One 150 m high and two 210 m high chimneys have been successfully demolished by blasting with 40 m high trapezoidal cuts in an insufficient collapse space.Directional collapse blasting was carried out for three times by combining in-hole and out-hole delays.The protection measures included laying a cushion in the direction of chimney collapse,piling up an impingement dike,excavating a vibration damping ditch,putting a dense screen at the blasting cut and overlaying geogrids.Blast vibrations monitoring proved that the flying objects and blast vibrations were both controlled within the safety allowable range and no damage was caused to surrounding structures.The blasting effect shows that high blasting cuts can effectively solve the problem of limited collapse space,and avoid the influence of factors such as soot platform at the bottom of the chimney and flue entrance on the collapse direction.At the same time,this technique can also limit the flyting distance of the splash on the ground and reduce the ground contact vibration and blast vibration.In addition,the chimney lining can be effectively treated by blasting boreholes through the concrete walls of the chimney into the lining and insulation layer.Another good practice is to pretreat the directional windows and guide windows by a drilling and coring machine,which can reduce explosive charge and promote the breakage of the blasting cuts so as to ensure the exact direction of collapse.