Study And Application On Blasting Demolition Of Ultrahigh Reinforced Concrete Chimneys With Numerical Simulation

Directional controlled blasting is a widespread technology used in the demolition of reinforced concrete chimney at present, while numerical simulation, as a economical, reliable and repeatable technique, is attached more and more importance by engineering technicians. In this paper, the collapsing rule of reinforced concrete chimney, especially the failure of reserved support, is elaborated and analyzed on the background of a real demolition project and the platform of ANSYS/LS-DYNA. Afterward, the body fracture in the air is reproduced in the simulation as well and the vibration after ground contact is studied from a perspective of adverse effects control in the end.ANSYS/LS-DYNA, as the most popular finite element analysis(FEA) software, is introduced in the beginning. A flow sheet of reinforced concrete chimney integral model is builded, of which some key steps are emphasized with details. After that, an integrated FEA model is set up and a successful simulation is operated.Due to the crucial importance of reserved support to the whole process, the failure rules of the support model in the collapse is studied based on theoretical analysis and observational research. From the result, we can know that the moving direction of neutral axis is determined by the domination of tension and compression, which means that the tensile failure of central zone leads to the forward shift or immobility of the axis and the compressive failure of kerf area leads the axis moving backward, which may be result in sudden fall of chimney body.Body fracture in the air is a common phenomenon in the collapsing. By theoretical calculation, the maximum shear force is in the two-thirds height and the maximum bending moment is in the one-thirds. In spite of the main effect of bending fracture, the fracture of240m chimney emerges in the two-third height both real situation and simulation result. A conjecture is that the sharp change of body diameter makes the location of the maximum bending moment move up to that height, where generates tensile stress concentration in the model.Vibration after ground contact is the most adverse effect in blasting demolition. A empirical formula of the vibration is obtained by dimension analysis and experiment induction. One important work in this paper is to get vibration data from the simulation, and fortunately, the data is approximate to the result of measured value and calculated value. Besides, some protective measures such as damping ditch and dike are carried out in the progress and the effects are compared.