Investigating the influence of blasting operations at the surge tanks and storage facilities on the underground structures of Gotvand Olya dam

Ground vibration is an inevitable consequence of blasting operations in open pit miningand civil engineering projects. A large amount of energy is released in every blastingexercise in the form of wave propagation, which can cause serious damage to thesurrounding environment. Safe design of blasting for underground structures andtunneling are nowadays carried out mainly based on the permissible peak particle velocity(PPV), which has become a major criterion in setting out the appropriate safety standardsenvisaged to prevent structural damage near such operations. Many published studieshave produced correlations for PPV prediction using experimental data The GotvandOlya Dam is one of the major civil engineering projects in the last thirty years in Iran, constructed as the last dam on the Karoon River with the aim of increasingenvironmentally friendly electrical energy of the country, seasonal flood control in theprovince, and a supply of agricultural water for the strategic farming grounds ofKhoozestan. The geological formations of Gotvand include the two main formations ofBakhtiyari and Aghajari. The existence of discontinuities in these formations as well asjoint sets and their low inherent strength caused a number of challenges in blasting designoperations. This dam is 30 km north west of Shoshtar in the Khoozestan province, and 12km away from Gotvand. In this study, 16 records of 3 components produced from 4 blastswere obtained using 4 seismographs of the type PG-2002 at Intac and surge tanks of theGotvand Olya Dam in order to investigate their effects on underground structures. Thethree-component seismometers were of the GS-11D type and the records were analyzedusing DADISP software. The explosion materials used were ANFO and dynamite, andthe maximum weight of the explosions per delay in the Intac and surge tank were in therange of 32.0 to 343.3 kg. The positions of the seismometers were in the range of 56.2 to 145.5 meters away from the centre of blast blocks. The permissible peak particle velocity was taken from the Korean Institute of Geology, Mining and Materials. Using the scale distance, an exponential equation based on the cubic root of the charge weight per delay and coefficient correlation of 85% was proposed for predicting the PPV. In thisrelationship, the geological coefficients of the Gotvand area were estimated to be 20.339and -3.08. Using a genetic algorithm, an improved coefficient correlation between theexperimental and predicted PPV of 89% was obtained. The results from the geneticalgorithm applied for the coefficients of a, b, and n in the equation of PPV=b(d/wn)a were -9.286849, 9.769703 and 0.745959, respectively. Considering this proposed relationship,the minimum distance of 56.2 m to the centre of the blast block and the permissible peak particle velocity of 254 mm/s for a 10 day old concrete, the maximum charge weight per delay was found to be 254.4 kg.