Research On Touchdown Process And Safety Control Of Demolition Blasting Of Reinforced Concrete Chimney

In the process of urban reconstruction and expansion,demolition blasting is being paid attention to quickly and simply,and occupies an important position in the demolition market.However,most of the demolition blasting projects are located in buildings and densely populated areas.The harmful factors such as the deviation of the collapse direction and the vibration of the ground and the scattered objects with pose a great threat to the surrounding environment.In this paper that based on the engineering field test with this paper uses the similarity theory to simulate the ground vibration of the demolishing of the reinforced concrete chimney and the distribution characteristics of the flying objects and the characteristics of the disintegration of the cylinder body and mainly carry out the following research work:(1)Propagation law of blasting vibration and touchdown vibration and analysis of control area.The results show that:(1)For the chimney type linear vibration source when the central position of the chimney is the center of the vibro source,the prediction error of the vibration velocity in each direction is larger.When the chimney vibration source center is located at the height of 4/5,the accuracy of the prediction error is the highest in all directions.(2)There will be two critical points equal to the velocity of blasting vibration and the vibration velocity of the ground.Between the two critical points,the blasting vibration intensity is greater than the vibration intensity of the ground.When the vibration protection is designed the blasting vibration protection should be taken as the main protection;the other areas should be dominated by the vibration control of the ground.(2)The influence of location and height of different incisions on the attenuation of touchdown vibration.The results show that:(1)On the lateral vertical line from theequidistant location of the source,the vibration velocity increases with the position of the side vertical line moving towards the source.(2)With the increase of the opening height,the vibration velocity of the rear and lateral side decreases gradually while the vibration speed increases gradually before the collapse.(3)Analysis of the dispersion rule of explosive particles and touchdown.The results show that:(1)The blasting flying objects are mainly distributed in the 2/5 range of the height of the chimney dumping direction,and the scattered objects are mainly distributed over the area of more than 2/5 of the height of the barrel,and the flying objects of far distance are appeared at the height of the barrel of the barrel about 2/3.(2)The initial velocity of the flying debris in the chimney is less than the instantaneous line velocity of the cone touch ground and the velocity of the toppling touch ground line can be calculated according to the height of the chimney and the maximum flying distance of the flying objects is estimated.(4)Analysis of the characteristics of the disintegration of the chimney toppling ground.The results show that:(1)When the chimney falls to the ground,there will be two parts of the disintegration area.The other part in the top area of the cylinder is near the 2/3 position above the length of the cylinder.(2)With the increase of the position of the incision,the length of the disintegration of the barrel is reduced and the crushing effect becomes better.The research of this subject has some reference value for improving and optimizing the demolition blasting plan of chimney and controlling the harmful effects on the surrounding environment.