« Back

 Vol. 9  No 5 October  2001            

Safety

Safe Explosive Mass Storage Structures (IGLOO)

Conventional reinforced concrete cement (RCC) used for magazines/bunkers is known to have limited ductility and concrete confinement capabilities These properties are especially required for structures subjected to blast and impact loading environment.  The efforts are on to prove these properties of RCC.  The structural properties of RCC can  be improved by modifying the concrete matrix and by suitably detailing the reinforcements.

IGLOO magazine during explosionTwo new construction techniques, namely Steel Fibre Reinforced Concrete ( (SFRC) and Laced Reinforced  Concrete (LRC) have been trial evaluated vis-a-vis RCC for  their   shock mitigation efficiency and for use in the design of blast resistant structures and blast containment structures. The SFRC techniques involves mixing of steel fibres in concrete matrix which increases the energy absorption capability of concrete. It also increases ductility of the structure, arrests the formation and propagation of cracks, and also improves the spall resistance by 30 per cent compared to conventional RCC. On the other hand, LRC consists of continuous bent shear lacings along with longitudinal reinforcements on both faces of a structural element. The LRC enhances the ductility and provides better concrete confinement. Moreover, LRC technique is cost-effective
compared to RCC for same level of protection: the reinforcement requirements can be lesser by 30 to 40 per cent for LRC.

The conventional storage magazines require large safety distances between the two adjacent storage magazines. Due to paucity of land there is a need to develop compact layout of storage magazines without compromising on safety aspects. When a large quantity of explosive is required to be stored in the limited space, the total quantity of explosive is distributed in a number of storage magazines constructed according to a planned layout in such a manner that if accident occurs in one of the magazines, its destructive effects remained confined to that unit only. In other words, at a time only one unit is at risk. This unit risk principle has been established for an IGLOO explosive storage magazine of 5 ton capacity. The simulated accidental explosion were conducted to study the efficacy of the LRC. The safe distance between two IGLOO structures of W kg capacity has been proven as 0.7 W1/3 m which is just outside the crater radius. This distance for a conventional magazine may vary from 2.4W1/3 to 3.6 W1/3.