Study On The Control Blasting Mechanism Of Rock-plug Contour

For the purpose of fetching water in irrigation, expanding hydroelectric project,supplying urban drinking water and some other purposes, new hydraulic tunnels on oldpower station reservoirs or natural lakes are needed. Usually, the entrances of thesehydraulic tunnels are tens of meters deep under the water, sometimes even a hundredmeters. However, the conventional ways of cofferdam would take a long duration andcost a large quantity of money and sometimes they are unpractical. Fortunately,underwater rock plug blasting, which is specific, can provide supplement and guaranteefor these conventional ways. The key is to blast through at a time. Thus, the rock plugcan be well shaped so as to ensure the tunnels are in good condition and are stable forlong time running as well as to ensure that the buildings around are safe. In a word, thepurpose is to ensure that the tunnel is blasted through, well-shaped and safe. However,tunnel lining is impossible through underwater rock pug blasting. In order to gain goodcross-section contour surfaces and stability for long time running, adopting practicalcontrolled blasting technique and reasonable blasting parameter is the only way.Accordingly, the study on the underwater rock plug blasting mechanism with regard tothe cross-section contour surface is of great significance for the engineering practice.This thesis starts with illustrating underwater rock plug blasting techniques whichare adopted both at home and abroad as well as the present studies on controlled blastingtechnique on cross-section contour surface. In detail, the blasting characteristics of rocksare introduced and analyzed on the basis of two aspects, that is, the dynamiccharacteristics of rocks and the principle of dynamic damage of rocks; then, the principleof stitching with regard to controlled blasting technique on cross-section contour surfaceare presented. Furthermore, the study focuses on how can in-situ stress influence on theformation of cracks; then, experiment on controlled blasting technique on cross-sectioncontour surface is introduced according to field tests and the conclusion is that smoothblasting can obtain better effect; finally, numeric situation analysis, which focuses onwhat effects can in-situ stress have on controlled blasting technique on cross-section contour surface, has been conducted with the help of ANSYS/LS-DYNA. The analysiscan help us choose the right blasting way.The focal points and innovation points are as follow: firstly, the thesis discusses thatin-situ stress has different influences on smooth blasting and pre-split blasting. Whenthere is in-situ stress, smooth blasting should come first; secondly, the thesis presentsreasonable controlled blasting parameter on the basis of site blasting tests; thirdly, basedon the situation when several blast holes are blown up simultaneously, three-dimensionalnumerical modals of the smooth blasting and pre-split blasting are constructedrespectively and contrastive analysis on how can different in-situ stresses affect thecontour surface of controlled blasting are conducted.