Ditching blasting technology of shallow-hole and deep-hole combined at single initiation under urban complex environment
In order to achieve one-time excavation of foundation pits with blasting in complex urban environments while controlling harmful effects such as flying rocks,a shallow-deep hole combined one-time initiation trenching technique was employed in the excavation project of underground basement foundation pits.The one-time initiation excavation successfully achieved the desired open space without generating flying rocks,with the maximum blasting vibration velocity near adjacent structures not exceeding 1 cm/s,and the blasting noise below 70 dB.The ditch blasting mechanism of one-time initiation trenching was analyzed based on the blasting sequence and blasting vibration waveform.The blasting process of trenching can be roughly divided into four stages:the independent stage of shallow hole pulling trench blasting,the strong cooperative stage of shallow hole pulling trench blasting and deep hole step blasting for trench expansion,the cooperative stage of deep hole step blasting for strong pressure slag blasting and shallow hole pulling trench or pressure slag blasting,and the weak stage of deep hole step blasting for independent pressure slag blasting.
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