Dynamic Fracture Characteristics Of Jointed Rock Mass Based On 3D Printing And DIC Technology

Due to the long-term geological tectonic movement and the late excavation disturbance,there are a lot of joints and fissures in the surrounding rock,which control the stability of the surrounding rock to a certain extent.In addition to joint defects,the surrounding rock of deep roadway often bears the influence of dynamic load,leading to the deformation and failure of surrounding rock.Therefore,the study of rock dynamic mechanical properties,damage evolution and failure mechanism under rough joints and impact loads is of great significance for the safety of deep tunnel engineering.In order to study the stability of surrounding rock of underground engineering of concealed rough joint characteristics,custom five rough joint surface,through 3D printing and3D scanning technology to rough quantitative evaluation on the joint surface,and then through the rock similar material casting include built-in rough joint rock specimens,by split hopkinson pressure bar(SHPB)system for rough joint rock dynamic impact test series,using high-speed cameras on joint rock dynamic damage process in real-time,the indoor experiment and numerical simulation method of combining the,the effects of joint roughness and dynamic strain rate on the dynamic strength,deformation and failure modes of jointed rock mass are studied.The main research results are as follows:(1)The filling type rough joint was prepared based on 3D printing,and then the rough joint surface was quantitatively evaluated by 3D scanning technology.Through physical and mechanical orthogonal tests of similar materials,the basic mechanical properties of similar materials at different proportions were measured,and the optimal similar proportions were finally determined.The rock mass samples with internal rough joints were then poured with similar materials.(2)The dynamic impact test of jointed rock mass was carried out by means of the split Hopkinson bar(SHPB)system.With the help of high-speed camera and digital image correlation technology,the effects of joint roughness coefficient JRC and dynamic impact strain rate on mechanical properties and fracture characteristics of jointed rock mass were studied.With the increase of JRC,the peak strength,failure strain,elastic modulus and energy dissipation of jointed rock mass all increase gradually.The dynamic mechanical parameters of jointed rock mass have obvious strain rate effect,and the peak stress and energy dissipation are positively correlated with the strain rate,and their values increase linearly with the increase of the strain rate.The dynamic elastic modulus increases exponentially with the increase of strain rate and the failure strain increases as a quadratic function with the increase of strain rate.(3)The particle flow model of SHPB system was established by using PFC^2D to reappear the crack evolution law and failure mode of jointed rock mass under dynamic impact,and the influence law of joint dip angle and joint roughness coefficient JRC on the total number of cracks,peak stress and failure mode of the sample was analyzed.With the increase of joint inclination angle,the peak stress of jointed rock mass decreases gradually with the increase of inclination angle,while the number of cracks increases first and then decreases with the increase of inclination angle.The total number of cracks is the largest when the inclination angle is 45°.With the increase of JRC,the dynamic peak strength of jointed rock mass and the total number of cracks increase gradually.There are 55 figures,11 tables and 112 references in this paper.