Study On The Influence Of Blast Stress Field In Rock Mass Due To Modification Of Charge Structure

Blast stress field in rock mass, which including quasi-static and dynamical field, initiated by explosion was solved theoretically according to detonation theory and stress theory. Taking laboratory concrete coupon as model and applying high dynamic strain indicator, radial stress in model was measured. In the presence of large-scale universal finite element software ANSYS/LS-DYNA, Blast stress field in rock mass was numerical simulated under various charge conditions.Based on difference of air between water mediums in physical property, the influence of air and water radial, axial and both radial and axial charge structures to blast field in rock mass was contrast analyzed, and through theoretical calculation, the relationship of injection and quasi-static pressure in hole between decouple parameter under various charge structure. The calculation results indicates: under the condition of the type of explosion and property are fixed, decouple coefficient and decouple medium are the chief factors of the influence of wall of hole pressure and quasi-static pressure in hole, the decompression effect of air decouple medium is better than water's, and the influence of changing the value of decouple coefficient to the peak value of stress when charge structure applies water decouple charge is less significant difference than when it applies air decouple charge.Calculation method of critical decouple coefficient related with critical expansion pressure in two steps expansion theory of air initiated by explosion blasting was extracted for the first time, and the influence of the factors such as decouple coefficient and decouple medium to blast stress field in rock mass was analyzed systematically. Through the contrast analysis of laboratory model test and numerical simulation, the trueness and rationality of theory were proved.The results of test measurement and numerical simulation indicates, under the same condition, the peak value of stress generated by water decouple charge blasting is larger than that of air, and the effect time is longer than that of air. Whatever radial or axial stress, compression stress first occurred in rock mass and transformed tensile stress later. The peak value of compression stress is larger than that of tensile stress near the blasting field, but with the development of distance, their difference became small, and at last, c tensile stress is larger than compression stress.