Research Of Vibration Damping Effect Of Pre-splitting Crack

The prediction and control of blasting hazard is always an important subject in engineering blasting felid, especially the hazard of blasting seismic. Pre-splitting blasting, as an effective control blasting technology for vibration isolation and damping, is widely applied in the engineering construction felids of utilities, railroads, mines and so on, and it has already achieved tremendous economic and social benefits. Currently the research on vibration damping effect of pre-splitting blasting is limited, and it still stays on the qualitative analysis stage. Quantitative analysis of vibration damping effect of pre-splitting blasting takes an important role in guiding actual engineering design, it is also a try to improve the pre-splitting blasting theory in the vibration damping field.Pre-splitting blasting develops on the basis of smooth blasting, and it is one of the important measures to lower blasting seismic wave. Pre-splitting crack's effect upon wave propagation is the main research targets in the essay. Basing on the theories of the strength pre-splitting crack whose interface is described with M-C law and the strength pre-splitting crack whose interface is described with joint stiffness, it introduces pre-splitting crack mechanisms and its limitations, and it expounds clearly the basic characteristics of blasting seismic waves. It also uses the mechanisms above make a research and explanation for the developing course of seismic waves when spreading through the pre-splitting crack.The slop-reserved blasting project for excavation as the subject is studied in the essay, and it establishes a model of pre-splitting crack contingency of materials whose flexibility plasticity is the same in different directions. Using display dynamical finite element analysis software ANSYS/LS-DYNA, it calculates the dynamic responses in detail and changes law of the surrounding rock around the pre-splitting crack under changing weight;It explores the effects of the length , breadth and depth of pre-splitting crack upon vibration isolation. The result shows: a relatively low-speeding violating shield region exists in adjacent protected areas near pre-splitting cracks due to the shielding effect of pre-splitting crack;the length, depthof pre-splitting crack and its distance to the source effect upon the vibration are damping larger. With the increasing length and depth of the crack, the vibration damping effect becomes better and better, and the shield region of pre-splitting crack increasing and effect of pre-splitting crack's shield become worse and worse;The shield region is larger, the shielding effect becomes weaker;When the width of pre-splitting crack reaches a certain value, it makes little sense in damping vibration.The dissemination of seismic waves and its vibration damping law in the pre-splitting region is studied through theoretical analysis and numerical simulation, and it explores quantitative calculation of the vibration damping effect of pre-splitting blasting, which is useful for the damping effect of pre-splitting blasting.