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Abstract The objectives，conditions and methods for anti-blast effect tests of the new optimized and nonoptimized weakened composite anchorage structures are described. The only difference between the two types of structures is the length of weakened hole section. The former is optimized，while the latter is empirically determined. The experiments are characterized by low initial loads and small load increments. The experiments truly represent the whole process of chamber from deformation through failure to collapse and blockage. Experimental results show that the critical failure resistance of the former is more than 2.1 times as much as that of the latter. Under the extreme failure conditions，the large deformation dimension(arch crown lowering) and the surface spalling area of the former are only 25% and 33% that of the latter，respectively. The mechanism of weakening hole group is to form a weakened zone in the surrounding rock to turn the original two-medium system (support structure and surrounding rock) into a three-medium system(support structure，weakened zone and surrounding rock). The weakened zone will absorb a great deal of explosion energy during explosion，and transfer the crisis of the support structure at the same time.
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Received: 19 May 2010
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2010, Vol. 29 
