A series of small-scale laboratory tests were carried out to investigate the effects of short delay times on fragmentation. The aim is to test the hypothesis that improve fragmentation through stress wave superposition. These tests have subsequently been modeled using a coupled FEM-BPM-PBM model in LS-DYNA code. In the model, the remaining rock is represented by a finite element model (FEM) and the rock to be blasted is represented by a bonded particle model (BPM). The detonation of explosive is described with a particle blast method (PBM). The fragment size distribution was obtained with a code developed in Perl programming language. The numerical results showed that although the short delay times induced improved fragmentation compared to the simultaneous initiation, the longer delay times also resulted in improved fragmentation, implying that stress wave superposition may not be the primary factor governing fragmentation.