Simulation Study Of Blasting Of Jointed Rock Mass Using PFC

Blasting process is an important technical means for engineering andconstruction services, because it can produce a huge amount of energy, which is akind of advantage that cannot be replaced by the general mechanical or human.From the1950s.blasting become the main method of breaking rock in the industrialfield of hydropower, coal, metallurgy, and railway and infrastructure construction inour china. The vast majority of surface rock in practical engineering is dividedinto jointed rock masses by fissures, caves and other weak structural plane.Joints destroy the integrity of the rock and reduce its strength. Joints also affectsthe rock blasting damage form for providing escape channel of blasting energy,making uneven distribution of energy, Therefore, the study of jointed rockmass blasting failure mechanism and analyzing the influence of different formsof jointed to blasting energy distribution and dissemination have practical significanceand important theoretical value for selecting reasonable blasting location, improvingthe utilization of explosive energy, optimizing blasting results and ensuringconstruction safety.Based on the above issues, This article rely on the National Natural ScienceFoundation of China (40972189,51038009) and the Beijing Natural ScienceFoundation (8111001), as background to blasting excavation in ChiCheng of hebeiprovince, and obtaining parameters of rock mass，the typical joints，blasting and so on.Establishing the jointed rock mass bursting model with LS-DYNA and PFC, studyingand summarizing the influence of different forms joints to energy propagation in rockmass and blasting funnel molding effect. The following is the main research contents：1.Introducing Particle Flow Code（PFC）. Using biaxial compression test toanalyze the law of influence of micro-parameter (contact models, the coefficient offriction, bond strength, etc.) and macroscopic mechanical properties, and to provide atheoretical basis for micro-parameter selection; using LS-DYNA software simulationof rock blasting process, and selecting the unit from the kits close enough to recordthe speed-time curve, and then convert the data into a file format readableby the PFC, in order to achieve the simulation of explosives in the PFC;2. Combining actual engineering rock mass parameters and the laboratorytest curve fitting the curve to get particles micro-parameter to build model.Through analysis an example of the blasting energy spread attenuation law in the joints rock to validate effectiveness of model parameters, boundary conditionsand damping setting.3. Building different inclination Jointed Rock model, through analysis theparticles velocity peak changing of incident and reflected wave on both sidesof the joints to draw the influence law with the angle of jointed and kits andblasting energy absorption, reflection and attenuation, the results showed that whenthe angle is90o, the attenuation of energy is the least obvious;4. Summary influence law of joint spacing ratio (the ratio of joint spacing andblasting wave length) and blasting energy spread with the model, that havingtwo parallel joints,The results showed that when δ is1.2,the attenuation of energy isthe most obvious;5. Consider the diversity of the relative position of joints and kits, analysis ofblasting crater forming effect by establishing the model of joints intersect withextended line of minimum resist line， intersect with the minimum resist line,vertical, parallel to the minimum resist line;In the final section comes the conclusion, which summarizes the whole thesisand points out its inadequacies that call for further studies.