Mechanics Analysis On Safety Of Demolition Of Tall Chimneys By Controlled Blasting

In resent years, with the recognition of safety of controlled blasting demolition tallchimneys, the technique of blasting demolition chimneys must be developed fromexperience designing to the direction of scientific and normative. This paper summarizedthe current situations of theories and practices of blasting demolition chimneys, pointed outfour main factors which effect the safety of blasting demolition tall chimneys: the veracityof falling direction, fling, recoil, break. Aimed at the four factors, based on mechanicstheory, safety of blasting demolition tall chimneys was analysised, calculation models ofdemolition parameter were discussed.This paper concentrated on two essential factors which ensure that tall chimneysfalling down in the intended direction: cut angle and cut height, according to the mechanicsstate variety on the remainder cross section at the time of cut blasting, consider themechanics character of chimney structure, the mathematical models of cut angle for brickchimneys and reinforced concrete chimneys are found. Based on this, by the closing wayof upper and lower cut in the second falling phase, according to chimney structure andmechanics theory, the mathematical models of cut height for brick chimneys andreinforced concrete chimneys are found. It is a creative in this paper to found a set ofmathematical models of cut parameter which aimed at different structure form anddifferent cut shape.This paper started from different cut shape, analysised time-falling angle, time-speedand supporting stress, deduced the condition of fling and recoil and then found theirmathematical models. According to inner force distribution on the every section ofchimney in the falling process, consider the mechanics character of chimney structure, themathematical models of chimney break are found. It is the other creative in this paper.This paper had discussed the function of directional cut in blasting demolition tallchimneys and the affect of wind power to blasting demolition tall chimneys, thenanalysised the size and angle of directional cut.This paper had chosen some engineering examples of blasting demolition tallchimneys, the mathematical models are used to calculate and analysis these examples. Theresult shows that the mathematical models in this paper is valid, they have a great usefulvalue to ensure the safety of demolition chimneys.