Study On The Blast-induced Damage Zone For Rock Excavation

Most hydroelectric projects locate at the areas of remote mountains and gorges。During the process of rock excavation by blasting,as a result of the action ofdetonation stress wave,a blast-induced damage zone is occurred in the preservedrockmass after the excavation。In the damage zone parameters of rock mechanics getworse because of the actions of blast stress wave and explosion product,and this mayproduce potential dangers to the preserved rock and the constructions built on it。Sothe control of the blast-induced damage zone is a key problem in the rock blastresearch field。 In this thesis,the current theoretical models of rock blasting on the basic ofanalysis to the detonation pressure produced by explosive in different kinds of chargeduring the rock blasting and the reciprocity mechanism of the explosion load and rockmass are firstly discussed。Then the sonic measurements currently used to evaluate theblast-induced damage zone in our country and it's theory basic are analyzed。Thewide-adopted criterion of the Peak Particle Velocity(PPV)for blast-induced damageis also present。Finally the result of the further study on the newly derived equationfor the attenuation of the PPV during rock blasting on the basis of the analysis of thetheory of the cylindrically elastic wave,the theory of the seed wave induced by acylindrical charge and the Heelan Solution for stress wave field induced by a shortcylindrical charge is present。The following conclusion are concluded: (1) With the data from the blasting excavation of the diversion tunnel on the leftbank of Laxiwa hydroelectric project,a comparison between the new equation and thetraditional equation is present,the result shows the improved equation is bothreasonable and feasible。 (2) The author studies the relation between the multi-hole-blasting-modifiedfactor and the distance away from the blasting source is studied,The result shows thatthe factor is approximately equal to the number of the blasting holes when holes aredetonated in a distance far than 200 times of the diameter of blast holes。 (3)An equation to calculate the blast-induced damage zone in rockmass iseduced,and the damage zone for the blasting excavation of the diversion tunnel on theleft bank of Laxiwa hydroelectric project is calculated。The comparison between thecalculated results and the measured results in the site is made,the result shows thatthe educed equation is both reasonable and feasible。...