Study On Dynamic Response Of Surrounding Rock With Energy-gathering Smooth Hydraulic Blasting

The technique of energy-gathering smooth hydraulic blasting is a new controlled blasting technique,which has been used in practical engineering in recent years.Although the principle of energy-gathering smooth hydraulic blasting needs further research,the selection and optimization of blasting design parameters is the most fundamental problem that must be solved in engineering practice at present.Based on Nankunshan tunnel of the Shan-Zhan expressway engineering,combined with energy-gathering smooth hydraulic blasting construction technology,using the ANSYS/LS-DYNA explicit dynamic analysis commercial software,the peripheral parameters were optimized,and dynamic response of surrounding rock of the Ⅴ grade marble were characterized.Firstly,the rock breaking theory of plain blasting,the application of energy accumulation effect in blasting and the equivalent method of applying blasting load in numerical simulation are briefly described.The flow-solid coupling method and ALE algorithm were used to study the blasting process of single energy-gathering hole.The expansion characteristics of shaped charge jet in the blasting process of single hole with different radial uncoupling coefficients,different existence of shaped charge tubes and different uncoupled media were analyzed.Meanwhile,the analysis of the distribution of the equivalent effect force and the pressure verifies that the energy-gathering smooth hydraulic blasting technique can reduce the blasting energy loss and increase the blasting load to achieve the purpose of controlling expanding groove.Secondly,based on the result of single peak pressure in the hole wall,peripheral parameters optimization research of grade Ⅳ and Ⅴ marble in the surrounding rock were conducted with equivalent load method.By analyzing the expansion and distribution range of plastic zone,the maximum principal stress curve feature and vibration velocity curve characteristics respectively,it is determined that the reasonable pitch in the grade Ⅳ rock can be optimized to 60 cm,and the reasonable charge intensity is 0.55 kg/m;and in the grade Ⅴ surrounding rock,the reasonable distance of the peripheral eye can be adjusted to 80 cm,and the reasonable charge intensity is 0.48 kg/m.Finally,according to the optimized peripheral parameters and engineering experience,the design parameters of smooth blasting in Nankunshan tunnel are determined.Through the definition of millisecond blasting method in calculation,load in the whole section to pay all slots and auxiliary hole blasting load,calculated the Nankunshan tunnel Ⅴ grade marble wall rock stress distribution characteristics,characteristics of maximum principal stress time history and velocity distribution characteristics.The results show that the stress concentration may occur at the arch foot and the stress deficiency may occur at the arch waist in a single detonation of the whole section.The influence of blasting load on surrounding rock decreases with the increase of range,and is most obvious within 1m.