The Study Of The Vibration Control Of Cofferdam Demolition Blasting On Hydropower Station

Normally, large hydropower stations were built in the high mountains or deep valleys. Being restricted by topography, the blocking all the riverway in once (also called full section cofferdaming method) or blocking the riverway in a stage manner (also called successive section cofferdaming method), were usually taken in stream guiding when constructing, and the open channel or tunnel were used in stream guiding. However, no matter foundation constructing on riverbed or other hydraulic structures is hardly going on in running water. For this reason, temporary cofferdam for water blocking should be constructed to enclose the foundation ditch all or partly on riverbed, and then the foundation course or other constructing. While the water blocking was no need, for not obstructing stream guiding in another period or running permanent constructions, or water distributing in open channel and stream guiding tunnel, usually, the cofferdam will be demolitted.As an economical,quick and effective way, blasting had being widely applied in numerous projects. While, how to control the effect of blasting vibration on other constructions into safe range, was still a big difficulty in blasting cofferdam.The most effective way to control vibration blasting, is to control the max charge amount per delay interval. How to determine the ideal max charge amount per delay interval, which is a key problem in blasting cofferdam design and vibration control, involves determination for blasting vibration-control standard, experiences of success in blasting cofferdam and a criterion on safety of blasting vibration.In the paper, the response spectrum of blasting earthquake was used to calculate the force corresponding of neighboring constructions to the cofferdam blasting, and a method to determine the criterion of cofferdam-blasting vibration was put forward. The fact that the method was successfully applied in blasting cofferdam of stream guiding tunnel in Shenxi Gou hydropower station, showed that it was workable, which could afford reference for building the criterion on safety control of blasting vibration in similar cofferdam demolition.