application of 3D printing technology in geotechnical engineering can effectively overcome the shortcomings of traditional methods,such as time-consuming and laborious sample preparation,and large dispersion of test results.In this paper,GS19 sand and furan resin are selected as printing base materials,and a3 D structure model is established by Solid Works,and 3D printing rock samples are prepared.Then,the macro and micro level tests of 3D printed rock samples with different temperatures are carried out,and the optimal mechanical temperature is determined,which makes 3D printed rock samples show the best mechanical properties.Finally,the physical and mechanical properties and damage fracture mode of 3D printed rock samples with different forms of prefabricated cracks under the optimal mechanical temperature are studied.The main work and research results are as follows:(1)In this paper,3D printing technology is introduced in detail from the perspectives of materials,forming process,advantages and prospects.Based on the application of 3D printing technology in the field of geotechnical engineering and the previous research results of the research group,the author selected GS19 sand and furan resin as the printing substrate,and prepared 3D printed rock samples with various structures,and applied 3D printing technology to the research of geotechnical engineering.(2)We heated the 3D printed rock samples according to the temperature gradient of50?,and carried out uniaxial compression test and splitting tensile test after the samples were dried to room temperature.We found that the tensile and compressive strength of the samples increased first and then decreased with the increase of temperature,and the maximum value of the samples was reached after the temperature of 150 ?,and the bearing capacity was lost after the temperature of 300 ?.We further combined thescanning electron microscopy and thermogravimetry experiments to study from the micro level,and found that the change of glue is the main reason for the difference of mechanical properties of 3D printed rock samples under different temperatures.We defined 150 ? as the optimal mechanical temperature of 3D printed rock samples.(4)We heated the 3D printed rock samples with different forms of prefabricated cracks at the optimal mechanical temperature(150 ?)and then aired them to room temperature to carry out uniaxial compression test.It was found that the changes of fracture angle,rock bridge angle and fracture combination form make the physical and mechanical properties and damage fracture mode of 3D printed rock samples different,but there is no lack of commonality:Tensile failure,tensile shear mixed failure and shear failure mainly occur in the specimen,which is characterized by brittle failure;Under the load,the specimen undergoes four stages: compaction,microcrack initiation,stable crack growth and through failure;The initial position of crack initiation is mostly at the tip of prefabricated crack due to stress concentration,in which wing crack is nearly perpendicular to prefabricated crack initiation,and develops stably in the form of central symmetry along the direction of load loading,while secondary crack grows faster than wing crack.