In January 2021,the Anning River Bridge 1 was assessed as a class-4 dangerous bridge.In order to prevent the bridge from collapsing during the flood season,the local government planned to demolish the bridge by blasting.This Bridge was a double-curved arch bridge,with a length of 207.7 m and a width of 9.5 m.It was located in the downtown area of the city center and had a complex surrounding environment.The nearest distance to the existing Rainbow Bridge was 3 m.As the height of the bridge piers above the river bed was only 1.7~3 m,the collapse height of the bridge was insufficient.Therefore,the 3# bridge pier,which was far from the downtown on both sides of the bank,was selected for full blasting disintegration first.The powder factor of the 3# bridge pier,the upper cross wall of the pier and the upper cross wall of the arch was 1.5~2.13 kg/m3,which ensured the 3# pier could be fully broken and the space for the bridge to collapse could be created.Meanwhile,some stress components which affect the overall collapse of the bridge,such as arch ribs,piers,cover beams,transverse walls on piers,partial transverse walls on arches and connection beams,were destroyed locally,which resulted in the collapse of the bridge from the middle to both sides with powder factor of 1.44~1.96 kg/m3.A mixing initiation network of Nonel detonators and electronic detonators was adopted for different blast sections.In each section,equal interval short delay initiation was used according to the order of height and upstream to downstream,so that the initiation times of different sections of the bridge were different.For the same section,the difference of the initiation times and bridge collapse heights were made full use to realize the uneven settlement and full dislocated disintegration of the bridge under the low drop condition.In addition,multiple internal and external protection methods with rigidity and flexibility were utilized,including high-strength soft covering rubber,medium-strength covering geogrid plastic net,hard covering bamboo raft,soft covering straw mat and dense mesh safety net.Among them,the rigid and medium-high strength covering could control the large flying rocks,and the soft covering could play a buffering role to suppress the small flying rocks,which effectively protected the surrounding buildings(structures).