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Under Water Blasting for Rock Dredging & Protection of Structures: A Case Study

V. Rama Sastry, G. Raghu Chandra, C. Karthik

Abstract


Rock dredging in ports involves under water blasting for the pretreatment of hard sea bed. A rock dredging project covering an area of about 257,058m2 involving 400,000 cu.m of hard Khondalite rock mass was taken up in a port in the east coast of Southern India, for deepening of Turning Circle and Inner Harbour Channel. Pre-blast survey was carried out to assess type and condition of various structures standing on different distances from the dredging area and safe Peak Particle Velocities (PPV) were assigned. STADDPro analysis was carried out for determining the natural frequency of some marine structures with pile foundation. Under water blasts were planned with varying blast configurations at different locations from the structures in order to maintain the vibration levels to within prescribed threshold values. In total, 1,150 under water blasts were conducted till date, consuming about 425t of explosives. Down the hole initiation was implemented for protecting nearby structures from blast vibrations. The paper gives details of the methodology of underwater blasting and related studies carried out.

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References


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DOI: https://doi.org/10.37628/jgget.v2i1.76

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