Blasting Demolition of Single-tower Cable-stayed Bridge in Complex Environment

A combined demolition method of directional tilting of main tower and in-situ collapse of bridge beam has been designed for the blasting demolition of a single-tower reinforced concrete cable-stayed bridge in complex environment. An "inverted step" cut with a height of 4 m was designed for the middle tower pillar, and the mechanical pre-processing method was used in the lower tower pillar to form two windows with a width of 1.3 m and a height of 4 m to reduce its strength. The loose blasting was used for the bridge beam at four locations where the cables were anchored on the beam. Decked charge was adopted for the blast holes deeper than 2.1 m and initiated by detonating cords, which effectively dispersed the explosive energy. The middle tower pillar, lower tower pillar and the beam were initiated as 3 stages with nonel detonators. A “rigid+flexible” composite protection method was proposed for the culvert crossing the bridge. Two sandbag damping walls were settled on the touchdown area of the bridge beam to form a "flexible" protection. Meanwhile, a welded steel skeleton and rubber cushion layer were arranged along the direction of the culvert to form the “rigid” protection. Grass curtains, bamboo fences, and steel wire layers were covered on the blasting area. After the blast, the tower toppled on the predetermined direction. And the main beam collapsed in place, divided into several sections which were then processed with mechanical methods. In this project, good blasting results have been achieved without causing flyrock accidents or impact damage to the culvert.