Numerical Simulation Study On Demolition Blasting Of Tilted Chimney

Nowadays, with the rapid development of cities, many buildings and structures must be demolished by blasting. However, instability poor security of high-risk buildings and structures,the difficulty of blasting demolition, all of these make them face a severe test for blasting staff. The researchers had not done much research on the blasting theory and construction technology for upstanding tall buildings and had not made great progress, therefore there’s a lack of research on the subject in academia. Based on the background that a sloping brick chimney demolition blasting is applied and the research methods that simple indoor experiments, theoretical calculations and numerical simulation is adopted, the main contents and conclusions of this article are as follows:(1)Through the establishment of the easy indoor chimney of trapezoidal and rectangular-shaped cutout, these three aspects, including the direction of the chimney collapsed, the collapse process and the vibration velocity, were compared, preliminary view is that the process of chimney blasting selected trapezoidal cutout form is more reasonable and reliable.(2)From the side of stress, this is, after blasting incision formed remaining support tensile stress, compressive stress must be met this condition that σtmin≥fbr,σcmax≤fbc,it is determined that inclined brick chimney dumping conditions and deduced stress calculation expression of the remaining support; From the side of overturning moment, that is the resultant moment of blasting cut after the formation is greater than the moment of resistance remaining support body, it is determined that inclined brick chimney dumping conditions and deduced the expression on the moment of resistance remaining support body; At the same time to meet the condition of stress and overturning moment, the appropriate notch blasting central angle could be selected.And based on the linear superposition principle, the angle between the actual direction of the dumping notch and center line direction could be determined.(3)For the basic principles of mechanics of material and engineering mechanics, leaning chimney is simplified to rigid rod model,carrying on dynamic analysis of the blasting demolition of a dangerous chimney during the three stages including the angular velocity and linear velocity at any time of overturning, the time needed to rotated to any angle, the support reaction of pivot point and the selection of minimum height of blasting cut.(4)Based integral model,the dimensional finite element of ladder blasting incision model is established by using ANSYS/LS-DYNA. Compared with the simulation results the actual engineering and theoretical calculations, the following results were obtained that the launch of the theoretical formula can provide a reference for the actual demolition blasting and the numerical simulation can predict in advance the effect of blasting demolition. They have guiding significance for engineering practice.(5)Under the same conditions of blasting trapezoidal cutout, using ANSYS/LS-DYNA to simulate for blasting rectangular cutout, after then comparative analysis of the simulation results and the results of trapezoidal blasting cutout simulation, the following conclusions are drawn that trapezoidal blasting cut more favorable than the curved incision for the directional blasting of inclined brick chimney.